Serial stereotactic body radiation therapy (SBRT) directed by positron emission tomography (PET) using novel radiotracers may offer clinical benefits in patients with oligometastatic prostate cancer, according to a recent retrospective study.

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, Daniel H. Kwon, MD, of the University of California, San Francisco, and colleagues reported in Urologic Oncology.

The study included 25 men with 1-5 prostate cancer metastases detected on PSMA (prostate-specific membrane antigen) 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 PSA level (PSA50), Dr Kwon’s team reported. The median progression-free survival (PFS) time 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, Dr Kwon’s team reported.

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,” they concluded.

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, according to the investigators.

“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 authors wrote.

The authors wrote that their preliminary findings provide a rationale for larger and prospective studies of serial SBRT.


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