[Dosimetric comparison of left-side whole breast irradiation with IMRT and hybrid IMRT]

To evaluate the potential dosimetric benefits and optimal indications of intensity modulated radiation therapy (IMRT) and hybrid intensity modulated radiation therapy (Hybrid IMRT) for the left side breast cancer patients after breast-conservation therapy.

Eight patients with left breast carcinoma who received breast-conservation surgery were selected for this study. Two plans were designed in 3-dimensional treatment planning system. The dose distributions of target volume and normal tissues, conformal index (CI) and heterogeneous index (HI) were analyzed by dose-volume histogram (DVH).

The PTV coverage was the same in the two radiotherapy plans. A better dose uniformity throughout the whole breast in Hybrid IMRT plan was achieved. The CI, the percentage of PTV receiving more than 105% prescribed dose (V105%), the percentage of PTV receiving more than 110% prescribed dose (V110%), and the Dmax, Dmin and Dmean of PTV were similar in the two plans. We compared the Hybrid IMRT with IMRT: V13 of the ipsilateral lung decreased from 27.66% to 20.7%, V5 of the contralateral lung decreased from 8.01% to 2.25%, V10 and V20 of the heart decreased from 35.23% and 16.77% to 19.22% and 10.6% respectively, V5 and V10 of the contralateral breast decreased from 35% and 10.39% to 20.38% and 5.7% respectively, all with significant difference. V30 and V40 of the ipsilateral lung and V40 of the heart increased by 1.28%, 1.48%, and 2.48%, with significant difference.

Hybrid IMRT is a better choice for patients whose treatment position is inaccurate or cannot be repeated well.