Re-analysis of large trials shows greatest benefit of chemotherapy in ER-negative tumors

Despite the common belief in the oncology community that cancer research and treatment have focused on breast tumors that are estrogen receptor (ER)-positive, a researcher from The University of Texas M. D. Anderson Cancer Center maintains that clinicians have made “enormous strides” in treating patients with tumors that are ER-negative.

In a presentation at the annual meeting of the San Antonio Breast Cancer Symposium, Donald Berry, Ph.D., a professor and chair of the Department of Biostatistics and Applied Mathematics, looked at decades of breast cancer clinical trial experience and found that “the benefit of chemotherapy advances over the last 20 years to ER-negative patients has been surprisingly dramatic.”

In examining the impact of chemotherapy treatment of node-positive breast cancer in three national clinical trials, which enrolled more than 6,000 patients cumulatively, Berry found that chemotherapy has reduced the risk of death in ER-negative patients by 56 percent. “The absolute benefit has been similarly impressive, especially in comparison with the corresponding absolute benefit of chemotherapy to ER-positive patients,” he says.

The studies, conducted by the Cancer and Leukemia Group B (CALGB) and the U.S. Breast Intergroup, all tested different chemotherapy regimens and doses in women whose cancer had spread to their lymph nodes, and all three showed statistically significant results. But, patients were treated “irrespective of hormone sensitivities or whether they had received tamoxifen or not,” Berry says. In women who are ER-positive, tamoxifen and other SERMs (selective estrogen receptor modulators) have been shown to help prevent cancer development or recurrence.

The impact of such preventive treatments, however, was not “weighted” in these trials, he says. “People accept and act as though chemotherapy is equally beneficial independent of ER status,” he says. In his analysis, Berry found that all three studies show that chemotherapy provided a statistically significant benefit for patients with ER-negative tumors, but “only a little bit of an effect for ER-positive tumors that had been treated with tamoxifen, and none of the trials showed a statistically significant benefit for higher doses of chemotherapy in ER-positive patients.”

Berry says that the results will likely surprise oncologists “because everyone has assumed that ER status doesn’t matter in chemotherapy treatment, but here we show it does.” That doesn’t mean, however, that patients with ER-positive tumors should not receive chemotherapy, Berry warns.

He adds that the study proves that breast cancer patients of both hormonal types are being aided by clinical advances. “The prevailing wisdom has been that science has focused on ER-positive tumors, with development of SERMs and now aromatase inhibitors, but ER-negative patients have been left in the lurch,” Berry says. “Not so. This analysis demonstrates that chemotherapy use has more than doubled survival rates in women with ER-negative tumors.”