Introduction For early young and non-pregnant patients with endometrioid carcinoma. Drug treatment can reverse the carcinoma. But there are several problems: (1) there is a significant individual difference in reaching complete regression(CR) after 3-month treatment. (2) The recurrence rate after CR is high. The purpose of this study is to investigate the correlation between TCGA molecular typing and immunohistochemical markers with 3-month CR and recurrence in patients with conservative treatment.

Methods The paraffin pathological specimens of 71 patients with stage IA and G1-G2 endometrioid carcinoma who underwent conservative treatment in Peking University Third Hospital from January 2010 to October 2022 were collected retrospectively for TCGA molecular typing and immunohistochemical staining (including PTEN, PIK3CA, β- catenin, ARID1A, ER, PR) to explore the influencing factors of 3-month CR and recurrence.

Results There were 2 MSI-H subtypes, 1 high copy-number subtype, 68 low copy-number subtypes and no POLE mutations. Univariate and multivariate logistic analysis showed those PTEN-positive, ER and PR high-expression were more likely to achieve 3-month CR (OR=24.811, P=0.034; OR=9.428, P=0.025; OR=29.178, P=0.011). Univariate and multivariate COX regression analysis showed that patients with high-expression PIK3CA were more likely to recurrence (OR=12.750, P=0.017).

Conclusion/Implications Patients with PTEN positive, ER and PR high-expression are more likely to achieve 3-month CR after treatment. Individuals with high expression of PIK3CA are more likely to relapse after CR. Further expansion of sample size is needed to confirm the impact of TCGA molecular typing on the prognosis of endometrioid carcinoma with fertility-sparing treatment.