To evaluate the side effects and causes of discontinuation of either combined oral contraceptives or dienogest (DNG) used to prevent recurrence in patients with surgically confirmed endometriosis.

We retrospectively analyzed the medical records of 213 women with endometriosis who had been treated with combined oral contraceptives (ethinyl estradiol 0.02 mg/drospirenone 3 mg [EE/DRSP]) or DNG 2 mg for 12 months or more. The side effects reported by the patients, laboratory parameters, causes of discontinuation of medication, and recurrence rates were evaluated one, two, three, four, and five years after starting medication (Y1, Y2, Y3, Y4, and Y5).

EE/DRSP were administered to 59 patients, while DNG was administered to 154 patients. The mean durations of postoperative use of EE/DRSP and DNG were 44.5 ± 22.6 months and 23.6 ± 13.5 months, respectively. The prevalence of side effects was 27.1%, 19.0%, 10.0%, 10.5%, and 7.4% in the EE/DRSP group and 29.2%, 15.7%, 14.0%, 23.1%, and 0.0% in the DNG group at Y1, Y2, Y3, Y4, and Y5, respectively. The discontinuation rates were 1.7%, 1.7%, 4.0%, 0.0%, and 7.4% at Y1, Y2, Y3, Y4, and Y5, respectively, in the EE/DRSP group and 10.4%, 3.3%, 4.0%, 3.8%, and 0.0% at the same times in the DNG group. The recurrence rates were less than 4% in both the groups.

The side effects of commonly prescribed postoperative hormone treatments were relatively mild, and the occurrence of side effects decreased with continuous administration. Further, the long-term use of postoperative hormone treatments is likely to prevent recurrence of endometriosis after surgery.