"Cumulative incidence of toxicity between 2 and 5 years following SBRT to the prostate and pelvis nodes in patients with high-risk prostate cancer ".

Abstract

Stereotactic body radiotherapy (SBRT) is increasingly used for localized prostate cancer, but data on SBRT with pelvic nodal irradiation in patients with high-risk disease remain limited. We report late genitourinary (GU) and gastrointestinal (GI) toxicities and clinical outcomes in patients with high-risk prostate cancer treated with SBRT in 5 fractions to the prostate and pelvic lymph nodes. We reviewed 101 patients with high-risk prostate cancer treated with SBRT between August 2019 and May 2023. Treatment consisted of 36.25 Gy in 5 fractions to the prostate with a simultaneous dose of 25 Gy to the pelvic lymph nodes. Patients received 6 to 18 months of androgen deprivation therapy. Toxicity was prospectively assessed according to CTCAE version 4.0. Late toxicity was defined as events occurring ≥ 3 months after SBRT. Survival outcomes were estimated using Kaplan-Meier methods. All patients had a minimum follow-up of 24 months. With a median follow-up of 43.8 months (range 26-70 months), late grade 1 and 2 GI toxicity occurred in 4 patients (4%), including three cases of rectal bleeding and one case of fecal incontinence. Late grade 1 and 2 GU toxicity occurred in 13 patients (13%), including 5 grade 2 events (5%). No grade ≥ 3 GI or GU toxicity was observed. The 5-year actuarial biochemical recurrence-free survival was 89.5%, with distant metastasis-free survival of 96.2% and overall survival of 98.8%. SBRT delivered in five fractions with pelvic nodal irradiation appears feasible and associated with low rates of late GU and GI toxicity in patients with high-risk prostate cancer. Ongoing randomized trials will provide definitive evidence regarding the role of SBRT with pelvic nodal irradiation in this population.