Retention of chromosome arm 5q in stage II colon cancers identifies 83% of liver metastasis occurrences.

The decision to use chemotherapy in the treatment of colon cancer patients depends on the risk of developing metastases, as estimated by clinicopathological staging combining body imaging and pathological findings. The aim of this study was to identify all chromosome arms that, when allelotyped, correlate with the metastatic process, add prognostic information to pathology, and are of relevance for predicting metachronous metastases. A 5-year follow-up survey enrolled 401 MSS (microsatellite stable) colon cancer patients who were divided into three groups. Staging was performed with and without imaging data (called tumor and patient staging, respectively). The first 192 patients were used to construct a model prognosticating metastases. The subsequent 146 patients were used to validate this model. The third group evaluated its consistency by comparing the status of the relevant chromosome arms in 63 liver metastases and primary tumors that did or did not metastasize. The first group identified three factors: tumor staging (P < 0.0001), 5q status (P = 0.003), and gender (P = 0.02). The second group confirmed 5q as a marker of metastasis occurrence (P = 0.004). Merged data predicted that, when both 5q arms are retained, metastatic risk increases 4.3-fold in stage II patients. The third group corroborated these findings, with a 5q retention rate in metastases comparable to that of primary tumors that metastasize, but significantly higher than that observed in nonmetastatic tumors (one-tail, P = 0.0005). Long arm of chromosome 5 allelotyping detects high-risk stage II tumors. This simple, easily implemented, and inexpensive test increases the power of randomized studies that evaluate chemotherapy. Copyright 2005 Wiley-Liss, Inc