Guest Editorial
Magnetic Resonance Sentinel Lymph Node Detection in Prostate Cancer: A New Solution to a Longstanding Problem? Andrew B. Rosenkrantz, MD, MPA, Samir S. Taneja, MD Accurately identifying nodal metastases at the time of radical prostatectomy in men with prostate cancer is important for achieving optimal staging and consideration of additional therapy. Providing adjuvant hormonal treatment to men with nodal metastases prolongs disease-free survival and can improve cancer-specific survival as well (1). In addition, knowledge of the location of nodal metastases impacts planning of conformal radiotherapy and may guide the extent of lymphadenectomy (2,3). Despite the postulated benefits of lymphadenectomy, considerable variability exists in surgeons’ approach to performing lymph node dissection at the time of radical prostatectomy. A limited pelvic lymph node dissection targeting nodes within the obturator fossa is a commonly applied scheme (4). A limited obturator dissection provides partial nodal sampling of the pelvis to guide staging without requiring additional dissection beyond the requisite surgical bed of the prostate. This approach is supported by a traditional perception that the frequency of nodal metastasis is very low, such that more extensive dissection is generally not warranted (5). More recently, the appropriateness of a limited pelvic nodal dissection has been questioned (6). Prostate cancer nodal metastatic disease is frequently solitary (7,8), although does not consistently first involve the obturator fossa before involving other, more remote, sites. Rather, potential sites of initial involvement are widespread, including the obturator fossa, iliac chains, presacral space, and para-aortic region (5). This variation contributes to reports of a higher frequency of nodal metastasis than reported by earlier investigations based on limited nodal dissections (6,9). In one study, up to 75% of nodal metastases were missed by performing solely an obturator dissection (10).
Acad Radiol 2015; 22:545–547 From the Department of Radiology, NYU Langone Medical Center, 660 First Avenue, New York, NY 10016 (A.B.R.); and Division of Urologic Oncology, Department of Urology, NYU Langone Medical Center, New York, New York (S.S.T.). Received February 25, 2015; accepted February 25, 2015. Conflicts of Interest: S.S.T. is a Consultant for Hitachi-Aloka Medical and for HealthTronics, receives payments for lectures and travel/accommodation expenses from Hitachi-Aloka Medical, and receives royalties from Elsevier. Address correspondence to: A.B.R. e-mail: [email protected] ªAUR, 2015 http://dx.doi.org/10.1016/j.acra.2015.02.007
The primary alternative approach is to perform an extended pelvic lymph node dissection that routinely incorporates more cranial dissection of the external and common iliac, presacral, and para-aortic regions. The act of performing an extended lymph node dissection is more likely to remove lymph node metastases than a limited sampling and has been postulated by some authors to improve disease-free survival (11). However, this potential benefit has not been clearly established, and any overall therapeutic benefit of extended lymphadenectomy in men with nodal metastasis remains highly controversial. Poor preoperative localization of nodal metastases may in fact limit the benefit of even an extended lymphadenectomy, such that improved localization may still be required to improve the theoretical efficacy of lymph node–directed therapy. In addition to the aforementioned considerations, extended pelvic lymph node dissection also entails greater cost and operative time (5,12), as well as substantially greater complications (7,13), than limited dissection. Although lymphocele and lymphedema are the most common complications, nerve and ureteral injury are also reported (14,15). One study observed that when performing limited and extended nodal dissections on contralateral sides, the complication rate was approximately three times greater on the side undergoing extended dissection (15). Finally, even an extended nodal dissection does not provide a true gold standard, as this technique has been observed to miss a small fraction of nodal metastases (5,16). Given these concerns, as well as persistent uncertainty regarding the actual likelihood of nodal metastatic disease and thus the yield of this procedure, extended pelvic lymph node dissection is not currently widely performed in clinical practice. Sentinel lymph node evaluation offers what would seem to be a balance between the aims of seeking to identify any metastatic node that may be present and avoiding excessive morbidity from a large number of extended dissections in N0 patients. This approach is based on the principle that if the node serving as the primary nodal drainage site of the prostate, termed the sentinel node, is free of disease, then the presence of nodal metastasis at any site is effectively excluded and that no other lymph nodes warrant evaluation (17). Sentinel lymph node evaluation is commonly performed via lymphoscintigraphy and has been conducted successfully for breast cancer (18), 545
ROSENKRANTZ AND TANEJA
penile cancer (19), and melanoma (20). For prostate cancer evaluation, a nanoparticle colloid is typically injected into each lobe of the prostate, which then travels via the lymphatic system and is ultimately taken up and retained within the reticuloendothelial system of the sentinel node on each side (21). Technetium Tc-99m is the radiotracer most commonly bound to the injected colloid (14). At standardized time intervals after injection, pelvic imaging using a gamma camera is performed to visualize the location of the sentinel node, the reliability of which is improved using single-photon emission computed tomography computed tomography (SPECT/CT) (22). Finally, intraoperatively, a portable gamma probe is used to confirm the location of the sentinel node, which then undergoes complete resection and careful histologic evaluation (23). If metastatic, an extended pelvic lymph node dissection is performed. If benign, further nodal dissection is deferred. Sentinel lymph node evaluation for prostate cancer is supported by strong data from studies in which both sentinel lymph node evaluation and extended lymph node dissection were performed in prospective cohorts (7,24). Such studies demonstrate a much higher yield of sentinel lymph node biopsy compared to limited pelvic dissection, yet an exceedingly low risk of a benign sentinel lymph node evaluation in patients found to have metastatic nodes elsewhere (7,8,24). In additional, sentinel lymph node biopsy occasionally identifies a metastatic node not identified by standard extended lymphadenectomy (16). However, sentinel lymph node evaluation has challenges as well. This procedure requires specialized equipment and surgical skill and exposes the patient, as well as the surgical staff, to radiation (5,25). In addition, the low spatial resolution of lymphoscintigraphy may confound the interpretation of the postinjection imaging (26). Furthermore, radioactivity from excreted radiotracer in the bladder or radiotracer that has leaked from the lymphatic system may contribute to falsepositive findings (17,27). Improper intraoperative handling of the gamma probe can also lead to a misinterpretation (28). Accordingly, sentinel lymph node evaluation is not commonly used in prostate cancer patients at the present time. In this issue, Turkbey et al. (26) demonstrate the ability to reliably visualize the lymph nodes draining the prostate by magnetic resonance (MR) imaging (MRI) using the agent gadofosveset trisodium (ABLAVAR; Lantheus Medical, North Billerica, MA). Gadofosveset trisodium is a gadolinium chelate that received Food and Drug Administration approval in 2008 and that reversibly binds albumin, leading to macromolecule-like behavior, including lymphatic uptake and retention. In this study, the agent was mixed with human serum albumin before intraprostatic injection in three rodents at various doses (26). At low injected volumes, enhancement and subsequent washout within draining nodes was well visualized in all cases, with minimal periprostatic extravasation (26). Although requiring validation in a human setting, this alternate approach to sentinel lymph node evaluation has clear potential advantages compared to lymphoscintigraphy. The process no longer entails radiation exposure or skill by the sur546
Academic Radiology, Vol 22, No 5, May 2015
geon in proper use of an intraoperative gamma probe. In addition, the higher spatial resolution of MRI may facilitate detection of very small metastatic lymph nodes. The ability to reliably localize primary tumors within the prostate using multiparametric MRI allows for an additional intriguing possibility raised by the study’s authors of injecting the agent under direct MRI guidance into the tumor itself to directly assess the tumor’s actual lymphatic drainage. This ability is in contrast to the current approach for sentinel lymph node evaluation in which the radiolabeled agent is injected into the prostate under ultrasound guidance in a nontargeted fashion. As no radiolabel is used, the authors suggest labeling the gadolinium chelate with indocyanine green to allow for optical localization intraoperatively (26). The results of the study of Turkbey et al. are clearly preliminary. The most immediate clinical benefit of the proposed technique would seem to be avoiding unnecessary nodal dissections. However, given the relative infrequency of nodal metastases, as well as uncertainty whether the sentinel node technique would in fact positively identify more metastatic nodes, additional investigation is needed to explore whether the described method would indeed achieve greater therapeutic efficacy. In addition, although conventional CT, MRI, and fluorodeoxyglucose position emission tomography all have limited diagnostic accuracy for nodal metastatic disease in prostate cancer patients (29,30), continual improvements in noninvasive imaging techniques for nodal disease, for instance through diffusion–weighted MRI (31) and MRI using ultrasmall superparamagnetic iron oxide agents (32), may limit the potential added value of invasive sentinel node procedures. Nonetheless, even these more sophisticated noninvasive imaging techniques have yet to show sufficient accuracy to allow for confidently avoiding nodal dissection, such that improvement of sentinel lymph node approaches remains warranted. Ultimately, optimization of both noninvasive and invasive methods of lymph node localization is useful for allowing individualized selection of a given approach based on a patient’s level of risk and the therapeutic intent of any node-directed surgical intervention. In summary, if the efficacy of MR sentinel lymph node evaluation, as described by Turkbey et al., can be established in prostate cancer patients, then, such a technique would greatly reduce the extent of pelvic lymph node dissections and associated morbidity while providing improved prognostic information. This more reliable identification of early nodal metastatic disease may, in turn, allow more accurate evaluation of the theoretical oncologic benefit of lymphadenectomy and lymph node–directed therapeutic modalities. Therefore, additional investigations of this novel approach are anticipated. REFERENCES 1. Cheng L, Zincke H, Blute ML, et al. Risk of prostate carcinoma death in patients with lymph node metastasis. Cancer 2001; 91(1):66–73. 2. Morikawa LK, Roach M, 3rd. Pelvic nodal radiotherapy in patients with unfavorable intermediate and high-risk prostate cancer: evidence, rationale,
Academic Radiology, Vol 22, No 5, May 2015
3.
4.
5. 6.
7.
8.
9.
10.
11.
12. 13.
14.
15.
16. 17.
18.
MRI FOR PROSTATE CANCER SENTINEL LYMPH NODE DETECTION
and future directions. International journal of radiation oncology, biology, physics 2011; 80(1):6–16. Casamassima F, Masi L, Menichelli C, et al. Efficacy of eradicative radiotherapy for limited nodal metastases detected with choline PET scan in prostate cancer patients. Tumori 2011; 97(1):49–55. Shackley DC, Irving SO, Brough WA, et al. Staging laparoscopic pelvic lymphadenectomy in prostate cancer. BJU international 1999; 83(3): 260–264. Meinhardt W. Sentinel node evaluation in prostate cancer. EAU-EBU Update 2007; 5:223–231. 5. Heidenreich A, Varga Z, Von Knobloch R. Extended pelvic lymphadenectomy in patients undergoing radical prostatectomy: high incidence of lymph node metastasis. The Journal of urology 2002; 167(4):1681–1686. Beri A, Janetschek G. Technology insight: radioguided sentinel lymph node dissection in the staging of prostate cancer. Nature clinical practice Urology 2006; 3(11):602–610. Wawroschek F, Vogt H, Weckermann D, et al. The sentinel lymph node concept in prostate cancer—first results of gamma probe-guided sentinel lymph node identification. European urology 1999; 36(6):595–600. Burkhard FC, Bader P, Schneider E, et al. Reliability of preoperative values to determine the need for lymphadenectomy in patients with prostate cancer and meticulous lymph node dissection. European urology 2002; 42(2): 84–90; discussion -2. Allaf ME, Palapattu GS, Trock BJ, et al. Anatomical extent of lymph node dissection: impact on men with clinically localized prostate cancer. The Journal of urology 2004; 172(5 Pt 1):1840–1844. Bader P, Burkhard FC, Markwalder R, et al. Disease progression and survival of patients with positive lymph nodes after radical prostatectomy. Is there a chance of cure? The Journal of urology 2003; 169(3):849–854. Loeb S, Partin AW, Schaeffer EM. Complications of pelvic lymphadenectomy: do the risks outweigh the benefits? Reviews in urology 2010; 12(1):20–24. Briganti A, Chun FK, Salonia A, et al. Complications and other surgical outcomes associated with extended pelvic lymphadenectomy in men with localized prostate cancer. European urology 2006; 50(5):1006–1013. van den Berg NS, Valdes-Olmos RA, van der Poel HG, et al. Sentinel lymph node biopsy for prostate cancer: a hybrid approach. Journal of nuclear medicine : official publication, Society of Nuclear Medicine 2013; 54(4):493–496. Clark T, Parekh DJ, Cookson MS, et al. Randomized prospective evaluation of extended versus limited lymph node dissection in patients with clinically localized prostate cancer. The Journal of urology 2003; 169(1): 145–147; discussion 7–8. Joniau S, Van den Bergh L, Lerut E, et al. Mapping of pelvic lymph node metastases in prostate cancer. European urology 2013; 63(3):450–458. Meinhardt W, van der Poel HG, Valdes Olmos RA, et al. Laparoscopic sentinel lymph node biopsy for prostate cancer: the relevance of locations outside the extended dissection area. Prostate cancer 2012; 2012:751753. Zanghi G, Di Stefano G, Caponnetto A, et al. Breast cancer and sentinel lymph node micrometastases: indications for lymphadenectomy and literature review. Il Giornale di chirurgia 2014; 35(11-12):260–265.
19. Horenblas S. Sentinel lymph node biopsy in penile carcinoma. Seminars in diagnostic pathology 2012; 29(2):90–95. 20. Gyorki DE, Henderson MA. Sentinel lymph node biopsy for melanoma: an important risk-stratification tool. The Medical journal of Australia 2015; 202(2):79. 21. Meinhardt W, Valdes Olmos RA, van der Poel HG, et al. Laparoscopic sentinel node dissection for prostate carcinoma: technical and anatomical observations. BJU international 2008; 102(6):714–717. 22. Vermeeren L, Valdes Olmos RA, Meinhardt W, et al. Value of SPECT/CT for detection and anatomic localization of sentinel lymph nodes before laparoscopic sentinel node lymphadenectomy in prostate carcinoma. Journal of nuclear medicine : official publication, Society of Nuclear Medicine 2009; 50(6):865–870. 23. Vermeeren L, Valdes Olmos RA, Meinhardt W, et al. Intraoperative radioguidance with a portable gamma camera: a novel technique for laparoscopic sentinel node localisation in urological malignancies. European journal of nuclear medicine and molecular imaging 2009; 36(7):1029–1036. 24. Weckermann D, Dorn R, Holl G, et al. Limitations of radioguided surgery in high-risk prostate cancer. European urology 2007; 51(6):1549–1556; discussion 56–8. 25. Winter A, Woenkhaus J, Wawroschek F. A novel method for intraoperative sentinel lymph node detection in prostate cancer patients using superparamagnetic iron oxide nanoparticles and a handheld magnetometer: the initial clinical experience. Annals of surgical oncology 2014; 21(13):4390–4396. 26. Turkbey B, Hoyt RF, Jr, Agarwal HK, et al. Magnetic resonance sentinel lymph node imaging of the prostate with gadofosveset trisodiumalbumin: preliminary results in a canine model. Acad Radiol 2015; 22(5): 646–652. 27. Ganswindt U, Schilling D, Muller AC, et al. Distribution of prostate sentinel nodes: a SPECT-derived anatomic atlas. International journal of radiation oncology, biology, physics 2011; 79(5):1364–1372. 28. Jeschke S, Nambirajan T, Leeb K, et al. Detection of early lymph node metastases in prostate cancer by laparoscopic radioisotope guided sentinel lymph node dissection. The Journal of urology 2005; 173(6):1943–1946. 29. Hovels AM, Heesakkers RA, Adang EM, et al. The diagnostic accuracy of CT and MRI in the staging of pelvic lymph nodes in patients with prostate cancer: a meta-analysis. Clinical radiology 2008; 63(4):387–395. 30. Schoder H, Herrmann K, Gonen M, et al. 2-[18F]fluoro-2-deoxyglucose positron emission tomography for the detection of disease in patients with prostate-specific antigen relapse after radical prostatectomy. Clinical cancer research : an official journal of the American Association for Cancer Research 2005; 11(13):4761–4769. 31. Thoeny HC, Froehlich JM, Triantafyllou M, et al. Metastases in normalsized pelvic lymph nodes: detection with diffusion-weighted MR imaging. Radiology 2014; 273(1):125–135. 32. Heesakkers RA, Hovels AM, Jager GJ, et al. MRI with a lymph-nodespecific contrast agent as an alternative to CT scan and lymph-node dissection in patients with prostate cancer: a prospective multicohort study. The Lancet Oncology 2008; 9(9):850–856.
547
Magnetic Resonance Sentinel Lymph Node Detection in Prostate Cancer: A New Solution to a Longstanding Problem? Andrew B. Rosenkrantz, MD, MPA, Samir S. Taneja, MD Accurately identifying nodal metastases at the time of radical prostatectomy in men with prostate cancer is important for achieving optimal staging and consideration of additional therapy. Providing adjuvant hormonal treatment to men with nodal metastases prolongs disease-free survival and can improve cancer-specific survival as well (1). In addition, knowledge of the location of nodal metastases impacts planning of conformal radiotherapy and may guide the extent of lymphadenectomy (2,3). Despite the postulated benefits of lymphadenectomy, considerable variability exists in surgeons’ approach to performing lymph node dissection at the time of radical prostatectomy. A limited pelvic lymph node dissection targeting nodes within the obturator fossa is a commonly applied scheme (4). A limited obturator dissection provides partial nodal sampling of the pelvis to guide staging without requiring additional dissection beyond the requisite surgical bed of the prostate. This approach is supported by a traditional perception that the frequency of nodal metastasis is very low, such that more extensive dissection is generally not warranted (5). More recently, the appropriateness of a limited pelvic nodal dissection has been questioned (6). Prostate cancer nodal metastatic disease is frequently solitary (7,8), although does not consistently first involve the obturator fossa before involving other, more remote, sites. Rather, potential sites of initial involvement are widespread, including the obturator fossa, iliac chains, presacral space, and para-aortic region (5). This variation contributes to reports of a higher frequency of nodal metastasis than reported by earlier investigations based on limited nodal dissections (6,9). In one study, up to 75% of nodal metastases were missed by performing solely an obturator dissection (10).
Acad Radiol 2015; 22:545–547 From the Department of Radiology, NYU Langone Medical Center, 660 First Avenue, New York, NY 10016 (A.B.R.); and Division of Urologic Oncology, Department of Urology, NYU Langone Medical Center, New York, New York (S.S.T.). Received February 25, 2015; accepted February 25, 2015. Conflicts of Interest: S.S.T. is a Consultant for Hitachi-Aloka Medical and for HealthTronics, receives payments for lectures and travel/accommodation expenses from Hitachi-Aloka Medical, and receives royalties from Elsevier. Address correspondence to: A.B.R. e-mail: [email protected] ªAUR, 2015 http://dx.doi.org/10.1016/j.acra.2015.02.007
The primary alternative approach is to perform an extended pelvic lymph node dissection that routinely incorporates more cranial dissection of the external and common iliac, presacral, and para-aortic regions. The act of performing an extended lymph node dissection is more likely to remove lymph node metastases than a limited sampling and has been postulated by some authors to improve disease-free survival (11). However, this potential benefit has not been clearly established, and any overall therapeutic benefit of extended lymphadenectomy in men with nodal metastasis remains highly controversial. Poor preoperative localization of nodal metastases may in fact limit the benefit of even an extended lymphadenectomy, such that improved localization may still be required to improve the theoretical efficacy of lymph node–directed therapy. In addition to the aforementioned considerations, extended pelvic lymph node dissection also entails greater cost and operative time (5,12), as well as substantially greater complications (7,13), than limited dissection. Although lymphocele and lymphedema are the most common complications, nerve and ureteral injury are also reported (14,15). One study observed that when performing limited and extended nodal dissections on contralateral sides, the complication rate was approximately three times greater on the side undergoing extended dissection (15). Finally, even an extended nodal dissection does not provide a true gold standard, as this technique has been observed to miss a small fraction of nodal metastases (5,16). Given these concerns, as well as persistent uncertainty regarding the actual likelihood of nodal metastatic disease and thus the yield of this procedure, extended pelvic lymph node dissection is not currently widely performed in clinical practice. Sentinel lymph node evaluation offers what would seem to be a balance between the aims of seeking to identify any metastatic node that may be present and avoiding excessive morbidity from a large number of extended dissections in N0 patients. This approach is based on the principle that if the node serving as the primary nodal drainage site of the prostate, termed the sentinel node, is free of disease, then the presence of nodal metastasis at any site is effectively excluded and that no other lymph nodes warrant evaluation (17). Sentinel lymph node evaluation is commonly performed via lymphoscintigraphy and has been conducted successfully for breast cancer (18), 545
ROSENKRANTZ AND TANEJA
penile cancer (19), and melanoma (20). For prostate cancer evaluation, a nanoparticle colloid is typically injected into each lobe of the prostate, which then travels via the lymphatic system and is ultimately taken up and retained within the reticuloendothelial system of the sentinel node on each side (21). Technetium Tc-99m is the radiotracer most commonly bound to the injected colloid (14). At standardized time intervals after injection, pelvic imaging using a gamma camera is performed to visualize the location of the sentinel node, the reliability of which is improved using single-photon emission computed tomography computed tomography (SPECT/CT) (22). Finally, intraoperatively, a portable gamma probe is used to confirm the location of the sentinel node, which then undergoes complete resection and careful histologic evaluation (23). If metastatic, an extended pelvic lymph node dissection is performed. If benign, further nodal dissection is deferred. Sentinel lymph node evaluation for prostate cancer is supported by strong data from studies in which both sentinel lymph node evaluation and extended lymph node dissection were performed in prospective cohorts (7,24). Such studies demonstrate a much higher yield of sentinel lymph node biopsy compared to limited pelvic dissection, yet an exceedingly low risk of a benign sentinel lymph node evaluation in patients found to have metastatic nodes elsewhere (7,8,24). In additional, sentinel lymph node biopsy occasionally identifies a metastatic node not identified by standard extended lymphadenectomy (16). However, sentinel lymph node evaluation has challenges as well. This procedure requires specialized equipment and surgical skill and exposes the patient, as well as the surgical staff, to radiation (5,25). In addition, the low spatial resolution of lymphoscintigraphy may confound the interpretation of the postinjection imaging (26). Furthermore, radioactivity from excreted radiotracer in the bladder or radiotracer that has leaked from the lymphatic system may contribute to falsepositive findings (17,27). Improper intraoperative handling of the gamma probe can also lead to a misinterpretation (28). Accordingly, sentinel lymph node evaluation is not commonly used in prostate cancer patients at the present time. In this issue, Turkbey et al. (26) demonstrate the ability to reliably visualize the lymph nodes draining the prostate by magnetic resonance (MR) imaging (MRI) using the agent gadofosveset trisodium (ABLAVAR; Lantheus Medical, North Billerica, MA). Gadofosveset trisodium is a gadolinium chelate that received Food and Drug Administration approval in 2008 and that reversibly binds albumin, leading to macromolecule-like behavior, including lymphatic uptake and retention. In this study, the agent was mixed with human serum albumin before intraprostatic injection in three rodents at various doses (26). At low injected volumes, enhancement and subsequent washout within draining nodes was well visualized in all cases, with minimal periprostatic extravasation (26). Although requiring validation in a human setting, this alternate approach to sentinel lymph node evaluation has clear potential advantages compared to lymphoscintigraphy. The process no longer entails radiation exposure or skill by the sur546
Academic Radiology, Vol 22, No 5, May 2015
geon in proper use of an intraoperative gamma probe. In addition, the higher spatial resolution of MRI may facilitate detection of very small metastatic lymph nodes. The ability to reliably localize primary tumors within the prostate using multiparametric MRI allows for an additional intriguing possibility raised by the study’s authors of injecting the agent under direct MRI guidance into the tumor itself to directly assess the tumor’s actual lymphatic drainage. This ability is in contrast to the current approach for sentinel lymph node evaluation in which the radiolabeled agent is injected into the prostate under ultrasound guidance in a nontargeted fashion. As no radiolabel is used, the authors suggest labeling the gadolinium chelate with indocyanine green to allow for optical localization intraoperatively (26). The results of the study of Turkbey et al. are clearly preliminary. The most immediate clinical benefit of the proposed technique would seem to be avoiding unnecessary nodal dissections. However, given the relative infrequency of nodal metastases, as well as uncertainty whether the sentinel node technique would in fact positively identify more metastatic nodes, additional investigation is needed to explore whether the described method would indeed achieve greater therapeutic efficacy. In addition, although conventional CT, MRI, and fluorodeoxyglucose position emission tomography all have limited diagnostic accuracy for nodal metastatic disease in prostate cancer patients (29,30), continual improvements in noninvasive imaging techniques for nodal disease, for instance through diffusion–weighted MRI (31) and MRI using ultrasmall superparamagnetic iron oxide agents (32), may limit the potential added value of invasive sentinel node procedures. Nonetheless, even these more sophisticated noninvasive imaging techniques have yet to show sufficient accuracy to allow for confidently avoiding nodal dissection, such that improvement of sentinel lymph node approaches remains warranted. Ultimately, optimization of both noninvasive and invasive methods of lymph node localization is useful for allowing individualized selection of a given approach based on a patient’s level of risk and the therapeutic intent of any node-directed surgical intervention. In summary, if the efficacy of MR sentinel lymph node evaluation, as described by Turkbey et al., can be established in prostate cancer patients, then, such a technique would greatly reduce the extent of pelvic lymph node dissections and associated morbidity while providing improved prognostic information. This more reliable identification of early nodal metastatic disease may, in turn, allow more accurate evaluation of the theoretical oncologic benefit of lymphadenectomy and lymph node–directed therapeutic modalities. Therefore, additional investigations of this novel approach are anticipated. REFERENCES 1. Cheng L, Zincke H, Blute ML, et al. Risk of prostate carcinoma death in patients with lymph node metastasis. Cancer 2001; 91(1):66–73. 2. Morikawa LK, Roach M, 3rd. Pelvic nodal radiotherapy in patients with unfavorable intermediate and high-risk prostate cancer: evidence, rationale,
Academic Radiology, Vol 22, No 5, May 2015
3.
4.
5. 6.
7.
8.
9.
10.
11.
12. 13.
14.
15.
16. 17.
18.
MRI FOR PROSTATE CANCER SENTINEL LYMPH NODE DETECTION
and future directions. International journal of radiation oncology, biology, physics 2011; 80(1):6–16. Casamassima F, Masi L, Menichelli C, et al. Efficacy of eradicative radiotherapy for limited nodal metastases detected with choline PET scan in prostate cancer patients. Tumori 2011; 97(1):49–55. Shackley DC, Irving SO, Brough WA, et al. Staging laparoscopic pelvic lymphadenectomy in prostate cancer. BJU international 1999; 83(3): 260–264. Meinhardt W. Sentinel node evaluation in prostate cancer. EAU-EBU Update 2007; 5:223–231. 5. Heidenreich A, Varga Z, Von Knobloch R. Extended pelvic lymphadenectomy in patients undergoing radical prostatectomy: high incidence of lymph node metastasis. The Journal of urology 2002; 167(4):1681–1686. Beri A, Janetschek G. Technology insight: radioguided sentinel lymph node dissection in the staging of prostate cancer. Nature clinical practice Urology 2006; 3(11):602–610. Wawroschek F, Vogt H, Weckermann D, et al. The sentinel lymph node concept in prostate cancer—first results of gamma probe-guided sentinel lymph node identification. European urology 1999; 36(6):595–600. Burkhard FC, Bader P, Schneider E, et al. Reliability of preoperative values to determine the need for lymphadenectomy in patients with prostate cancer and meticulous lymph node dissection. European urology 2002; 42(2): 84–90; discussion -2. Allaf ME, Palapattu GS, Trock BJ, et al. Anatomical extent of lymph node dissection: impact on men with clinically localized prostate cancer. The Journal of urology 2004; 172(5 Pt 1):1840–1844. Bader P, Burkhard FC, Markwalder R, et al. Disease progression and survival of patients with positive lymph nodes after radical prostatectomy. Is there a chance of cure? The Journal of urology 2003; 169(3):849–854. Loeb S, Partin AW, Schaeffer EM. Complications of pelvic lymphadenectomy: do the risks outweigh the benefits? Reviews in urology 2010; 12(1):20–24. Briganti A, Chun FK, Salonia A, et al. Complications and other surgical outcomes associated with extended pelvic lymphadenectomy in men with localized prostate cancer. European urology 2006; 50(5):1006–1013. van den Berg NS, Valdes-Olmos RA, van der Poel HG, et al. Sentinel lymph node biopsy for prostate cancer: a hybrid approach. Journal of nuclear medicine : official publication, Society of Nuclear Medicine 2013; 54(4):493–496. Clark T, Parekh DJ, Cookson MS, et al. Randomized prospective evaluation of extended versus limited lymph node dissection in patients with clinically localized prostate cancer. The Journal of urology 2003; 169(1): 145–147; discussion 7–8. Joniau S, Van den Bergh L, Lerut E, et al. Mapping of pelvic lymph node metastases in prostate cancer. European urology 2013; 63(3):450–458. Meinhardt W, van der Poel HG, Valdes Olmos RA, et al. Laparoscopic sentinel lymph node biopsy for prostate cancer: the relevance of locations outside the extended dissection area. Prostate cancer 2012; 2012:751753. Zanghi G, Di Stefano G, Caponnetto A, et al. Breast cancer and sentinel lymph node micrometastases: indications for lymphadenectomy and literature review. Il Giornale di chirurgia 2014; 35(11-12):260–265.
19. Horenblas S. Sentinel lymph node biopsy in penile carcinoma. Seminars in diagnostic pathology 2012; 29(2):90–95. 20. Gyorki DE, Henderson MA. Sentinel lymph node biopsy for melanoma: an important risk-stratification tool. The Medical journal of Australia 2015; 202(2):79. 21. Meinhardt W, Valdes Olmos RA, van der Poel HG, et al. Laparoscopic sentinel node dissection for prostate carcinoma: technical and anatomical observations. BJU international 2008; 102(6):714–717. 22. Vermeeren L, Valdes Olmos RA, Meinhardt W, et al. Value of SPECT/CT for detection and anatomic localization of sentinel lymph nodes before laparoscopic sentinel node lymphadenectomy in prostate carcinoma. Journal of nuclear medicine : official publication, Society of Nuclear Medicine 2009; 50(6):865–870. 23. Vermeeren L, Valdes Olmos RA, Meinhardt W, et al. Intraoperative radioguidance with a portable gamma camera: a novel technique for laparoscopic sentinel node localisation in urological malignancies. European journal of nuclear medicine and molecular imaging 2009; 36(7):1029–1036. 24. Weckermann D, Dorn R, Holl G, et al. Limitations of radioguided surgery in high-risk prostate cancer. European urology 2007; 51(6):1549–1556; discussion 56–8. 25. Winter A, Woenkhaus J, Wawroschek F. A novel method for intraoperative sentinel lymph node detection in prostate cancer patients using superparamagnetic iron oxide nanoparticles and a handheld magnetometer: the initial clinical experience. Annals of surgical oncology 2014; 21(13):4390–4396. 26. Turkbey B, Hoyt RF, Jr, Agarwal HK, et al. Magnetic resonance sentinel lymph node imaging of the prostate with gadofosveset trisodiumalbumin: preliminary results in a canine model. Acad Radiol 2015; 22(5): 646–652. 27. Ganswindt U, Schilling D, Muller AC, et al. Distribution of prostate sentinel nodes: a SPECT-derived anatomic atlas. International journal of radiation oncology, biology, physics 2011; 79(5):1364–1372. 28. Jeschke S, Nambirajan T, Leeb K, et al. Detection of early lymph node metastases in prostate cancer by laparoscopic radioisotope guided sentinel lymph node dissection. The Journal of urology 2005; 173(6):1943–1946. 29. Hovels AM, Heesakkers RA, Adang EM, et al. The diagnostic accuracy of CT and MRI in the staging of pelvic lymph nodes in patients with prostate cancer: a meta-analysis. Clinical radiology 2008; 63(4):387–395. 30. Schoder H, Herrmann K, Gonen M, et al. 2-[18F]fluoro-2-deoxyglucose positron emission tomography for the detection of disease in patients with prostate-specific antigen relapse after radical prostatectomy. Clinical cancer research : an official journal of the American Association for Cancer Research 2005; 11(13):4761–4769. 31. Thoeny HC, Froehlich JM, Triantafyllou M, et al. Metastases in normalsized pelvic lymph nodes: detection with diffusion-weighted MR imaging. Radiology 2014; 273(1):125–135. 32. Heesakkers RA, Hovels AM, Jager GJ, et al. MRI with a lymph-nodespecific contrast agent as an alternative to CT scan and lymph-node dissection in patients with prostate cancer: a prospective multicohort study. The Lancet Oncology 2008; 9(9):850–856.
547
