On Prediction of Cardio-Pulmonary Complications during Hypofractionated versus Conventional Fractionated Regimens of Left Breast Radiation Therapy Using Monte Carlo and Collapsed Cone Convolution Based Algorithms

Introduction: Due to the challenge of choosing the optimal treatment regimen as well as the accurate dose calculation algorithm (DCA), this study aimed to evaluate the DCAs to compare the conventional fractionation radiotherapy (CFRT) and hypofractionation radiotherapy (HFRT) of breast cancer (BC) in the prediction of cardio-pulmonary complications. Material and Methods: For ۱۹ patients with left-sided BC, treatment regimens, CFRT (۵۰Gy/۲۵frs) vs. HFRT (۴۲.۵Gy/۱۶frs), were simulated. Normal tissue complication probability (NTCP) and tumor control probability (TCP) values for each regimen using radiobiological models were calculated via Monte Carlo (MC) and Collapsed Cone Convolution (CCC) algorithms. For statistical comparison of the results obtained from the regimens and algorithms, the t-test and Wilcoxon test were used in SPSS Statistics. Statistical significance was defined as p<۰.۰۵. Results: The mean NTCP and TCP calculated in CFRT and HFRT were as follows: cardiac mortality (MC: CFRT=۰.۰۳۷۴±۰.۰۱۳۴ vs. HFRT=۰.۰۱۷۳±۰.۰۰۶۶; p<۰.۰۰۱) and (CCC: CFRT=۰.۰۳۷۳±۰.۰۱۳۴ vs. HFRT=۰.۰۱۶۸±۰.۰۰۶۴; p<۰.۰۰۱), pneumonitis (MC: CFRT=۰.۱۲۰۱±۰.۰۳۲۲ vs. HFRT=۰.۰۷۵۶±۰.۰۲۲۱; p<۰.۰۰۱) and (CCC: CFRT=۰.۱۱۳۱±۰.۰۳۱۰ vs. HFRT=۰.۰۶۹۷±۰.۰۱۲۰; p<۰.۰۱۰), and TCP (MC: CFRT=۰.۹۹۷۹±۰.۰۰۸۷ vs. HFRT=۰.۹۹۹۷±۰.۰۰۹۲; p=۰.۵۹۳) and (CCC: CFRT=۰.۹۹۸۲±۰.۰۰۲۹ vs. HFRT=۰.۹۹۸۶±۰.۰۰۱۶; p=۰.۸۲۱). Conclusion: The comparison of CFRT and HFRT using MC and CCC algorithms showed that the risk of cardiac mortality and pneumonitis in CFRT was significantly higher than in HFRT, and TCP was not significantly different in the two regimens. Applications of MC-based DCAs along with suitable biological parameters can help physicists in the prediction of radiation-induced complications accurately and precisely.