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 »