This study aimed to evaluate the clinical impact of hybrid intensity-modulated radiotherapy (IMRT) and hybrid volumetric-modulated arc therapy (VMAT) for early-stage breast cancer, including plan quality and second cancer risk (SCR).
Three different plans were designed in full IMRT, hybrid IMRT, and hybrid VMAT for each of eight patients with early-stage breast cancer. Target quality, organs at risk (OARs) sparing, and SCR were compared among the three plans.
Compared with the hybrid IMRT, full IMRT showed deterioration in terms of D2% of simultaneous integrated boost (SIB), V10 of ipsilateral lung, and excess absolute risk (EAR) to contralateral lung and esophagus. The homogeneity index (HI) of SIB, V5 of ipsilateral lung and combined lung, the Dmax and Dmean of the esophagus, the EAR to contralateral breast and lung, and the EAR to the esophagus with hybrid VMAT dramatically increased by 12.5%, 19.49%, 18.87%, 90.59%, 167.69%, 50.14%, 264.68%, and 160.95%, respectively (p = 0.022; 0.040; 0.044; 0.041; 0.003; 0.020; 0.000; 0.003). The EAR to contralateral breast and contralateral lung by full IMRT was significantly decreased compared with the hybrid VMAT (26.97%, p = 0.033; 50.01%, p = 0.026).
The results confirmed that hybrid IMRT could achieve better target quality and OARs sparing than full IMRT and hybrid VMAT for early-stage right breast cancer. Hybrid IMRT was the best treatment option, while hybrid VMAT performed the worst among the three plans in terms of SCR to peripheral OARs.