Fertility treatment and risk of non-gynecological cancer: a systematic review

Evidence on the relationship between fertility treatment and non-gynecologic cancers remains limited. This study synthesizes available research on the association between fertility treatments and the risk of non-gynecologic cancers in women with infertility.

We systematically searched MEDLINE, EMBASE, and the Cochrane Library for studies involving women with infertility who received fertility treatment, compared with untreated women or the general population. Primary outcomes included the incidence of thyroid, colorectal, gastric, and lung cancers. Subgroup analyses were conducted by type of ovarian stimulation drug, in vitro fertilization (IVF) status, parity, length of follow-up, and choice of reference group.

Fifteen studies met the inclusion criteria. Fertility treatment was positively, though imprecisely, associated with thyroid cancer (relative risk [RR] = 1.22; 95% confidence interval [CI]: 0.95-1.57). No increased risk of colorectal cancer was observed among treated women. Clomiphene citrate use was associated with a higher risk of thyroid cancer (RR = 1.28; 95% CI: 1.07-1.54) and a lower risk of colorectal cancer (RR = 0.79; 95% CI: 0.65-0.96).

Fertility medications may increase the risk of thyroid cancer while potentially reducing the risk of colorectal cancer in women with infertility. Given the small number of studies and their heterogeneity, these findings should be interpreted cautiously. Further research is needed to clarify these associations.