For women with early-stage breast cancer who need radiation, receiving higher doses on a weekly basis does not result in more side effects, according to a new study.

The FAST trial, by the London-based Institute of Cancer Research, launched in 2004 and followed 915 women from the United Kingdom with early-stage breast cancer during and after medical treatment. The medical treatment consisted of surgery followed by radiation therapy administered over a period of five weeks—either in small daily doses or in larger weekly doses. After completing treatment, the women were examined annually for adverse side effects, such as swelling, hardening, skin irritation and changes in breast size. 

The once-a-week regimen had a similar impact on tumor size as the once-a-day regimen.

The new 10-year results, published in the Journal of Clinical Oncology, show that both approaches were associated with only low rates of moderate or severe long-term adverse side effects. Most participants (86%) reported no changes in their breast tissue or only minor ones; the most common side effect was breast shrinkage.

"The FAST trial confirms the safety of a radiotherapy course consisting of a lower total dose of radiotherapy delivered in five fractions of radiation,” said chief investigator John Yarnold, a professor of clinical oncology at the Institute of Cancer Research, in a press release. He added that the findings “support treatment options that are more convenient for patients who cannot tolerate long courses of daily radiation, without increasing the risk of long-term side effects.” 

These patients include those who live far from radiation clinics or hospitals, those with medical conditions that make frequent travel infeasible and the elderly, said Arnie Purushotham, the senior clinical adviser of Cancer Research UK.

“Sparing women unnecessary treatment is always good news,” Yarnold said. “Ultimately, it’s important that we keep doing research which can give patients a better quality of life.” Further research will investigate the viability of regimens as short as one week.

To read more about research on streamlining radiation therapy treatment, click here. And to learn how chronic stress affects the effectiveness of radiation therapy, click here.