While researchers have found that colorectal cancer tumors that have mutated KRAS genes don’t respond to treatment with EFGR inhibitors Erbitux®(cetuximab) and Vectibix™(panitumumab), is the same thing true for other drugs?
5-FU (fluorouracil) is the backbone of most colorectal cancer treatment, given alone or in combination with other drugs. What does KRAS status mean when 5-FU is the only treatment?
To see whether or not, KRAS mutation status affected outcome of 5-FU treatment, researchers analyzed tumor tissue from patients who had 5-FU treatment only. Patients in the study had cancer that had spread to their liver (liver metastases), and the liver mets could not be surgically removed.
They found:
- 38.7 percent of the patients had a KRAS mutation in their tumors.
- KRAS mutations in liver tumors matched exactly with those in primary tumors in the colon.
- There was no significant difference in the percentage of liver tumors that got smaller with 5-FU treatment (objective response rate).
- There was no difference in survival between the group of patients with mutated KRAS and those with normal or wild-type KRAS.
Marie-Christine Etienne-Grimaldi and her French colleagues concluded,
The present data indicate a perfect concordance of K-Ras mutations between primary and liver metastasis and suggest that any predictive and/or prognostic value of K-Ras mutations in treatments combining anti-EGFR monoclonal antibodies with 5-FU should be exclusively linked to the anti-EGFR agent.
Other research has found that Avastin®(bevacizumab) treatment outcomes are not affected by KRAS status.
SOURCE:Etienne-Grimaldi et al.,Clinical Cancer Research, Volume 14, Number 15, August 1, 2008.
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