Hormone replacement therapy in relation to survival in women diagnosed with colon cancer

Colorectal cancer is the second leading cause of cancer death among US men and women. A number of studies report that hormone replacement therapy (HRT) reduces the risk of colorectal cancer, but fewer studies have examined the relation between HRT use and survival after diagnosis and none examined this relation by anatomic location of the primary colon tumor.

Data from a cohort of 699 women 50-79 years of age diagnosed with colon cancer between 1980 and 1998 in a large Health Maintenance Organization based in Seattle, Washington were analyzed to examine the relation between HRT use prior to diagnosis and survival. Use of HRT was ascertained from a computerized pharmacy database.

HRT use was associated with a 41% reduction in risk of death after adjustment for age, stage, and diagnosis year (p= 0.037). The association between HRT use and colon cancer survival was strongest among women with cancer in the distal colon (hazard rate ratio 0.33, 95% confidence interval, 95% CI: 0.13-0.83), while little or no association between HRT use and survival was observed among women with proximal tumors (HRR 0.78, 95% CI: 0.42-1.44).

These findings suggest that HRT use is associated with improved survival from colon cancer. Future observational and laboratory studies should shed light on how hormones may be related to reduced incidence and improved prognosis.