The researchers found that breast cancer patients whose disease had spread to the lymph nodes and was estrogen-receptor-negative (ER-negative) and who were received adjuvant treatments with modern chemotherapy had a much greater improvement in their five-year disease-free survival rate (22.8 percent) than those patients with hormone sensitive tumors (ER-positive) who were treated with the same chemotherapy and tamoxifen (7 percent). The improvement in overall survival rate with the newer chemotherapy regimens was 16.7 percent for ER-negative patients and 4 percent for ER-positive patients.
"Our observations add to a growing body of evidence that breast cancer is not one homogeneous disease, but rather a disease with many subtypes and requires a variety of new treatment approaches," said Eric Winer, MD, the paper's senior author and director of Dana-Farber's Breast Oncology Center.
Winer and his colleagues conducted a retrospective analysis of three large national breast cancer studies that collectively spanned 20 years and involved more than 6,600 patients to assess the cumulative benefits associated with contemporary chemotherapy regimens. These patients had been enrolled in three consecutive studies for patients with node-positive breast cancer conducted by the Cancer and Leukemia Group B, a National Cancer Institute funded cooperative group. They compared the disease-free and survival rates across the three studies for breast cancer patients with ER-negative tumors who were treated with chemotherapy. They did the same for patients with ER-positive tumors who were treated with chemotherapy and tamoxifen. The researchers then compared the rates between ER-negative and ER-positive breast cancer patients.
The researchers' analysis found that patients with ER-negative tumors experienced a 55 percent reduction in the relative risk of recurrence, when comparing the standard chemotherapy regimen administered in the 1980s to the current standard. These same patients also experienced a 55 percent reduction in the risk of death. The ER-positive breast cancer patients also benefited from the newer chemotherapies, but substantially less so (26 percent reduction in recurrence risk and 23 percent reduction in risk of death).
Although the improvements in chemotherapy provided the greatest benefit for women with ER-negative breast cancers, Winer points out that it would be a misinterpretation of the study's findings to assume that women with ER-positive tumors won't benefit from adjuvant chemotherapy. "Such a conclusion would be overstating the case. However, women with ER-negative and ER-positive cancers should be approached differently when it comes to making a decision about adjuvant chemotherapy" said Winer, who is also an associate professor of medicine at Harvard Medical School. "We need to work to identify which patients with ER-positive tumors get the largest benefit from chemotherapy. And, it must be remembered that women with ER-positive cancers also get a large benefit from treatment with adjuvant hormonal therapy."
In addition to Winer, the study's other authors are Donald Berry, PhD, University of Texas MD Anderson Cancer Center, Houston; Constance Cirrincione, MS, Cancer and Leukemia Group B Statistical Center, Durham, NC; I. Craig Henderson, MD, University of California at San Francisco; Marc Citron, MD, Albert Einstein College of Medicine, Lake Success, NY; Daniel Budman, MD, North Shore University Hospital, Manhasset, NY; Lori Goldstein, MD, Fox Chase Cancer Center, Philadelphia; Silvana Martino, DO, Angeles Clinic and Research Institute, Santa Monica, Calif.; Edith Perez, MD, Mayo Clinic, Jacksonville, Fla.; Hyman Muss, MD, Vermont Cancer Center, Burlington; and Larry Norton, MD, and Clifford Hudis, MD, Memorial Sloan-Kettering Cancer Center, New York.
The research was supported in part by a grant from the National Cancer Institute.
Dana-Farber Cancer Institute (www.dana-farber.org) is a principal teaching affiliate of the Harvard Medical School and is among the leading cancer research and care centers in the United States. It is a founding member of the Dana-Farber/Harvard Cancer Center (DF/HCC), designated a comprehensive cancer center by the National Cancer Institute.