WASHINGTONCertain breast cancer risk factors vary by tumor histology and grade, according to a new analysis of data from the Breast Cancer Detection Demonstration Project Follow-Up Study. Hala Nsouli, MPH, of the George Washington Cancer Institute, reported the findings at the International Union Against Cancer's World Cancer Congress (abstract 9-40).
Previous studies have shown that age-specific incidence rates vary by histology and tumor grade, but few studies have examined associations between the established breast cancer risk factors and tumor biology.
The study, which took place between 1979 and 1998, included 52,519 participants. Out of 2,855 breast cancer cases identified, The George Washington University researchers identified histologic subtype, including infiltrating ductal carcinoma (IDC) and lobular carcinoma (ILC), in 2,040 postmenopausal women. IDC was found in 76% of cases and ILC in 12.4%. The authors then calculated relative risks and 95% confidence intervals using Poisson regression.
IDC was significantly associated with body mass index (BMI), family history of breast cancer, a history of benign breast disease, high educational and income levels, later age at first live birth, and alcohol consumption. African-American women and women who had had at least one child were less likely to have IDC.
Benign breast disease, family history, and alcohol consumption were associated with ILC, but statistical significance was not as strong. Smoking was also associated with ILC.
Tumor grades also correlated with varying risk patterns. Of the 1,008 cases in which tumor grade was identified, those with grade 1 were more likely to have a high income level and an earlier age at first live birth. African-American women had a lower risk of grade 2 tumors, while the highest quartile for BMI was associated with grade 3. Associated with all grades were family history and a history of benign breast disease.
The findings suggest a possible link between breast carcinogenesis and pathogenesis, said the authors, who also included Donald Henson, MD, of George Washington, and Catherine Schairer, PhD, Kenneth Chu, PhD, and William Anderson, MD, MPH, from the National Cancer Institute.