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.