Breast cancer among black and white women in the 1980s. Changing patterns in the United States by race, age, and extent of disease.

BACKGROUND: This national study of breast cancer incidence and mortality was conducted to determine whether patterns of change differ for black and white women, to evaluate patterns by extent of disease, and to determine whether recent patterns of breast cancer are consistent with results that one would expect due to increases in use of screening examinations by women.
METHODS: The study included 104,351 cases of in situ or invasive breast cancer diagnosed between 1983 and 1989 among women from the nine geographic areas participating in the National Cancer Institute Surveillance, Epidemiology, and End Results program. Breast cancer incidence patterns were examined by extent of disease for black and white women and by age at diagnosis.
RESULTS: Significant increases occurred in the incidence of all early-stage breast cancers. Concomitantly, significant decreases occurred in the incidence of the most advanced-stage breast cancers. Although both white and black women experienced significant increases in early-stage breast cancer, black women have substantially lower rates of the least extensive breast cancers.
CONCLUSIONS: These results strongly suggest that a major explanation for the increase in breast cancer incidence in the 1980s may well be the increased prevalence of breast cancer screening among women in the United States. They also suggest a consistent benefit of screening across all age groups from 40 to 49 years through 70 years and older.