Recent trends and racial/ethnic differences in the incidence and treatment of ductal carcinoma in situ of the breast in California women

BACKGROUND. The rapid increase in the incidence of ductal carcinoma in situ (DCIS) of the breast in the U.S. has been associated with the widespread adoption of screening mammography. Little is known regarding the incidence and treatment of DCIS in women of racial/ethnic groups other than white and black. The current investigation examined recent trends and racial/ethnic differences in the incidence and treatment of DCIS in California. METHODS. All cases of DCIS diagnosed in women age greater than or equal to 40 years in California between 1988-1999 were included. Age-adjusted incidence rates for white, black, Hispanic, and Asian-Pacific Islander women were calculated using the 2000 U.S. female population as the standard. The estimated annual percent change (EAPC) in the rates was calculated using least squares regression. RESULTS. The average annual age-adjusted incidence of DCIS (1988-1999) was 45.3 per 100,000 in white women, 35.0 in black women, 30.9 in Asian-Pacific Islander women, and 21.8 in Hispanic women. Although a steady increase in the incidence of DCIS was noted in all racial/ethnic groups over the study period, Asian-Pacific Islander women were found to have experienced the steepest increase (EAPC = 9.1%), particularly in the age group 50-64 years (EAPC = 12.0%). The DCIS incidence was reported to increase with age in white, black, and Hispanic women, but remained fairly constant after the age of 50 years in Asian-Pacific Islanders. The proportion of women with DCIS treated with mastectomy decreased from 53% in 1988 to 32% in 1999. Younger women and Asian-Pacific Islander women reportedly were more likely to undergo mastectomy. CONCLUSIONS. Considerable differences by race/ethnicity and age were observed in DCIS incidence and the change in the incidence in California between 1988 and 1999. Further information is needed to determine whether these differences are because of differential utilization of screening mammography or biologic characteristics of DCIS lesions.