KEY POINTS
- The Reirradiation Collaborative Group identified 20 published and 11 ongoing prospective studies evaluating stereotactic body radiotherapy or brachytherapy for locally recurrent prostate cancer after previous radiotherapy.
- No phase 3 trial was identified. Published studies included phase 1 and phase 2 trials and prospective observational cohorts, with sample sizes ranging from 8 to 175 patients.
- Stereotactic schedules ranged from 25–42.5 Gy in five fractions and 36–38 Gy in six fractions. High-dose-rate brachytherapy schedules included 19 Gy in one fraction, 22–27 Gy in two fractions and 30 Gy in three fractions.
- Both focal and whole-gland approaches were used, with or without a simultaneous integrated boost. Gross tumour volume was generally defined using magnetic resonance imaging and positron emission tomography.
- Clinical target volume margins for focal treatment ranged from 0 to 7 mm, while planning target volume margins generally ranged from 2 to 5 mm.
- Organ-at-risk structures and constraints varied substantially. No published study used cumulative constraints incorporating the previous radiotherapy dose, and only one ongoing study applied cumulative bladder and rectal limits.
- Most studies reported acceptable gastrointestinal and genitourinary toxicity, but some dose-escalated or whole-gland approaches produced severe events, including grade 3 urinary toxicity and grade 4 prostate-rectal fistulae.
CLINICAL TAKEAWAY
Salvage stereotactic radiotherapy or brachytherapy may provide another curative-intent option for carefully selected patients with isolated intraprostatic recurrence. Treatment should preferably be delivered within prospective studies or registries because optimal dose, target volume and cumulative organ constraints remain undefined.