Randomised trials testing 15- or 16-fraction regimens of adjuvant radiotherapy in women with early breast cancer have reported favourable outcomes compared with standard fractionation. To evaluate hypofractionation further, two 5-fraction schedules delivering 1 fraction per week have been tested against a 25-fraction regimen.

Women aged ⩾50years with node negative early breast cancer were randomly assigned after microscopic complete tumour resection to 50Gy in 25 fractions versus 28.5 or 30Gy in 5 once-weekly fractions of 5.7 or 6.0Gy, respectively, to the whole breast. The primary endpoint was 2-year change in photographic breast appearance.

Nine hundred and fifteen women were recruited from 2004 to 2007. Seven hundred and twenty-nine patients had 2-year photographic assessments. Risk ratios for mild/marked change were 1.70 (95% CI 1.26-2.29, p<0.001) for 30Gy and 1.15 (0.82-1.60, p=0.489) for 28.5Gy versus 50Gy. Three-year rates of physician-assessed moderate/marked adverse effects in the breast were 17.3% (13.3-22.3%, p<0.001) for 30Gy and 11.1% (7.9-15.6%, p=0.18) for 28.5Gy compared with 9.5% (6.5-13.7%) after 50Gy. With a median follow-up in survivors of 37.3months, 2 local tumour relapses and 23 deaths have occurred.

At 3years median follow-up, 28.5Gy in 5 fractions is comparable to 50Gy in 25 fractions, and significantly milder than 30Gy in 5 fractions, in terms of adverse effects in the breast.