231O - Locoregional hypo vs normofractionated RT in early breast cancer: 5 years results of the HypoG-01 phase III UNICANCER trial

Background

Hypofractionated (HF) radiation therapy (RT) is the standard regimen for whole breast RT but normofractionated (NF) RT using 50 Gy/25 fr is still standard in most countries for loco-regional early breast cancer (EBC). HypoG-01, a UNICANCER, open-label, multicenter, randomized phase III trial (NCT03127995), assessed non-inferiority of HF RT with 40 Gy/15 fr (2.67 Gy/fr) versus NF RT 50 Gy/25 fr (2.0 Gy/fr).

Methods

Patients (pts) ≥18 years old operated for T1-3, N0-3, M0 breast cancer received nodal and thoracic wall or breast RT. The primary endpoint was time to occurrence of arm lymphedema evaluated by one-sided logrank test in the per-protocol (PP) population with a non-inferiority hazard ratio (HR) margin of 1.545. Secondary endpoints included locoregional relapse-free survival (LRFS), distant disease-free survival (DDFS), and overall survival (OS).

Results

Overall 1265 pts were randomized from Sep 2016 to Mar 2020 with 1221 in PP (HF: 614 pts, NF: 607 pts). Median age was 58 years (range 23-91), surgery included mastectomy (501 pts; 45%) and axillary clearance (921 pts; 82.8%) with a mean of 12 removed nodes. With a median follow-up of 4.8 years, 275 lymphedemas occurred. HF was non-inferior to NF RT regarding arm lymphedema risk (HR=1.02; 90% CI 0.83-1.26, non-inferiority p

Conclusions

Moderately HF loco-regional RT is non-inferior to NF RT in terms of arm lymphedema risk in EBC and did not lead to unfavorable safety nor LRFS, DDFS, OS concerns. This practice-changing trial supports the use of 40 Gy/15 fr for loco-regional radiation therapy in EBC.

Clinical trial identification

NCT03127995, Release date: 23/06/2016.

Editorial acknowledgement

Legal entity responsible for the study

UNICANCER.

Funding

The French National Cancer Institute (PHRC-K).

Disclosure

All authors have declared no conflicts of interest.