Food and Drug Administration recently approved the first genetic test that can
help some colorectal cancer (CRC) patients and physicians determine if the drug
Erbitux (cetuximab) would be an effective treatment based on the absence of a
gene mutation. U.S.
The “Therascreen KRAS RGQ PCR Kit” can provide information about the KRAS gene mutation in patients whose CRC has spread to other parts of their body (metastasized). Studies have found that Eribitux is not effective in those who have the mutation.
CRC is the third leading cause of cancer death in the
. According to the
American Cancer Society, there were more than 141,000 new CRC cases in 2011,
and nearly 50,000 deaths resulted from CRC. United States
Erbitux targets the epidermal growth factor receptor (EGFR) on the surface of CRC cells. When certain chemicals in the body bind to EGFR, the receptor starts a complex chain of biochemical reactions inside the cell that signals the cancer cell to reproduce. Erbitux blocks EGFR, interrupting a signal to reproduce which can stop the growth of CRC cells. However, when CRC cells have a mutation in the KRAS gene, they continue to reproduce even when Erbitux blocks EGFR.
The FDA first approved Erbitux in 2004 to treat EGFR-expressing late-stage colorectal cancer after patients stopped responding to chemotherapy. In 2009, the FDA approved updated recommendations for Erbitux, based on studies that found the drug is not effective in patients whose tumors have a mutated KRAS gene.
To support the approval of the test, tumor samples from patients in clinical trials used to support the approval of Erbitux were evaluated. The benefits of Erbitux were limited to patients whose tumors did not have one of the seven KRAS mutations detected by the test.
The FDA simultaneously approved a new indication for Erbitux for use in combination with FOLFIRI, chemotherapy drugs consisting of irinotecan, 5-fluorouracil, and leucovorin, as a first-line treatment in patients with metastatic CRC who have EGFR-expressing, and KRAS wild-type (no mutations) tumors.