First results of the randomised UK FAST Trial of radiotherapy hypofractionation for treatment of early breast cancer (CRUKE/04/015)

Background and purpose: 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. Materials and methods: Women aged ≥50 years with node negative early breast cancer were randomly assigned after microscopic complete tumour resection to 50 Gy in 25 fractions versus 28.5 or 30 Gy in 5 once-weekly fractions of 5.7 or 6.0 Gy, respectively, to the whole breast. The primary endpoint was 2-year change in photographic breast appearance. Results: 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 30 Gy and 1.15 (0.82-1.60, p = 0.489) for 28.5 Gy versus 50 Gy. Three-year rates of physician-assessed moderate/marked adverse effects in the breast were 17.3% (13.3-22.3%, p < 0.001) for 30 Gy and 11.1% (7.9-15.6%, p = 0.18) for 28.5 Gy compared with 9.5% (6.5-13.7%) after 50 Gy. With a median follow-up in survivors of 37.3 months, 2 local tumour relapses and 23 deaths have occurred. Conclusions: At 3 years median follow-up, 28.5 Gy in 5 fractions is comparable to 50 Gy in 25 fractions, and significantly milder than 30 Gy in 5 fractions, in terms of adverse effects in the breast.