(UroToday.com) The 2023 ASCO annual meeting included a prostate cancer session, featuring a presentation by Dr. Loic Djaileb discussing pre-surgical 68Ga-PSMA-11 PET for biochemical recurrence risk assessment as a potential surrogate of pelvic lymph node dissection. Given the detection rate of PSMA-PET for lymph node metastasis, there is increased interest as to whether there is utility in performing a lymph node dissection if imaging is negative, or perhaps performing an extended more thorough dissection if imaging is positive. As such, the objective of this study was to compare the prognostic value of presurgical PSMA-PET and pelvic lymph nodes invasion (pN1) for biochemical recurrence free-survival in patients with intermediate-risk to high-risk prostate cancer treated with radical prostatectomy and pelvic lymph node dissection.
This is a posthoc analysis of the surgery cohort included in the multicenter prospective phase 3 imaging trial (n=764; NCT03368547, NCT02611882, NCT02919111). Each 68Ga-PSMA-11-PET scan was read by three blinded independent readers. Local histopathology risk score (CAPRA-S score without pN data), PSMA-PET extra-prostatic disease (N1/M1), and pN were used to assess risk of biochemical recurrence. Patients were followed up after radical prostatectomy by the local investigators using electronic medical records. Biochemical recurrence was defined by a PSA level ≥0.2 ng/ml after radical prostatectomy or an initiation of prostate cancer specific secondary treatment (>6 months after surgery).
From December 2015 to December 2019, 277 patients underwent surgery after PSMA-PET. Clinical follow-up was obtained in 87% patients, median follow-up from surgery was 32.4 (IQR 23.3-42.9) months, and there were 91/240 biochemical recurrence events (38%) observed. The overall flow chart and breakdown for the study is as follows:
PSMA-PET N1/M1 and pN1 were found in 41/240 (17%) and 67/240 (28%) patients, respectively. Local histopathology risk score, PSMA-PET, and pN were significant univariate predictors of biochemical recurrence. However, only local histopathology risk score and PSMA PET were significant in multivariate analysis (HR 1.4, 95% CI 1.2-1.51) and (HR 1.7, 95% CI 1.0-2.9). Prognostic value of the model combining local histopathology and PSMA-PET was not significantly different than model combining local histopathology and pN (c-statistic 0.74 (95% CI 0.69-0.79) vs 0.73 (95% CI 0.68-0.78); p = 0.69).
In patients with low-risk local histopathology score and PSMA-PET N0-M0, only 4/109 (5%) were pN1. In patients with high-risk local histopathology score, a PSMA-PET N1/M1 was associated with a significant lower biochemical recurrence free-survival than a PSMA-PET N0-M0 (median survival 32.7 months, 95% CI 14.9-NR vs 8 months, 95% CI 3.2-15.5; p= 0.001). As follows is biochemical recurrence free-survival regarding histological and PSMA PET status:
pN1 was found in respectively 25/34 (74%) and 34/90 (38%).
Dr. Djaileb concluded this presentation discussing pre-surgical 68Ga-PSMA-11 PET for biochemical recurrence risk assessment as a potential surrogate of pelvic lymph node dissection with the following take-home points:
- Pre-surgical PSMA-PET and local histopathology was not statistically different than the reference standard (local histopathology + pN to predict biochemical recurrence free-survival)
- Interestingly, the rate of discrepancy with pN was low among patients with:
- Low histopathology risk and PSMA-PET (N0-M0)
- High histopathology risk and PSMA-PET (N1/M1)
- Future directions for research: The best management strategy of these patients remains unknown. Randomized trials powered for clinical outcome and using PSMA PET staging for treatment allocation are warranted.
Presented by: Loic Djaileb, MD, PhD, UCLA Ahmanson Translational Theranostics Division, Los Angeles, CA
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Associate Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the 2023 American Society of Clinical Oncology (ASCO) Annual Meeting, Chicago, IL, Fri, June 2 – Tues, June 6, 2023.