Colorectal cancer risk of Hormonal Contraception

There is little overall association between colon cancer and oral contraceptive use,  parity,  age at first birth,  hysterectomy or oophorectomy status,  or age at menopause. Use of contraceptive hormones at or after age 40, was associated with decreased risk of colon cancer (OR= 0.60), particularly among women with more than five years of use (OR =0.47).

While, results from previous studies showed as inconsistent any protective effect against colon cancer. Would be important given the continuing debate over its potential risks and benefits (69).  Evidence from epidemiologic studies suggests a possible role of exogenous and endogenous hormones in colorectal carcinogenesis in women.However,  with respect to exogenous hormones,  in contrast to hormone replacement therapy,  few cohort studies have examined oral contraceptive use in relation to colorectal cancer risk.

A   recent   study   performed   on   88.835   women   affirmed   that   use   of   oral contraceptives was associated with a modest reduction in the risk of colorectal cancer (OR 0.83). No trend was seen in the ratios with increasing duration of oral contraceptive use. The results are suggestive of an inverse association between oral contraceptive use and colorectal carcinogenesis (70).

Previous findings on the associations between oral contraceptive (OC)  use and reproductive factors and, risk of colorectal cancer have been inconclusive.

Women who had used OCs for 6 months to < 3 years had a relative risk of 0.61 relative to never users, with little additional   decreased   risk   being   seen   with   longer   duration   of   use   (p   for multivariate trend =  0.09).  No significant association was observed between reproductive factors and colorectal cancer risk.  These findings provide some support for a potential role of HCs in reducing risk of colorectal cancer. (71).

These data are consistent with a role for estrogen in altering susceptibility to diet and lifestyle factors possibly, via an insulin-related mechanism. (72).

It is hypothesized that estrogen up-regulates insulin-like growth factor (IGF-I) receptors and insuline receptor substrate (IRS-I) levels in the colon, which in turn increases susceptibility to, obesity-induced,  increased levels of insulin. 

It was further hypothesized that androgens may have similar effects in men given the decline in colon cancer risk associated with BMI with advancing age.  The association between body mass index (BMI)  and colon cancer has been reported to be different for men and women.  Scarce   literature   has   examined   if   estrogen   influences   these differences. (73)  Epidemiologic and experimental reports suggest that female hormones protect against the development of colorectal cancer,  but studies are limited. 

It was described a case of a patient,  in the placebo arm of a 4-year primary chemoprevention trial ,who developed adenomatous polyps and then had eradication of polyps after the administration of oral contraceptives. No change in the prostaglandin levels in the colonic mucosa was noted after polyp elimination, making nonsteroidal anti-inflammatory drug ingestion unlikely as a cause. 

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