San Francisco, CA USA (UroToday.com) Dr. Alberto Briganti of the Urological Research Institute at the IRCCS San Raffaele Hospital in Milan, Italy presented a discussion of the incidence and distribution of lymph node metastases in localized prostate cancer and described the varied roles of imaging and surgery in their evaluation. He set the stage for the discussion by reminding the audience that conventional
imaging’s sensitivity for detecting nodal disease is only approximately 35% and is based solely on identifying enlarged lymph nodes. [11C]/[18F]Choline PET-CT is only slightly better with a sensitivity of approximately 50%. 68Ga-PSMA PET/CT can be very accurate in detecting recurrent disease, but it also has a sensitivity of approximately 50% in detecting lymph node metastases in localized disease due to high uptake of tracer by the prostate and a lower limit of detection of avid metastatic lymph nodes of 5 mm.
Dr. Briganti also reviewed the role of pelvic lymph node dissection in the diagnosis of prostate cancer nodal metastases in localized disease. He reported data demonstrating that an extended pelvic lymph node dissection including ≥ 20 lymph nodes could accurately stage up to 90% of patients regardless of the tumor characteristics. However he suggests that we should aim to use a more precise method of diagnosing lymph node metastases based on a more accurate template for dissection. Use of a newer template of extended pelvic lymph node dissection proposed by Mattei et al in European Urology in 2008 may result in more accurate dissection of involved nodes and remove approximately 75% of possible landing sites for metastatic disease despite a more limited dissection. Performing an extended lymph node dissection in any fashion appears to upstage patients relatively frequently, with intermediate and high-risk patients being diagnosed with lymph node invasion 3-4 times more frequently with extended lymph node dissection than with limited lymph node dissection. Indeed, recent series report that men with high risk localized disease have lymph node involvement 30-40% of the time when assessed with an extended lymph node dissection. Ultimately guidelines support this, recommending extended lymph node dissection in cases in which a lymph node dissection is indicated based on risk calculating tools developed using data from extended pelvic lymph node dissection series. He also reported data demonstrating that extended lymph node dissection can be performed at least as well during robot assisted radical prostatectomy procedures as during open procedures.
Finally Dr. Briganti presented data on intra-operative imaging techniques to identify involved lymph nodes that should be included in a dissection template. He described a recently developed technique of intra-operative florescence imaging for image guided lymph node dissection, and reported sensitivity of 75-100% per patient overall. However, he noted that on a per-tumor-positive node basis, there was a sensitivity of only 50%. He also reported that a node was identified outside of the image identified pelvic lymph node dissection template during pre-operative imaging in up to 40% of patients who were at highest risk of lymph node invasion, indicating that some involved nodes may be missed with this approach. However, he suggests that this technology may still prove to be useful to identify high-risk lesions outside of the typical extended lymph node dissection field rather than being used as a technique to limit use of extended lymph node dissection in lower risk patients.
Overall, Dr. Briganti concludes by noting that although imaging techniques in identifying lymph node involvement are improving, limitations remain. The gold standard to identifying lymph node invasion in men with prostate cancer remains a lymph node dissection, and an extended lymph node dissection is the preferred approach. Decisions regarding the extent of lymph node dissection warranted should be made based on models developed using series of extended pelvic lymph node dissection, particularly because series with less extensive lymph node dissection have an unacceptably high false negative rate. Finally, techniques to identify involved lymph nodes using imaging to define a dissection template are being developed and have potential, though these are not yet ready for routine clinical use.
Presented By:
Dr. Alberto Briganti
Urological Research Institute, Università Vita—Salute, IRCCS Ospedale San Raffaele
Reported By:
Dr. Alicia K. Morgans, MD, at the 2016 Genitourinary Cancers Symposium - January 7 - 9, 2016 – San Francisco, CA
Assistant Professor of Medicine Medical Oncologist
Vanderbilt - Ingram Cancer Center