Optimal duration of fertility-sparing hormonal treatment for early-stage endometrioid endometrial cancer

Objectives To analyze the oncologic outcomes of long-term fertility-sparing treatment (FST) in patients with early-stage endometrial cancer (EC) and to determine the optimal duration of FST that would not hamper survival outcomes. Methods Patients undergoing FST for presumed stage IA, grade 1 EC between 2005 and 2018 were retrospectively analyzed. Oncologic outcomes were compared between the group with ≤6 months of FST and the group with >6 months of FST. Segmented regression analysis was used to estimate the dynamic changes in cumulative complete response (CR) rates according to FST duration. Results A total of 122 patients received oral progestin, with concurrent levonorgestrel-releasing intrauterine device use in 108 (88.5%) and 105 (86.1%) achieved CR with a median time to achieve CR of 10 (3–42) months. Of the patients not achieving CR at 6 months of FST, 95.1% (78/82) continued further FST. The overall CR rate (88.9% [32/36] vs. 84.9% [73/86], P = 0.436] was not significantly different between the groups with ≤6 and > 6 months of FST. The changes in cumulative CR rates were significantly different between the two segments divided by 15 months from the initial FST (P = 0.0015, segmented regression analysis). The overall progressive disease (PD) rate was 3.3% (4/122), and PD was first detected during 9–12 months of FST. Conclusion Patients not achieving CR and not showing PD at 6 months of FST could continue further FST. If disease progression is excluded, 15 months of FST can be considered as the cutoff for the optimal FST duration.