Microsatellite instability in the management of stage II colorectal patients

Up-to-date it is unclear whether stage II colorectal cancer patients should receive adjuvant chemotherapy.The presence of high risk features (T4, CEA 5 ng dl, less than 12 lymph nodes examined) is an indication for Oxaliplatin based treatment. In their absence, there is no consensus, 5 Fluorouracil regimens, or observation only being equally recommended by oncologists. Microsatellite instability is associated with good prognosis in stage II colorectal cancer and also with poor response to 5 Fluorouracil and should be used as a predictive marker.

We performed a prospective descriptive study on 115 consecutive patients who received surgical resection for colorectal cancer in our clinic during 2011 and 2012 using a risk stratification algorithm based on TNM staging, clinico pathologic and molecular markers.

From the 44 stage II colorectal cancer patients, 10 cases were classified as high risk, in 26 cases we performed Immunohistochemical analysis that identified 8 patients with low risk microsatellite instability phenotype, with no indication for adjuvant chemotherapy; 26 intermediate risk patients received 5-FluoroUracil regimens.

We believe that microsatellite instability testing provides a useful tool in the goal of better characterizing patients with stage II colorectal cancer in matters of risk of recurrence and likelihood of benefit from chemotherapy.