Cancer
Endometriosis and ovarian cancer risk by histotype: a pooled analysis from the Ovarian Cancer Cohort Consortium Holly Harris* Holly Harris Harris Harris Harris Harris Fred Hutchinson Cancer Center
Background: Endometriosis is a common inflammatory condition that is characterized by the presence of endometrial-like tissue outside the uterine cavity. People with endometriosis have approximately a two to three-fold increased risk of endometrioid and clear cell ovarian cancer. However, the associations with other histotypes are less certain given the potential for detection bias as well as small sample sizes.
Methods: Our objective was to examine the association between endometriosis and invasive epithelial ovarian cancer risk in 10 prospective cohorts in the Ovarian Cancer Cohort Consortium (n=725,122 total participants). Endometriosis was self-reported in most of the studies. We used pooled logistic regression with time divided into two-year intervals. This approach estimates beta coefficients interpreted as log ORs that are analogous to cause-specific HRs.
Results: 7.1% of participants reported an endometriosis diagnosis. During follow-up 4,327 incident ovarian cancer cases were diagnosed, with 380 cases among those with endometriosis and 3,947 cases among those without. We observe a 64% higher risk of ovarian cancer (95% CI=1.47-1.82) in those with endometriosis compared to those without endometriosis. We observed a higher risk of all major ovarian cancer histotypes among those with endometriosis with ORs (95% CI) of 1.23 (1.05-1.45) for high-grade serous, 2.09 (1.30-3.35) for mucinous, 2.24 (1.65-3.03) for endometrioid, 3.02 (1.63-5.57) for low-grade serous, and 4.21 (3.00-5.89) for clear cell.
Conclusions: This prospective consortium analysis is one of the largest to demonstrate associations with high grade serous and mucinous ovarian cancer histotypes as well as endometrioid, clear cell, and low-grade serous. Given the distinctive cell of origins proposed for distinct ovarian cancer histotypes, this may indicate that pathways linking endometriosis to ovarian cancer may differ across histotypes.