MRI-guided ultrafocal salvage high-dose-rate brachytherapy for localized radiorecurrent prostate cancer: updated results of 50 patients.

Most patients with local prostate cancer recurrence after radiation therapy undergo palliative androgen deprivation therapy (ADT), since whole-gland salvage treatments have a high risk of severe toxicity. Focal treatment reduces this risk while offering a second opportunity for cure. We report updated outcomes of ultrafocal salvage high-dose-rate brachytherapy (HDR-BT).

Prospectively collected data from the first 50 treated patients were analyzed. Disease status was assessed by 3T multiparametric MRI, 18F-Choline or 68Ga-PSMA PET/CT and systematic or tumor-targeted biopsies. Ultrafocal salvage HDR-BT (1x19 Gy) was performed by implanting the clinical target volume (CTV: gross tumor volume + 5mm margin) under fused TRUS/MRI guidance. Follow-up included toxicity grading (using CTCAE 4.0), quality of life (QoL) assessment and PSA-testing.

Median follow-up was 31 months. Median CTV D95% was 18.8 Gy. We observed 2% grade 3 genitourinary toxicity, no grade 3 gastro-intestinal toxicity and 22% newly developed grade 3 erectile dysfunction. Five out of 13 patients (38%) with self-reported pre-treatment potency (IIEF>17) remained potent. Clinically relevant QoL deterioration was reported for only 6/31 items, not statistically significant. Biochemical failure (nadir+2) occurred in 26 patients. Among intraprostatic recurrences, 73% were in-field. After 2.5 years, biochemical disease-free survival (BDFS) was 51% (95% CI 37-69%), metastases-free survival 75% (64-89%), ADT-free survival 90% (82-99%) and overall survival 98% (94-100%). Pre-salvage PSA, CTV size and stage ≥T3 were significantly associated with biochemical failure. Higher-risk patients (stage≥T3, PSA≥10, or PSADT≤9 months) had 25% BDFS at 2.5 years versus 71% for lower-risk patients.

At this early stage, MRI-guided ultrafocal HDR-BT seems to be a safe salvage treatment option, with acceptable biochemical control in a well-selected group of patients, and the potential of effectively postponing ADT.

International journal of radiation oncology, biology, physics. 2020 Jan 29 [Epub ahead of print]

M J van Son, M Peters, M A Moerland, J J W Lagendijk, W S C Eppinga, T T Shah, H U Ahmed, J R N van der Voort van Zyp

Department of Radiotherapy, University Medical Center Utrecht, the Netherlands. Electronic address: ., Department of Radiotherapy, University Medical Center Utrecht, the Netherlands., Division of Surgery, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, UK; Department of Urology, Charing Cross Hospital, Imperial College Healthcare NHS Trust, London, UK.