[Prognostic significance of chromosome and microsatellite instability in colorectal cancer]

The prediction of recurrence and the prognosis of colorectal cancer have always been related to the stage of the disease. Clinical pathological classifications are unable to predict the individual risk of recurrence and the prognosis which would also appear to be linked to additional factors, which have yet to be properly assessed, such as the genetic endowment of the tumour. In this study we assessed how microsatellite and chromosomal instability may help us to stratify two classes of risk of recurrence in patients at the same stage. From July 1996 to June 1999 we prospectively collected data on 112 patients (59 male, 53 female) affected by colorectal cancer and undergoing surgery with a radical intent. Biopsies of normal and tumor tissue were submitted to DNA extraction and amplification to evaluate the presence of chromosomal instability (loss of heterozygosity) and microsatellite instability. Analysis of the data revealed that loss of heterozygosity in the long arm of chromosome 18 is associated, in patients with stage III colorectal cancer, with a higher risk of recurrence and therefore with a worse prognosis. Microsatellite instability proved to be associated with a better prognosis even in cases of recurrence.