MICROSATELLITE INSTABILITY CORRELATES WITH REDUCED SURVIVAL AND POOR DISEASE PROGNOSIS IN BREAST-CANCER

Size changes in microsatellite sequences have been detected in many ty pes of cancer, but the influence of this form of genetic instability o n disease progression remains unclear. We determined the incidence of microsatellite instability in breast cancer by comparing PCR-amplified sequences from paraffin-embedded samples of normal and tumor tissue f rom affected individuals. This analysis showed that at least 30% of br east cancers exhibit microsatellite instability (MI). Of importance, M I correlated with indicators commonly associated with poor disease pro gnosis, including lymph node status, tumor size, and advanced tumor st age, Individuals with MI+ tumors also showed significantly reduced dis ease-free and overall survival. These data contrast with studies showi ng that Mi correlates with improved prognosis in colon and gastric can cers. We propose that defects resulting in MI promote disease progress ion and result in a poor prognosis in breast cancer.