NEW YORK, Nov 01 (Reuters Health) -- Older women on estrogen replacement therapy (ERT) may be significantly less likely to develop colon cancer than those never treated with the hormone, a researcher at the University of Southern California School of Medicine has found.
In a 14-year study of 7,700 women ages 44 to 98, those who were using ERT within a year of the start of the study were approximately one-third less likely to develop colon cancer than were women who never used ERT. Women who had been on estrogen replacement earlier in their lives had a close to 20% lower risk for the disease, according to a report in the October issue of the journal Diseases of the Colon and Rectum.
These findings are strong enough to consider reduced colon cancer risk a possible benefit of estrogen replacement therapy, Dr. Annlia Paganini-Hill, a professor of preventive medicine at the Los Angeles university, said in an interview with Reuters Health.
In the early 1980s, according to Paganini-Hill, research first suggested that hormones may influence colon cancer risk. Since then, studies have yielded conflicting results on whether or not estrogen replacement cuts women's risk. Many of these studies, Paganini-Hill noted, looked only at women who had never used ERT or had used it at some point in their lives. This study revealed that it may be recent use, in particular, that cuts colon cancer risk, she said.
Among all women in the study, 56% had received ERT at some point; 30% of these women were considered "recent users." Most of the women, Paganini-Hill reported, had used estrogen right after menopause but had discontinued it by the time of the study. Women who had discontinued therapy more than 15 years before the study showed no benefits in terms of risk of colon cancer, and risk was not affected by how long women were on estrogen replacement or by the hormone dose or by the way the dose was administered.
It is possible, Paganini-Hill noted, that women who go on ERT differ from non-users in ways that influence colon cancer risk. However, she added, in this study ERT's effect on risk was unchanged by other factors such as the women's diets, alcohol consumption, or body mass index. Further, according to her report, two recent reviews of studies on ERT's link to colon cancer also showed that hormone replacement cut women's risk by about one-third.
Colon cancer is the fourth most common and second most deadly cancer in the United States. Nevertheless, Paganini-Hill reported, the colon cancer death rate has declined in the past 30 years -- by 7% among men, and 30% among women. During the same period, she noted, use of estrogen replacement therapy has increased and ERT use could have contributed to reduced colon cancer incidence among women.
