At 10 Years, DCIS Patients' Risk of Breast Cancer Death Is Very Low

SAN FRANCISCO—A new analysis based on SEER data shows a very low probabilityof fatal breast cancer among women with DCIS for up to 10 years after diagnosisand treatment. Further, the data suggest that women with DCIS are, overall,healthier than the general population, Virginia L. Ernster, PhD, reportedat a poster session of the San Antonio Breast Cancer Symposium.

The findings came from an analysis of 12,946 DCIS cases in the NCI'sSurveillance Epidemiology and End Results (SEER) data base. The cases werediagnosed between 1978 and 1992, and all the women were at least 40 yearsold at the time of diagnosis. Virtually all the cases were treated surgically.Follow-up ranged from one to 16 years (average, 46 months).

Overall, 1,148 women had died since their DCIS diagnosis. Breast canceraccounted for 134 deaths, or 1.04% of the DCIS population, whereas 7.9%of women diagnosed with localized invasive breast cancer during the sameperiod died of their cancer, said Dr. Ernster, professor of epidemiologyand biostatistics, University of California, San Francisco. Among womenwith DCIS followed for 10 years, 2.6% died of breast cancer.

Dr. Ernster and her colleagues used a standard mortality ratio (SMR),which, in this case, is the ratio of observed deaths among women with DCISto expected deaths based on the experience of women in the general population.The analysis showed a higher relative breast cancer mortality among DCISpatients diagnosed between 1978 and 1983 (SMR of 3.16) than in those diagnosedand treated since 1984 (SMR of 1.5).

DCIS also was associated with a lower cardiovascular mortality thanthe general population. For women diagnosed with DCIS from 1978 to 1983,the SMR for cardiovascular disease death within five years of their DCISdiagnosis was 0.86, and for women diagnosed after 1983, the SMR was 0.62.

All-cause mortality was lower for the DCIS cohort than for women inthe general population after five years (SMR, 0.83 versus 1.00) but wasvirtually identical after 10 years.

The results suggest that women with DCIS represent a healthy segmentof the population, that they live healthier lifestyles, and that they havemore regular medical checkups, Dr. Ernster said.

However, she cautioned that a number of studies have suggested thatnot all DCIS is alike. Some forms of the cancer appear to be more aggressiveand more likely to develop into invasive breast cancer.

"Because almost all women with DCIS were treated surgically, itis impossible to tell from these data whether their very low risk of breastcancer death means that the disease is relatively benign or that the therapyis effective," she said. "We need longer follow-up to adequatelyassess that issue."