Modern Therapies Halve Risk of Breast Cancer Mortality

Middle-aged women today are about half as likely as their counterparts 25 years ago to die from breast cancer, thanks in large part to the collective effects of modern therapies, according to new data reported at SABCS. Results of the 2005-2006 update of the worldwide overview presented by Richard Peto, PhD, on behalf of the Early Breast Cancer Trialists' Collaborative Group were based on data from roughly 350,000 women and 400 randomized trials.

Richard Peto, PhD
Photo Courtesy © SABCS/Todd Buchanan 2007

In the meta-analysis, radiation therapy after mastectomy with axillary nodal dissection conferred an absolute reduction of breast cancer mortality at 15 years of 7% to 8%. All-cause mortality was reduced 5% to 6% among women with positive nodes, according to Dr. Peto. "If you do have nodal involvement, then really you do need to do something about treating the local area or at least consider doing so," he said. In contrast, among women with node-negative disease, this treatment increased all-cause mortality. For women with estrogen receptor (ER)-positive tumors, receipt of 5 years of tamoxifen conferred an absolute 9% reduction in 15-year breast cancer mortality without any significant effect on non-breast-cancer mortality. The curves further diverged during the decade after stopping tamoxifen, Dr. Peto said. "It's an extraordinary carryover effect -- not just continuing what they've got, they're gaining extra benefit," he said. Women with ER-positive disease had slightly lower 5-year breast cancer mortality if they received 5 years of an aromatase inhibitor, compared with 5 years of tamoxifen (6.5% vs. 7.4%). "It's not yet significant, but wait for the 2010 overview. Maybe it will be," he said. Finally, taking into account data on the relative benefits of CMF, anthracycline-based regimens, and taxane-based regimens, the risk of breast cancer mortality was reduced with taxane chemotherapy by one-half among women younger than age 50 (rate ratio, 0.46) and by one-third among women aged 50 to 69 (rate ratio, 0.66), Dr. Peto said. "I'm not making any treatment recommendations," he cautioned, noting that this chemotherapy is not without drawbacks. "Look at the prognosis, discuss the side effects, discuss the costs, and decide what to do." Dr. Peto concluded by underscoring the importance of continuing to collect long-term data. "What we need is for these trials not to get lost. These are unique experiments, they are not going to be reported. We want 20-year follow-up out of these trials," he said. "There will be a lot more to learn in the 2010 cycle of this collaboration."

Disclosures:

The author(s) have no significant financial interest or other relationship with the manufacturers of any products or providers of any service mentioned in this article.