Mismatch repair status influences response to fertility-sparing treatment of endometrial cancer

Background: Patients younger than 40 years usually present with early-stage endometrial cancer with favorable prognosis. However, such patients are usually in their childbearing age and may desire fertility-sparing options. The identification of biomarkers may improve the clinical outcomes in these patients and aid in fertility-sparing management; however, there has been no reports on biomarker analysis so far. Objective: This study aimed to evaluate the prognostic significance of Proactive Molecular Risk Classifier for Endometrial Cancer in the fertility-sparing management of endometrial cancer. Study Design: A total of 57 endometrial biopsy specimens obtained before hormone therapy were evaluated, and patients were classified according to the Proactive Molecular Risk Classifier for Endometrial Cancer molecular subtypes (mismatch repair deficiency, DNA polymerase epsilon mutation, wild-type p53, and abnormal p53). The primary endpoint was the response rate after hormone therapy. The secondary endpoint was the recurrence rate after the complete response, hysterectomy rate owing to treatment failure, and upstaged diagnosis rate after hysterectomy. Results: Of 57 patients, 9 (15.8%) had mismatch repair deficiency, 2 (3.5%) had DNA polymerase epsilon mutation, 45 (78.9%) had wild-type p53, and 1 (1.8%) had abnormal p53. Overall, the complete response rate was 75.4% after hormone therapy. Patients with mismatch repair deficiency had a significantly lower complete response or partial response rate than those with wild-type p53 in terms of the best overall response (44.4% [95% confidence interval, 4.0–85.0] vs 82.2% [95% confidence interval, 71.0–94.0]; P=.018) and complete response rate at 6 months (11.1% [95% confidence interval, 0.2–37.0] vs 53.3% [95% confidence interval, 38.0–68.0]; P=.010). Among patients with mismatch repair deficiency, 4 underwent immediate hysterectomy because of treatment failure and 3 presented upstaged diagnosis after hysterectomy. Conclusion: The Proactive Molecular Risk Classifier for Endometrial Cancer molecular classification has prognostic significance in the fertility-sparing management of endometrial cancer, thereby enabling early stratification and risk assignment to direct care. Mismatch repair status could be used as a predictive biomarker for selecting patients who could benefit from hormone therapy. These findings need to be validated in larger studies.