Suresh Moorthy, Elhateer H, Saroj Kumar Das Majumdar, Shubber Mohammed, Zainab Al Haddad and Narayana Murthy P
Purpose: Whole breast irradiation is part of breast conservative management for early breast cancer; addition of boost dose to tumor bed improves local recurrence rates and is currently the standard of care. Randomized trials reported low a/b ratio for breast cancer that predict a radiobiological advantage for hypofractionation. Simultaneous boost radiation as a method of hypofractionation proved safe and effective for head and neck tumors. In this study we attempt to compare and analyze the dosimetric aspects of adding Simultaneous Integrated Boost (SIB) over Sequential Boost (SB) to a hypofractionated treatment schedule in breast cancer patients after BCS.
Materials and methods: CT simulation data sets for 23 patients were selected for this planning study; Targets and OAR were delineated as per RTOG guidelines. Multiple dynamic field IMRT plans were generated for each patient. The prescribed dose was 40 Gy/15 fractions to whole breast (2.67 Gy/fraction) and 48 Gy/15fractions to lumpectomy cavity (3.2 Gy/fraction) for SIB, and 40 Gy/15 fractions followed by 10Gy/5 fractions for SB. Generated Treatment plans were evaluated by experienced radiation oncologist, and the best plan was selected for the dosimetric analysis.
Results: The pre specified target coverage criteria were met for the lumpectomy cavity as well as whole breast in all plans. All quality indices for PTV coverage showed to be significantly improved with SIB for both whole breast and tumor bed volumes. SB technique showed more dose spillage outside the boost volume. SIB-IMRT was better in sparing OAR ,the volume of the ipsilateral lung V20 Gy was 19.8 % compared to 22.8 % (p = 0.04), maximum dose to LAD was 17.6 Gy Vs. 21.6 (p= 0.01) and contralateral breast mean dose was 0.36 Gy Vs. 1.27 Gy (p = 0.01) for SIB and SB respectively.
Conclusions: Hypofractionated breast SIB is feasible with better PTV coverage and OAR. Along with further reduction of the overall period which may increase patient convenience and resource utilization benefit.
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