Nov. 1, 2010 (San Diego) -- Radiation therapy after breast-conserving surgery cuts the risk of breast cancer returning or the risk of dying from the disease even more than doctors thought, researchers report.
Radiation therapy after surgery is now a standard option for women with early breast cancer in the U.S. and Europe.
The study of nearly 11,000 women with early breast cancer shows that the addition of radiation reduces the risk of breast cancer returning within 10 years by almost 15%, from 37.3% for surgery alone to 22.7%.
The odds of dying from breast cancer within 15 years drop by nearly 4%, from 25.4% to 21.7%.
"The findings reinforce the message that radiation substantially reduces the risk of recurrence," says Sarah Darby, PhD, a professor of medical statistics at Oxford University in England, tells WebMD. "We can also see more clearly the extent to which it reduces mortality in the long term. The reductions were bigger than expected."
"A combination of moderate gains in treatment and screening led to a halving of breast cancer [deaths] among women ages 35 to 69 in the U.K. and U.S. since the 1980s," Darby says.
Darby presented her findings here today at the 52nd Annual Meeting of the American Society for Radiation Oncology (ASTRO).
When it comes to cancer coming back, the benefits of radiation are greatest in the first year or two after treatment, Darby says. In the first year, the risk of recurrence is 60% lower in women who get radiation, compared with women who don't, she says.
"In years two to 10, the effect continues, but is not quite as strong," she says.
The opposite pattern pertains to dying from breast cancer, Darby says.
"There is little effect in the first year. It comes on in the second year and lasts at least 10 years," she says.
By 15 years after treatment, the risk of dying from breast cancer is again similar among women who get radiation and those who don't.
Other findings from the study include:
- The risk of dying from any cause over 15 years is about 3% lower in women who get radiation: 34.6% died vs. 37.7% of those who did not get radiation.
- Younger women with fast-growing aggressive tumors benefit the most.
"Older women with slow-growing tumors still benefit, but not as much," Darby says.
When asked at what age a woman should be considered "younger" or "older," Darby says, "There are no set ages. The younger a woman is, the more she benefits, and the older she is the less she benefits."
Radiation Benefits Outweigh Risks
Radiation does carry risks, says Lynn Wilson, MD, MPH, vice chair of therapeutic radiation at Yale University School of Medicine. During treatment, many women become fatigued, he tells WebMD. Transient skin reactions can also occur. These reactions are often compared to a bad sunburn in which the treated area becomes red and inflamed and the skin can peel or even blister.
Since some healthy tissue is exposed to radiation during treatment, there "is some risk, although very small," of getting a secondary cancer or radiation-induced heart or lung disease, says Wilson, who moderated a news briefing to discuss the findings.
"But the risks are small compared to the benefits," he says.
The study was "well designed and very carefully done," Wilson says.
For the study, researchers from the Early Breast Cancer Trialists’ Collaborative Group reviewed the records of 10,906 women with early breast cancer who participated in 17 trials studying radiation therapy after breast-conserving surgery.
The trials were carried out in the U.S., Canada, and several European countries and were initiated between 1976 and 1999.
This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.