Objective: The objective of the study is to compare the efficacy of dienogest 2 mg vs continuous oral levonorgestrel/EE (levonorgestrel 0.1 mg/ethinyl estradiol 0.02 mg) on ovarian endometriomas, deep infiltrating endometriosis (DIE), chronic pelvic pain (CPP), dyspareunia, analgesic use, quality of life (QoL), compliance and side effects.

Methods: Prospective cohort study. Two cohorts of patients with endometriosis, 50 taking dienogest (group A) and 50 taking continuous levonorgestrel/EE (group B), were evaluated at the beginning of therapy (t0), after 3 (t3) and 6 months (t6). Size of endometriomas, DIE, QoL, pain symptoms, and side effects were assessed.

Results: Dienogest was significantly effective on CPP, dyspareunia ovarian endometriomas and DIE lesions reduction. Levonorgestrel/EE was significantly effective on dyspareunia. Analgesics consumption significantly decreased in both groups. Both treatments significantly improved the QoL. Over 6 months a significant improvement was found, more frequently in patients taking dienogest. The only side effect that both groups complained about was vaginal bleeding, present in the first 3 months of treatment.

Conclusions: Both treatments are effective and safe for patients with endometriosis. Patient’s compliance and side effects are similar in both groups; however, there was a significantly higher reduction in endometriotic lesions, pain symptoms, and improvement of the QoL in women taking dienogest than in women taking continuous COC.