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Vacuum-assisted breast biopsy with 7-gauge, 8-gauge, 9-gauge, 10-gauge, and 11-gauge needles: how many specimens are necessary? Heike Preibsch, Astrid Baur, Beate M Wietek, Bernhard Krämer, Annette Staebler, Claus D Claussen and Katja C Siegmann-Luz Acta Radiol published online 17 September 2014 DOI: 10.1177/0284185114549224 The online version of this article can be found at: http://acr.sagepub.com/content/early/2014/09/17/0284185114549224
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Acta Radiol OnlineFirst, published on September 17, 2014 as doi:10.1177/0284185114549224
Original Article
Vacuum-assisted breast biopsy with 7-gauge, 8-gauge, 9-gauge, 10-gauge, and 11-gauge needles: how many specimens are necessary?
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Heike Preibsch1, Astrid Baur1, Beate M Wietek1, Bernhard Kra¨mer2, Annette Staebler3, Claus D Claussen1 and Katja C Siegmann-Luz1
Abstract Background: Published national and international guidelines and consensus meetings on the use of vacuum-assisted biopsy (VAB) give different recommendations regarding the required numbers of tissue specimens depending on needle size and imaging method. Purpose: To evaluate the weights of specimens obtained with different VAB needles to facilitate the translation of the required number of specimens between different breast biopsy systems and needle sizes, respectively. Material and Methods: Five different VAB systems and seven different needle sizes were used: MammotomeÕ (11-gauge (G), 8-G), VacoraÕ (10-G), ATEC SapphireTM (9-G), 8-G MammotomeÕ RevolveTM, and EnCor EnspireÕ (10-G, 7-G). We took 24 (11-G) or 20 (7–10-G) tissue cores from a turkey breast phantom. The mean weight of a single tissue core was calculated for each needle size. A matrix, which allows the translation of the required number of tissue cores for different needle sizes, was generated. Results were compared to the true cumulative tissue weights of consecutively harvested tissue cores. Results: The mean tissue weights obtained with the 11-G / 10-G VacoraÕ / 10-G EnspireÕ / 9-G / 8-G Original / 8-G RevolveTM / 7-G needles were 0.084 g / 0.142 g / 0.221 g / 0.121 g / 0.192 g / 0.334 g / 0.363 g, respectively. The calculated required numbers of VAB tissue cores for each needle size build the matrix. For example, the minimum calculated number of required cores according to the current German S3 guideline is 20 / 12 / 8 / 14 / 9 / 5 / 5 for needles of 11-G / 10-G VacoraÕ / 10-G EnspireÕ / 9-G / 8-G Original / 8-G RevolveTM / 7-G size. These numbers agree with the true cumulative tissue weights. Conclusion: The presented matrix facilitates the translation of the required number of VAB specimens between different needle sizes and thereby eases the implementation of current guidelines and consensus recommendations into clinical practice.
Keywords Breast, vacuum-assisted biopsy, sample volume Date received: 16 March 2014; accepted: 28 July 2014
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Introduction Imaging-detected breast lesions are categorized according to the breast imaging reporting and data system (BI-RADSÕ ) of the American College of Radiology (1). BI-RADSÕ applies to lesions which were detected on mammography, ultrasound (US), or magnetic resonance imaging (MRI). Lesions which were assessed
University Department of Radiology Diagnostic and Interventional Radiology, Tu¨bingen, Germany 2 University Department of Gynecology and Obstetrics, Tu¨bingen, Germany 3 Institute of Pathology and Neuropathology (Department), Tu¨bingen, Germany Corresponding author: Heike Preibsch, University Department of Radiology Diagnostic and Interventional Radiology, Hoppe-Seyler-Straße 3, 72076 Tu¨bingen, Germany. Email: [email protected]
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as BI-RADSÕ 4 or 5 are suspicious or highly suggestive of malignancy. A biopsy should be performed to prove or exclude malignancy in cases presenting with these lesions, and minimal invasive imaging-guided percutaneous needle biopsy should preferably be used. For imaging, the least complicated method in which the lesion is surely visible should be employed (2,3). Vacuumassisted biopsy (VAB) has proven to be advantageous compared to large core needle biopsy as more tissue volume is obtained and therefore histological classification is more reliable (4,5). VAB has therefore replaced large core needle biopsy in several indications. In particular, VAB is the method of choice to clarify suspicious microcalcifications without accompanying solid lesions, and suspicious lesions which are only detectable on breast MRI (2,6,7). US-guided VAB is recommended to clarify lesions that are too small to make representative large core needle biopsy possible, or in case of a mismatch of imaging assessment and histological finding after US-guided core needle biopsy (2,8). The most commonly used needle sizes for VAB are 11gauge (G), 10-G, 8-G, and 7-G. Recently published national and international guidelines and results of consensus meetings give different recommendations with regard to the required number of tissue specimens depending on needle size and imaging method. Most of the recommendations refer to the 11-G needle. The current German S3 guideline for diagnosis, therapy, and follow-up of breast cancer recommends a sample number of at least 12 cores with the 10-G needle or an equivalent tissue volume if needle sizes between 8-G and 11-G were used for stereotactic VAB (2). An interdisciplinary consensus paper on the use and technique of vacuum-assisted stereotactic breast biopsy recommends at least an average number of 20 cores with the 11-G needle or a corresponding tissue volume if a larger probe is used (9). An interdisciplinary consensus paper on the use and technique of MRI-guided VAB recommends an average number of at least 24 cores with the 11-G probe or an equivalent tissue volume if a larger probe is used (7). In terms of the use of US-guided VAB, an interdisciplinary consensus paper recommends the removal of at least 10 specimens with an 11-G needle and at least six specimens with an 8-G needle (8). The authors recommend the removal of equivalent quantities of tissue when using needles of other sizes. Explicit statements referring to the number of specimens with different needle sizes are missing. None of the publications provide a translation of the required number of tissue cores for one needle size into another. In the literature, there are only studies about comparison of average tissue volumes with different 14-G biopsy guns (10) and the comparison of 11-G and 9-G VAB systems for tissue yield, length, and
fragmentation of specimens (11). Another study compared the use of 11-G and 8-G needles in benign breast disease (12). The latter presents estimated sizes, weights, and volumes of 10-G, 11-G, and 8-G specimens without true measurements of tissue cores. The aim of this study was to evaluate standardized weights of tissue specimens obtained with 11-G, 10-G, 9-G, 8-G, and 7-G VAB needles to facilitate the translation of the number of tissue specimens between different breast biopsy systems and needles, respectively.
Material and Methods Experimental setting of vacuum-assisted breast biopsy Tissue cores were consecutively taken from a turkey breast phantom with seven different sized needle probes: 11-G Original MammotomeÕ (Devicor, Inc., Cincinnati, OH, USA), 10-G VacoraÕ (BARD GmbH, Karlsruhe, Germany), 10-G EnCor EnspireÕ (BARD GmbH, Karlsruhe, Germany), 9-G ATEC SapphireTM (Hologic Inc., Bedford, MA, USA), 8-G Original MammotomeÕ (Devicor, Inc.), 8-G MammotomeÕ RevolveTM (Devicor, Inc.), and 7-G EnCor EnspireÕ (BARD GmbH, Fig. 1a, b). All biopsies were performed by the same radiologist (HP) who had 1 year of experience in performing VAB procedures with all of those biopsy systems. The tissue cores were removed one
(a)
(b)
Fig. 1. (a) The five different VAB needle sizes which were used in this study imaged with open biopsy chambers. From left to right: 11-G Original MammotomeÕ , 10-G VacoraÕ , 9-G ATEC SapphireTM, 8-G Original MammotomeÕ , and 7-G EnCor EnspireTM. (b) The two needle sizes, which were found twice in this study, imaged with open biopsy chambers. From left to right: 10-G EnCor EnspireTM, 10-G VacoraÕ , 8-G MammotomeÕ RevolveTM, and 8-G Original MammotomeÕ .
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after another and each core was weighed within 30 min after removal to avoid weight loss due to drying. According to the maximal requested number of current guidelines, 24 cores were taken with the 11-G needle and 20 specimens were obtained with each of the 10-G, 9-G, 8-G, and 7-G needles. Physical density (d) of tissue is defined as its weight (mass ¼ m) divided by its volume (d ¼ m/V (g/cm3)), so the tissue weight is proportional to the tissue volume if the density is non-varying. In this study, all specimens were obtained from the same turkey breast phantom to assure the same density of all tissue cores. Hence, in our experimental setting the tissue weight can be taken as reference variable for tissue volume.
Data acquisition and calculation The size of the tissue cores was measured as the length in millimeters (mm) (Fig. 2a–g). The mean size and standard deviation (SD) of the tissue cores were calculated for each needle size.
The weight of the tissue cores was measured by using a high-resolution balance of special accuracy for extremely precise measurement of mass (Sartorius LP 620 P, Sartorius AG, Goettingen, Germany), which allows an accuracy of 1 mg. The weight of every single specimen was noted and the mean weight and SD of a single core was calculated for each needle size. Minimum, maximum, and median were displayed in a box-whisker plot (Fig. 3). The weight of various cores was added to obtain the true cumulative weight (Fig. 4). The mean weight of an 11-G needle specimen was taken as reference to calculate the corresponding numbers of core specimens for the other needle sizes. The 11G needle was chosen as the reference needle size because most consensus recommendations refer to this size. The mean tissue weight of a single core of each needle size (10-G, 9-G, 8-G, 7-G) was divided by the mean weight of the 11-G tissue core to obtain corresponding translation factors which were 1.69 for the 10-G VacoraÕ needle, 2.63 for the 10-G EnspireÕ needle, 1.44 for the 9-G needle, 2.29 for the 8-G Original needle, 3.98 for the 8G RevolveTM needle, and 4.32 for the 7-G needle. Afterwards we multiplied the number of 11-G cores by the above calculated translation factor for each needle size to obtain the equivalent number of tissue cores. With regard to recent guidelines, we performed the calculation for a number of 10 to 24 cores with the 11-G needle. The resulting numbers of recommended tissue cores taken with different needle sizes were rounded and put into a spreadsheet. We thereby generated a matrix system from which the equivalent numbers of specimens, which constitute the same tissue volume, can be read (Table 1). To simulate the real biopsy setting, we calculated the cumulative tissue weights for each needle to assess the needed number of tissue cores to reach the recommended equivalent tissue volumes. To test the matrix system, the numbers of tissue cores were compared to the true cumulative tissue weights and corresponding numbers of specimens of consecutively harvested tissue cores (Fig. 4). Mean and SD were calculated by use of Excel 2003 (Microsoft, Redmond, WA, USA). Diagrams were created with Excel 2003.
Results Length and weight of tissue cores
Fig. 2. Specimens obtained with the (a) 11-G needle, (b) 10-G VacoraÕ needle, (c) 10-G EnspireÕ needle, (d) 9-G needle, (e) 8-G Original needle, (f) 8-G RevolveTM needle, and (g) 7-G needle.
Mean length of 11-G core specimens was 23.1 3.37 mm SD, of the 10-G VacoraÕ specimens 19.7 1.20 mm SD, of the 10-G EnspireÕ specimens 27.9 2.56 mm SD, of the 9-G specimens 21.8 1.52 mm SD, of the 8-G Original specimens 24.8 2.93 mm SD, of the 8-G
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Fig. 3. Box-plot diagram of specimen weight subject to needle size.
Fig. 4. Cumulative sample weights according to the number of specimens with seven different VAB needles. The black line marks the recommendations of the German S3 guideline (2) and the recommendations of a consensus meeting on the use of stereotactic VAB (9). The dotted black line demonstrates the recommendations of the consensus meeting on the use of MRI-guided VAB (7). The dashed black line marks the recommendations of a consensus meeting on the use of US-guided VAB (8).
RevolveTM specimens 27.3 1.25 mm SD, and the length of the 7-G cores was mean 27.4 2.81 mm SD. With the 11-G needle the mean weight of one tissue core was 0.084 0.032 g SD, with the 10-G VacoraÕ 0.142 0.006 g SD, with the 10-G EnspireÕ 0.221 0.039 g SD, with the 9-G needle 0.121 0.014 g SD, with the 8-G Original needle 0.192 0.027 g SD, with the 8-G RevolveTM 0.334 0.046 g SD, and with the 7-G needle 0.363 0.053 g SD (Fig. 3). The lowest variation of specimen weight was shown by the 10-G VacoraÕ needle and the highest by the 7-G needle, which is probably caused by the higher rate of tissue fragmentation with the 7-G needle (Fig. 2g). The lower mean weight of the 9-G specimens compared to the 10-G cores and the 8-G Original compared to the 10-G EnspireÕ might be explained by the different width in combination with the remarkable difference in length (Fig. 2b–d, f).
Recommended number of tissue cores and cumulative tissue weights Fig. 4 illustrates the comparison of cumulative tissue weights of different needle sizes in relation to different recommendations of recent guidelines and consensus meetings. The lowest number of tissue cores is requested for US-guided VAB (dashed line in Fig. 4). The highest number of tissue cores is requested by the consensus meeting on the use of MRI-guided VAB (dotted line in Fig. 4). The recommendations of the German S3 guideline for stereotactic breast biopsies and the recommendations of an interdisciplinary consensus meeting on the use of stereotactic VAB are similar and lie in between both others (black line in Fig. 4). The German S3 guideline recommends the removal of a tissue volume equivalent to at least 12 cores taken
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Table 1. The matrix system presents the calculated minimum number of tissue cores which should be taken with different VAB systems and needle sizes to gain an equivalent tissue weight. The following needles were used: 11-G Original MammotomeÕ , 10-G VacoraÕ , 10-G EnCor EnspireÕ , 9-G ATEC SapphireTM, 8-G Original MammotomeÕ , 8-G MammotomeÕ RevolveTM, and 7-gauge EnCor EnspireÕ . 11-G
10-G VacoraÕ
10-G EnspireÕ
Number of tissue cores depending on needle size 24* 14 9 23 14 9 22 13 8 21 12 8 20y 12z 8 (12)z 19 11 7 18 11 7 17 10 6 16 9 6 15 9 6 14 8 5 13 8 5 12 7 5 11 7 4 10§ 6 4
9-G
8-G Original
8-G RevolveTM
7-G
17 16 15 15 14 13 13 12 11 10 10 9 8 7 7
11 10 10 9 9 8 8 7 7 7 6 6 5 5 4 (6)§
6 6 6 5 5 5 5 4 4 4 4 3 3 3 3 (6)§
6 5 5 5 5 4 4 4 4 3 3 3 3 3 2
*Recommendations of an interdisciplinary consensus meeting on the use and technique of MR-guided vacuum-assisted breast biopsy (7). y Recommendations of an interdisciplinary consensus meeting on the use and technique of vacuum-assisted stereotactic breast biopsy (9). z Recommendations of the German S3 guideline for diagnosis, therapy, and follow-up of breast cancer (2). The calculated equivalent tissue volume of 12 cores with the 10-G VacoraÕ needle is 8 when using the 10-G EnspireÕ needle but the guidelines recommend a number of 12 cores with that needle size. § Recommendations of an interdisciplinary consensus meeting on the use of vacuum-assisted breast biopsy under sonographic guidance (8). The calculated equivalent tissue volume of 10 cores with the 11-G needle is 3 and 4 when using the 8-G needles but the paper recommends a total number of six cores with the 8-G needle.
with a 10-G needle (2). To reach this threshold, five specimens had to be obtained with the 7-G needle or nine and five specimens with the 8-G Original and RevolveTM needle, respectively, or 14 specimens with the 9-G needle or eight specimens with the 10-G EnspireÕ needle or 20 specimens with the 11-G needle. According to the recommendations of the interdisciplinary consensus on MRI-guided VAB, at least 24 cores should be removed with the 11-G needle (dotted line in Fig. 4). This corresponds to the cumulative weight of six specimens with the 7-G and the 8-G RevolveTM needle or 11 specimens with the 8-G Original needle or 17 specimens with the 9-G needle or to the weight of 14 and nine specimens with the 10-G VacoraÕ and EnspireÕ needle, respectively. According to the consensus recommendations for the use of US-guided VAB, a tissue volume of at least 10 cores with the 11-G needle should be removed. An equivalent tissue volume is reached by the cumulative weight of six and four tissue cores with the 10-G VacoraÕ and EnspireÕ needles, respectively, or seven
cores with the 9-G needle, four and three cores with the 8-G Original and RevolveTM needles, respectively, or two cores with the 7-G needle. Table 1 shows the matrix system with calculated equivalent numbers of necessary tissue cores on the basis of their mean weight. All numbers agree with the true cumulative tissue weights (Fig. 4).
Discussion We assessed the mean weights and standard deviations of tissue cores yielded with different vacuum-assisted biopsy systems and needle sizes. Thereby the 10-G system (VacoraÕ ) showed the most reliable results with the lowest standard variation. The 7-G system showed the highest variation of tissue weight because of tissue fragmentation, but it also demonstrated the heaviest cores. Similar results were published by Poellinger et al., who demonstrated that 9-G specimens were significantly larger and heavier than 11-G
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specimens (11). As far as we know, there is no publication about the size and weight of 7-G VAB specimens. With regard to the recommendations of the current German S3 guideline, a sample volume equivalent to at least 12 cores with the 10-G needle should be obtained. In our experimental setting we used the tissue weight as the reference variable for the corresponding tissue volume. We demonstrated that an equivalent cumulative tissue weight of 12 cores with the 10-G needle can be reached by harvesting five specimens with the 7-G needle or nine and five specimens with the 8-G Original and RevolveTM needle, respectively, or 14 specimens with the 9-G needle or eight specimens with the 10-G EnspireÕ needle or 20 specimens with the 11-G needle. We do not recommend obtaining fewer specimens than suggested by guidelines and consensus meetings. The observed lower weight of the 9-G cores compared to the 10-G specimens and of the 8-G Original compared to the 10-G EnspireÕ specimens might be the result of different shapes of the cores (lower width of the 9-G cores, greater length of the 10-G EnspireÕ cores). Because all cores were taken from the same turkey breast model, an influence of different tissue qualities can be excluded. The needle size (gauge) refers to the diameter of the needle. Some biopsy guns work with a cutter positioned inside the biopsy chamber (e.g. 10-G EnspireÕ ), some with a cutter outside the chamber (e.g. 10-G VacoraÕ ). This may result in different widths of the obtained specimens. The length of the biopsy chamber is not defined by the needle size, which results in different lengths of the obtained specimens. Different settings of the vacuum exhaust might also influence the volume of the harvested specimens. There is no information about the obtained tissue volume according to the particular needle given by the manufacturers. On the basis of the mean weights of single tissue cores, we calculated translation factors for each needle size and built the presented matrix system. Its validity was tested by comparing it with the measured true cumulative tissue weights. It showed total agreement. Therefore we are confident that the matrix can be used for the estimation of the recommended number of tissue cores depending on the used needle size and imaging method. We believe that the presented matrix system is helpful to implement recommendations of current guidelines and consensus meetings into clinical practice. In addition to that, the matrix might be helpful for the authors of future guidelines to define the number of recommended VAB tissue cores more precisely, especially as it could be shown that specimens of the same needle size do not necessarily equal in volume when biopsy guns of different manufacturers are compared.
Other authors compared the use of different needle sizes in VAB. For instance, a comparison of 11-G and 8G needles has shown no relevant differences between the two needle sizes concerning the performance of VAB under US or mammographic guidance (12). Contrarily, a recent comparison of 11-G and 8-G in the stereotactic core biopsy showed an improved performance and increased diagnostic ability of the 8-G over the 11-G needle (13). Further studies have pointed out advantages of larger needle sizes as higher sample volumes result in increasing accuracy of histologic diagnosis (4,5). Another advantage might be the shorter interventional time, as fewer specimens have to be obtained with larger needle sizes (11,14). Siegmann et al. (15) reported a mean interventional time of 56.8 min for 11-G stereotactic VAB while they took a mean number of 26.4 specimens. Diebold et al. performed 8-G VAB within a mean time of 28.2 min to obtain an average of 12.6 specimens (16). Wang et al. reported a shorter procedure duration of the 7-G EnspireÕ system compared to 8-G Original MammotomeÕ and 10-G VacoraÕ (17). The use of 7-G needles probably further decreases the time of intervention and achieves the same or better diagnostic accuracy compared to smaller needle sizes. However, the definition of procedure time is not consistent across the studies and the 7-G needle has not been analyzed yet with respect to procedural time and accuracy. In our study the time of VAB was not measured. However, we firstly defined the number of requested tissue cores of VAB procedures with 7-G needles. Because not more than six tissue cores are necessary, the use of this system could possibly further decrease interventional time. However, the recommended removal of a certain tissue volume for each needle size can only serve to optimize intervention. The assessment of a successful vacuum-assisted breast biopsy depends on a partly or complete removal of the target lesion on imaging and a conclusive pathologic–radiologic correlation. In case of suspicious microcalcifications the specimen x-ray must show at least a substantial part of those microcalcifications. In case of masses the postinterventional mammography should show a decrease in size or a disappearance of the mass to diagnose a representative biopsy. These facts should be considered at every breast biopsy (15,18). In conclusion, the presented matrix facilitates the translation of the required numbers of VAB specimens between different needle sizes and thereby eases the implementation of current and future national and international guidelines and consensus recommendations into clinical practice. As larger needle sizes do not necessarily correlate with larger specimen volume this matrix provides helpful information about five of the most frequently used VAB systems in Europe.
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Conflict of interest None declared.
Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
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Vacuum-assisted breast biopsy with 7-gauge, 8-gauge, 9-gauge, 10-gauge, and 11-gauge needles: how many specimens are necessary? Heike Preibsch, Astrid Baur, Beate M Wietek, Bernhard Krämer, Annette Staebler, Claus D Claussen and Katja C Siegmann-Luz Acta Radiol published online 17 September 2014 DOI: 10.1177/0284185114549224 The online version of this article can be found at: http://acr.sagepub.com/content/early/2014/09/17/0284185114549224
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Acta Radiol OnlineFirst, published on September 17, 2014 as doi:10.1177/0284185114549224
Original Article
Vacuum-assisted breast biopsy with 7-gauge, 8-gauge, 9-gauge, 10-gauge, and 11-gauge needles: how many specimens are necessary?
Acta Radiologica 0(0) 1–7 ! The Foundation Acta Radiologica 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0284185114549224 acr.sagepub.com
Heike Preibsch1, Astrid Baur1, Beate M Wietek1, Bernhard Kra¨mer2, Annette Staebler3, Claus D Claussen1 and Katja C Siegmann-Luz1
Abstract Background: Published national and international guidelines and consensus meetings on the use of vacuum-assisted biopsy (VAB) give different recommendations regarding the required numbers of tissue specimens depending on needle size and imaging method. Purpose: To evaluate the weights of specimens obtained with different VAB needles to facilitate the translation of the required number of specimens between different breast biopsy systems and needle sizes, respectively. Material and Methods: Five different VAB systems and seven different needle sizes were used: MammotomeÕ (11-gauge (G), 8-G), VacoraÕ (10-G), ATEC SapphireTM (9-G), 8-G MammotomeÕ RevolveTM, and EnCor EnspireÕ (10-G, 7-G). We took 24 (11-G) or 20 (7–10-G) tissue cores from a turkey breast phantom. The mean weight of a single tissue core was calculated for each needle size. A matrix, which allows the translation of the required number of tissue cores for different needle sizes, was generated. Results were compared to the true cumulative tissue weights of consecutively harvested tissue cores. Results: The mean tissue weights obtained with the 11-G / 10-G VacoraÕ / 10-G EnspireÕ / 9-G / 8-G Original / 8-G RevolveTM / 7-G needles were 0.084 g / 0.142 g / 0.221 g / 0.121 g / 0.192 g / 0.334 g / 0.363 g, respectively. The calculated required numbers of VAB tissue cores for each needle size build the matrix. For example, the minimum calculated number of required cores according to the current German S3 guideline is 20 / 12 / 8 / 14 / 9 / 5 / 5 for needles of 11-G / 10-G VacoraÕ / 10-G EnspireÕ / 9-G / 8-G Original / 8-G RevolveTM / 7-G size. These numbers agree with the true cumulative tissue weights. Conclusion: The presented matrix facilitates the translation of the required number of VAB specimens between different needle sizes and thereby eases the implementation of current guidelines and consensus recommendations into clinical practice.
Keywords Breast, vacuum-assisted biopsy, sample volume Date received: 16 March 2014; accepted: 28 July 2014
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Introduction Imaging-detected breast lesions are categorized according to the breast imaging reporting and data system (BI-RADSÕ ) of the American College of Radiology (1). BI-RADSÕ applies to lesions which were detected on mammography, ultrasound (US), or magnetic resonance imaging (MRI). Lesions which were assessed
University Department of Radiology Diagnostic and Interventional Radiology, Tu¨bingen, Germany 2 University Department of Gynecology and Obstetrics, Tu¨bingen, Germany 3 Institute of Pathology and Neuropathology (Department), Tu¨bingen, Germany Corresponding author: Heike Preibsch, University Department of Radiology Diagnostic and Interventional Radiology, Hoppe-Seyler-Straße 3, 72076 Tu¨bingen, Germany. Email: [email protected]
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as BI-RADSÕ 4 or 5 are suspicious or highly suggestive of malignancy. A biopsy should be performed to prove or exclude malignancy in cases presenting with these lesions, and minimal invasive imaging-guided percutaneous needle biopsy should preferably be used. For imaging, the least complicated method in which the lesion is surely visible should be employed (2,3). Vacuumassisted biopsy (VAB) has proven to be advantageous compared to large core needle biopsy as more tissue volume is obtained and therefore histological classification is more reliable (4,5). VAB has therefore replaced large core needle biopsy in several indications. In particular, VAB is the method of choice to clarify suspicious microcalcifications without accompanying solid lesions, and suspicious lesions which are only detectable on breast MRI (2,6,7). US-guided VAB is recommended to clarify lesions that are too small to make representative large core needle biopsy possible, or in case of a mismatch of imaging assessment and histological finding after US-guided core needle biopsy (2,8). The most commonly used needle sizes for VAB are 11gauge (G), 10-G, 8-G, and 7-G. Recently published national and international guidelines and results of consensus meetings give different recommendations with regard to the required number of tissue specimens depending on needle size and imaging method. Most of the recommendations refer to the 11-G needle. The current German S3 guideline for diagnosis, therapy, and follow-up of breast cancer recommends a sample number of at least 12 cores with the 10-G needle or an equivalent tissue volume if needle sizes between 8-G and 11-G were used for stereotactic VAB (2). An interdisciplinary consensus paper on the use and technique of vacuum-assisted stereotactic breast biopsy recommends at least an average number of 20 cores with the 11-G needle or a corresponding tissue volume if a larger probe is used (9). An interdisciplinary consensus paper on the use and technique of MRI-guided VAB recommends an average number of at least 24 cores with the 11-G probe or an equivalent tissue volume if a larger probe is used (7). In terms of the use of US-guided VAB, an interdisciplinary consensus paper recommends the removal of at least 10 specimens with an 11-G needle and at least six specimens with an 8-G needle (8). The authors recommend the removal of equivalent quantities of tissue when using needles of other sizes. Explicit statements referring to the number of specimens with different needle sizes are missing. None of the publications provide a translation of the required number of tissue cores for one needle size into another. In the literature, there are only studies about comparison of average tissue volumes with different 14-G biopsy guns (10) and the comparison of 11-G and 9-G VAB systems for tissue yield, length, and
fragmentation of specimens (11). Another study compared the use of 11-G and 8-G needles in benign breast disease (12). The latter presents estimated sizes, weights, and volumes of 10-G, 11-G, and 8-G specimens without true measurements of tissue cores. The aim of this study was to evaluate standardized weights of tissue specimens obtained with 11-G, 10-G, 9-G, 8-G, and 7-G VAB needles to facilitate the translation of the number of tissue specimens between different breast biopsy systems and needles, respectively.
Material and Methods Experimental setting of vacuum-assisted breast biopsy Tissue cores were consecutively taken from a turkey breast phantom with seven different sized needle probes: 11-G Original MammotomeÕ (Devicor, Inc., Cincinnati, OH, USA), 10-G VacoraÕ (BARD GmbH, Karlsruhe, Germany), 10-G EnCor EnspireÕ (BARD GmbH, Karlsruhe, Germany), 9-G ATEC SapphireTM (Hologic Inc., Bedford, MA, USA), 8-G Original MammotomeÕ (Devicor, Inc.), 8-G MammotomeÕ RevolveTM (Devicor, Inc.), and 7-G EnCor EnspireÕ (BARD GmbH, Fig. 1a, b). All biopsies were performed by the same radiologist (HP) who had 1 year of experience in performing VAB procedures with all of those biopsy systems. The tissue cores were removed one
(a)
(b)
Fig. 1. (a) The five different VAB needle sizes which were used in this study imaged with open biopsy chambers. From left to right: 11-G Original MammotomeÕ , 10-G VacoraÕ , 9-G ATEC SapphireTM, 8-G Original MammotomeÕ , and 7-G EnCor EnspireTM. (b) The two needle sizes, which were found twice in this study, imaged with open biopsy chambers. From left to right: 10-G EnCor EnspireTM, 10-G VacoraÕ , 8-G MammotomeÕ RevolveTM, and 8-G Original MammotomeÕ .
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after another and each core was weighed within 30 min after removal to avoid weight loss due to drying. According to the maximal requested number of current guidelines, 24 cores were taken with the 11-G needle and 20 specimens were obtained with each of the 10-G, 9-G, 8-G, and 7-G needles. Physical density (d) of tissue is defined as its weight (mass ¼ m) divided by its volume (d ¼ m/V (g/cm3)), so the tissue weight is proportional to the tissue volume if the density is non-varying. In this study, all specimens were obtained from the same turkey breast phantom to assure the same density of all tissue cores. Hence, in our experimental setting the tissue weight can be taken as reference variable for tissue volume.
Data acquisition and calculation The size of the tissue cores was measured as the length in millimeters (mm) (Fig. 2a–g). The mean size and standard deviation (SD) of the tissue cores were calculated for each needle size.
The weight of the tissue cores was measured by using a high-resolution balance of special accuracy for extremely precise measurement of mass (Sartorius LP 620 P, Sartorius AG, Goettingen, Germany), which allows an accuracy of 1 mg. The weight of every single specimen was noted and the mean weight and SD of a single core was calculated for each needle size. Minimum, maximum, and median were displayed in a box-whisker plot (Fig. 3). The weight of various cores was added to obtain the true cumulative weight (Fig. 4). The mean weight of an 11-G needle specimen was taken as reference to calculate the corresponding numbers of core specimens for the other needle sizes. The 11G needle was chosen as the reference needle size because most consensus recommendations refer to this size. The mean tissue weight of a single core of each needle size (10-G, 9-G, 8-G, 7-G) was divided by the mean weight of the 11-G tissue core to obtain corresponding translation factors which were 1.69 for the 10-G VacoraÕ needle, 2.63 for the 10-G EnspireÕ needle, 1.44 for the 9-G needle, 2.29 for the 8-G Original needle, 3.98 for the 8G RevolveTM needle, and 4.32 for the 7-G needle. Afterwards we multiplied the number of 11-G cores by the above calculated translation factor for each needle size to obtain the equivalent number of tissue cores. With regard to recent guidelines, we performed the calculation for a number of 10 to 24 cores with the 11-G needle. The resulting numbers of recommended tissue cores taken with different needle sizes were rounded and put into a spreadsheet. We thereby generated a matrix system from which the equivalent numbers of specimens, which constitute the same tissue volume, can be read (Table 1). To simulate the real biopsy setting, we calculated the cumulative tissue weights for each needle to assess the needed number of tissue cores to reach the recommended equivalent tissue volumes. To test the matrix system, the numbers of tissue cores were compared to the true cumulative tissue weights and corresponding numbers of specimens of consecutively harvested tissue cores (Fig. 4). Mean and SD were calculated by use of Excel 2003 (Microsoft, Redmond, WA, USA). Diagrams were created with Excel 2003.
Results Length and weight of tissue cores
Fig. 2. Specimens obtained with the (a) 11-G needle, (b) 10-G VacoraÕ needle, (c) 10-G EnspireÕ needle, (d) 9-G needle, (e) 8-G Original needle, (f) 8-G RevolveTM needle, and (g) 7-G needle.
Mean length of 11-G core specimens was 23.1 3.37 mm SD, of the 10-G VacoraÕ specimens 19.7 1.20 mm SD, of the 10-G EnspireÕ specimens 27.9 2.56 mm SD, of the 9-G specimens 21.8 1.52 mm SD, of the 8-G Original specimens 24.8 2.93 mm SD, of the 8-G
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Fig. 3. Box-plot diagram of specimen weight subject to needle size.
Fig. 4. Cumulative sample weights according to the number of specimens with seven different VAB needles. The black line marks the recommendations of the German S3 guideline (2) and the recommendations of a consensus meeting on the use of stereotactic VAB (9). The dotted black line demonstrates the recommendations of the consensus meeting on the use of MRI-guided VAB (7). The dashed black line marks the recommendations of a consensus meeting on the use of US-guided VAB (8).
RevolveTM specimens 27.3 1.25 mm SD, and the length of the 7-G cores was mean 27.4 2.81 mm SD. With the 11-G needle the mean weight of one tissue core was 0.084 0.032 g SD, with the 10-G VacoraÕ 0.142 0.006 g SD, with the 10-G EnspireÕ 0.221 0.039 g SD, with the 9-G needle 0.121 0.014 g SD, with the 8-G Original needle 0.192 0.027 g SD, with the 8-G RevolveTM 0.334 0.046 g SD, and with the 7-G needle 0.363 0.053 g SD (Fig. 3). The lowest variation of specimen weight was shown by the 10-G VacoraÕ needle and the highest by the 7-G needle, which is probably caused by the higher rate of tissue fragmentation with the 7-G needle (Fig. 2g). The lower mean weight of the 9-G specimens compared to the 10-G cores and the 8-G Original compared to the 10-G EnspireÕ might be explained by the different width in combination with the remarkable difference in length (Fig. 2b–d, f).
Recommended number of tissue cores and cumulative tissue weights Fig. 4 illustrates the comparison of cumulative tissue weights of different needle sizes in relation to different recommendations of recent guidelines and consensus meetings. The lowest number of tissue cores is requested for US-guided VAB (dashed line in Fig. 4). The highest number of tissue cores is requested by the consensus meeting on the use of MRI-guided VAB (dotted line in Fig. 4). The recommendations of the German S3 guideline for stereotactic breast biopsies and the recommendations of an interdisciplinary consensus meeting on the use of stereotactic VAB are similar and lie in between both others (black line in Fig. 4). The German S3 guideline recommends the removal of a tissue volume equivalent to at least 12 cores taken
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Table 1. The matrix system presents the calculated minimum number of tissue cores which should be taken with different VAB systems and needle sizes to gain an equivalent tissue weight. The following needles were used: 11-G Original MammotomeÕ , 10-G VacoraÕ , 10-G EnCor EnspireÕ , 9-G ATEC SapphireTM, 8-G Original MammotomeÕ , 8-G MammotomeÕ RevolveTM, and 7-gauge EnCor EnspireÕ . 11-G
10-G VacoraÕ
10-G EnspireÕ
Number of tissue cores depending on needle size 24* 14 9 23 14 9 22 13 8 21 12 8 20y 12z 8 (12)z 19 11 7 18 11 7 17 10 6 16 9 6 15 9 6 14 8 5 13 8 5 12 7 5 11 7 4 10§ 6 4
9-G
8-G Original
8-G RevolveTM
7-G
17 16 15 15 14 13 13 12 11 10 10 9 8 7 7
11 10 10 9 9 8 8 7 7 7 6 6 5 5 4 (6)§
6 6 6 5 5 5 5 4 4 4 4 3 3 3 3 (6)§
6 5 5 5 5 4 4 4 4 3 3 3 3 3 2
*Recommendations of an interdisciplinary consensus meeting on the use and technique of MR-guided vacuum-assisted breast biopsy (7). y Recommendations of an interdisciplinary consensus meeting on the use and technique of vacuum-assisted stereotactic breast biopsy (9). z Recommendations of the German S3 guideline for diagnosis, therapy, and follow-up of breast cancer (2). The calculated equivalent tissue volume of 12 cores with the 10-G VacoraÕ needle is 8 when using the 10-G EnspireÕ needle but the guidelines recommend a number of 12 cores with that needle size. § Recommendations of an interdisciplinary consensus meeting on the use of vacuum-assisted breast biopsy under sonographic guidance (8). The calculated equivalent tissue volume of 10 cores with the 11-G needle is 3 and 4 when using the 8-G needles but the paper recommends a total number of six cores with the 8-G needle.
with a 10-G needle (2). To reach this threshold, five specimens had to be obtained with the 7-G needle or nine and five specimens with the 8-G Original and RevolveTM needle, respectively, or 14 specimens with the 9-G needle or eight specimens with the 10-G EnspireÕ needle or 20 specimens with the 11-G needle. According to the recommendations of the interdisciplinary consensus on MRI-guided VAB, at least 24 cores should be removed with the 11-G needle (dotted line in Fig. 4). This corresponds to the cumulative weight of six specimens with the 7-G and the 8-G RevolveTM needle or 11 specimens with the 8-G Original needle or 17 specimens with the 9-G needle or to the weight of 14 and nine specimens with the 10-G VacoraÕ and EnspireÕ needle, respectively. According to the consensus recommendations for the use of US-guided VAB, a tissue volume of at least 10 cores with the 11-G needle should be removed. An equivalent tissue volume is reached by the cumulative weight of six and four tissue cores with the 10-G VacoraÕ and EnspireÕ needles, respectively, or seven
cores with the 9-G needle, four and three cores with the 8-G Original and RevolveTM needles, respectively, or two cores with the 7-G needle. Table 1 shows the matrix system with calculated equivalent numbers of necessary tissue cores on the basis of their mean weight. All numbers agree with the true cumulative tissue weights (Fig. 4).
Discussion We assessed the mean weights and standard deviations of tissue cores yielded with different vacuum-assisted biopsy systems and needle sizes. Thereby the 10-G system (VacoraÕ ) showed the most reliable results with the lowest standard variation. The 7-G system showed the highest variation of tissue weight because of tissue fragmentation, but it also demonstrated the heaviest cores. Similar results were published by Poellinger et al., who demonstrated that 9-G specimens were significantly larger and heavier than 11-G
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specimens (11). As far as we know, there is no publication about the size and weight of 7-G VAB specimens. With regard to the recommendations of the current German S3 guideline, a sample volume equivalent to at least 12 cores with the 10-G needle should be obtained. In our experimental setting we used the tissue weight as the reference variable for the corresponding tissue volume. We demonstrated that an equivalent cumulative tissue weight of 12 cores with the 10-G needle can be reached by harvesting five specimens with the 7-G needle or nine and five specimens with the 8-G Original and RevolveTM needle, respectively, or 14 specimens with the 9-G needle or eight specimens with the 10-G EnspireÕ needle or 20 specimens with the 11-G needle. We do not recommend obtaining fewer specimens than suggested by guidelines and consensus meetings. The observed lower weight of the 9-G cores compared to the 10-G specimens and of the 8-G Original compared to the 10-G EnspireÕ specimens might be the result of different shapes of the cores (lower width of the 9-G cores, greater length of the 10-G EnspireÕ cores). Because all cores were taken from the same turkey breast model, an influence of different tissue qualities can be excluded. The needle size (gauge) refers to the diameter of the needle. Some biopsy guns work with a cutter positioned inside the biopsy chamber (e.g. 10-G EnspireÕ ), some with a cutter outside the chamber (e.g. 10-G VacoraÕ ). This may result in different widths of the obtained specimens. The length of the biopsy chamber is not defined by the needle size, which results in different lengths of the obtained specimens. Different settings of the vacuum exhaust might also influence the volume of the harvested specimens. There is no information about the obtained tissue volume according to the particular needle given by the manufacturers. On the basis of the mean weights of single tissue cores, we calculated translation factors for each needle size and built the presented matrix system. Its validity was tested by comparing it with the measured true cumulative tissue weights. It showed total agreement. Therefore we are confident that the matrix can be used for the estimation of the recommended number of tissue cores depending on the used needle size and imaging method. We believe that the presented matrix system is helpful to implement recommendations of current guidelines and consensus meetings into clinical practice. In addition to that, the matrix might be helpful for the authors of future guidelines to define the number of recommended VAB tissue cores more precisely, especially as it could be shown that specimens of the same needle size do not necessarily equal in volume when biopsy guns of different manufacturers are compared.
Other authors compared the use of different needle sizes in VAB. For instance, a comparison of 11-G and 8G needles has shown no relevant differences between the two needle sizes concerning the performance of VAB under US or mammographic guidance (12). Contrarily, a recent comparison of 11-G and 8-G in the stereotactic core biopsy showed an improved performance and increased diagnostic ability of the 8-G over the 11-G needle (13). Further studies have pointed out advantages of larger needle sizes as higher sample volumes result in increasing accuracy of histologic diagnosis (4,5). Another advantage might be the shorter interventional time, as fewer specimens have to be obtained with larger needle sizes (11,14). Siegmann et al. (15) reported a mean interventional time of 56.8 min for 11-G stereotactic VAB while they took a mean number of 26.4 specimens. Diebold et al. performed 8-G VAB within a mean time of 28.2 min to obtain an average of 12.6 specimens (16). Wang et al. reported a shorter procedure duration of the 7-G EnspireÕ system compared to 8-G Original MammotomeÕ and 10-G VacoraÕ (17). The use of 7-G needles probably further decreases the time of intervention and achieves the same or better diagnostic accuracy compared to smaller needle sizes. However, the definition of procedure time is not consistent across the studies and the 7-G needle has not been analyzed yet with respect to procedural time and accuracy. In our study the time of VAB was not measured. However, we firstly defined the number of requested tissue cores of VAB procedures with 7-G needles. Because not more than six tissue cores are necessary, the use of this system could possibly further decrease interventional time. However, the recommended removal of a certain tissue volume for each needle size can only serve to optimize intervention. The assessment of a successful vacuum-assisted breast biopsy depends on a partly or complete removal of the target lesion on imaging and a conclusive pathologic–radiologic correlation. In case of suspicious microcalcifications the specimen x-ray must show at least a substantial part of those microcalcifications. In case of masses the postinterventional mammography should show a decrease in size or a disappearance of the mass to diagnose a representative biopsy. These facts should be considered at every breast biopsy (15,18). In conclusion, the presented matrix facilitates the translation of the required numbers of VAB specimens between different needle sizes and thereby eases the implementation of current and future national and international guidelines and consensus recommendations into clinical practice. As larger needle sizes do not necessarily correlate with larger specimen volume this matrix provides helpful information about five of the most frequently used VAB systems in Europe.
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Conflict of interest None declared.
Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
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