Safety and Efficacy of IMPT or IMRT for Breast Cancer

Radiotherapy was administered using IMPT or IMRT. The target volume includes the ipsilateral whole breast, chest wall, and/or regional lymph nodes. A hypofractionated regimen of 40-42.5 Gy (RBE) in 15-16 fractions is preferred. A conventional fractionated regimen of 45-50.4 Gy (RBE) at 1.8-2 Gy per fraction in 25-28 fractions or an ultra-hypofractionated regimen of 26 Gy (RBE) in 5 fractions is also allowed. A tumor bed boost will be provided to patients with high-risk factors following breast-conserving surgery, at the discretion of the radiation oncologist. The tumor bed boost regimen may consist of a sequential boost of 10-16 Gy (RBE) in 5-8 fractions, or 10-13.35 Gy (RBE) in 4-5 fractions or 10.4 Gy (RBE) in 2 fractions, or a simultaneous integrated boost of 48-49.5 Gy (RBE) in 15-16 fractions.

Radiotherapy was administered using IMPT or IMRT. The target volume includes the ipsilateral whole breast, chest wall, and/or regional lymph nodes. A hypofractionated regimen of 40-42.5 Gy (RBE) in 15-16 fractions is preferred. A conventional fractionated regimen of 45-50.4 Gy (RBE) at 1.8-2 Gy per fraction in 25-28 fractions or an ultra-hypofractionated regimen of 26 Gy (RBE) in 5 fractions is also allowed.

Radiotherapy was delivered using IMPT or IMRT. The target volume encompassed the ipsilateral whole breast and regional lymph nodes. A hypofractionated regimen of 40-42.5 Gy (RBE) in 15-16 fractions was preferred. Alternatively, a conventional fractionated regimen of 45-50.4 Gy (RBE) at 1.8-2 Gy per fraction in 25-28 fractions or an ultra-hypofractionated regimen of 26 Gy (RBE) in 5 fractions was permitted. Dose escalation was applied in high-risk areas, resulting in a total prescribed dose exceeding 66 Gy (RBE) when calculated as equivalent doses in 2-Gy fractions (EQD2), with an α/β ratio of 4.