ESTRO 2024 - Abstract Book

S424

Brachytherapy - Urology

ESTRO 2024

Kelvin Yu 1 , Sarat Chander 1 , David Chang 1 , Scott Williams 1 , Tomas Kron 1 , Nick Hardcastle 1 , Sylvia Van Dyk 1 , Angelo Tzovaras 1 , David Jong 2 1 Peter MacCallum Cancer Centre, Department of Radiation Oncology, Melbourne, Australia. 2 Peter MacCallum Cancer Centreq, Department of Radiation Oncology, Melbourne, Australia

Purpose/Objective:

There is still no consensus on the optimal management of locally recurrent prostate cancers (LRPC) after definitive radiotherapy (RT). This study aims to describe the oncologic outcomes and toxicity of previously irradiated patients who had re-irradiation for LRPC at our centre.

Material/Methods:

Patients with LRPC after definitive RT between 2012 to 2023 were included. A retrospective review of electronic medical records was done to collect patient and tumour characteristics, clinical outcomes and toxicity rates. The primary endpoint included recurrence-free survival (RFS). Secondary endpoints consisted of local progression-free survival (lPFS), Metastasis-free survival (MFS) and acute and late toxicities.

Results:

A total of 11 patients were included. All patients were staged using PSMA PET, and histopathological confirmation was done in 90.9% of the cases. Seven patients were treated with SABR (7.25Gy x 5 fractions), and four patients were treated with HDR brachytherapy (12Gy x 2 fractions). Median follow-up was 27 months [range: 1-57 months]. One and two-year RFS was 62.5% and 37.5%, respectively. Castration resistance is significantly associated with lower RFS [p=0.027], while there is no significant difference in RFS between SABR and HDR (p=0.637). Four patients experienced local recurrence, resulting in one and two-year lPFS of 100% and 75%, respectively. The median time to local recurrence was 24 months, and all are out-of-field (100%). A targeted biopsy is significantly associated with lower lPFS (p=0.016). One and two-year MFS was 62% and 50%, respectively. For the six patients who did not get androgen deprivation therapy (ADT) during salvage therapy, the median ADT-free survival was 40 months. No grade 3 or higher acute and late toxicities were noted.

Conclusion:

Salvage prostate re-irradiation after definitive radiotherapy using HDR and SABR appears to be safe. Prospective, randomised studies are needed to establish patient selection, timing and effectiveness of reirradiation as salvage therapy for LRPCs

Keywords: Brachytherapy, Salvage, SABR

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