About 15 percent of people with stage III colon cancer may have fewer recurrences and better survival when they are treated with irinotecan. Although all stage III colon cancers don’t have an additional benefit when irinotecan is added to bolus 5-FU and leucovorin in a treatment called IFL, this smaller group does.

About 15 percent of colon cancers develop when damaged DNA is not repaired and mutated cells grow into malignant tumors.  So-called deficient mismatch repair (dMMR) tumors have features different from most colorectal cancer, including a better prognosis.  They also have a very poor response to 5-FU-based chemotherapy.

However, researchers studying tumor tissue from patients enrolled in a clinical trial comparing 5-FU and leucovorin alone to 5-FU, leucovorin, and irinotecan found that those with deficient mismatch repair tumors who received irinotecan had better disease-free survival and overall survival at five years than patients whose mismatch repair genes were working.  Those with dMMR on the 5-FU-only arm of the trial had no similar benefit. Read the rest of this entry »

Some of the most interesting data presented at ASCO was the data on MSI and 18qLOH in a European clinical trial.

Last year at ASCO, Dr. Daniel Sargent presented new data that patients with stage II disease with microsatellite instability do not only not benefit from 5-FU, but they may be harmed, and it was recommended to test for MSI in all stage II colon cancer patients and in the presence of MSI-high not to give 5-FU. For stage III colon cancer that was not the case.

This year, the PETACC-3 clinical trial was analyzed for MSI and did not show the same the same findings. It seems that chemotherapy does not harm these patients, and they may benefit. Read the rest of this entry »

Since the last ASCO meeting in June 2008 not only has KRAS made headlines but also microsatellite instability (MSI).

Microsatellite instability has developed into the most important prognostic and predictive marker for patients with stage II colon cancer. Recent studies presented by Dr. Daniel Sargent at ASCO showed that patients with stage II colon cancer who have microsatellite instability did not benefit from 5-FU chemotherapy. Therefore these patients with no risk factors such as clinical obstruction, lymphovascular invasion, poorly differentiated adenocarcinoma, or insufficient lymph node collection should not receive 5-FU. Read the rest of this entry »