Recently with the simultaneous advent of both prostate-specific PET imaging and highly conformal, stereotactic body radiation therapy (SBRT), there has been great enthusiasm for the treatment of locally recurrent prostate cancer with SBRT. A recent meta-analysis has suggested that salvage SBRT may provide an excellent therapeutic index for local salvage with acceptable effectiveness and manageable toxicity (PMID: 33309278). However, to our knowledge, there have been no prospective studies profiling this treatment post-brachytherapy.
Here we present the first prospective trial for salvage SBRT paradigm after brachytherapy, NCT03253744 (summarized in the video overview below). Of note, this trial had a complementary arm investigating treatment post-EBRT which was previously reported (PMID: 37442430) and discussed on UroToday. The principal finding of our trial is that while salvage SBRT is tolerable by our pre-specified stopping rules, it did result in clinically significant toxicities amongst the patients treated, especially in the subacute period (~6-12 months post-treatment).
The early evidence from this trial also points to the efficacy of this treatment, although it should be noted that this is in a well selected cohort of patients with minimal baseline toxicity from prior treatment who underwent thorough re-staging with state-of-the-art imaging and targeted biopsy mapping. The doses evaluated were associated with excellent biochemical control in this small cohort but significant moderate grade toxicity, thus the optimal dose to provide control for recurrence with minimal toxicity in this setting remains uncertain. Finally, the radiation therapy was administered under research conditions with ideal bowel preparation prior to each treatment and an expert, prostate-specialized radiation oncologist monitoring intra-fraction motion with intra-fraction imaging. As such, we do not believe that these findings would currently generalize to routine clinical practice and we continue to advocate that such patients be treated in clinical trials.
Written by: Krishnan R. Patel, MD, Radiation Oncology Branch, National Cancer Institute, NIH, Bethesda, MD
References:
- Dr. Krishnan Patel on Salvage SBRT for Radiorecurrent PCa after Brachytherapy. International Journal of Radiation Oncology, Biology, Physics. 2024. https://www.redjournal.org/video-do/dr-krishnan-patel-salvage-sbrt-radiorecurrent-pca-after-brachytherapy.
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