Mortality among women with ductal carcinoma in situ of the breast in the population-based surveillance, epidemiology and end results program

Background: Over 14% of breast cancers diagnosed in the United States annua lly are ductal carcinomas in situ (DCIS). There are no published population -based reports of the likelihood of breast cancer death among US women with DCIS. Methods: We used data from the Surveillance, Epidemiology and End Results p rogram to determine the likelihood of breast cancer death at 5 and 10 years among US women aged 40 and older diagnosed with DCIS from 1978 to 1983 (be fore screening mammography was common; n = 1525) and from 1984 to 1989 (whe n screening mammography became common; n = 5547). We also calculated standa rdized mortality ratios (SMRs) to compare observed deaths from breast cance r, cardiovascular disease, and all causes combined among women with DCIS wi th deaths expected based on general population mortality rates. Results: Among women diagnosed with DCIS from 1978 to 1983, 1.5% died of br east cancer within 5 years and 3.4% within 10 years. Among women diagnosed from 1984 to 1989, 0.7% died of breast cancer within 5 years and 1.9% withi n 10 years. Relative to the general population, risk of breast cancer death was greater for women diagnosed from 1978 to 1983 (SMR, 3.4; 95% confidenc e interval [CI], 2.5-4.5) than for women diagnosed from 1984 to 1989 (10-ye ar SMR, 1.9; 95% CI, 1.5-2.3). Women diagnosed from 1984 to 1989 were signi ficantly less likely than women in the general population to have died of c ardiovascular diseases (10-year SMR, 0.6; 95% CI, 0.5-0.7) or of all causes combined (SMR, 0.8; 95% CI, 0.7-0.8). Conclusions: Among women diagnosed with DCIS, risk of death from breast can cer was low, at least within the 10 years following diagnosis. This may ref lect the effectiveness of treatment for DCIS, the "benign" nature of DCIS, or both. At 10 years, women diagnosed from 1984 to 1989 were less likely th an women diagnosed from 1978 to 1983 to have died of breast cancer, and the ir risk of dying of all causes combined was lower than that in the general population.