Lower doses of radiation may offer women the same level of protection from breast cancer recurrence with fewer side effects, according to British researchers at the annual meeting of the American Society of Clinical Oncology.
Lowering the dose could also make the treatments more convenient for women. Currently, women who have breast-conserving surgery (lumpectomy) must receive radiation treatments 5 days a week for about 5 or 6 weeks.
"This is very disruptive to your life, as I'm sure you can imagine," explained Julie Gralow, MD, a medical oncologist at the University of Washington and Fred Hutchinson Cancer Research Center in Seattle. She moderated a press conference where researchers presented their results.
"If we could achieve the same outcome with less frequent visits to the radiation center, either by giving the doses every other day or by giving them over 3 weeks, this would be a tremendous benefit for our patients," she said.
The new British research suggests that may be possible. More than 4,000 women treated with lumpectomy took part in 2 studies designed to test the effectiveness of different radiation doses and measure their side effects.
In the first study, called START-A, women were randomly assigned to either a standard radiation dose delivered 5 days a week over 5 weeks, or to 1 of 2 lower doses delivered in higher individual treatments every Monday, Wednesday, and Friday for 5 weeks.
In the second study, called START-B, women got either the standard 5-week therapy, or a lower dose of radiation delivered 5 days a week over 3 weeks. Although the total radiation dose for women in those groups was slightly lower, each individual treatment session used more radiation than would typically be given in a single sitting.
After about 5 years, the researchers looked at how many breast cancers had come back in the different groups, and at side effects.
Only about 3.4% of women in the studies had suffered a relapse of their cancer, and the rates were similar in each of the radiation groups. Because there were so few relapses, it's possible that differences between the groups may become evident as more time passes. But it's likely that any differences will be minimal, said researcher John A. Dewar, MD, who presented the findings.
"We can be reasonably confident that the cancer control rate is unlikely to be significantly greater," said Dewar, a clinical oncologist at the University of Dundee in Dundee, Scotland.
As for side effects, women who got lower total doses of radiation generally experienced fewer physical changes in the breast as a result of the treatment. Side effects were judged by the patients themselves, by their doctors, and with photographs. Lower doses resulted in fewer cases of breast shrinkage, swelling (edema), hardening of the breast, and telangiectasia, a condition where small blood vessels in the breast become enlarged and visible.
This finding could be very important to patients, said Gralow.
"I see patients every day in my clinical practice who have fibrosis and edema and changes that are long-term from their radiation, so it would be terrific if we could get less long-term complications for our patients and do it in less amount of time," she said.
Gralow noted that several ongoing studies are examining other ways of giving radiation therapy for breast cancer over an even shorter period of time. The techniques known as accelerated partial breast radiation promise to complete therapy in about a week -- but are still experimental.
"We need to see the long-term outcome from those studies before they become standard of care, but the exciting news is, we're looking at ways of giving less and getting potentially better outcomes," Gralow said.
Dewar also called for more studies to learn how much radiation can be given safely in a single session and how low total doses can get without compromising efficacy.
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