Preliminary Results of a Randomized Study on Postmenopausal Women With Early Stage Breast Cancer: Adjuvant Hypofractionated Whole Breast Irradiation Versus Accelerated Partial Breast Irradiation (HYPAB Trial).

BACKGROUND

The purpose of this study was to report preliminary data of a randomized phase III trial comparing hypofractionated whole breast irradiation (HWBI) and accelerated partial breast irradiation (APBI) using volumetric modulated arc therapy (VMAT).

MATERIAL AND METHODS

The HYPAB trial enrolled postmenopausal women with biopsy-proven infiltrating breast cancer, clinically negative axilla, single T1 to T2 tumors, who were treated with breast-conserving surgery. Patients were randomized 1:1 after surgery to HWBI (40.5 Gy whole breast, 48.0 Gy to surgical bed, 15 fractions over 3 weeks) or APBI (30 Gy delivered in 5 fractions of 6 Gy given on alternate days on the surgical bed). Cosmetic outcome was the primary end point of the study.

RESULTS

A total of 172 patients were enrolled. After a median follow-up of 36 months, 5 local failures and 3 locoregional failures were recorded, with no difference between the 2 treatment arms. Use of HWBI as compared with APBI was significantly correlated with increased incidence of overall (62% vs. 14%; P < .001) and grade 2 (18% vs. 1%; P < .001) acute skin toxicity. APBI was correlated with a lower incidence of overall late toxicity as compared with HWBI (18% vs. 41%; P = .001), but no significant difference was found in term of occurrence of grade 2 events (1% vs. 4%; P = NS). At comparative assessment between baseline and post-radiotherapy evaluation, impairment in cosmetic outcome was reported in 19 (11%) patients. Owing to premature closure of the study, no per-protocol comparison between the treatment arms was performed.

CONCLUSION

APBI with the VMAT technique is safe and feasible, with lower acute toxicity when compared with HWBI.