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A shorter course of more intense radiation therapy for some breast cancer patients is just as beneficial as a longer period of treatments, according to a Canadian study that has now tracked the same women for more than a decade.

Results of the study that followed women with early-stage breast cancer who received only three weeks of the radiation therapy after surgery to remove a malignant lump, instead of the conventional five weeks, show it's just as effective.

The findings were presented Monday at the annual meeting of the American Society of Therapeutic Radiology and Oncology in Boston.

Dr. Timothy Whelan, professor of oncology at the Michael G. DeGroote School of Medicine at McMaster University in Hamilton, had previously reported results in 2002 after a median follow-up of 69 weeks.

Those results were very promising, he said, but a number of doctors, particularly in the United States, were still concerned about the risk for long-term toxicity associated with the “accelerated hypofractionated” schedule, or more intensive treatments.

“And so the treatment, although it was adopted fairly well in Canada, was not sort of universally adopted,” Dr. Whelan said in an interview.

The study involved 1,234 women randomly assigned to treatment for either three weeks or five weeks of radiation after lumpectomy between April 1993 and September 1996. The women have now been tracked for a median time of 12 years.

“What we discovered was that the results continued to be very promising or very good, in that the rates of cancer recurrence were very low,” he said.

“But perhaps most importantly, [study participants] continued to demonstrate very good results with respect to limited radiation toxicity and a good cosmetic outcome for women, and no evidence that the hypofractionation was any worse than a more standard approach.”

It's less costly to the health-care system when a shorter course of radiation can be offered, he said, and it's less costly to patients because they travel less for treatments and don't miss as much work.

“I think given that this treatment clearly results in improved convenience and reduced costs, and we now have long-term data confirming its efficacy and safety that I think it should be routinely offered to women who are eligible for this therapy,” Dr. Whelan said.

He noted that if radiation is too toxic, it will cause scarring and thickening and the breasts will be deformed. Nurses across the country looked at this in patients during follow-ups at 10 years, and results were still very good, he said. More than 70 per cent of women had an excellent or good result, and results were almost exactly similar between the two different treatment arms.

Survival was about 85 per cent, about the same for both treatment arms, he said.

The findings of this study have led to the development of another area of research, Dr. Whelan said. A large trial has begun across Canada looking at an even shorter, more intensive treatment given in a week, but just to part of the breast.

“It's partial treatment, so it's even less exposure essentially, to women with radiation, and we're hoping the same efficacy.”