Assessment of the Second Cancer Risk after Prostate Cancer Treatment: Comparison of ۳D Conformal Radiotherapy and Intensity Modulated Radiotherapy

Introduction: Radiation-induced secondary primary cancer is one of the significant late side effects and an undesired outcome of radiotherapy that can be observed in long-term cancer survivors. The present study aimed to estimate the risk of second cancer risk after Three-dimensional conformal radiotherapy (۳DCRT) and intensity modulated radiotherapy (IMRT) for early stage prostate cancer patient.Material and Methods: In this study, ۱۰ patients with early stage prostate cancer have been chosen. Three-dimensional conformal radiotherapy (۳DCRT), intensity-modulated radiotherapy (IMRT) plans were designed. The organ equivalent dose (OED) was calculated based on linear, linear-exponential, and plateau dose-response models. The Second cancer risks (SCR) were estimated by Excess absolute risk (EAR).Results: The target dose coverage parameters were significantly improved in IMRT compared to ۳DCRT. The rectum and bladder mean dose DMean, V۵۰Gy% and V۴۰Gy % were significantly decreased with IMRT. The maximum dose (DMax), DMean, V۳۰Gy % and V۲۰Gy % for head of femurs significantly decreased with IMRT plans. However, the colon DMean significantly increased with in IMRT compared with ۳DCRT. The IMRT plans were decreased SCR for the rectum by ۱۰%, ۲۶.۶% and ۱۹.۵% for linear, plateau and linear-exponential dose- response models respectively. The bladder second cancer risk was decreased by ۱۴% with linear dose-response model in comparison to ۳DCRT plans. However, the second cancer risk for colon was significantly increased in average by ۹۱.۲% with IMRT plans.Conclusion: IMRT technique demonstrated a clear advantage in dose coverage, conformity, and homogeneity over ۳DCRT and was superior in terms of OAR-sparing. The Second cancer risk for in field organs (rectum and bladder) was decreased with IMRT compared ۳DCRT plan.

Keywords:

Three , Dimensional Conformal Radiotherapy (۳DCRT) Intensity Modulated Radiotherapy (IMRT) Second Cancer Risk Prostate Cancer Organ Equivalent Dose (OED) Excess Absolute Risk (EAR)