Whole-breast irradiation with lumpectomy cavity boost and regional nodal irradiation: Dosimetric comparison of 3D-CRT using sequential boost and dual partial-arc VMAT using simultaneous integrated boost.

Abstract

Objective: To compare volumetric modulated arc therapy (VMAT) with simultaneous tumor bed boost (dpSIB-VMAT) to the whole breast and regional nodal irradiation (RNI) against standard three-dimensional conformal radiotherapy plus RNI with sequential tumor bed boost (3D-CRT-seqB).

Methods: Thirty patients who underwent breast cancer surgery (BCS) with axillary lymph node dissection (ALND) were enrolled. Two plans were generated for each case: (1) dpSIB-VMAT, and (2) 3D-CRT-seqB plans. Planning target volume (PTV)-Breast and PTV-Nodes were prescribed at a dose of 50 Gy in 25 fractions in both plans. PTV-Boost was prescribed at a dose of 60 Gy in 25 fractions simultaneously in the dpSIB-VMAT plans, whereas it was planned sequentially in the 3D-CRT-seqB plans at 10 Gy in 5 fractions. Dosimetric parameters were compared between the two plans.

Results: Both plans achieved the target coverage. D_mean of the heart was lower with dpSIB-VMAT in left-sided cases (7.17 ± 0.66 Gy vs. 10.12 ± 2.91 Gy; t = 4.02; p = 0.001). Ipsilateral mean lung dose (15.87 ± 1.40 Gy vs. 19.82 ± 3.20 Gy; t = 6.30; p<0.001) was significantly lower but mean doses of the contralateral breast (4.30 ± 1.76 Gy vs. 1.48 ± 0.76 Gy; t = -7.84; p<0.001), contralateral lung (3.86 ± 1.21 Gy vs. 0.96 ± 0.25 Gy; t = -13.13; p<0.001) and esophagus (13.11 ± 2.63 Gy vs. 10.32 ± 3.56 Gy; t = -6.65; p<0.001) were relatively higher with dpSIB-VMAT.

Conclusion: Dosimetrically, dpSIB-VMAT reduced doses to the ipsilateral lung and heart (in left breast but not right breast cases) compared to 3D-CRT-seqB plans for adequate target coverage.