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DES AND BREAST CANCER: 30+ YEARS LATER.

A 1984 study linked diethylstilbestrol (DES) exposure during pregnancy with a slightly increased risk for breast cancer (relative rate, 1.4) that seemed to rise with increasing time from exposure (the average follow-up was 29 years). To determine whether the risk continued to rise, the same investigators collected 10.8 additional years of follow-up data from 3029 DES-exposed women and 3029 unexposed women.

The total woman-years of follow-up exceeded 100,000 in each group. A total of 194 breast cancers were reported in exposed women and 147 in unexposed women. After adjustment for age at diagnosis, age at menarche, reproductive history, and other factors, the cumulative relative rate of breast cancer associated with DES exposure was 1.35. The increase in risk was not greater in women followed for 30 years or more (relative rate, 1.33). There were 52 deaths from breast cancer in the exposed women versus 40 in the unexposed women (relative rate, 1.27).

These data show that DES is associated with a modest increase in the risk for breast cancer, but that the risk does not continue to rise after 30 years or more from the time of exposure.

— THL

Published in Journal Watch General Medicine May 4, 1993

Citation(s):

Colton T et al. Breast cancer in mothers prescribed diethylstilbestrol in pregnancy: further follow-up. JAMA 1993 Apr 28 269 2096-2100.

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