Is microsatellite instability a negative prognostic factor in early stage endometrial cancer patients?

Abstract

e17107 Background: Endometrial cancer(EC) is a heterogeneous disease with diverse histological features and biological behaviour. Microsatellite instability (MSI) which occurs in cancerous tissue secondary to mismatch repair (MMR) defect of hereditary or somatic origin is a well-known feature further diversifying genetic tumor landscape. In this study, we aim to investigate the relationship between MSI and prognosis in patients with early stage EC. Methods: The patients diagnosed with EC between 2004 and 2017 were retrospectively analysed in the study. The demographic characteristics, disease stage, menopausal status, and clinical and laboratory values were noted. MLH1, MSH2, MSH6 and PMS2 antibodies were used to detect microsatellite status within the tumor tissue samples. Results: The mean age of the 93 patients and menopause was 60.6 ± 9.8 and 49.68 ± 4.5 years , respectively. The median follow-up period was 28 (1-110) months. At the time of diagnosis, number of the patients with stage IA, IB, II, III, and IV were 5, 64, 8, 14, and 2, respectively. Forty three patients were grad 1, 23 patients grad 2, and 27 patients were grade 3. In terms of microsatellite status, 59 patients (63.4%) were microsatellite stable (MSS) and 34 patients (36.6%) were microsatellite instable(MSI). There was no significant association between MSI and tumor stage or grade (X2 = 1.97 p = 0.74 and X2= 3.2, p = 0.19, respectively). There was a significant relationship between peritumoral lymphocyte infiltration rate (pTIL) and MSI. PTIL ratio was higher in tumoral tissues with MSI, whereas pTIL was low in MSS tumor tissues (X2= 28.6, p < 0.0001). Patients with MSI tended to have poorer survival than patients with MSS irrespective of disease stage; mOS rates were 76 and 91 months, respectively (p = 0.086). However, patients with early stage disease and MSI had significantly poorer survial in comparison to patients with similar disease stage and MSS: Overall survival rates for patients with MSI and MSS were 75.8 and 94.7 months, respectively (Log-rank p = 0.048). Conclusions: There is a limited number of studies assessing the association between MSI and clinical outcomes in EC. Our study hints at the presence of potential relationship between MSI and pognosis in patients with MSI. Similar to previous studies performed with various types of tumors we found that EC with MSI attract more immune cells to tumor microenvironments. Interestingly, patients with MSI tended to have poorer prognosis despite augmented immune-cell inftration.