Salvage radiotherapy with volumetric modulated arc therapy (VMAT) for recurrent prostate cancer after high-intensity focused ultrasound (HIFU): A large French retrospective series and literature review

Abstract

Background and purpose: Although not validated as a standard treatment, high-intensity focused ultrasound (HIFU) is increasingly used in the management of localised prostate cancer (PCa). In case of recurrence after HIFU, treatment is currently not standardised. Our aim was to evaluate normofractionated (NFRT) and hypofractionated (HFRT) salvage radiotherapy (RT) using volumetric modulated arc therapy (s-VMAT) with doses used in first-line management of localised PCa.

Material and methods: We identified all patients with local or locoregional recurrence after HIFU treated with s-VMAT in 3 RT centres between 2014 and 2023. We evaluated acute and late toxicity and oncological outcomes.

Results: Fifty-six patients were identified. Median age at recurrence was 75 (70-80) years. Median time between HIFU and s-VMAT was 26.5 months (13.9-47.2). S-VMAT was delivered to the prostate only in 35 (62.5 %) patients and to the prostate and pelvis in 21 (37.5 %) patients. NFRT and HFRT were delivered in 46 (82.1 %) and 10 (17.9 %) patients, respectively. Androgen deprivation therapy (ADT) was given to 27 (48.2 %) patients. Eighteen (32 %) and four (7 %) patients reported an acute grade 2 genitourinary (GU) and gastrointestinal (GI) adverse event (AE), respectively. Two patients presented with a late grade 2 GU AE, and one with a late grade 2 GI AE. No grade 3+ toxicity was reported. With a median follow-up of 19.5 months (12 - 47), no patient had a biochemical, local or distant relapse.

Conclusions: This is the largest series of salvage RT after HIFU using VMAT and escalated doses (78-80 Gy/39-40Fr., or 60 Gy/20Fr.). Acute toxicity was acceptable and late AEs were few. Longer follow-up is required to assess efficacy. Overall, available series suggest that salvage RT could represent a valuable option in the treatment of relapses after HIFU.

Keywords: High-intensity focal ultrasound; Localised prostate cancer; Radiotherapy; Salvage treatment; VMAT; Volumetric modulated arc therapy.