Impact of 3D conformal and Intensity Modulated Radiotherapy on secondary cancer risk for patients with early prostate cancer

Secondary cancer resulting from radiation exposure to normal tissues is always a concern. Thus, present study aimed to estimate this risk for patient receiving radiotherapy using advanced techniques like Intensity-modulated radiation therapy (IMRT) and Three-dimensional conformal radiotherapy (3DCRT). Ten prostate cancer cases were chosen, and CT images were acquired for each patient. 3DCRT and IMRT plans were generated and were compared with respect to several dosimetric parameters for Planning Target Volume (PTV) and for Organs at Risk (OARs). The second cancer risks were estimated by Excess absolute risk (EAR) for OARs. For prostate, the PTV dose coverage parameters were significantly improved in IMRT compared to 3DCRT. The rectum and bladder mean dose DMean, V50Gy, and V40Gy were significantly decreased with IMRT in comparison to 3DCRT. The maximum dose (DMax), DMean, V30Gy, and V20Gy for head of femurs significantly decreased with IMRT plans. However, the colon DMean significantly increased with IMRT compared with 3DCRT plans. Compared with the 3DCRT the IMRT plans decreased the organ equivalent dose (OED) in rectum based on the linear, plateau and linear-exponential models. The OED for the bladder also decreased with linear model in IMRT plan. While, the OED for the colon significantly increased in IMRT. The IMRT plans were decreased second cancer risk for the rectum by 10%, 26.6% and 19.5% for linear, plateau and linear-exponential dose-response models respectively. The bladder second cancer risk was decreased by 14% with linear dose-response model in comparison to 3DCRT plans. However, the second cancer risk for colon was significantly increased in average by 91.2% with IMRT plans. IMRT technique demonstrated a clear advantage in dose coverage, conformity, and homogeneity over 3DCRT and was superior in terms of OAR-sparing. The Second cancer risk for in field organs (rectum and bladder) was decreased with IMRT compared to 3DCRT plan.