comparison of hybrid imrt plans for breast cancer utilizing the variable ratio of 3dcrt and imrt components to establish an optimal plan for target coverage with sparing lung and heart

Introduction: intensity modulated radiation therapy (imrt) and volumetric modulated arc therapy vmat  enhance ptv coverage, compliance, and homogeneity while minimizing heart and ipsilateral (il) lung exposure. however, they may increase organ at risks (oars) dosage and require additional mus, raising cancer recurrence risk. hybrid treatment planning is ideal for ca-breast treatments without complex treatment planning technique.study aims to achieve the optimal ratio of 3dcrt and imrt treatment plans in the hybrid imrt plan.material and methods: the study involved 15 left-side breast cancer patients selected from our hospital’s medical records. three different planning strategies were created namely 3dcrt, imrt and hybrid imrt plans. different ratios of 3dcrt and imrt treatment plans were kept while creating the hybrid imrt treatment plans. all treatment plans were made in the treatment planning system (tps) eclipse (version 16.1, varian medical systems, palo alto, ca, usa), with a prescription dose 40.05gy in 15 fractions.results: hybrid imrt 80%, 60%, 40%, and 20% had unique dosimetric index (udi) scores of 0.989 ±0.022, 0.997±0.256, 0.0999±0.026, and 0.9958±0.0291. the hybrid imrt80% treatment plan had the lowest total mu of 497.33±45.36, and v20gy of ipsilateral lung was 16.93±3.50%, compared to 17.14±3.39%, 17.51±3.14%, and 17.73±3.0% in imrt60%, imrt40%, and imrt20%. heart mean dose was lowest in imrt80% (4.13±1.47gy) and increased insignificantly from 4.426±1.344gy to 4.51±1.344gy in 3dcrt and imrt100%.conclusion: the present dosimetry analysis recommends that hybrid imrt should be 80% 3dcrt open field and 20% imrt plan to spare lungs and heart and cover the planning target volume.