Aim: To identify factors influencing toxicity in patients affected by localized prostate cancer treated with conformal image-guided radiotherapy.
Background: Image guidance in combination with conformal techniques is the standard of care in localized prostate cancer, but factors affecting toxicity are still under investigation.
Materials and methods: 294 patients were analyzed. Median age at diagnosis was 71 year. 76 Gy (38 × 2 Gy) were delivered to the target volume. We used the χ2 test to analyse associations between toxicity and dosimetric and clinical parameters. Multivariate analysis was performed using binary logistic regression. Kaplan-Meier method was used for survival analysis.
Results: Median follow-up was 62.9 months. Acute grade ≥2 gastro-intestinal toxicity (GI) was 12.1%. Acute genito-urinary (GU) toxicity of grade ≥2 was 33.9%. Actuarial 4 and 5 years late grade ≥2 GI was 3% and 4%, respectively. Four and 5-year late grade ≥2 GU toxicity was 6% and 10%. At multivariate analysis for acute toxicity rectal V70 was correlated with GI toxicity (p = 0.01, HR 2.73 CI 1.19-6.26), and smoking habit with GU toxicity (p < 0.01, HR 2.50 CI 1.51-4.14). For late toxicity, rectal V70 was correlated with gastro-intestinal toxicity (p = 0.04, HR 4.76 CI 1.07-21.13), and pre-radiotherapy urinary symptoms with genito-urinary toxicity (p = 0.01, HR 2.84 CI 1.29-6.22).
Discussion: Conformal image-guided radiotherapy shows low rates of toxicity. Smoking should be avoided during radiotherapy. Besides the evaluation of high doses received by the organs at risk, individual factors, such as co-morbidities and lifestyle choices, have an impact on normal-tissue complication risk.
Keywords: Cone-beam CT; Conformal radiotherapy; Prostate cancer; Toxicity; Volumetric image-guidance.