Most fertility drugs pose no risk of colorectal cancer

The use of most types of fertility drugs does not appear to put infertile women at risk of developing colorectal cancer, according to a study.

The study used data from the Danish Infertility Cohort and included all women with infertility aged 20–45 years living in Denmark during 1995–2017. Researchers obtained information regarding the use of specific types of fertility drugs, colorectal cancer diagnoses, covariates, and vital status, applying Cox proportional hazard models in their analysis.

A total of 148,036 women were included in the final analysis, among whom 205 were diagnosed with colorectal cancer. Compared with nonuse, ever use of clomiphene citrate was associated with a lower incidence of colorectal cancer (unadjusted hazard ratio [HR], 0.67, 95 percent confidence interval [CI], 0.51–0.89; adjusted HR, 0.68, 95 percent CI, 0.50–0.93).

However, the lower cancer incidence associated with clomiphene citrate use was only observed among women who initiated treatment >8 years ago (unadjusted HR, 0.56, 95 percent CI, 0.41–0.76; adjusted HR, 0.52, 95 percent CI, 0.36–0.75).

None of the other types of fertility drugs showed associations with colorectal cancer.

In an analysis that evaluated colon and rectal cancer separately, the results were consistent except for a trend toward a decreased risk of rectal cancer associated with the use of gonadotropins (adjusted HR, 0.46, 95 percent CI, 0.20–1.08).

The investigators acknowledged that the findings on rectal cancer may be related to the underlying conditions in infertile women or are chance findings. They called for large epidemiological studies to validate the results of the present study.