Serial stereotactic body radiation therapy (SBRT) directed by PET using novel radiotracers may offer clinical benefits in patients with oligometastatic prostate cancer, according to a study published in Urologic Oncology.

The study’s findings suggest that a second course of SBRT for men with recurrent oligometastatic prostate cancer following an initial course of SBRT is an important therapeutic strategy to consider, according to researchers.

The study included 25 men with 1-5 prostate cancer metastases detected on prostate-specific membrane antigen (PSMA) or fluciclovine PET and who underwent 2 consecutive courses of SBRT. At the time of the second SBRT course, PSMA and fluciclovine PET detected oligorecurrent disease in 17 (68%) and 8 (32%) patients, respectively. Of the 25 patients, 15 (60%) had castration-sensitive disease and 10 (40%) had castration-resistant disease.


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Following the second SBRT course, 16 patients (64%) achieved a 50% or greater decline in prostate-specific antigen level (PSA50). The median progression-free survival (PFS) was 11 months. The median survival time without initiation or intensification of androgen deprivation therapy (ADT) was 23.2 months. From the first SBRT course to the last follow-up (a median of 48 months), 7 patients (28%) remained ADT-free.

A PSA50 response after the first SBRT course was significantly associated with a 64% decreased risk for disease progression and a 93% decreased risk for ADT initiation or intensification after the second SBRT course.

“Degree of biochemical response to first SBRT warrants further study as a potential predictor of PSA response, PFS, and ADT initiation/intensification-free survival following a subsequent SBRT course,” the researchers wrote.

After controlling for potential confounders, the degree of biochemical response after the first SBRT course and concurrent change in systemic therapy with the second SBRT course were significantly associated with a greater likelihood of a PSA50 response and longer PFS after the second SBRT course.

“Our study adds to the limited but growing literature supporting the feasibility and potential clinical benefit of serial metastasis-directed SBRT guided by novel radiotracers and PET imaging,” the researchers wrote.

They added that their preliminary findings provide a rationale for larger and prospective studies of serial SBRT.

Reference

Kwon DH, Shakhnazaryan N, Shui D, et al. Serial stereotactic body radiation therapy for oligometastatic prostate cancer detected by novel PET-based radiotracers. Urol Oncol. Published online November 24, 2022. doi:10.1016/j.urolonc.2022.10.025

This article originally appeared on Renal and Urology News