One-Week Radiotherapy Standard for Early Invasive Breast Cancer

Susan London

January 11, 2021

Compared with the standard 3-week regimen, a 1-week hypofractionated regimen of adjuvant whole-breast radiotherapy had similar efficacy and safety at 5 years of follow-up, according to the U.K. FAST-Forward trial.

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The historic 5-week regimen (50 Gy in 25 fractions) has been replaced by a 3-week regimen (40 Gy in 15 fractions) in the United Kingdom and elsewhere, and ongoing efforts are exploring whether further hypofractionation can be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%).

A New Standard

"We have shown noninferiority in terms of local tumor control for both 5-fraction schedules, compared with the control group of 40 Gy in 15 fractions," Ms. Haviland summarized. "Late adverse effects in normal tissues were similar after 26 Gy in 5 fractions to 40 Gy in 15 fractions, and although rates were higher for the 27-Gy schedule, we noted that these are consistent with the historic standard of 50 Gy in 25 fractions."

"There are obvious benefits to patients and health care systems of shorter radiotherapy treatments, particularly at the current time, and in fact, the COVID pandemic has accelerated uptake of the 26-Gy schedule around the world," she added. "At a recent consensus meeting organized by the Royal College of Radiologists, the U.K. adopted the 26-Gy schedule as a new standard, also integrating this with partial breast irradiation, in close collaboration with the U.K. IMPORT Low trial."

"This is very important work. I think this is one of the most important trials in the past few years. It has really changed practice," commented session co-chair Ben Slotman, MD, PhD, of Vrije Universiteit Medical Center, Amsterdam, and AMC Amsterdam, who was not involved the trial.

Slotman wondered how extensive uptake of the new hypofractionated regimen has been. "I know it's being used in the U.K. and the Netherlands, but do you have any idea about the rest of Europe? What do we need to make it the new standard?"

"I think there has been uptake in other countries in Europe and elsewhere around the world as well," Ms. Haviland replied. But feedback suggests adoption has been tempered because of reservations related to the regimen's safety in certain patient subgroups.

"We haven't found any cause for concern in the subgroups, and also backed up by meta-analysis in the many patients randomized in the START trials," she noted. "So I think there is very convincing evidence that it is safe as a new standard."

FAST-Forward was sponsored by the Institute of Cancer Research and funded by the National Institute for Health Research Health Technology Assessment Programme. Ms. Haviland disclosed no conflicts of interest. Slotman has relationships with ViewRay and Varian Medical Systems.

SOURCE: Haviland J et al. ESTRO 2020, Abstract OC-0610.

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