Impact of sirtuin‑1 expression on progression‑free survival in non‑endometrioid endometrial cancer: A retrospective cohort study

Sirtuin-1 (SIRT1) expression levels are upregulated in various types of cancer and are associated with adverse outcomes. However, there is limited research on SIRT1 expression in types of gynecological cancer. The present study primarily sought to investigate the expression characteristics of SIRT1 in non-endometrioid endometrial cancer (EC) using immunohistochemistry. The secondary endpoint was to evaluate the impact of SIRT1 expression levels on progression-free survival (PFS). The present study was a single-center, retrospective cohort study that included patients who underwent hysterectomy between June 2017 and December 2021 and had a postoperative histopathological diagnosis of non-endometrioid EC. The tissue slides were stained with a monoclonal antibody targeting the SIRT1 protein. The nuclear staining reaction of SIRT1 was considered to be positive in the presence of any percentage of nuclear staining. The cytoplasmic staining reaction of SIRT1 was assessed using the immune reactivity scoring (IRS) system, which was determined by multiplying the scores for the staining percentage and staining intensity. IRS values of 0 to 2 were considered as negative expression; 3 to 4 as low expression; 6 to 8 as moderate expression; and 9 to 12 as high expression. Cox proportional hazards regression models were used to identify factors influencing PFS. Data from a total of 43 patients who met the eligibility criteria were presented. Cytoplasmic staining with SIRT1 was detected in all samples (100%), whereas no nuclear staining was evident in any of the tissue samples. According to the IRS results, 20.9% of samples exhibited negative cytoplasmic expression, 14.0% exhibited low expression, 37.2% exhibited moderate expression and 27.9% exhibited high expression. The estimated 3-year PFS rate was 43.6%. Cox regression models demonstrated no independent factor influencing PFS. In conclusion, SIRT1 expression was found to be cytoplasmic in non-endometrioid EC. According to the IRS, ~80% of cases exhibited varying degrees of SIRT1 expression. However, SIRT1 expression levels had no significant impact on PFS.