Do Fertility Drugs Increase Your Risk of Getting Cancer?

The Cancer Risk of Fertility Drugs vs. the Risks Infertility Itself Brings

Doctor talking with a woman about the possible risk of cancer after fertility drugs and infertility
While fertility drugs don't seem to increase your risk of cancer, infertility itself does. It's important for your doctor to follow-up after treatment.. JGI/Tom Grill / Getty Images

Do fertility drugs cause cancer? What about IVF treatment? It is true that a few studies seemed to find a connection between fertility drug use and an increased risk of breast or uterine cancer, specifically with the drug Clomid

All medications, including fertility drugs, come with risks.

But is cancer a risk you should be concerned about? Let's take a look.

Fertility Drugs May Increase... or Decrease Your Cancer Risk?

In 2005, a widely publicized study reported that Clomid use may increase the risk of uterine cancer.

However, since that time, more studies have been done, and most have found no significant increase in cancer risk after Clomid use.

In fact, ironically, one study showed that women treated with fertility drugs seemed to show a decreased risk of developing uterine cancer when compared to infertile women who did not seek treatment.

Another study found a decreased risk of developing breast cancer after Clomid.

Why the discrepancies?

Clomid and Uterine Cancer Risk

In a study conducted by the National Cancer Institute, researchers looked at 8,431 women who sought treatment for infertility between 1965 and 1988. Using questionnaires or death records, they found that 39 of the women developed uterine cancer, more than you’d expect if you compared this to the general population.

The researchers concluded that use of Clomid may have increased their risk of developing uterine cancer.

They found that the risk of uterine cancer increased if higher dosages were used and if the drug was taken for six months or more.

Notably, they found that the risk of developing uterine cancer was even stronger if the women were obese or never became pregnant, with a combination of these two factors raising the risk even higher.

The problem with this research study is it didn’t take into account other potential risk factors for uterine cancer.

Namely, if a woman never experiences pregnancy, her risk of cancer increases.

Also, obesity is not only a risk factor for infertility, but it is also a risk factor for cancer.

It may not have been the fertility drugs at all. Instead, the increased incidence may be attributed to the reason behind infertility itself, or any number of other factors not taken into account in this study.

Many studies have found a possible connection between certain causes of infertility and an increased risk of cancer.

Other studies that have found a connection between fertility drug use and cancer risk have similar problems.

Either they failed to take into account other risk factors, including infertility itself, or the study sizes were too small to be considered strong evidence.

IVF and Ovarian Cancer

At the 2015 American Society of Reproductive Medicine (ASRM) conference, Dr. Alastair Sutcliffe of Institute of Child Health at University College London presented a study looking at the cancer risk in women who had gone through IVF treatment.

This study included over 250,000 British women and spanned treatment cycles between 1991 and 2010. 

The good news was that they found no increased risk of breast or uterine cancer in the former IVF patients. 

The bad news is that found an increased risk in ovarian cancer.

While women who had never gone through IVF had an 11 in 10,000 chance of developing ovarian cancer, the IVF patients had a 15 in 10,000 risk.

The risk is small but important to recognize.

Like in the studies mentioned above, the general consensus is that the increased risk isn't caused by IVF treatment itself but the fact that the women needed treatment. 

Infertility and the need for IVF are suspected as the risk. Not the fertility drugs used during treatment.

With that said, the study also found that the cancer risk was higher in the first three years after treatment.

So, it's not possible to completely rule out that the fertility drugs played a role in the cancer risk. Close monitoring in the years after IVF treatment may be smart.

No Increased Risk of Cancer

A meta-analysis is a research study that gathers information from several studies and evaluates them together. The University of Ottawa conducted a meta-analysis to look into whether fertility drug use increased the risk of cancer when compared to infertile women who were not treated.

The analysis included the data collected by 10 different research studies, with information on women taking fertility drugs like Clomid, gonadotropins, human chorionic gonadotropin (hCG), and gonadotropin releasing hormone agonists (GnRH).

The researchers found that when comparing infertile women treated with fertility drugs, against infertile women who were not treated, those treated with fertility drugs were not at an increased risk of developing uterine cancer.

Most interestingly, they did find that women who were treated seemed to have a lower incidence of ovarian cancer when compared to infertile women who were not treated.

In another study, this one conducted by the Danish Cancer Society, researchers did a cohort study of 54,362 women with infertility. (A cohort study is when they look at a large group of people with similar circumstances, typically over a long period of time.)

In this study, the researchers found no significant increase in risk for breast cancer after fertility drug use, specifically gonadotrophins, Clomid, hCG, or GnRH.

There are other studies that have found similar results.

Where It Stands

The general consensus is that fertility drugs do not increase your risk for developing breast or uterine cancer.

In addition, some studies have looked at fertility drug use and other kinds of cancers (thyroid and skin cancers, for example), and they have also found no significant increase in risk.

However, because infertility itself is a risk factor for cancer, follow-up after an infertility diagnosis is important.

Women with primary infertility, who never become pregnant and give birth, as well as women diagnosed with endometriosis, may particularly have an increased risk of developing cancer. 

PCOS, a common cause of infertility, is also known to come with an increased risk of developing endometrial cancer.

While more research should be done, for now, fertility drugs are (mostly) off the hook.

Sources:

Althuis MD, Moghissi KS, Westhoff CL, Scoccia B, Lamb EJ, Lubin JH, Brinton LA. Uterine cancer after use of clomiphene citrate to induce ovulation. American Journal of Epidemiology. 2005 Apr 1; 161(7):607-15.

Althuis MD, Scoccia B, Lamb EJ, Moghissi KS, Westhoff CL, Mabie JE, Brinton LA. Melanoma, thyroid, cervical, and colon cancer risk after use of fertility drugs. American Journal of Obstetrics and Gynecology. 2005 Sep; 193(3 Pt 1):668-74.

Brinton LA, Lamb EJ, Moghissi KS, Scoccia B, Althuis MD, Mabie JE, Westhoff CL. Ovarian cancer risk associated with varying causes of infertility. Fertility and Sterility. 2004 Aug; 82(2):405-14.

Burkman RT, Tang M, Malone K, Marchbanks PA, McDonald JA, Folger SG. Infertility drugs and the risk of breast cancer: findings from the National Institute of Child Health and Human Development Women’s Contraceptive and Reproductive Experiences Study. Fertility and Sterility. 2003 April; 79(4):844-51.

Jensen A, Sharif H, Svare EI, Frederiksen K, Kjaer SK. Risk of breast cancer after exposure to fertility drugs: results from a large Danish cohort study. Cancer Epidemiol Biomarkers Prev. 2007 Jul; 16(7):1400-7. Epub 2007 Jun 21.

Kashyap S, Moher D, Fung MF, Rosenwaks Z. Assisted reproductive technology and the incidence of ovarian cancer: a meta-analysis. Obstetrics and Gynecology. 2004 Apr; 103(4):785-94.

Knapton, Sarah. "IVF women third more likely to develop ovarian cancer.” The Telegraph. Accessed Oct 21, 2015.

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