Study of Impacts on Lung Dose-Distribution as Increasing Number of Beams in Left-Sided Breast Irradiation


Objectives: The aim of this study was to analyze the impacts of increasing  number of    IMRT-beams on left lung dose-distribution in left-sided breast irradiation. Methods: We selected 105 patients retrospectively for this study diagnosed with left-sided breast cancer aged ranging from 33 to 74 years.  There were 52 cases of chest wall (CW) irradiation including SCF, 20 cases of BCS and 33 cases were of CW including supra-clavicular fossa (SCF) and internal mammary lymph nodes (IMLN). Result: Our main objective was to analyze dose-distribution of left lung. Monitor Units (MUs) were also recorded and found almost same in these three modalities ranging from 1200 to 2000. The mean value of V20Gy (cc) in 11-bIMRT technique was found less by 8-17cc as compared to 7-and 9-bIMRT technique. It was observed that 11-bIMRT technique yielded slightly better outcomes in terms of V20Gy (cc). Discussion: For this purpose, patients diagnosed with left-sided breast cancer were considered under this study. Our medical physicist team surveyed 563 studies related to randomize controlled trials of IMRT in conservatively resected breast carcinoma. Conclusion: As the number of IMRT beams increases, it translates into better outcomes in terms of reducing high-dose volume as well as mean-dose of left lung. So, it is prudent to use ‘N’ number of IMRT fields such as 7≤ N ≤11 in left breast RT


Breast Cancer, Beam, Irradiation, IMRT, Planning Target Volume