Endometriosis as a risk factor for Ovarian or Endometrial Cancer – Results of a hospital based case control study

Background: There is no screening program for ovarian or endometrial cancer. One way to address the problem could be the utilization of risk factors to define sub-populations with a higher incidence. Recently, there were hints that endometriosis could be a risk factor for ovarian cancer.

Methods: We conducted a hospital based case control analysis. Cases were patients with endometrial or ovarian cancer who participated in studies aiming at risk assessment for these diseases. Controls were women who were invited by newspaper advertisement. A total of 289 cases and 1016 controls were included. Two logistic regression models were used, one with the predictors age, number of pregnancies and previous oral contraceptive (OC) use and another one including additionally whether the patient was diagnosed with endometriosis.

Results: Endometriosis was present in 21 controls (2.1%) and 14 cases (4.8%). Relevant predictors for case control status were previous OC use (OR = 0.41; 95% CI: 0.30 – 0.55) and endometriosis (OR = 2.53; 95% CI: 1.23 – 5.21). The prediction model that included endometriosis was slightly better (p = 0.01, likelihood ratio test) than the model without endometriosis (AUC = 0.67 vs. AUC = 0.66).

Conclusion: In our case control study endometriosis could be described as a risk factor for endometrial or ovarian cancer. Studies addressing this question are rare and the implementation into a clinical prediction model would demand a precise characterization of the risk factor endometriosis. For this purpose we initiated a multicentric cohort study (www.myendometriosis.org), the International Endometriosis Evaluation Program where centers all over the world are invited to participate.