The findings could change how early-stage breast cancer is treated in North America, says Dr. Timothy Whelan. (CBC)

Shorter courses of radiation therapy work just as well as the longer standard therapy for women with early-stage breast cancer, according to the results of a Canadian-led trial.

The researchers randomly assigned 1,234 women to be treated with either three weeks of a more intensive radiation to the whole breast or the standard five weeks of radiation to the whole breast.

Currently, many women with early-stage breast cancer have a lumpectomy to remove the cancer, followed by radiation therapy to kill any remaining cancer cells. The standard radiation treatment takes about 15 minutes a day, Monday through Friday, for five weeks.

"We were surprised that the risk of local recurrence and side-effects for women treated with accelerated whole breast irradiation was so low even at 12 years," said the study's lead author, Dr. Timothy Whelan, a radiation oncologist at McMaster University in Hamilton.

"Our study shows that this treatment should be offered to select women treated with early-stage breast cancer."

Although the shorter approach is more intensive, the total dose of radiation is slightly reduced, Whelan said.

The shorter approach is also more convenient because patients don't need to take as many trips to the cancer centre.

At Monday's annual meeting of the American Society for Therapeutic Radiology and Oncology in Boston, Whelan presented the findings of the 12-year study that concluded the accelerated approach was equally effective in terms of breast cancer recurrence.

At 10 years after treatment, cancer returned locally in 6.2 per cent of patients treated with the accelerated radiation therapy, compared with 6.7 per cent for those patients treated with standard therapy, the researchers found.

Whelan said he expects the findings will change the way early-stage breast cancer is treated in North America.

Both groups of women also had excellent or good cosmetic outcomes from the radiation treatments, the researchers said.

The shorter treatment, called accelerated hypofractionated whole breast irradiation, is two-thirds of the cost of the standard whole breast radiation, according to the researchers. It is also less expensive than other approaches such as partial breast irradiation.

The findings will also help cut wait times for radiation therapy, said Dr. Ida Ackerman, a radiation oncologist at Toronto's Sunnybrook Health Sciences Centre. Ackerman wasn't among the authors of the study, but she did enrol some patients in the '90s.

"It means that we can see and treat more women with the same resources that we have in a timely fashion," said Ackerman, who has been using the shorter approach for qualified patients.

A large trial has begun across Canada looking at shorter, more intensive treatment given in a week to just part of the breast.

With files from the Canadian Press