Eligible patients with early breast cancer who have undergone breast-conserving surgery will be stratified into a high-risk group or a low-risk group according to the presence or absence of predefined high-risk factors.
Patients in the high-risk group will receive whole-breast irradiation with a simultaneous integrated boost to the tumor bed. The prescribed dose will be 36 Gy in 15 fractions over 3 weeks to the whole breast and 48 Gy in 15 fractions over 3 weeks to the tumor bed.
Patients in the low-risk group will receive partial-breast irradiation. Two hypofractionated schedules may be used: 40.05 Gy in 15 fractions over 3 weeks or 26 Gy in 5 fractions over 1 week.
Patients will be followed during and after radiotherapy to evaluate treatment efficacy, recurrence rates, and acute and late radiation-related toxicities.
