Comparison of Hybrid IMRT Plans for Breast Cancer Utilizing the Variable Ratio of ۳DCRT 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 ۳DCRT and IMRT treatment plans in the Hybrid IMRT Plan. Material and Methods: The study involved ۱۵ left-side breast cancer patients selected from our hospital's medical records. Three different planning strategies were created namely ۳DCRT, IMRT and Hybrid IMRT plans. Different ratios of ۳DCRT 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 ۱۶.۱, Varian Medical Systems, Palo Alto, CA, USA), with a prescription dose ۴۰.۰۵Gy in ۱۵ fractions. Results: Hybrid IMRT ۸۰%, ۶۰%, ۴۰%, and ۲۰% had Unique Dosimetric Index (UDI) scores of ۰.۹۸۹ ±۰.۰۲۲, ۰.۹۹۷±۰.۲۵۶, ۰.۰۹۹۹±۰.۰۲۶, and ۰.۹۹۵۸±۰.۰۲۹۱. The hybrid IMRT۸۰% treatment plan had the lowest Total MU of ۴۹۷.۳۳±۴۵.۳۶, and V۲۰Gy of Ipsilateral lung was ۱۶.۹۳±۳.۵۰%, compared to ۱۷.۱۴±۳.۳۹%, ۱۷.۵۱±۳.۱۴%, and ۱۷.۷۳±۳.۰% in IMRT۶۰%, IMRT۴۰%, and IMRT۲۰%. Heart mean dose was lowest in IMRT۸۰% (۴.۱۳±۱.۴۷Gy) and increased insignificantly from ۴.۴۲۶±۱.۳۴۴Gy to ۴.۵۱±۱.۳۴۴Gy in ۳DCRT and IMRT۱۰۰%. Conclusion: The present dosimetry analysis recommends that hybrid IMRT should be ۸۰% ۳DCRT open field and ۲۰% IMRT plan to spare lungs and heart and cover the planning target volume.

Keywords:

۳DCRT , FiF Hybrid , IMRT IMRT Dosimetry left , sided Chest wall