Accelerated partial breast irradiation (APBI) is commonly delivered over 5 treatment days. In this nonrandomized trial, 161 patients with hormone receptor positive breast cancer or DCIS measuring 2.5cm or less were treated with a 3-fraction APBI regimen. Photons, protons, and brachytherapy were used. The doses were designed to be comparable to 40 Gy in 15 fractions. The proton and photon prescription was 21.9 Gy in 3 fractions and the brachytherapy prescription was 21 Gy in 3 fractions. The target volume was the lumpectomy cavity plus a 1 cm CTV margin and an additional 3mm PTV margin for proton/photon plans. Adverse cosmesis at 3 years was low with a rate of 2.3% judged by trained nurses, 3.3% by a panel reviewing digital photographs, and 2.8% by patient report. The rate of local recurrence was 2.4%, and the factor associated with recurrence was the presence of grade 3 disease. | Mutter, Int J Radiat Oncol Biol Phys 2024
