Dosimetric comparison of left-sided whole breast irradiation with 3D-CRT, IP-IMRT and hybrid IMRT.

The aim of this study was to compare the dosimetric characteristics of left-sided whole breast irradiation among 3-dimensional conformal radiotherapy (3D-CRT), 4-field inverse-planned intensity-modulated radiotherapy (IP-IMRT) and hybrid IMRT technique (combining 3D-CRT beams and IP-IMRT beams) with respect to target coverage and irradiation of organs at risk. The 3 different planning techniques were analyzed for 8 patients with left-sided breast conserving surgery. Plans were compared on the basis of planning target volume (PTV) dose conformity, homogeneity and the volumes of normal tissues treated based on dose-volume histograms (DVHs). DVHs were calculated for the PTV, heart, and the bilateral lungs, contralateral breast, and soft tissue surrounding the breast PTV (VOB) volume. IP-IMRT and hybrid IMRT techniques comparably improved the PTV dose homogeneity and conformity (CI) significantly, compared to the conventional 3D-CRT technique (P<0.017); the IP-IMRT technique only could additionally benefit patients by decreasing the high-dose (40 Gy) volume for heart and ipsilateral lung compared with the hybrid IMRT technique (P<0.017); the hybrid IMRT plans achieved a further improvement by compromising the increase of low-dose volume (total lung V13, contralateral lung V5, heart V10 and soft tissue surrounding the breast V5) compared with IP-IMRT plans (P<0.017). Hybrid IMRT plans achieved equivalent PTV dose uniformity to IP-IMRT plans and compromised the low-dose volume and requirement of clinic resource between IP-IMRT and 3D-CRT plans, promoting it as a standard practice of left-sided breast irradiation for patients in good-ordered cardiopulmonary health.