Three‐year outcomes of a once daily fractionation scheme for accelerated partial breast irradiation ( APBI ) using 3‐D conformal radiotherapy (3D‐ CRT )

The aim of this study was to report 3‐year outcomes of toxicity, cosmesis, and local control using a once daily fractionation scheme (49.95 Gy in 3.33 Gy once daily fractions) for accelerated partial breast irradiation ( APBI ) using three‐dimensional conformal radiotherapy (3D‐ CRT ). Between July 2008 and August 2010, women aged ≥40 years with ductal carcinoma in situ or node‐negative invasive breast cancer ≤3 cm in diameter, treated with breast‐conserving surgery achieving negative margins, were accrued to a prospective study. Women were treated with APBI using 3–5 photon beams, delivering 49.95 Gy over 15 once daily fractions over 3 weeks. Patients were assessed for toxicities, cosmesis, and local control rates before APBI and at specified time points. Thirty‐four patients (mean age 60 years) with Tis 0 ( n  = 9) and T1N0 ( n  =   25) breast cancer were treated and followed up for an average of 39 months. Only 3% (1/34) patients experienced a grade 3 subcutaneous fibrosis and breast edema and 97% of the patients had good/excellent cosmetic outcome at 3 years. The 3‐year rate of ipsilateral breast tumor recurrence ( IBTR ) was 0% while the rate of contralateral breast events was 6%. The 3‐year disease‐free survival ( DFS ), overall survival ( OS ), and breast cancer‐specific survival ( BCSS ) was 94%, 100%, and 100%, respectively. Our novel accelerated partial breast fractionation scheme of 15 once daily fractions of 3.33 Gy (49.95 Gy total) is a remarkably well‐tolerated regimen of 3D‐ CRT ‐based APBI . A larger cohort of patients is needed to further ascertain the toxicity of this accelerated partial breast regimen.