Cohort study of the association of medically assisted reproduction with risk of hormone-related cancers

Medically assisted reproductive (MAR) treatment may be associated with an increased risk of hormone-related cancers. An Australian cohort study using an emulated target trial design investigated the risk of hormone-related cancer following assisted reproduction therapy, intrauterine insemination or ovarian stimulation, and ovulation induction with clomphene citrate. Hormone-related invasive cancer (identified in the Australian Cancer Database) included breast, ovarian, uterine, thyroid, colorectal cancer and melanoga. Three cancers with no hormonal links – pancreatic, lung, and hematological, were included as negative controls. A total of 1 748 927 women aged 18 to 55 years were identified, including 396 661 with history of MAR exposure. Hormone-related cancers were higher after some types of MAR treatment (HRs, 1.09-1.64). This excess may be partly or wholly due to detection bias and unmeasured confounding from infertility-related conditions, like endometriosis or polycystic ovary syndrome, and anovulation, obesity, and race and ethnicity. The authors conclude that these findings suggest that clinicians and women seeking medically assisted reproduction should be aware that hormone-related cancer risk could be associated with treatment, although this risk may not be attributable to the treatment itself.