Salvage radiotherapy following HiFU: An institutional series and literature review

INTRODUCTION: Algorithms for the treatment of prostate cancer (PrCa) rely on risk grouping, and those who fall into low (LR) and favourable intermediate risk (FIR) categories have multiple options for treatment. High-intensity focused ultrasound (HiFU) is a local treatment modality that uses ultrasound waves to ablate prostate cancer. In case of treatment failure, optimal salvage modality after HiFU remains unclear. METHODS: Here, we describe a retrospective review of our regional cancer database for men who underwent salvage radiotherapy after failure of HiFU treatment for prostate cancer. Oncologic and toxicity outcomes of the men identified in our database are discussed. RESULTS: We identified 14 men in our regional database who received salvage radiotherapy (70-74 Gy with or without androgen deprivation therapy (ADT) after primary HiFU, in the period of 2009-2017. No cases of any grade 3 or higher toxicity were observed. In our cohort, 50% (7/14) of patients developed secondary biochemical failure at a median follow-up of 54 months post-radiotherapy, with a mean time to biochemical failure of 39 months. We compare our data to other available reports to date consisting mostly of small, non-randomized studies. Our biochemical control rates are noticeably lower compared with those reported by other studies but our length of follow-up is longer, compared with other studies. CONCLUSION: The available data to date suggest that salvage radiotherapy after HiFU failure is well-tolerated albeit with only modest efficacy.