Mechanism-Driven Evolution of Fertility-Sparing Treatment and Precision Management of Special Populations in Endometrial Cancer: A Review

Endometrial cancer is increasingly diagnosed in patients who have not yet completed childbearing. For carefully selected patients with grade 1 endometrioid endometrial carcinoma confined to the endometrium, fertility-sparing treatment (FST) can preserve reproductive potential but requires rigorous histologic surveillance. In eligible patients, oral progestins and/or the levonorgestrel-releasing intrauterine system (LNG-IUS) remain the mainstay of fertility-sparing treatment, with hysteroscopic lesion resection incorporated in selected cases. Obesity, polycystic ovary syndrome, abnormalities in glucose metabolism, molecular subtype, and primary or acquired progestin resistance collectively contribute to heterogeneity in treatment response and the risk of recurrence. This narrative review critically integrates current guidelines, randomized controlled trials, prospective studies, retrospective cohorts, and early exploratory evidence to evaluate the biological rationale, clinical positioning, efficacy, safety, and maturity of evidence for progestin-based therapy, metabolic interventions, combined endocrine approaches, molecularly guided strategies, and exploratory immunotherapeutic approaches. We further propose an integrated clinical pathway encompassing candidate selection, molecular assessment, response evaluation, transition to pregnancy, retreatment after recurrence, and timely conversion to definitive surgery. Importantly, this review distinguishes guideline-supported approaches from adjunctive, investigational, and exploratory strategies. Major evidence gaps include inconsistent definitions of treatment response, limited prospective molecularly stratified data, uncertain reproductive safety of emerging systemic therapies, and insufficient long-term data on pregnancy outcomes and offspring.