CHICAGO — In premenopausal women with breast cancer, a higher number of pregnancies may predict estrogen-receptor status, a small preliminary study suggests.
Presented at a poster session during the combined annual meeting of the Central Society for Clinical Research and the Midwestern section of the American Federation for Medical Research, the study is one of the few to analyze hormonal risk factors in premenopausal women, according to Jacqueline Ogutha, the study's lead investigator and a second-year medical student at the University of Chicago. She and her associates reported results from 100 women with breast cancer diagnosed before age 50 years (64 African Americans and 36 whites) and 67 healthy, age-matched controls (39 African Americans and 28 whites).
A logistical regression analysis of this hospital-based cohort detected a near-significant predictive effect of the number of pregnancies for estrogen-receptor status. African American women were significantly more likely than were white women to have estrogen-receptor-negative tumors and a higher mean number of pregnancies.
By omitting postmenopausal women from their study, the researchers found surprising information, said coinvestigator Olufunmilayo Olopade, M.D., professor of medicine at the university. “What we thought was protective may not be protective at young ages,” she said in an interview. “Our preliminary finding suggests that it is not the case that the more pregnancies you have, the higher the protective effect.”
The small size of the patient population may have affected the results, Dr. Olopade said. Although racial differences in breast cancer incidence and mortality are well recognized, the differences remain largely unexplained, Ms. Ogutha said.
The researchers found striking differences in hormonal risk factors between races in their young population, she said. African American women were significantly more likely than whites to have a higher body mass index and younger age at first live birth and were less likely to breast feed.
Other hormonal factors, including age at first menstrual period and oral contraceptive use, as well as tumor size and grade, appeared to have no statistically significant effect across racial groups.