Deciding what chemotherapy treatment is best for an individual patient is difficult. Only about half of patients with colon or rectal cancer will respond to a specific drug combination and even the responders will eventually become resistant to the drug.
Chemotherapy becomes a process of trial and error, giving drugs and watching for tumors to shrink (respond), remain the same (stable disease), or get larger or more numerous (progress.) This is a slow and tedious process during which up to half of patients are actually getting treatment that doesn’t benefit them — and missing out on a different treatment that might help.
Researchers in France have identified a signature of 14 genes that predict response to FOLFIRI — the combination of irinotecan fluorouracil, and leucovorin. FOLFIRI is one of the standard first-line combination treatments for colorectal cancer.
Working with tumors from 21 patients with colorectal cancer that had spread to the liver but could not be surgically removed, they found that there were 14 genes that very accurately predicted who would and who would not respond to FOLFIRI treatment. Nine patients (43%) did respond to FOLFIRI and all had the 14 gene signature. Eleven did not respond, and 10 of the 11 did not have the profile.
There was no difference in other patient characteristics that might have predicted the difference in response.
While the gene signature analysis was based on a small number of patients, the research team believes that it stable and reliable. However, they are currently involved in a larger study with more patient in several different institutions to validate their findings.
Eventually, they plan on a large, randomized clinical trial that would test whether using the 14 gene signature to choose treatment with FOLFIRI would improve survival of people with metastatic colorectal cancer.
SOURCE: Del Rio et. al, Journal of Clinical Oncology, Vol 25, No 7 (March 1), 2007: pp. 773-780.
WHAT THIS MEANS FOR PATIENTS
This is an early study which needs to be validated in a larger group of patients and then tested in a randomized clinical trial. It isn’t ready to be used to predict response to treatment yet.
It is not available to help make decisions about the right treatment for an individual patient right now.
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