Development and validation of a multi-institutional nomogram of outcomes for PSMA-PET–based salvage radiotherapy in recurrent prostate cancer.

Abstract

355 Background: We aimed to develop and to validate a multi-institutional nomogram of outcomes for PSMA-PET based salvage radiotherapy (sRT) following radical prostatectomy (RP) for patients with recurrent or persistent prostate cancer (PCa). Methods: Data from patients with a detectable post-RP prostate-specific antigen (PSA) treated with sRT with or without concurrent androgen-deprivation therapy (ADT) were obtained from 11 academic institutions from 5 countries. All patients had a PSMA-PET scan prior sRT and patients with distant metastases on PET were excluded from this analysis. The freedom from biochemical failure (FFBF) rate was estimated, and a predictive nomogram was generated and validated. Biochemical relapse (BR) was defined as PSA nadir +0.2 ng/ml after sRT. Results: Overall, 1029 patients (training set n=821, external validation set n=208) with a median follow-up of 33 months were included. On PSMA-PET, 427 (42%) and 313 (30%) patients had local and nodal recurrences, respectively. Elective pelvic lymphatics were irradiated in 368 (36%) patients. All patients received sRT to the prostatic fossa receiving a dose of <66 Gy, 66-70 Gy and >70 Gy in 103 (10%), 551 (54%) and 375 (36%) patients, respectively. Androgen deprivation therapy (ADT) was given in 325 (32%) patients. On multivariable Cox regression analysis, pre-SRT PSA, ISUP grade, pT stage, surgical margins, ADT use, sRT dose and nodal recurrence on PSMA PET were associated with FFBF. The nomogram concordance index was 0.7 for FFBF in external validation. Conclusions: We present an externally validated contemporary nomogram which can estimate individual patient outcomes after PSMA-PET guided sRT. Positive lymph nodes on PSMA-PET seem to be a new risk factor for BR after sRT.

Salvage Therapy for Prostate Cancer: AUA/ASTRO/SUO Guideline Part II: Treatment Delivery for Non-metastatic Biochemical Recurrence After Primary Radical Prostatectomy

“…In addition, the utility of PSMA-PET in the post-operative space for BCR is evolving with no clear guidelines on whether ADT should be incorporated into treatment depending on a positive or negative PSMA-PET scan. [18][19][20] However, if there is macroscopic disease detected, addition of ADT should generally be considered.…”

“…3,17 Thus, for patients with highrisk features requiring salvage RT, clinicians may extend ADT duration to 18 to 24 months while data matures from the RADICALS-HD trial (NCT00541047), which directly compares short-term versus long-term ADT with salvage RT. 19. In patients with BCR following RP undergoing salvage RT with ADT, clinicians may use expanded radiation fields that include the regional lymph nodes.…”

Clinical practice in prostate PET imaging

“…Metastases to lymph nodes detected by PSMA PET are risk factors for poor outcomes in risk prediction nomograms being developed for salvage radiotherapy. 50 A small study of choline PET in the setting of BCR for salvage radiotherapy showed choline PET changed the extent of RT in 13% of patients. However, this was a small (37 patients) retrospective study with no control group.…”