SAN FRANCISCOA new analysis based on SEER data shows a very low probability
of fatal breast cancer among women with DCIS for up to 10 years after diagnosis
and treatment. Further, the data suggest that women with DCIS are, overall,
healthier than the general population, Virginia L. Ernster, PhD, reported
at a poster session of the San Antonio Breast Cancer Symposium.
The findings came from an analysis of 12,946 DCIS cases in the NCI's
Surveillance Epidemiology and End Results (SEER) data base. The cases were
diagnosed between 1978 and 1992, and all the women were at least 40 years
old 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 cancer
accounted for 134 deaths, or 1.04% of the DCIS population, whereas 7.9%
of women diagnosed with localized invasive breast cancer during the same
period died of their cancer, said Dr. Ernster, professor of epidemiology
and biostatistics, University of California, San Francisco. Among women
with 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 DCIS
to expected deaths based on the experience of women in the general population.
The analysis showed a higher relative breast cancer mortality among DCIS
patients diagnosed between 1978 and 1983 (SMR of 3.16) than in those diagnosed
and treated since 1984 (SMR of 1.5).
DCIS also was associated with a lower cardiovascular mortality than
the general population. For women diagnosed with DCIS from 1978 to 1983,
the SMR for cardiovascular disease death within five years of their DCIS
diagnosis 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 in
the general population after five years (SMR, 0.83 versus 1.00) but was
virtually identical after 10 years.
The results suggest that women with DCIS represent a healthy segment
of the population, that they live healthier lifestyles, and that they have
more regular medical checkups, Dr. Ernster said.
However, she cautioned that a number of studies have suggested that
not all DCIS is alike. Some forms of the cancer appear to be more aggressive
and more likely to develop into invasive breast cancer.
"Because almost all women with DCIS were treated surgically, it
is impossible to tell from these data whether their very low risk of breast
cancer death means that the disease is relatively benign or that the therapy
is effective," she said. "We need longer follow-up to adequately
assess that issue."