Fewer Radiotherapy Sessions Show Long-Term Safety in Early Breast Cancer

By David Douglas

July 24, 2020

NEW YORK (Reuters Health) – In women with low-risk invasive breast cancer, long-term side effects after five weekly whole-breast radiotherapy sessions are low and similar to what’s seen with many more sessions over the same period, according to 10-year results from the FAST trial.

"The FAST trial has established that it is possible to find a 5-fraction regimen that is equivalent to the standard with regard to side effects, in other words equally well tolerated," Dr. Adrian Murray Brunt told Reuters Health by email.

“The FAST regimen of once weekly radiotherapy for 5 weeks is appropriate for patients who are unable to attend daily for breast radiotherapy due to frailty for instance," he said.

In the Journal of Clinical Oncology, Dr. Brunt of the University Hospitals of North Midlands, Stoke-on-Trent, and colleagues report on 915 women who had breast cancer surgery between 2004 and 2007 at age 50 or older and were assigned to one of three different courses of radiotherapy.

The standard regimen at the time was 50 Gray (Gy) in 2 GY fractions daily for a total of 25 doses. Women in the other two study arms received 30 or 28.5 Gy, delivered in fractions of 6 or 5.7 Gy once a week over five weeks.

The primary end point was change in photographic breast appearance. Photographs were available in 615 (71%) of the patients who were assessed annually for up to 10 years. At 5 years, the odds ratios for change compared to the 50 Gy approach were 1.64 for 30 Gy and 1.10 for 28.5 Gy.

Corresponding odds ratios for any moderate/marked physician-assessed breast normal tissue effects including shrinkage, induration, and edema were 2.12 and 1.22. At a median follow-up of 9.9 years, there were 3 ipsilateral breast cancer events in the 50 Gy group and 4 in each of the other groups.

There have been a total of 96 deaths of which 25 have been due to breast cancer. The latter fatalities occurred in 7 of the 50 Gy group, 8 of the 30 Gy group and 10 of the 28.5 Gy patients. Although the numbers are small, say the investigators, "Schedules appeared similar regarding breast cancer related events, new primary cancers, or deaths."

“A once-weekly 5-fraction schedule of 28 Gy is estimated to be radiobiologically equivalent to 50 Gy in 25 fractions in terms of late adverse effects at 10 years of follow-up,” they conclude

In a statement, study co-leader Dr. Judith Bliss, of The Institute of Cancer Research, London, concluded, "Our initial results showed that when the total dose is adjusted appropriately, it is safe to deliver radiotherapy in fewer doses and now we can confirm that this is still the case 10 years down the line."

"These findings have supported a change in clinical practice that is already helping relieve pressures on the NHS (National Health Service) - and it is great to see that after so many years, side effects from fewer but larger doses of radiation are still low."

SOURCE: https://bit.ly/2BpKtX8 Journal of Clinical Oncology, online July 14, 2020.