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Dosimetric comparison of moderate deep inspiration breath-hold and free-breathing intensity-modulated radiotherapy for left-sided breast cancer Comparaison dosimétrique de l’inspiration modérément profonde en apnée et de la respiration libre pour la radiothérapie avec modulation d’intensité du cancer du sein gauche F. Chi a,1 , S. Wu b,1 , J. Zhou c,1 , F. Li a , J. Sun a , Q. Lin b , H. Lin a , X. Guan a , Z. He a,∗ a Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou 510060, PR China b Xiamen Cancer Center, Department of Radiation Oncology, the First Affiliated Hospital of Xiamen University, Xiamen 361003, PR China c Xiamen Cancer Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Xiamen University, Xiamen 361003, PR China

a r t i c l e

i n f o

Article history: Received 4 August 2014 Received in revised form 9 January 2015 Accepted 26 January 2015 Keywords: Breast cancer Radiotherapy Active breathing control Moderate deep inspiration breath-hold Intensity-modulated radiotherapy

a b s t r a c t Purpose. – This study determined the dosimetric comparison of moderate deep inspiration breath-hold using active breathing control and free-breathing intensity-modulated radiotherapy (IMRT) after breastconserving surgery for left-sided breast cancer. Patients and methods. – Thirty-one patients were enrolled. One free breathe and two moderate deep inspiration breath-hold images were obtained. A field-in-field-IMRT free-breathing plan and two fieldin-field-IMRT moderate deep inspiration breath-holding plans were compared in the dosimetry to target volume coverage of the glandular breast tissue and organs at risks for each patient. Results. – The breath-holding time under moderate deep inspiration extended significantly after breathing training (P < 0.05). There was no significant difference between the free-breathing and moderate deep inspiration breath-holding in the target volume coverage. The volume of the ipsilateral lung in the free-breathing technique were significantly smaller than the moderate deep inspiration breath-holding techniques (P < 0.05); however, there was no significant difference between the two moderate deep inspiration breath-holding plans. There were no significant differences in target volume coverage between the three plans for the field-in-field-IMRT (all P > 0.05). The dose to ipsilateral lung, coronary artery and heart in the field-in-field-IMRT were significantly lower for the free-breathing plan than for the two moderate deep inspiration breath-holding plans (all P < 0.05); however, there was no significant difference between the two moderate deep inspiration breath-holding plans. Conclusion. – The whole-breast field-in-field-IMRT under moderate deep inspiration breath-hold with active breathing control after breast-conserving surgery in left-sided breast cancer can reduce the irradiation volume and dose to organs at risks. There are no significant differences between various moderate deep inspiration breath-holding states in the dosimetry of irradiation to the field-in-field-IMRT target volume coverage and organs at risks. © 2015 Société française de radiothérapie oncologique (SFRO). Published by Elsevier Masson SAS. All rights reserved.

∗ Corresponding author. Sun Yat-sen University Cancer Center, Collaborative Innovation Center of Cancer Medicine, State Key Laboratory of Oncology in South China, Department of Radiation Oncology, 650 Dongfeng Road, Guangzhou 510060, PR China. E-mail address: [email protected] (Z. He). 1 Feng Chi, Sangang Wu and Juan Zhou contributed equally to this work. http://dx.doi.org/10.1016/j.canrad.2015.01.003 1278-3218/© 2015 Société française de radiothérapie oncologique (SFRO). Published by Elsevier Masson SAS. All rights reserved.

Please cite this article in press as: Chi F, et al. Dosimetric comparison of moderate deep inspiration breath-hold and free-breathing intensity-modulated radiotherapy for left-sided breast cancer. Cancer Radiother (2015), http://dx.doi.org/10.1016/j.canrad.2015.01.003

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r é s u m é Mots clés : Cancer du sein Radiothérapie Contrôle de la respiration active Inspiration profonde modérée Radiothérapie avec modulation d’intensité

Objectif de l’étude. – L’objectif de cette étude était la comparaison dosimétrique de l’inspiration modérément profonde en utilisant le contrôle actif de la respiration et la respiration libre pour la radiothérapie conformationelle avec modulation d’intensité (RCMI) après chirurgie mammaire conservatrice du cancer du sein gauche. Patientes et méthodes. – Trente et une patientes ont participé à cette étude. Il a été obtenu une image de respiration libre et deux en inspiration modérément profonde. Des plans de RCMI, un en respiration libre, deux en inspiration modérément profonde avec la technique du champ dans le champ ont été réalisés pour comparer la distribution de dose dans le volume cible du tissu glandulaire du sein et les organes à risques pour chaque patiente. Résultats. – La durée de l’apnée a été évidemment allongée par l’inspiration modérément profonde (p < 0,05). Il n’y avait pas de différence significative entre la respiration libre et l’inspiration modérément profonde avec la technique du champ dans le champ pour la couverture du volume cible. Le volume du poumon homolatéral irradié était évidemment plus petit avec la respiration libre qu’avec la respiration modérément profonde (p < 0,05) ; pourtant, il n’y avait pas de grande différence entre les deux plans en inspiration modérément profonde avec la technique du champ dans le champ. Il n’y avait pas non plus de différence significative pour couverture du volume cible entre les plans de RCMI avec la technique du champ dans le champ, celui en respiration libre et les deux en inspiration modérément profonde (p > 0,05). Les doses dans le poumon homolatéral, l’artère coronaire et le cœur étaient évidemment plus faibles avec la technique de RCMI champ dans le champ en respiration libre qu’avec les deux plans en inspiration modérément profonde (p < 0,05) ; de même, il n’y avait pas de différence significative entre les deux plans en inspiration modérément profonde. Conclusion. – La RCMI du sein avec la technique du champ dans le champ en inspiration modérément profonde et le contrôle actif de la respiration après chirurgie conservatrice du sein gauche permettent de réduire le volume irradié et la dose délivrée aux organes à risque. Il n’y avait pas de différence significative entre les plans en inspiration modérément profonde en RCMI avec la technique du champ dans le champ pour la couverture du volume cible et les organes à risque. © 2015 Société française de radiothérapie oncologique (SFRO). Publié par Elsevier Masson SAS. Tous droits réservés.

1. Introduction Radiotherapy improved survival in breast cancer after breast conservation surgery and mastectomy [1–4]. However, cardiovascular disease and lung cancer mortality rates had significantly increased after radiotherapy with more than 15 years follow-up [5]. Recent studies have indicated that the reduction in breast cancer mortality is offset by the increased risk in cardiac mortality due to breast irradiation [6,7]. The risks due to breast irradiation are further exacerbated when radiotherapy is used as an adjuvant treatment with biological therapy, such as trastuzumab and anthracycline-based chemotherapy [8,9]. Further, it has shown that increased cardiac radiation exposure from the deep edge of the tangential beams, which are normally used in left-sided breast cancer, is associated with increased risks of heart disease and cardiac mortality [1]. Development of intensity-modulated radiotherapy (IMRT) is regarded as a milestone of radiotherapy in the 21st century. The clinical target volume of glandular breast tissue is the target volume referred to for radiation therapy after breast-conserving surgery. IMRT not only improves dose homogeneity in the target volume coverage, but also reduces the radiation dose to the organs at risks, including the heart and lungs [10,11]. The target volume movement is an important factor affecting the dose–volume parameters of whole-breast IMRT. After online correction of the set-up errors, the target volume movement due to this error is reduced significantly; however, the impact of target volume movement caused by respiratory motion on the dose–volume parameters is a major area of interest in current relevant studies. Although the impact of respiratory motion on target volume movement is milder during quiet breathing, there is no consistent agreement on changes in dose–volume parameters of the target volume coverage and organs at risks due to movements caused by respiratory motion, which inhibits the widespread development of IMRT in the treatment of breast cancer.

It has been reported that the active breathing control-IMRT technique could further reduce the dosimetric difference in the target volume coverage caused by the respiratory motion and reduce target movement under 5 mm [12,13]. The active breathing control technique currently used in radiotherapy can decrease the uncertainties caused by respiratory motion [14–16]. In addition, studies have shown that deep inspiration results in an increased distance between the heart and the left anterior chest wall [17]. Therefore, we applied the active breathing control technique to 31 patients with left-side breast cancer who underwent breastconserving surgery between January 2008 and July 2011. We compared the dosimetric differences of forward-planned wholebreast field-in-field-IMRT between the free breath state and the moderate deep inspiration breath-hold state, and between different moderate deep inspiration breath-hold states to further clarify the value of the breathing control technique during radiotherapy for breast cancer. 2. Patients and methods 2.1. Patients Patients who underwent breast-conserving surgery for earlystage left breast cancer at Sun Yat-Sen University Cancer Center were recruited according to the following inclusion criteria: • female patient aged 18 years or older; • pathologically-confirmed breast cancer; • axillary lymph node dissection or sentinel lymph node biopsyconfirmed pathology-negative lymph nodes; • stage I or II (pT1N0M0, pT2N0M0) according to the 2009 7th edition of the American Joint Committee on Cancer (AJCC) TNM staging;

Please cite this article in press as: Chi F, et al. Dosimetric comparison of moderate deep inspiration breath-hold and free-breathing intensity-modulated radiotherapy for left-sided breast cancer. Cancer Radiother (2015), http://dx.doi.org/10.1016/j.canrad.2015.01.003

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Fig. 1. Patient with the active breathing control device for intensity-modulated radiotherapy of a left-sided breast cancer. PTV: planning target volume; CTV: clinical target volume; PTV Eval: planning target volume evaluation. Patient et dispositif de contrôle actif de la respiration pour la radiothérapie avec modulation d’intensité d’un cancer du sein gauche.

• cardiac capacity and good cognitive ability based on active breathing control technology. Patients or their legal surrogates provided signed informed consent. The study was approved by the ethics committee of Sun Yat-Sen University Cancer Center. 2.2. Breath-holding training All patients were trained with the active breathing control device (ABC; Elekta Oncology Systems Ltd., Crawley, West Sussex, UK) before CT simulation, according to the manufacturer’s guidelines [18]. The duration of active breath-holding was set to over 25 s because of the time of one field beam, and set to 75% of the maximum deep breath control as moderate deep inspiration breath-hold so that the heart volume could be reduced in radiation and welltolerated by the patient. Patients who could hold their breath for more than 25 s were accepted for CT simulation scan. The breathholding time was twice recorded before and after training. Fig. 1 shows the patients with an active breathing control device. 2.3. CT simulation Patients were placed in the supine position on vacuum bags with their hands over their head. The scanning was performed using a Discovery ST 16 slice PET/CT (General Electric Medical Systems) with the active breathing control device. A metal marker was placed on the patient’s body as a laser reference point for CT positioning. Contiguous 5-mm CT axial images were obtained from the larynx to the upper abdomen, including the breasts and lungs bilaterally. All patients were scanned in the free-breathing state and moderate deep inspiration breath-holding state (mDIBH1). Then, after an approximate 2-min break, the patients were scanned in the moderate deep inspiration breath-holding state again (mDIBH2). 2.4. Target volume and organs at risks delineation Target volume and organs at risks were delineated in the CT images of free-breathing and the two moderate deep inspiration breath-holding states using a three-dimensional treatment planning system (Pinnacle 9.0 m; ADAC, Philips).

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Fig. 2. Target volume and organs at risks in intensity-modulated radiotherapy for a left-sided breast cancer. Volume cible et organes à risque dans la radiothérapie avec modulation d’intensité d’un cancer du sein gauche.

The clinical and planning target volumes for the breast were delineated according to the recommendation of ICRU report #83. The breast clinical target volume included all visible breast parenchyma. The planning target volume was added to a 7-mm expansion in all directions around the clinical target volume, except the skin surface, including the set-up margin and patient movement. The planning target volume evaluation was limited anteriorly to exclude the part outside the patient and the first 5 mm of tissue under the skin, and posteriorly was limited no deeper to the anterior surface of the ribs (excluding the boney thorax and lungs). The planning target volume evaluation was the structure used for dose–volume histogram constraints and analysis. Organs at risks, including the spinal cord, thyroid gland, contralateral breast, heart, coronary artery area, left lung, and right lung were contoured. Delineation of the coronary artery area was according to the research methods of Memorial Sloan Kettering Cancer Center [19]. Fig. 2 shows the target volumes and organs at risks.

2.5. Plan design The field-in-field-IMRT technique with 6-MV photons of the Elekta Synergy linear accelerator was used for the free-breathing and first moderate deep inspiration breath-holding plans. Heterogeneity correction was used in all plans. Briefly, the contribution of two tangential beams and multiple subfields were needed to achieve the desired homogeneity without wedges. An open beam configuration was first calculated and evaluated. Twoto-four subfields per gantry angle were used to produce optimal breast pain. Lung block was formed by fitting the multileaf collimator to the shape of the lung and used to smooth out the lateral hot spots (3 to 4% of the dose prescription as a grade). Additional subfields were generated by manually fitting the multileaf collimator to “hot” areas. The fields within 5 monitor units (MU) were removed. Generally, the open beam portion receives 80–90% of the dose, while the subfields contribute 10–20%. The planning target volume was prescribed to 50 Gy. All plans were evaluated using Radiation Therapy Oncology Group (RTOG) criteria [20]. According to the coordinates of the isocentre and dose points, the field-in-field-IMRT plans the second moderate deep inspiration breath-holding state were copied from the plans of the first breathholding plan, including the angles of the collimator and gantry, multileaf collimator, prescription dose, and MU.

Please cite this article in press as: Chi F, et al. Dosimetric comparison of moderate deep inspiration breath-hold and free-breathing intensity-modulated radiotherapy for left-sided breast cancer. Cancer Radiother (2015), http://dx.doi.org/10.1016/j.canrad.2015.01.003

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2.6. Calculation of conformity index and homogeneity index The conformity index is calculated as follows: CI =

VTref VTref × VT Vref

where VTref represents the target volume covered by the isodose, VT is the target volume, and Vref is the total volume covered by 95% of the isodose. The conformity index range is 0–1; conformity was better when the conformity index value is larger [21]. The homogeneity index is calculated as follows: HI =

D5 D95

where Dx represents the irradiation dose received by x% of the planning target volume evaluation. The closer to 1 the homogeneity index value is, the better the target uniformity will be [22].

Fig. 3. Breath-holding time before and after training. Temps en apnée avant et après la formation sur le contrôle de la respiration.

2.7. Statistical analysis 3.2. Target and organs at risks volumes A paired-sample t-test was used to compare the time of breathholding between before and after training. One-way analysis of variance (ANOVA) was used to compare dosimetric differences between any two of the three plans. All statistical tests were twosided, and were performed using SPSS software (release 17.0; SPSS, Inc., Chicago, IL, USA). Statistical significance was defined as a P < 0.05. 3. Results Between January 2008 and July 2011, 31 patients were enrolled in our study, and the characteristics of the patients are listed in Table 1. 3.1. Compliance Breath-holding times were 19.83 ± 2.68 s and 20.32 ± 3.58 s before training. After training, the breath-holding times were significantly longer and all patients could hold their breath for more than 25 s (39.09 ± 4.39 s and 39.58 ± 3.79 s, P < 0.001). Fig. 3 shows the breath-holding times before and after training.

Table 1 Clinical characteristics of 31 patients with breast cancer. Caractéristiques cliniques des 31 patientes de l’étude, prises en charge pour un cancer du sein. Characteristic Age (years) Median Range Menopausal status (n) Premenopausal Postmenopausal Tumor stage (n) T1 T2 Pathology type (n) Invasive ductal carcinoma Mucinous adenocarcinoma Estrogen/progesterone receptor status (n) Negative Positive Her-2 (n) Negative Positive

Value

(%)

39.5 26–54

– –

26 5

83.9 16.1

20 11

64.5 35.5

28 3

90.3 9.7

3 28

9.7 90.3

27 4

87.1 22.9

Table 2 presents the target and organs at risks volume for all plans. The volumes of the lung and ipsilateral lung in the plan with free-breathing were lower than those with moderate deep inspiration breath-holding (P < 0.05), but there was no significant difference between the two moderate deep inspiration breathholding plans (P > 0.05). The planning target volume evaluation, heart and contralateral breast volumes between any two of the three plans were not statistically different (P > 0.05). 3.3. Dose to planning target volume and organs at risks Table 3 shows a comparison of dose parameters of planning target volume evaluation and organs at risks. The dose parameters of planning target volume evaluation between any two of the three plans were not statistically different (P > 0.05). The Dmean , V10 , V20 and V30 , for the ipsilateral lung, heart and coronary artery area of the free-breathing plan were higher than the moderate deep inspiration breath-holding plans (P < 0.05), but the difference was not significant between the two moderate deep inspiration breath-holding plans (P > 0.05). The Dmean of the contralateral lung, contralateral breast, thyroid gland and spinal cord was not statistically different between any two of the three plans (P > 0.05). 4. Discussion IMRT has become a major radiotherapeutic modality for malignant tumours because it can improve dose homogeneity in the target volume and further reduce radiation injury. Because respiratory motion can result in movement and deformation of the target volume during radiotherapy for breast cancer, a change in the dose distribution in the target volume coverage limits the wide application of radiotherapy for breast cancer. The deep inspiration breath-hold technique can reduce or eliminate target movement caused by respiration, and more importantly, it can decrease the radiation volume and dose to organs at risks to reduce radiation injury, especially for the lung, heart, and coronary artery [23–28]. In another study, deep tangential field whole-breast IMRT was applied together with the active breathing control technique and the dose distribution in the IMRT target volume coverage became more homogeneous compared with conventional tangential field irradiation; in addition the radiation dose to the heart and lung was significantly reduced in the moderate deep inspiration breath-holding technique compared

Please cite this article in press as: Chi F, et al. Dosimetric comparison of moderate deep inspiration breath-hold and free-breathing intensity-modulated radiotherapy for left-sided breast cancer. Cancer Radiother (2015), http://dx.doi.org/10.1016/j.canrad.2015.01.003

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Table 2 Comparison of the planning target volume evaluation and organs at risks volumes between the three intensity-modulated irradiation techniques (¯x ± S cm3 ). Comparaison du volume cible prévisionnel et du volume des organes à risque entre les différentes techniques de radiothérapie conformationnelle avec modulation d’intensité (¯x ± S cm3 ). Target volume and organs at risks

Free-breathing

mDIBH1

mDIBH2

Lung Ipsilateral lung Heart Contralateral breast Planning target volume evaluation

2589.9 ± 463.6A,a 1023.2 ± 197.8A,a 534.5 ± 107.2 393.1 ± 147.3 474.9 ± 240.0

4024.2 ± 575.9B 1757.1 ± 354.5B 585.3 ± 127.2 403.7 ± 152.8 470.2 ± 235.6

4023.1 ± 564.5b 1713.4 ± 486.9b 594.8 ± 132.3 398.5 ± 154.0 471.1 ± 233.2

mDIBH: moderate deep inspiration breath-holding; A had significant difference with B (P < 0.05); a had significant difference with b (P < 0.05). Otherwise, the difference was not significant between any two (P > 0.05).

with free-breathing [12]. Thus, the combination of the active breathing control technique and intensity-modulation can further improve the advantage of radiotherapy. Breast volume of Chinese women is relatively small compared with that of women in Western countries, and in the current study, it was approximately 400 cm3 , which is less by one-third than in Western patients [29]. There are no relevant published data regarding the advantage of forward-planned whole-breast IMRT under moderate deep inspiration breath-holding control after breast-conserving surgery in Chinese patients with breast cancer. Because different respiration states may result in morphologic changes in target volume coverage, the current study used a uniform evaluation standard (RTOG 1005), and designed fieldin-field-IMRT plans on the CT images in the free-breathing and moderate deep inspiration breath-holding states. When the dose coverage of target volume was identical, we found that the Dmean , V10 , V20 and V30 of the ipsilateral lung, heart and coronary artery area were significantly higher after field-in-field-IMRT in the freebreathing state compared with the moderate deep inspiration

breath-holding state (P < 0.05). The active breathing control technique can reduce the radiation dose and volume to the heart and lung and further reduce radiation injury, and this result is similar to other reports [12,14,30,31]. Because the volume of the ipsilateral lung increases under moderate deep inspiration breath-holding control, the heart is far from the chest wall, and the active breathing, control technique reduces the irradiated lung and heart volumes to improve the efficiency of treatment. The maximum movement of the breast in the left-to-right, superior-to-inferior, and anterior-to-posterior direction under quiet breathing are 1.07, 1.40 and 1.86 mm, respectively, which become 2.0, 5.5 and 4.8 mm, respectively, under deep breathing [32]. After applying the active breathing control technique, the leftto-right, superior-to-inferior, and anterior-to-posterior movement are 0.25–0.50, 0.00–0.25 and 0.00–0.25 mm, respectively [33]. In the current study, we compared the irradiated volumes of the target volume coverage and organs at risks in two moderate deep inspiration breath-holding states and found that there were no significant differences. In addition, we copied the field-in-field-IMRT

Table 3 Comparison of dose parameters of the planning target volume evaluation and organs at risks between the three intensity-modulated radiotherapy techniques (¯x ± S cm3 ). Comparaison des paramètres dosimétriques concernant l’évaluation du volume cible prévisionnel et des organes à risque entre les différentes techniques de radiothérapie conformationnelle avec modulation d’intensité (¯x ± S cm3 ). Parameters Planning target volume evaluation Dmax (cGy) Dmean (cGy) D95 (%) D97.5 (%) D102.5 (%) Homogeneity index Conformity index Ipsilateral lung Dmean (cGy) V10 (%) V20 (%) V30 (%) Heart Dmean (cGy) V10 (%) V20 (%) V30 (%) Coronary artery Dmean (cGy) V10 (%) V20 (%) V30 (%) Contralateral lung Dmean (cGy) Contralateral breast Dmean (cGy) Thyroid gland Dmean (cGy) Spinal cord Dmean (cGy)

Free-breathing

mDIBH 1

mDIBH 2

5242.6 ± 31.2 5019.3 ± 32.6 96.0 ± 1.1 87.1 ± 5.1 5.5 ± 3.1 1.1 ± 0.1 0.8 ± 0.1

5245.8 ± 34.1 5017.8 ± 13.4 96.0 ± 1.2 87.1 ± 5.6 5.6 ± 3.9 1.1 ± 0.1 0.9 ± 0.1

5238.5 ± 43.4 5012.3 ± 26.4 96.0 ± 1.1 87.0 ± 5.7 5.5 ± 3.7 1.1 ± 0.1 0.9 ± 0.1

795.2 ± 129.3A,a 16.5 ± 3.0A,a 13.0 ± 3.0A,a 11.4 ± 2.9A,a

645.2 ± 156.5B 13.0 ± 3.0B 9.2 ± 2.6B 7.9 ± 2.3B

695.2± 155.8b 13.0 ± 3.2b 9.2 ± 2.5b 7.9 ± 2.2b

282.3 ± 83.4A,a 6.3 ± 2.2A,a 4.8 ± 1.8A,a 3.4 ± 1.8A,a

156.8 ± 46.1B 4.4 ± 2.2B 3.2 ± 1.3B 1.6 ± 1.0B

156.8 ± 46.1b 4.4 ± 2.0b 3.2 ± 1.2b 1.6 ± 0.9b

1887.7 ± 609.2A,a 48.4 ± 16.7A,a 40.7 ± 14.4A,a 30.5 ± 12.4A,a

1557.6 ± 573.6B 35.4 ± 13.4B 29.4 ± 12.4B 24.5 ± 10.3B

1587.6 ± 546.4b 34.6 ± 13.7b 29.3 ± 13.6b 24.3 ± 10.7b

20.1 ± 4.9

18.6 ± 4.4

18.7 ± 4.5

25.3 ± 7.8

24.0 ± 6.7

24.4 ± 6.8

23.1 ± 4.7

24.7 ± 4.9

24.7 ± 4.9

13.9 ± 5.0

14.7 ± 6.0

14.7 ± 6.1

mDIBH, moderate deep inspiration breath-hold; A had significant difference with B (P < 0.05); a had significant difference with b (P < 0.05). Otherwise, the difference was not significant between any two (P > 0. 05).

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plan designed in the first moderate deep inspiration breath-holding state to the image in the second moderate deep inspiration breathhold state, which showed that there were no significant differences in the dosimetric parameters of the target volume coverage and the organs at risks. Thus, there are no significant differences between various moderate deep inspiration breath-holding states in the irradiation dose, and our study had high reproducibility. Jagsi et al. studied the movement of the target volume and the reproducibility of the combined active breathing control technique and wholebreast radiotherapy, and found that breathing control could reduce target movement and had higher reproducibility [34]. Therefore, there is no significant difference in target movement caused by respiration motion in various states, which has higher reproducibility and can effectively reduce the impact of respiration motion on radiotherapy for breast cancer. We performed breath-holding training for 31 patients with left breast cancer and showed that all patients cooperated well. The breath-hold time became significantly longer after standardized training (P < 0.05), met the clinical requirements, and had good compliance. Our study had some limitations, as follows: • a dosimetric study; • the active breathing control technique has some uncertainties, such as different functional residual capacities and involuntary movements of the heart that may affect its effectiveness; • the impact of different moderate deep inspiration breath-holding states on target displacement was not studied.

[4]

[5]

[6] [7]

[8]

[9]

[10]

[11]

[12]

[13]

Therefore, further studies should be carried out in the future. [14]

5. Conclusion Combined whole-breast field-in-field-IMRT and active breathing control technique after breast-conserving surgery in patients with left breast cancer under moderate deep inspiration breathholding can reduce the irradiated volume and irradiation dose to the ipsilateral lung, coronary artery, and heart. There was no significant dosimetric difference in the target volume and organs at risks between various moderate deep inspiration breath-holding states after field-in-field-IMRT, which may further reduce the incidence of radiotherapy complications and improve the quality of long-term survival in patients with early-stage breast cancer. Disclosure of interest The authors declare that they have no conflicts of interest concerning this article.

[15]

[16]

[17]

[18]

[19]

[20]

[21]

Acknowledgments [22]

This work was supported by grants from the National Natural Science Foundation of China (No. 81402527), the Sci-Tech Office of Guangdong Province (No. 2013B021800157) and the Education Scientific Research Project of Young Teachers in Fujian Province (No. JB13131).

[23]

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Please cite this article in press as: Chi F, et al. Dosimetric comparison of moderate deep inspiration breath-hold and free-breathing intensity-modulated radiotherapy for left-sided breast cancer. Cancer Radiother (2015), http://dx.doi.org/10.1016/j.canrad.2015.01.003

Dosimetric comparison of moderate deep inspiration breath-hold and free-breathing intensity-modulated radiotherapy for left-sided breast cancer.

This study determined the dosimetric comparison of moderate deep inspiration breath-hold using active breathing control and free-breathing intensity-m...
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