Prostate cancer: evaluation of outcomes and prognostic factors in adjuvant and salvage radiation treatment

Adjuvant radiotherapy in prostate cancer: impact of older age and hypofractionated regimens on acute and late toxicity. A multicenter comprehensive analysis Background: The objective of this study was to assess the impact of patient and treatment characteristics on toxicity in prostate cancer patients receiving adjuvant radiotherapy (RT). Materials and methods: This observational study evaluated both acute and late toxicity. Patient- (age; Charlson’s comorbidity index) and treatment-related characteristics (nodal irradiation; previous TURP; use, type, and duration of ADT, RT fractionation and technique, image-guidance systems, EQD2 delivered to prostate bed and pelvic nodes) were recorded and analyzed. Results: A total of 381 patients were enrolled. The median EQD2 to the prostate bed was 71.4 Gy. 75.4% of patients were treated with intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT). Acute G3 gastrointestinal (GI) and genitourinary (GU) toxicity rates were 0.5% and 1.3%, respectively. No patients experienced >G3 acute toxicity. The multivariable analysis of acute toxicity showed a statistically significant association between older age (> 65) and decreased odds of G≥2 GI acute toxicity (OR: 0.569; 95%CI: 0.329-0.973; p: 0.040) and decreased odds of G≥2 GU acute toxicity (OR: 0.956; 95%CI: 0.918- 0.996; p: 0.031). The 5-year late toxicity-free survival rates for G≥3 GI and GU toxicity were 98.1% and 94.5%, respectively. The only significant correlation found (Cox’s regression model) was a reduced risk of late GI toxicity in patients undergoing hypofractionation (HR: 0.38; 95% CI: 0.18-0.78; p: 0.008). Conclusions: The unexpected results of this analysis could be explained by a “response shift bias” concerning the protective effect of older age and by treatment in later periods (using IMRT/VMAT) concerning the favorable effect of hypofractionation. However, the study suggests that age should not be a reason to avoid adjuvant RT and that the latter is well-tolerated even with moderately hypofractionated regimens.