Into a conference room literally frozen with doubt from a hyperactive air-conditioning system came a few warming breezes about the future of research, and funding, into cancers caused by the 1950's drug diethylstilbestrol. Participants at a recent 2-day DES meeting noted the potential for stepped-up research efforts given confirmation of several earlier studies showing that women exposed to DES decades ago may now face an increased risk for breast cancer.
"Based on continued cohort studies, we are now fairly sure that DES women face a 20% to 30% excess risk for breast cancer," said Robert Hoover, M.D., director of the Epidemiology and Biostatistics Program at the National Cancer Institute. This finding alone, he said, should validate the need for continued follow-up and research in this field. But Hoover also cited a 1998 study that confirmed a cumulative excess risk (of 1/1000 to 1/2000) in DES-exposed women in utero for a fairly rare cancer called clear cell adenocarcinoma.
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From the 1940s to 1971, DES thought then to be an anti-abortive agent was used by over 2.5 million women, but by the early 1990s its only proven carcinogenic property was an increased risk of clear cell adenocarcinoma in daughters of the women who used the drug during pregnancy. That rare cancer risk alone, no matter how devastating, might not have been sufficient to sustain national interest and funding of research into the chemical's long-term effects.
At the July meeting at the National Institutes of Health, where more DES advocates than scientists were in attendance, Rep. Louise Slaughter (D-N.Y.) gave the advocates their due, noting that it was the "mothers, daughters, and sons [who] would not let DES research die." And the latest research findings about other cancers associated with DES bear out their vigilance, she said.
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The history of DES research is littered with twists and turns not dissimilar to its legislative struggles. Charles Dodds, M.D., Ph.D., created DES, the first synthesized estrogen while at the University of London. By 1948, other researchers postulated that DES might help treat complications of pregnancy, particularly spontaneous abortions.
Only 5 years later was it determined that DES was ineffective, but it wasn't until 1971 that the U.S. Food and Drug Administration issued a drug bulletin warning of the drug's possible side effects. Shortly thereafter in 1975, DES Action USA was formed in Oakland, Calif., to fight for the rights of those exposed to the chemical. In the late 1970s, the NCI conducted a nationwide education initiative to alert women to the drug's side effects and to help health professionals detect and manage those side effects.
At an NIH conference on DES in 1992, said pioneering DES researcher Arthur Herbst, M.D., University of Chicago, Ill., the only solid evidence of increased cancer risk to DES-exposed women was to clear cell adenocarcinoma, a cancer which occurs in non-exposed women in middle age, but much earlier ( in the late teens and early 20s) in DES-exposed women. Herbst maintains a registry of DES-exposed women with clear cell adenocarcinoma that now numbers 715. According to Herbst, a majority of these women were diagnosed with early-stage disease which has 5-and 10- year-survival estimates of 93%, and 87% respectively.
Hoover said that since that conference there may be several other good reasons for heightened concern and awareness for those exposed to DES in addition to its breast cancer risk. Research by former NIH researcher Heinz Berendes, M.D., in 1993, Hoover said, showed that DES caused more abortions and premature births than a control group exactly the opposite of what the drug was supposed to do (see DES ad from 1957).
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A nationwide program to gauge awareness was begun 5 years ago as were queries to physicians to try and determine their familiarity with DES. The next step of the education effort is now up to the Centers for Disease Control and Prevention, in Atlanta, Ga. According to Carol Rubin, D.V.M., at CDC's National Center for Environmental Health, the CDC intends to contract with NCI for a national educational campaign, which will have "a high priority." Rubin said that the American Medical Association is also interested in partnering in this effort.
As part of the final recommendations that emerged from the conference, meeting organizer Susan Sieber, Ph.D., associate director for special projects, NCI, stressed the concerns voiced by DES sons in attendance. Hoover said that definitive cancer risks will be difficult to discern in this group, however. Even though a few studies have shown an excess cancer risk, he said, the measures of hormone exposure have been crude, and there are few DES sons in the combined cohort studies.
Another recommendation from the group was that researchers start to examine grandchildren of DES-exposed women, as they too may have a potential for DES cancers.
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