ASCO GU 2023: Influence of Molecular Imaging on Patient Selection for Treatment Intensification Prior to Salvage Radiation Therapy for Prostate Cancer: A Post Hoc Analysis of the PROPS Trial

( On the first day of the American Society for Clinical Oncology (ASCO) Genitourinary Cancer Symposium 2023 focussing on prostate cancer, Dr. Samuel Trombley presented a post hoc analysis of the PROPS trial in Poster Session A, assessing the influence of molecular imaging on patient selection for treatment intensification in the context of salvage radiotherapy for prostate cancer.

There have been numerous studies, including prospective registration data, demonstrating the effect of molecular imaging using PSMA-based PET/CT on patient management after biochemical recurrence (BCR) following radical prostatectomy. However, it is not known if there is a clinical benefit to patients as a result of the changes in treatment due to molecular imaging, of if these management changes are appropriate. Thus, these authors sought to determine if the androgen deprivation therapy (ADT) management plan is improved by molecular imaging in patients who are candidates for salvage radiation therapy.

The authors relied upon data from the prospective multicenter PROPS trial evaluating PSMA/Choline PET in patients being considered for salvage radiotherapy (sRT) with BCR after prostatectomy. They compared the ADT management plans for each patient preceding and following results from molecular imaging, as well as cancer outcomes as predicted by the MSKCC nomogram. A higher percentage of predicted BCR associated with ADT treatment intensification after the use of molecular imaging was considered as an improvement in a patient’s management.

PROPS trial-0.jpg

They included 73 patients with a median PSA of 0.38 ng/mL. In bivariate analysis, a positive finding on molecular imaging (local or metastatic) was associated with decision to use ADT with an odds ratio of 3.67 (95% CI, 1.25 to 10.71; p=0.02). No factor included in the nomogram was associated with decision to use ADT.

PROPS trial-1.jpg

When examined using the MSKCC nomogram, the use of molecular imaging improved selection of patients to receive ADT based on predicted BCR after sRT: the predicted nomogram 5-year biochemical-free survivals were 52.5 % and 43.3%, (mean difference, 9.2%; 95% CI 0.8 to 17.6; p=0.03) for sRT alone and ADT±sRT subgroups, while there was no statistically significant difference between subgroups before the use of molecular imaging.

PROPS trial-2.jpg

Thus, the authors conclude that the use of molecular imaging studies such as PSMA or Choline PET/CT before sRT can improve patient ADT management by directing clinicians towards more appropriate intensification.

Presented by: Samuel Tremblay, Resident, Laval University