Spotlight on Research

Risk Factors for Triple-Negative Breast Cancer: A Critical Gap in Knowledge
by Amanda Phipps, Department of Epidemiology

Amanda Phipps

Breast cancer is the most commonly diagnosed cancer among U.S. women—more than 180,000 women are diagnosed each year—and the second most common cause of cancer death. While overall breast cancer mortality rates have declined and survival rates have improved over the past several years, some forms of breast cancer continue to be associated with a poor prognosis. One such form of particular clinical relevance is triple-negative breast cancer, so named for the lack of expression of three commonly tested biological markers in tumors of this subtype. Less than 20% of breast cancers are triple-negative, but women with triple-negative disease have a particularly poor prognosis and fewer treatment options. Although the clinical significance of this subtype is well known, however, the causes of triple-negative breast cancer remain poorly understood.

As a Ph.D. candidate in Epidemiology, I have centered my research on identifying what puts women at risk for developing triple-negative breast cancer. I recently completed a study in collaboration with Drs. Christopher Li, Kathi Malone, Peggy Porter, and Janet Daling at the Fred Hutchinson Cancer Research Center, in which we observed a reduced risk of triple-negative breast cancer in women who had breastfed for at least six months during their lifetime and an increased risk in postmenopausal obese women compared to normal weight women. I am now collaborating with the Breast Cancer Surveillance Consortium to examine how a woman’s breast cancer family history, reproductive history, and breast density on a mammogram relate to her risk of triple-negative breast cancer and risk of less aggressive breast cancers.

Figuring out how risk factors for triple-negative breast cancer compare to those for other breast cancers could provide useful clues. And from a public health perspective, such results could ultimately be useful in identifying those women most at risk for these poor prognosis breast cancers.

Further reading:
Phipps AI, Malone KE, Porter PL, Daling JR, Li CI. Reproductive and hormonal risk factors for postmenopausal luminal, HER-2-overexpressing, and triple-negative breast cancer. Cancer. 2008;113(7):1521-1526.
Phipps AI, Malone KE, Porter PL, Daling JR, Li CI. Body size and risk of luminal, HER2-overexpressing, and triple-negative breast cancer in postmenopausal women. Cancer Epidemiol Biomarkers Prev. 2008;17(8):2078-2086.