Clinical significance of microsatellite instability in endometrial carcinoma

BACKGROUND. The purpose of this study was to compare the clinical character istics of endometrial carcinomas with and without microsatellite instabilit y (MSI). METHODS. The authors prospectively acquired DNA from patients with endometr ial carcinomas at Washington University Medical Center. Tumors were assigne d MSI (+) status when two or more of five microsatellite repeat markers rev ealed novel bands in tumor DNA not present in the corresponding normal DNA. Clinical characteristics and survival data of patients with and without MS I were abstracted from patient charts. Statistical significance was calcula ted with the chi-square test, and survival was assessed with Kaplan-Meier m ethods. RESULTS. The authors found 65 of 70 (93%) patients with MSI (+) tumors to b e of white race, whereas only 124 of 159 (78%) patients with MSI (-) tumors were white (P = 0.012). Advanced disease (International Federation of Gyne cology and Obstetrics Stage III-nr) was observed in 9 of 70 (13%) MSI (+) p atients and 44 of 159 (28%) MSI (-) patients (P = 0.017). In addition, aggr essive histologic subtypes were observed less frequently in MSI (+) tumors (6/70 [8%]) than in MSI (-) tumors (30 of 159 [19%]) (P = 0.034). Race and stage were shown by multivariate analysis to be different in MSI (+) and MS I (-) patients. Recurrence and overall survival were similar in the two gro ups. CONCLUSIONS, Patients with MSI (+) tumors were more likely to be of white r ace and to present with early stage disease. Further investigation is neede d to explain why patients with MSI (+) tumors have similar survival to pati ents with MSI (-) tumors, despite presenting at earlier stages, being of wh ite race, and being less likely to be associated with virulent histologic s ubtypes. Cancer 2000;89:1758-64. (C) 2000 American Cancer Society.