Medically assisted reproductive treatment may be linked to hormone-related cancers

Women undergoing medically assisted reproductive treatment seem to be at heightened risk of hormone-related cancers, as suggested in a study.

Researchers emulated a target trial using Australian health registries and administrative datasets. They looked at 1,748,927 women enrolled in Medicare, among whom 396,661 had a history of medically assisted reproductive treatment.

Outcomes included hormone-related invasive cancers such as breast, ovarian, uterine, thyroid, colorectal cancers, and melanoma. Cancers with no hormonal links, including pancreatic, lung, and haematological, were included as negative controls.

Results indicated that medically assisted reproductive treatment was associated with elevated risks of most hormone-related cancers, with hazard ratios ranging between 1.09 and 1.64. However, further analysis suggested confounding, with underlying infertility conditions (ie, endometriosis, polycystic ovarian syndrome) possibly accounting for the observed increase in the risks of uterine, ovarian, and thyroid cancers.

For any specific invasive cancer, the incidence was low, with fewer than 20 extra cancers per 100,000 women each year estimated for treated vs comparator groups. Emulated trials on the six hormone-related cancers and pancreatic and haematological cancers showed increased cancer risk in the first years after treatment, indicating detection bias.

The hazard ratios for haematological cancers ranged from 1.18 to 1.27, indicating that uncontrolled confounding by race and ethnicity could account for the observed excess risk seen for several cancers.

Meanwhile, some treatments were associated with reduced lung cancer risk (hazard ratios, 0.72–0.82).