Reducing risks of colorectal cancer

According to a study led by Dr. Polly Newcomb of the Public Health Sciences Division, women who take estrogen-plus-progestin postmenopausal hormones have a 40 percent lower risk of developing colorectal cancer as compared to nonusers of hormones or those who take estrogen alone. More specifically, estrogen-progestin hormone use was associated with a reduction in the risk of developing certain types of colorectal tumors-those that display little to no microsatellite instability, a generally acquired genetic characteristic that indicates defects in DNA-repair machinery.

Newcomb, head of the Cancer Prevention Program, and colleagues, including Allyson Templeton, Drs. Yingye Zheng, Victoria Chia, Libby Morimoto, V. Paul Doria-Rose and John Potter, conducted a population-based, case-control study to evaluate the relationship between postmenopausal-hormone type and colorectal-cancer incidence.

"The association between hormones and colorectal cancer was postulated in my doctoral work in Australia in the 1980s," said co-author Potter. "It is good to see that after 25 years, we are beginning to understand how it works."

The report, which appeared in the Aug. 1 issue of Cancer Research, extends the findings of previous about hormones and colorectal cancer by noting that a specific type of hormone therapy is associated with decreased risk. This relationship was also observed in the Women's Health Initiative. However, this report represents the largest study of its kind to date, involving 1,030 case patients and 1,074 control subjects from western Washington.

To view the paper, "Estrogen Plus Progestin Use, Microsatellite Instability and the Risk of Colorectal Cancer in Women," visit http://cancerres.aacrjournals.org/cgi/content/full/67/15/7534.