impacts of increasing the number of imrt beams on heart’s dose distribution in left breast irradiation: dosimetric study

Introduction: the main objective of this study was to assess the impacts of an increasing the number of imrt beams on cardiac dose distribution in left-sided breast irradiation so that we can reduce the heart’s mean dose up to clinically acceptable level. material and methods: for this study 107 female patients, diagnosed with left-sided breast cancer were selected retrospectively. in 107 patients, there were 52 patients of chest wall irradiation including supra-clavicular fossa, while 22 patients were of breast-conserving surgery excluding supra-clavicular fossa and internal mammary lymph nodes, and 33 patients were of chest wall irradiation including internal mammary lymph nodes and supra-clavicular fossa. exclusion criteria were previous history of left-sided breast radiation therapy, uncommon fractionated dose delivered in past, and indication of palliative radiation therapy. intensity modulated radiotherapy plans were generated using 7, 9 and11 beams for each patient and the prescribed dose was 40.05 gy in 15 fractions (2.67 gy /fraction) for the targets. results: heart: v5gy(cc): this was a low-dose volume of our study in which the 11-bimrt technique yielded better result as compared to 9- and 7-bimrt. maximum and minimum values of v5 were found 539.60cc in 9-bimrt and 141.32cc in 11-bimrt techniques respectively.v25gy(cc): the maximum value of v25gy was found 41.73cc in 7-bimrt technique, while the lowest value was 0.29cc in 11-bimrt. the imrt technique with 11 beams showed comparatively better result on this parameter as well as 3-5cc volume of v25gy was spared. mean dose (gy): maximum value of mean dose was found 8.51gy in 7-bimrt while it was 6.53gy in 11-bimrt technique. conclusion: the study indicates that increasing the number of imrt beams reduces heart’s high-dose volume and improves the quality of treatment plans. it is judicious to use 11-bimrt technique in left-sided breast irradiation as it produces clinically acceptable mean heart dose.