A Retrospective Dosimetric Study in Breast Cancer Patients Who Received Conformal Radiation Therapy for Achievability of Recommended Dose Constraints of RTOG, DBCG, EORTC for Lung and Heart

Abstract

In India, carcinoma of breast is the commonest malignancy among women. In multidisciplinary approach of its management, radiotherapy (RT) is an important component. Different cooperative groups have defined dose constraints to lungs and heart to minimize these late side effects such as radiation pneumonitis and coronary artery disease. To assess the achievability of dose constraints given for lung and heart by RTOG, EORTC and DBCG in our cohort of breast cancer patients who underwent conformal radiation therapy to chest wall / breast along with supraclavicular nodal region. This retrospective dosimetric study included all breast cancer patients who underwent conformal radiation in our institute from Jan 2021 to Dec 2022 and was treated with a dose of 40 Gy in 15 fractions. A total of 302 patients (162 - Left sided, 140 - Right sided) were in the study cohort. Majority of them received RT with 3DCRT with FiF (266 patients) and 36 patients received RT by VMAT technique. Respiratory gating was done in left sided breast cancer by DIBH for 46.2 % of patients due to COVID pandemic during this period. Our analysis showed that for the ipsilateral lung, EORTC (77.8%) dose constraints were easy to achieve followed by DBCG (65.2%) and RTOG (61.9 %). For the heart constraints in left sided breast cancer patients, easily achievable constraints were by DBCG (91.9 %) followed by RTOG (66.6 %) and EORTC (53.1%). The DBCG constraints of Dmean <5 Gy was more liberal than any other recommendations. All the dose constraint recommendations were easily achieved for heart in right sided breast cancer patients, by more than 90 % of the population. Usage of respiratory gating with DIBH technique improves the rates of achievability of lung constraints in 56 (74.6%) out of 75 patient and heart constraints in 54 (72 %) out of 75 patients. Our institutional policy is to treat chest wall / breast along with supraclavicular nodal chain in case of NACT or T3/T4 disease and this could have been the reason why we were unable to achieved the dose constraints recommended. The DBCG dose constraint recommendations for heart was achieved in the left chest wall treatment in majority of women and EORTC was best achieved for ipsilateral lung. All heart dose constraint recommendations were achieved for right chest wall treatment. Respiratory gating improves achievability rates of the recommendations. It is difficult to achieve all the dose constraints as recommended by different cooperative groups as there is variation among them.