Variation In Mean Heart Dose By Treatment Plan Optimization During Radiotherapy For Left Sided Breast Cancer

Introduction: Radiotherapy (RT) plays a major role in the management of breast cancer. Cardiac Toxicity is an important late complication of radiotherapy for left sided Breast cancer. Cardiac morbidity can be minimized through careful treatment planning. Aim: To study the variation of dose to the heart by change in the depth of normalization point during Radiotherapy planning. Settings and design: Prospective , dosimetric evaluation study. Materials & Methods: Twenty patients who underwent Left sided Breast Conservation Surgery and registered for Radiotherapy (RT) were simulated on CT Simulator and the Computed tomography images were transferred to the treatment planning system. Target volume and the organ at risks were contoured. Radiotherapy Planning for whole breast was done with tangential fields with additional loco-regional nodal radiotherapy where indicated. The tangential fields were optimized with change of normalization points (P1, P2, P3 and P4) in four different RT plans. Dose to the whole breast and heart was compared for all plans. Patients under went pretreatment cardiac assessment and echocardiography Results: In optimization of the tangential field for whole breast RT all plans have shown adequate coverage of Planning Target Volume (PTV). The mean heart dose received was 5.07 Gray (Gy), 4.85 Gy, 5.0 Gy and 5.86 Gy by normalization at P1, P2, P3 and P4 respectively. Simple optimization can vary mean heart dose by 17% with absolute decrease in mean heart dose by 1.01Gy. Conclusion: Optimization of tangential fields can be a useful and easy tool to decrease mean dose to the heart for treating left sided breast cancer especially at centers with limited resources.