KEY POINTS
- The study included 31 patients with biopsy-confirmed localized prostate cancer recurrence after whole-gland cryosurgery (n=21) or HIFU (n=10) treated with salvage proton therapy between 2007 and 2017. No patient had known nodal or distant metastatic disease at salvage.
- Median age at proton therapy was 71.1 years and median follow-up was 8.0 years. The median proton dose was 74 CGE, ranging from 70.2-82 CGE, delivered in 1.8-2.0 CGE fractions; 12 patients also received androgen deprivation therapy for a median of 7 months.
- Freedom from biochemical failure was 72.4% at 5 years and 64.7% at 10 years. Overall survival was 86.0% and 71.1% at the same time points.
- Ten-year freedom from regional failure was 73.7%, while freedom from distant failure remained 96.8%. Twelve patients developed biochemical failure, and 8 of those 12 subsequently developed pelvic nodal failure; only one patient experienced distant failure.
- Severe late toxicity was uncommon. One patient (3.2%) developed grade 3 hematuria requiring transfusion, and two (6.4%) developed transient grade 2 rectal bleeding. There were no grade ≥3 gastrointestinal toxicities, and reported events resolved after treatment.
- Patient-reported urinary and bowel outcomes remained broadly stable through 5 years. Median EPIC bowel score was 96.4 at baseline and 98.2 at 5 years, urinary score 95.5 and 95.2, and IPSS 6.5 and 6.0, respectively, although long-term responders had better baseline urinary and bowel function.
- The study predates routine PSMA-PET, pencil-beam scanning and rectal spacers, and only four patients received elective pelvic nodal irradiation. The frequent nodal component among biochemical failures raises an important staging and treatment-volume question but does not establish a benefit from elective nodal radiotherapy.
CLINICAL TAKEAWAY
Salvage proton therapy appears feasible after local recurrence following cryotherapy or HIFU, with encouraging decade-long control and low severe toxicity. The study does not demonstrate that protons are superior to modern photon salvage radiotherapy, and the small sample plus frequent subsequent nodal failures warrant prospective multicentre evaluation.