Radiotherapy in fewer doses safe for early breast cancer

Giving fewer but larger doses of radiotherapy is as safe in the long term for breast cancer treatment, according to the final results of a 10-year study.

According to findings of the FAST trial, five larger radiotherapy doses after surgery – once-a-week sessions for five weeks instead of daily radiotherapy over the same time, totalling 25 doses – cause similarly low rates of side-effects in women with early-stage breast cancer in the long run.

Fewer treatment sessions would particularly benefit patients at low risk of relapse who are not able to tolerate daily radiation over long periods of time because of frailty or other chronic conditions, the researches note.

In the trial, 915 women from 19 centres across the UK who had early-stage breast cancer were assigned to one of three different courses of radiotherapy following breast cancer surgery – a regimen of daily doses and two courses delivering five larger doses once weekly, all over the same time period of five weeks.

The standard radiotherapy regimen consisted of the now outdated international standard of 50 Gray (Gy) of radiation, divided into 25 daily doses of 2 Gy, delivered every day over five weeks.

The trial treatments consisted of 30 or 28.5 Gy delivered once a week for five weeks in fractions of 6 or 5.7 Gy.

After receiving radiotherapy women were then assessed annually for up to 10 years by researchers for side effects to healthy breast tissue – including hardening of the breast, swelling, skin reactions and changes in breast size.

Moderate or severe long-term effects were low across the three treatment groups and the most common effect was breast shrinkage. The researchers observed no changes or minor changes in healthy breast tissue in 86% of all women in the trial at the 10-year time point.

The data showed that moderate or marked effects were two-thirds more likely in women on the 30 Gy regimen than with 50 Gy – but the 28.5 Gy and 50 Gy regimens had a similar risk of moderate or marked effects.

Therefore, it was concluded that administering 28.5 Gy in five fractions as a once-weekly schedule is safe in the long-term for certain patients, particularly those who are frailer.

“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,” commented study co-leader Professor Judith Bliss, Professor of Clinical Trials at The Institute of Cancer Research, London, and director of its Cancer Research UK-funded Clinical Trials and Statistics Unit.

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

Results of the FAST trial, which was led by The Institute of Cancer Research, London, and funded by Cancer Research UK, are published in the Journal of Clinical Oncology.