Introduction The Proactive Molecular Risk Classifier for Endometrial Cancer (ProMisE) has developed as a molecular classification tool for endometrial cancer. Abnormal expression of p53 (p53abn) is identified as the worst prognostic group. We explored the association of p53abn and progesterone receptor (PR) in endometrioid endometrial cancer.

Methods We included 397 consecutive endometrial cancer cases of endometrioid histology with adequate tumor tissue in the formalin-fixed, paraffin-embedded (FFPE) block and available follow-up information. This study was granted by Chang Gung Medical Foundation IRB 201702242B0D001. Immunohistochemical staining on FFPE tumor tissue sections for p53, and PR were performed. We arbitrarily defined intensity of the immunohistochemical p53 expression of cancer cell nucleus as abnormal or wild, and progesterone receptor score as positive or negative. Progression-free survival (PFS) and endometrial cancer-specific overall survival (OS) starting at the date of diagnosis were evaluated using Kaplan-Meier method and compared by log-rank test between groups.

Results 48 and 339 cases were identified as p53abn and p53wt, respectively. Thirty-five (73%) p53abn cases were PR+. With a median follow-up of 74 months, the PFS and OS of patients with PR+ tumors (N = 310) were 93% and 96.8%, respectively, compared with 75% and 85.7% of those with PR- tumors (N = 70) (both p < 0.001, log-rank test). Among those with P53abn, PR+ expression was associated with a favorable PFS (p = 0.081) and better OS (p = 0.044).

Conclusion/Implications Our study showed that incorporating PR into prognostic molecular markers for endometrioid endometrial cancer might provide further risk stratification.