PSMA PET: An Important Tool for Prostate Cancer Treatment Planning

PSMA PET is an important tool for postoperative treatment planning in prostate cancer (PCa) and should be used in a redefinition of radiotherapy (RT) guidelines, according to a study presented at the 2022 American Society for Radiation Oncology Annual Meeting.

In this large-scale study, presenting author Alan Dal Pra, MD, and colleagues assessed patterns of recurrence in the prostate bed (PB) of PCa patients with disease recurrence using ⁶⁸Ga-PSMA-11 positron emission tomography (PET)/computed tomography (CT) (PSMA PET). They analyzed 2415 PSMA PET scans between November 2016 and November 2020. In total, 230 scans of patients with prostate cancer following radical prostatectomy without previous history of PB RT were retrospectively assessed if their PSMA PET showed evidence of recurrence in the PB. A team of radiation oncologists, masked to PSMA PET-based delineations, contoured the Radiation Therapy Oncology Group (RTOG)-based clinical target volumes (CTVs) based on the imaging.

According to the results, 55% of patients had miTrN0M0, 13% had miTrN1M0, 15% had miTrN0M1, and 17% had miTrN1M. In the miTrN0M0 (PB) cohort, PSMA-positive recurrences were fully covered by the CTV in 54% of the patients but only partly covered 34% of patients. PSMA-positive recurrences were fully outside the PB in 13% of patients. “To our knowledge, this is the largest study with a detailed mapping of recurrences in the prostate bed using PSMA PET imaging. In patients with recurrences exclusive to the prostate bed (miTrN0M0), the RTOG contouring guidelines showed suboptimal coverage of the disease in 46% of patients,” the researchers said.

The results indicate that “PSMA PET can be an invaluable tool for postoperative radiotherapy planning and should be incorporated into a redefinition of RT contouring guidelines,” they concluded.

Source: Sonni I, Dal Pra A, O’Connell D, et al. PSMA PET/CT-based atlas for prostatic bed recurrence of prostate cancer after radical prostatectomy: clinical implications for salvage radiation therapy. Abstract 157. Presented at the 2022 ASTRO Annual Meeting; October 23-26, 2022; San Antonio, TX.