Risk factors for the long‐term persistent genitourinary toxicity after stereotactic body radiation therapy for localized prostate cancer: A single‐center, retrospective study of 306 patients

Abstract

ObjectivesTo identify risk factors for the long‐term persistent genitourinary toxicity (GUT) after stereotactic body radiation therapy (SBRT) for localized prostate cancer (PCa).MethodsA total of 306 patients who underwent SBRT at our institution between March 2017 and April 2022 were retrospectively evaluated. SBRT was performed at 35 Gy in five fractions over 5 or 10 days. Factors related to the long‐term persistence of acute GUT after SBRT were analyzed.ResultsDuring the median follow‐up period of 39.1 months, 203 (66%) patients experienced any grade of acute GUT, which remained in 78 (26%) patients 6 months after SBRT. Multivariate analysis revealed that age ≥75 years was consistently a significant independent risk factor for any grade of acute GUT 6, 12, and 24 months after SBRT (hazard ratio [HR] 2.31, p = 0.010; HR 2.84, p = 0001; and HR 3.05, p = 0.009, respectively). Older age was not a significant risk factor for the development of grade ≥2 acute GUT. The duration of acute GUT was significantly longer in the older group than in the nonolder group (median duration = 234 vs. 61 days, p < 0.001), and the incidence of persistent GUT was significantly more frequent in the older group beyond 6 months after SBRT.ConclusionsOlder age is a significant independent risk factor for the long‐term persistent GUT after SBRT for localized PCa.