Post-lumpectomy RT lowers risk of recurrence

Benefits of radiation go beyond saving the breast to reducing mortality.

In a data analysis involving more than 10,000 breast cancer patients, adding radiation therapy to breast-conserving surgery reduced the risk of breast cancer recurrence within 10 years by nearly 15% and reduced the overall chance of dying from the disease by nearly 4% (from 25.4% to 21.7%). These findings provide oncologists with specific numbers they can give their patients when discussing the use of post-lumpectomy radiation therapy and the risk of recurrence, according to the study authors.

Researchers with the Early Breast Cancer Trialists' Collaborative Group reviewed the records of 10,906 women in 17 randomized trials analyzing radiation therapy after breast-conserving surgery (BCS). The trials were carried out in the U.S., Canada, and several European countries, between 1976 and 1999
(ASTRO 2010 abstract LB2).

For the 7,334 women with pathological node-negative disease, adding radiation therapy reduced the 10-year risk of recurrence by 14.5% and the 15-year risk of death by 3.2% (from 20.6% to 17.4%). The benefit of RT varied depending on the woman's age, tumor grade, and tamoxifen use. For example, in women with ER-positive tumors in the trials where tamoxifen was planned, radiotherapy reduced the 10-year risk of recurrence for women aged 40 and younger with high-grade tumors by about 35% (from 55% to 20%), while for women aged 70 and older with low-grade tumors, the reduction was only about 5% (from 11% to 6%).
Among the 1,108 women in the study with pathological node-positive disease, radiation therapy reduced the 10-year risk of recurrence by 18%, and reduced the 15-year risk of dying from breast cancer by nearly 8% (from 51.2% to 43.4%). In the node-positive group, no independent predictive factors for reduced risk of recurrence with RT were identified.

"These studies confirm that, after lumpectomy, radiation therapy reduces a woman's risk of her breast cancer returning and her chances of dying of the disease," said Sarah Darby, PhD, a professor of medical statistics at the Clinical Trial Service Unit and Epidemiological Studies Unit at Oxford University in the UK.
She said oncologists are now getting a changing view of radiotherapy. "The message for oncologists is that they should consider very seriously the beneficial effects of radiotherapy after breast-conserving therapy. There has been a tendency for people to think that the benefits of radiotherapy are just in terms of stopping local recurrence. However, as more data are collected, it is clear that its benefits are not just limited to saving the breast. It does reduce mortality," Dr. Darby said.

VANTAGE POINT

Data validate the role of radiotherapy after BCS
Charlotte Dai Kubicky, MD

The benefit of post-lumpectomy radiotherapy in preventing local recurrences has been well demonstrated by a number of randomized phase III trials. However, whether radiotherapy in this setting can reduce the risk of dying from breast cancer is still under some debate. With longer follow up, we are now seeing an impact of radiotherapy on mortality, and the benefit was seen in both node-negative and node-positive patients, said Dr. Kubicky, an assistant professor of radiation/oncology at Oregon Health & Science University in Portland.

"Results from this meta-analysis concurred with the previous reports from the Early Breast Cancer Trialists' Collaborative Group. There is ‘the rule of 4,' meaning for every four local recurrences prevented, one breast cancer death would be avoided. I will now be using this data in my daily discussions with patients," she said.