Joanne S. Haviland
The trial was designed to compare the standard regimen (40 Gy in 15 fractions over 3 weeks) with a higher-dose hypofractionated regimen (27 Gy in 5 fractions over 5 days) and a lower-dose hypofractionated regimen (26 Gy in 5 fractions over 5 days) in women who had undergone surgery for early invasive breast cancer.
The 5-year rate of ipsilateral breast tumor relapse was similar with all regimens – 2.1% with the 40-Gy regimen, 1.7% with the 27-Gy regimen, and 1.4% with the 26-Gy regimen. The 26-Gy regimen also had similar safety as the 40-Gy regimen.
These results were presented at the European Society for Radiology and Oncology 2020 Online Congress by Joanne S. Haviland, MSc, of the Institute of Cancer Research in London. Results were also published in The Lancet.
Ms. Haviland said that hypofractionated regimens are attractive because of their shorter overall treatment times, which translate to greater convenience and lower treatment costs.
The historic 5-week regimen (50 Gy in 25 fractions) has been replaced by a 3-week regimen (40 Gy in 15 fractions) in the United Kingdom and elsewhere, and ongoing efforts are exploring whether further hypofractionation can be achieved without compromising efficacy and safety.
“The FAST-Forward trial was the next step on from testing hypofractionated schedules evaluated in earlier trials, including the START trials in the early 2000s and the FAST trial, which published its 10-year results earlier this year,” Ms. Haviland explained.
FAST-Forward enrolled 4,096 women who had undergone breast-conserving surgery or mastectomy for early invasive breast cancer. The patients were randomized into the aforementioned groups for adjuvant whole-breast or chest-wall radiotherapy: 40 Gy in 15 fractions over 3 weeks, 27 Gy in 5 fractions over 5 days, or 26 Gy in 5 fractions over 5 days. Boosts were permitted for all regimens.
Relapse, safety, and patient reports
The median follow-up was 6 years. The 5-year rate of ipsilateral breast tumor relapse was 2.1% with the 40-Gy standard regimen, 1.7% with the 27-Gy hypofractionated regimen, and 1.4% with the 26-Gy hypofractionated regimen.
The upper bound of the 95% confidence interval for the difference comparing the hypofractionated regimens against the standard fell well within the 1.6% excess predefined for noninferiority for both the 27-Gy regimen and the 26-Gy regimen (0.9% and 0.3%, respectively).
The hazard ratio for ipsilateral breast tumor relapse, compared with the standard regimen, was 0.86 for the 27-Gy hypofractionated regimen and 0.67 for the 26-Gy hypofractionated regimen.
In terms of safety, the 5-year rate of late adverse effects of the breast or chest wall – distortion, shrinkage, induration, telangiectasia, or edema – rated as “moderate” or “marked” by clinicians was 10% with the standard regimen, 15% with the 27-Gy regimen (relative risk, 1.55 ; P < .001), and 12% with the 26-Gy regimen (RR, 1.19; P = .17).
Over the entire follow-up, women had significantly higher odds of all moderate or marked individual late adverse effects (except discomfort) with the 27-Gy regimen versus the standard regimen, whereas their odds were significantly higher only for induration and edema with the 26-Gy regimen.
However, absolute rates and risk differences between groups were small, Ms. Haviland pointed out. For example, the most common moderate or marked late adverse effect with the standard regimen was breast shrinkage, seen in 5% of patients, followed by discomfort, seen in 4%.
Patient-assessed change in breast appearance and shrinkage did not differ significantly across groups. But women in the 27-Gy group were more likely than peers in the standard regimen group to report a moderate or marked increase in breast hardness/firmness (21% vs. 14%; P = .008), and women in both the 27-Gy and 26-Gy groups were more likely to report moderate or marked breast swelling (5%; P = .007 and 4%; P = .02, respectively, vs. 2%).