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Do Fertility Medications Cause Cancer?

By: Dr Paul Chang, MD, FRCSC, REI

The hot weather has finally arrived after a long cold winter followed by a cool and wet spring. During summer months, accidents are more likely to happen. The city and provincial police are doing blitzes to curtail drunk drivers and to enforce seat belt use. Children are told to wear helmets when biking, skateboarding or rollerblading. Suddenly, I am reminded of the importance of Smart Risk, an injury prevention organization founded by Dr. Robert Conn, a paediatric cardiac surgeon. The organization acknowledges that risk taking is a part of life and promotes the concept of taking ‘smart risk’. I believe that taking ‘smart risk’ also applies to health care decision making, including the use of fertility medication.

Medication use may cause side effects just as operating a motor-vehicle may cause injuries, but neither is likely to happen. We do not stop driving because there was an accident on the highway last night. When medically indicated, we should not be afraid to take fertility medication because Dr. Google said so. Cancers are considered chronic illnesses. A broad range of risk factors for chronic disease have been identified. These can be demographic, behavioural, biomedical, genetic, environmental, social or other factors, which can act independently or in combination. According to the Center for Disease Control, the most important modifiable risk factors for developing cancer includes tobacco smoking, excess weight, physical inactivity, poor diet, and excessive alcohol intake.

The risk of chronic disease generally depends upon the mean exposure received by the individual over time. For example, we do not expect one exposure to tobacco smoke, one meal with super-sized fries, or one fever that was treated with antibiotics to cause chronic diseases. But constant exposure over a long period of time, without allowing the body a chance to heal, may result in health concerns.

The effects of a medication typically begin to taper as its first half-life point is reached. In most cases, 90 to 95 percent of a medication is eliminated after four half-life cycles. For instance, if a medication’s half-life is 10 hours, it will take 40 hours for approximately 95 percent of the medication to be eliminated from the body. Below is a table of the most commonly used fertility medications and their half-lives:

 

                Drug Name                        Half Life
                  Menpur                           50h
                  Puregon                           40h
                  Gonal-F                            53h
                  Pregnyl                            23h
                 Letrazole                            48h

Therefore, if we take 48 hours as the average half-life of the most commonly used fertility drugs, after about 8 days, 95 percent of these drugs would have been effectively cleared from the body.

Research on fertility medication and cancer risk gives us further reassurances. Published in the medical journal Fertility and Sterility, Dr. Asante’s group from Mayo Clinic compared 1900 women of similar age with and without ovarian tumours. Among women who had a history of infertility, use of fertility drugs was reported by 44 (24 percent) of 182 without ovarian tumours and 38 (17 percent) of 226 with ovarian tumours. Dr. Asante concluded that there was no increased risk of ovarian tumours between infertile women who used fertility medication to those who did not. Dr. Fei published in the Journal of National Cancer Institute compared 1422 sisters, one with breast cancer and one without, and then looked at their past exposure to fertility medication. The study found that women who took the drugs and did not get pregnant had a slightly lower risk of developing breast cancer before age 50. Those who took the drugs and reported a pregnancy lasting 10 weeks or more had a slightly increased risk, but the risk was different from the risk of women who never took fertility medication at all.

When we consider the favourable biological effects of fertility drugs, their short half-life, and the large epidemiological studies that showed no increased risk of ovarian and breast cancer with use of fertility drugs, I am confident that judicious use of fertility drugs does not cause cancer. Public funding of In-Vitro Fertilization (IVF) in Ontario since late November of 2015 is a further reassurance of safety. If you are still worried about taking fertility medication due to fear of developing cancer, your time will likely be better served by remembering to eat well, quit smoking, drink responsibly and exercise regularly.

Remember life is about taking ‘smart risk’.