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

Objective: 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. Methods: 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). Results: 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. Conclusion: Hybrid IMRT is a better choice for patients whose treatment position is inaccurate or cannot be repeated well.