Objective: To study the efficacy of long-term treatment with norethindrone acetate (NETA) in patients with rectovaginal endometriosis.

Study design: This retrospective cohort study included 103 women with pain symptoms caused by rectovaginal endometriosis. Patients received NETA alone (2.5mg/day up to 5mg/day) for 5 years. Primary outcome was the degree of satisfaction with treatment after 5 years of progestin therapy. Secondary outcomes were the assessment of any variation in pain symptoms and the volumetric assessment of the disease by magnetic resonance imaging (MRI).

Results: Sixty-one women completed the 5-year follow-up (61/103, 59.2%) with 16 women withdrawing because of adverse effects (38.1%). Overall, 68.8% (42/61) of the women who completed the study were satisfied or very satisfied of this long term NETA treatment. This represents a 40.8% (42/103) of the patients enrolled. Intensity of chronic pelvic pain and deep dyspareunia significantly decreased during treatment (p<0.001 versus baseline at 1 and 5year). Dyschezia improved after 1-year respect to baseline (p=0.008) but remained stable between first and second year (p=0.409). At the end of 5 years treatment, a radiological partial response was observed in 33 patients (55.9%, n 33/59); a stable disease in 19 patients (32.2%, n 19/59). Seven women (7/59, 11.9%) displayed a volumetric increase of rectovaginal endometriosis under NETA treatment.

Conclusion: Five-year therapy with NETA is safe and well tolerated by women with rectovaginal endometriosis. Due to its low cost and good pharmacological profile, it represents a good candidate for long-term treatment in this setting.