Hypofractionated Hybrid Radiotherapy Techniques for Synchronous Bilateral Breast Cancer

This study intends at a dosimetric comparison of four different hybrid plans which is a combination of different radiation therapy techniques, for synchronous bilateral breast cancer (SBBC) irradiation using a hypofractionated dose regimen.

Four different hybrid techniques: 3DCRT+IMRT, 3DCRT+VMAT, IMRT+VMAT, and VMAT+IMRT were planned using computed tomography (CT) images of fifteen SBBC patients.  All hybrid plans were generated using a hypofractionated dose prescription of 40.5 Gy in 15 fractions. 70% of the dose was planned with a base-dose component and the remaining 30% of the dose was planned with a hybrid component. The plans were evaluated based on the PTV and organs at risk (OARs) dosimetric parameter results and computed a plan quality score for each plan.

The results for PTV parameters have shown that the 3DCRT+VMAT and 3DCRT+IMRT plans were better than other plans. The 3DCRT±IMRT plan was provided better results for OARs, while IMRT±VMAT and VMAT+IMRT plans were increased the low dose volumes to the heart and lungs. The 3DCRT+VMAT plan was required less monitor units and treatment time compared to other plans.

The overall plan quality score that integrated the dosimetric parameters of PTV and OARs indicated that the 3DCRT+VMAT hybrid plan is superior for SBBC treatment.