Dienogest and the Risk of Reoperation in Endometriosis

Background: This retrospective cohort study aimed to determine whether there is a difference in reoperation rates between patients who used dienogest (DNG) and patients who did not use DNG. Methods: Using Health Insurance Review and Assessment Service (HIRA) data generated between 1 January 2010 and 30 June 2018, we identified women with an endometriosis diagnosis code who used GnRH agonists after gynecological surgery. Among them, women prescribed DNG were selected as the DNG group, and those who did not receive DNG were selected as the control group. A survival analysis of the reoperation between the two groups was performed. Results: DNG and control groups were extracted from 9735 people each. The reoperation rates were 0.4% and 0.6% in the DNG and control groups, respectively, without adjusting. In the Cox proportional risk analysis, DNG use increased the reoperation rate {hazard ratio (HR), 1.599; 95% confidence interval (CI), 1.005–2.545}. The site of endometriosis and the number of GnRH agonist injections were not associated with reoperation (HR, 1.008; 95% CI, 0.739–1.374; HR, 1.062; 95% CI, 0.690–1.635). In the subgroup survival analysis, according to the period between the last GnRH agonist injection and the first DNG dose, DNG did not increase the reoperation rates up to 9 months (~3 months: HR, 0.968; 95% CI, 0.551–1.699; 4~6 months: HR, 1.094; 95% CI, 0.58–2.063; 7~9 months: HR, 2.419; 95% CI, 0.735–7.962), but DNG increased the reoperation rate from 10 months onwards (10~12 months: HR, 3.826; 95% CI, 1.164–12.579 and ~13 months: HR, 8.436; 95% CI, 4.722–15.072). Conclusions: Women who used DNG had a higher endometriosis reoperation rate than women who did not use DNG. However, the initiation of DNG treatment within nine months after the last GnRH agonist injection did not affect the endometriosis reoperation rate.