Study: Estrogen-Receptor Positive Women May Not Benefit From Chemotherapy

Postmenopausal women with estrogen-sensitive breast cancer tumors may not benefit from chemotherapy after surgery, according to researchers at the International Breast Cancer Study Group and the Dana-Farber Cancer Institute.

Chemotherapy treatment is often prescribed along with the estrogen-blocking drug tamoxifen as a means to increase a patient's odds of survival.

Researchers found that patients whose tumors were unresponsive to estrogen did benefit from chemotherapy. These women were significantly less likely to have a recurrence and less likely to die within five years of treatment than women who did not receive chemotherapy, the researchers reported in the Journal of the National Cancer Institute.

But investigators now question the value of chemotherapy following breast surgery for postmenopausal women who have early tumors that have not spread to the lymph nodes, and who are estrogen positive.

"I'm hoping it will cause physicians and research investigators to examine more carefully whether or not these postmenopausal women with node-negative, estrogen-positive diseases should routinely be offered chemotherapy," said Richard Gelber, PhD, biostatistician at Dana-Farber who led the statistical analysis of the trial data.

The study consisted of 1,669 patients from all over the world. All of the patients were postmenopausal and had node-negative cancer. About 75 percent of the women had estrogen-positive tumors and 23 percent had tumors that were estrogen-negative. About 2 percent were undetermined. The women were randomly assigned to receive either chemotherapy followed by tamoxifen or to receive only tamoxifen for five years.

The women with estrogen-negative tumors who received chemotherapy had a 15 percent increase in disease-free survival at five years compared to the women who did not receive chemotherapy (84 percent vs. 69 percent). The overall survival at five years was 89 percent in the chemotherapy group compared to 81 percent who were only given tamoxifen.

However, for the women with estrogen-positive tumors, the addition of chemotherapy gave them no added survival benefit. Their five-year disease-free survival rate was 85 percent without chemotherapy and 84 percent with chemotherapy. Their overall survival rate at five years was 95 percent with chemotherapy and 93 percent without it.

Researchers speculate that the chemotherapy was more beneficial to the estrogen-negative women due to their higher rate of relapse and the fact that tamoxifen is less effective in this group.

Other sources: Dana Farber Cancer Institute