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AUA 2019

AUA 2019: Rising PSA after Local Therapy: New Imaging for Recurrent Prostate Cancer

Chicago, IL (UroToday.com) At the SUO 2019 AUA meeting, Dr. Peter Carroll discussed new imaging for recurrent prostate cancer. Dr. Carroll notes that biochemical recurrence has several definitions, however regardless there is a large population of men with biochemical recurrence estimated to be 528,770. Guidelines for evaluation and treatment vary – adjuvant radiotherapy after surgery is uncommon, which salvage radiotherapy is more common. When and how to image these patients is also debatable.

Dr. Carroll presented a case of a 69-year-old male that underwent a radical prostatectomy in 2014, pathology showing pT2cN0, Gleason 3+4 with a positive margin. Salvage radiation therapy was started at a PSA of 0.341 and PSA then started rising to 0.059. At that time, he received a PSMA-PET which showed several suspicious lesions in the pelvis. At UCSF and UCLA, Dr. Carroll designed a prospective trial of men with detectable PSA or formal biochemical recurrence (PSA > 0.2) following radical prostatectomy. Patients (n=635) were included if they had prior adjuvant or salvage radiation therapy and were excluded if they had castrate-resistant disease.1 In their patient cohort, 32% had received prior ADT, >65% were pT3a, 17% were N1, and 36% of patients had positive surgical margins. On a per-patient basis, positive predictive value (PPV) was 0.84 (95% CI, 0.75-0.90) by histopathologic validation and 0.92 (95% CI, 0.88-0.95) by the composite reference standard. 68Ga-PSMA-11 PET localized recurrent prostate cancer in 75% of patients. Detection rates significantly increased with PSA: 38% for <0.5 ng/mL (n = 136), 57% for 0.5 to <1.0 ng/mL (n = 79), 84% for 1.0 to <2.0 ng/mL (n = 89), 86% for 2.0 to <5.0 ng/mL (n = 158), and 97% for ≥5.0 ng/mL (n = 173, p < 0.001).

Furthermore, the result of PSMA-PET imaging has an impact on radiation treatment planning. Among 45 patients (89% high or very high risk by NCCN criteria) who underwent 68Ga-PSMA-11 PET imaging prior to definitive treatment, 25 (56%) had N1/M1a disease on imaging, of whom 21 (47%) were previously N0.2 Six patients (13%) had bone metastases, of whom four had prior negative bone scans. Eight patients (18%) had lymph node metastases outside the consensus clinical target volume. Twelve patients (27%) received a radiation therapy boost to nodes within the consensus clinical target volume. Overall PSMA PET imaging resulted in major and/or minor changes to radiation plans in 24 patients (53%).

Dr. Carroll summarized his talk with several take-home messages:
  • The majority of men with biochemical recurrence have PSMA avid lesions
  • The prostate bed is an uncommon site of recurrent disease
  • At initial diagnosis and at recurrence, the regional disease may be outside of regional disease may be outside the standard templates for lymph node dissection of regional radiation.


Presented by: Peter Carroll, MD, MPH, Department of Urology, University of California-San Francisco, San Francisco, California

Written by: Zachary Klaassen, MD, MSc – Assistant Professor of Urology, Georgia Cancer Center, Augusta University - Medical College of Georgia, Twitter: @zklaassen_md at the American Urological Association's 2019 Annual Meeting (AUA 2019), May 3 – 6, 2019 in Chicago, Illinois

References:
  1. Fendler WP, Calais J, Eiber M, et al. Assessment of 68Ga-PSMA-11 PET Accuracy in Localizing Recurrent Prostate Cancer: A Prospective Single-Arm Clinical Trial. JAMA Oncol 2019 Mar 28 [Epub ahead of print].
  2. Wu SY, Boreta L, Shinohara K, et al. Impact of Staging 68Ga-PSMA-11 PET Scans on Radiation Treatment Plans in Patients with Prostate Cancer. Urology 2019 Mar;125:154-162.