Combined Oral Contraceptives and Endometrial Cancer Among Southeast Asian Women: A Secondary Analysis of Multicenter...

To determine the association of combined oral contraceptives (COCs) use and endometrial cancer risk in Southeast Asian women.

This is a secondary analysis of a previously conducted multicenter case-control study with the recruitment between 2015 and 2021. Cases were women with histologically confirmed diagnoses of endometrial cancer. Controls were women admitted to different wards for other medical conditions and were individually matched to cases by age and admission date, at a ratio of three controls per case. Data regarding contraception practices were collected through interviews conducted by trained personnel using a standardized questionnaire. Conditional logistic regression models were used to calculate adjusted odds ratios (aORs) and 95% confidence intervals (CIs).

In total, 115 (30.4%) out of 378 cases and 574 (50.6%) out of 1134 controls reported a history of COCs use. The odds of endometrial cancer were lower in women who had ever used COCs than those who reported never use (aOR 0.60; 95% CI 0.44-0.82). For every additional 12 months of COCs use, the odds of endometrial cancer decreased by 10% (aOR 0.90; 95% CI 0.86-0.93). Former COCs users had a reduced odds of endometrial cancer for up to 30 years after discontinuation (aOR 0.44; 95% CI 0.25-0.77).

A noticeable trend was observed indicating a decline in the odds of endometrial cancer with increasing duration of COCs use. COCs users continued to receive long-term protection against endometrial cancer after discontinuation.