Extreme hypofractionated stereotactic radiotherapy for elderly prostate cancer patients: side effects preliminary analysis of a phase II trial

Purpose: Aim of this study is to evaluate safety and efficacy of SBRT in elderly patients affected by localized prostate cancer (PC). Material and methods: Men aged 70 years or older were enrolled and analyzed. The SBRT schedule was 35 Gy in 5 fractions administered in 1-2 weeks. According to risk group, androgen deprivation therapy (ADT) was prescribed. Urinary symptoms were evaluated at baseline using the International Prostate Symptom Score (IPSS). Genitourinary (GU) and gastrointestinal (GI) toxicities were assessed at the end of treatment, 2 weeks after SBRT and during follow-up using the Common Terminology Criteria for Adverse Events (CTCAE). PSA values were recorded before treatment and during follow-up as biochemical response criteria. Results: Between 07/2019 and 09/2021, 111 patients were enrolled. Median age was 77 years. At the end of treatment, no acute GU/GI toxicities ≥ G2 were observed. At 2-3 weeks after treatment, 3 patients reported G2 GU toxicity, while 14 patients referred G2 GI toxicity. During the last follow up, 26 and 2 patients reported, respectively, G1 and G2 GU toxicity, while 22 and 1 cases described, respectively, G1 and G2 GI toxicity. No late toxicities ≥ G3 were recorded. GU toxicity is related to absence of urethra sparing, increasing PTV volume, Dmax PTV and IPSS; GI toxicity is related to RT schedule (each other day is better than consecutive day), Dmax rectum and IPSS, At a median follow-up of 24 months, excellent biochemical disease control was achieved in all cases with median PSA of 0.5 ng/ml. Conclusion: SBRT in elderly patients affected by PC is feasible and well tolerated with excellent biochemical disease control. Longer follow-up is needed to assess late toxicity profile and long-term clinical outcome.