The efficacy of the levonorgestrel intrauterine system versus oral megestrol acetate in treating atypical endometrial hyperplasia: a superior randomized controlled trial.

Objective: To compare the efficacy of the levonorgestrel intrauterine system (LNG-IUS) versus megestrol acetate (MA) in inducing complete regression among women with atypical endometrial hyperplasia (AEH) who declined hysterectomy.

Methods: In this single-center, open-label randomized controlled trial, we included 148 women with AEH who declined hysterectomy. We randomized participants to receive either daily oral MA 160 mg (n=74) or apply LNG-IUS (n=74) and scheduled their follow-up by endometrial sampling at 3, 6, 9, 12, 18, and 24 months. The success rate and duration until complete regression were the primary outcomes.

Results: The mean duration until complete regression was 5.52 months (95% confidence interval [CI]=4.85-6.18) for the LNG-IUS group versus 6.87 months (95% CI=6.09-7.64) for the megestrol group (log-rank test p-value=0.011). The cumulative regression rate after 12 months was 91.9% with the LNG-IUS versus 77% with MA (p=0.026). Weight gain in the MA group vs LNG-IUS group after one year (4.7±4 kg vs. 2.7±2.6 kg, 95% CI=0.89-3.12; p=0.001) and after two years of therapy (7.8±5.1 kg vs. 4.1±2.9 kg, 95% CI=2.29-5.06; p<0.001).

Conclusion: Compared to MA, the LNG-IUS was more efficacious in treating AEH in women who declined hysterectomy, especially those with moderate/severe obesity, with fewer adverse effects and less weight gain. Extending therapy to 12 months for persistent cases would improve regression rates with reasonable safety. Alternate hysteroscopic and office sampling seemed convenient for follow-up.

Trial registration: ClinicalTrials.gov Identifier: NCT04385667.