Dose Volume Relationship in Estimating Cardiac Doses in Breast Cancer Radiotherapy

Abstract

Introduction: Radiation therapy is an integral part of adjuvant treatment for breast cancer which reduces local recurrence and significantly increases survival. But, radiation therapy also has the propensity to increase cardiac morbidity and mortality due to dose received by the heart which is more in left-sided breast cancer. Mean Heart dose and Maximum Heart Distance (MHD) are two parameters to study dose received by the heart. Aim: The purpose of this study was to determine individual doses received by the heart and to correlate MHD with the mean heart dose received by heart in carcinoma breast patients receiving radiotherapy. Materials and Methods: Ninety patients of histologically proven carcinoma breast who attended the Department of Radiotherapy, Acharya Harihar Regional Cancer, Cuttack from January 2017 to January 2019 were selected for a prospective observational study. All patients were treated with 3D Conformal Radiotherapy technique using free breathing multi slice Computed Tomography (CT) scans to contour target and vital organs. Parallel opposed tangential treatment plans were generated for each patient. Individual dose received by the heart and MHD was assessed for each case. SPSS version 21 used for statistical analysis. The Spearman’s Rho test was used for correlation of MHD with Mean heart dose. The Mann-Whitney U test was used for comparing mean of MHD in left-sided and right-sided breast cancer. The Independent t-test was used for comparing means of Mean heart dose in left-sided and right-sided breast cancer. A p-value <0.05 was considered as statistically significant. Results: The Mean Heart Dose was 4.63 Gy for left-sided breast carcinoma patients and 0.846 Gy for right-sided breast cancer and there was a significant difference (p<0.001). Mean MHD for left-sided breast cancer was 2.974 cm while for right-sided it was 0.017 cm, the difference was statistically significant (p-value <0.001). MHD also correlated positively with Mean Heart Dose with correlation coefficient of 0.849 and p-value <0.001. Conclusion: MHD and Mean Heart dose were significantly higher in left-sided breast cancer receiving radiotherapy. MHD was also found to be positively related to Mean Heart dose and therefore found to be an important predictor of cardiac dose. For right-sided breast carcinoma receiving radiotherapy, free breathing technique using 3-Dimensional Conformal Radiotherapy (3DCRT) will suffice in terms of cardiac dose.