Dr. Julie Bowen, radiation oncologist and medical leader, Radiation Treatment Program, Northeastern Ontario Regional Cancer Centre
“It is thanks to the women who are willing to participate that you get these movements forward,” she said, adding that the patients were pleased to be part of a study recently published in the New England Journal of Medicine called Long-Term Results of Hypofractionated Radiation Therapy for Breast Cancer.
Led by Dr. Tim Whelan, director of Supportive Cancer Care Research, Hamilton Health Sciences, the study was designed to determine whether a hypofractionated three-week schedule of whole-breast irradiation was as effective as a five-week schedule.
The Canadian study had participants from cancer centres in Hamilton, Toronto, Ottawa, Sudbury, London, Windsor, Kingston and Thunder Bay as well as Toronto’s Princess Margaret Hospital and Montreal General Hospital in Quebec.
The subjects were women with invasive breast cancer who had undergone breast-conserving surgery and in whom resection margins were clear and auxiliary lymph nodes were negative. A total of 1,234 women were randomized into two groups. The hypofractionated group received 42.5 Gy (gray) in 16 fractions over a period of 22 days and the control group received a standard dose of 50.0 Gy in 25 fractions over a period of 35 days.
Patients were classified according to age, tumour size and systematic adjuvant therapy (tamoxifen, any chemotherapy, or no therapy).
The results proved that the shorter time span in which a slightly higher dose of radiation is administered (hypofractionation) is just as effective as the longer, five-week schedule that delivered a standard dose, without any significant long-term effects. The survival rate was 85 per cent at 10 years.
The study began in April 1993 and accepted patients through to September 1996. Originally a 10-year study, it has been extended to 16 years. In Sudbury, approximately 65 women participated.
“We’ll continue to see them (participants) to ensure there are no issues that come up later,” Bowen said.
“With radiation, we’re not as concerned about the acute toxicity. We know people get through that. Our larger concern is around the late permanent toxicity that could arise, such as cardiac, cosmetic effects on the skin like telangiectasia or pigmentation changes, breast fibrosis, and late rib fractures.”
Bowen pointed out that hypofractionation has been administered in other countries, but the United States has adhered to the standard procedure of administering smaller doses over a longer period of time, which influenced Canadian practice.
As a result of the study, hypofractionation is performed throughout the country as well as in the U.S., indicating it has influenced American practice.
“The reasons for considering hypofractionation is convenience for the patient. That is why it was so attractive to our patients.” She added that it also has resource implications for both patient and hospital, because there were nine fewer fractions administered. “This study consolidated everyone’s comfort level with using the shorter fractionation.”
Bowen pointed out that the participants in the study were “good prognosis patients” and lymph node negative, meaning no cancer in the lymph nodes.
Hypofractionation treatments are more commonplace now and longer fractionation is more the exception. Bowen confirmed that the patients much prefer the shorter fractionation.