Left-sided whole breast irradiation with hybrid-IMRT and helical tomotherapy dosimetric comparison.

Purpose: Limited-tomotherapy and hybrid-IMRT treatment techniques were compared for reductions in ipsilateral and contralateral lung, heart, and contralateral breast radiation doses.

Methods And Materials: Thirty consecutively treated left-sided early-stage breast cancer patients were scheduled for lTomo and hIMRT. For the hIMRT plan conventional tangential-field and four-field IMRT plans were combined with different weightings in the prescribed dose. For the lTomo plan a geometrically limited arc was designed for the beamlet entrance. A D p of 50.4 Gy in 28 fractions was used for the PTV. The dose coverage, homogeneity index, conformity index of the target, and the dose volumes of critical structures were compared.

Results: Both modalities presented similar target coverage. The homogeneity and conformity were improved for lTomo with P < 0.001 and P = 0.006, respectively. In the lTomo plan a concave dose distribution was generated with significant dose reductions in both high and low dose regions for ipsilateral lung and heart (P < 0.001). Conclusions. lTomo plan can have similar dose coverage and better homogeneity and conformity to the target. By properly designing the directionally and completely blocked structure, lTomo plan was developed successfully in reducing doses to the healthy tissues for early-stage left-sided breast cancer radiotherapy.