FDA approves genetic test to help some colon cancer patients, physicians considering Erbitux therapy
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 United States. 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.
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.
“This test helps clinicians determine whether this specific treatment is an effective option,” said Alberto Gutierrez, Ph.D., director of the Office of In Vitro Diagnostic Device Evaluation and Safety in the FDA’s Center for Devices and Radiological Health.
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.
Among those whose tumors did not have a KRAS mutation, median survival was 8.6 months for those receiving Erbitux compared with five months for those who did not. Among patients whose tumors had a KRAS mutation, median survival was similar between those who received Erbitux compared with those who did not (4.8 months and 4.6 months, respectively).
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.
Among patients with tumors that did not have one of the seven KRAS mutations, median survival was 23.5 months for those who received Erbitux plus FOLFIRI compared with 19.5 months for those who received FOLFIRI. Among patients whose tumors had a KRAS mutation, median survival was similar between those who received Erbitux compared with those who did not.
“The approval of this new Erbitux indication with the concurrent approval of a genetic test provides clear guidance on selecting patients who will optimally benefit,” said Richard Pazdur, M.D., director of the Office of Oncology Drug Products in the FDA’s Center for Drug Evaluation and Research. “Clinical trial data leading to the approval of this new indication supports the recommendation to treat those patients whose colorectal tumors do not have KRAS mutations and to avoid treating those with KRAS mutations.”