The results from the Australian study may have implications for US consumers, since similar to Australia, US law bars health insurers from discriminating based on genetic information, but not companies providing life and disability insurance.
"If approved by the FDA, the DxS TheraScreen: K-RAS Mutation Kit would become a companion diagnostic for use with Erbitux in metastatic colorectal cancer to determine which patients have wild-type KRAS status in the US," DxS said this week.
A Phase III prospective study shows Vectibix combined with an irinotecan-based chemotherapy regimen improves progression-free survival in patients with wild-type KRAS tumors compared to chemotherapy alone. The study did not reach statistical significance for showing improvement in overall survival, however.
Testing colorectal cancer patients for their UGT1A1*28 status before prescribing irinotecan is cost-effective only when reduced doses of the drug are as effective as full doses in patients who are homozygous for the variant.
In order to make the labeling change, the agency reviewed retrospective data from seven clinical trials. But this is the exception, according to one official from a diagnostic company who believes FDA's lengthy deliberations have further nudged drug companies to advance diagnostics at the same time as therapeutics in prospective studies.
The FDA has updated the drugs' labels to note that "retrospective analyses of metastatic colorectal cancer trials have not shown a treatment benefit for the EGFR inhibitors in patients whose tumors had KRAS mutations in codon 12 or 13" and that the use of the drugs is not recommended for the treatment of colorectal cancer patients with these mutations.