Marc Peeters, MD, PhD, department of oncology, Antwerp University Hospital, Antwerpen, Belgium, discusses an analysis of RAS
mutations in the phase III study 20050181, which compared panitumumab plus FOLFIRI versus FOLFIRI for second-line treatment of metastatic colorectal cancer (mCRC).
Peeters says before patients with mCRC are treated with anti-EGFR agents, they are tested for KRAS
exon 2 status of their tumor. If the patient has a mutated tumor, they are not treated with anti-EGFR agents such as panitumumab or cetuximab.
In an analysis of the phase III study 20050181, researchers first looked for the wild-type patients in KRAS
exon 2 and then looked at the exon 3 and exon 4 in the KRAS
genes and NRAS
genes, Peeters says. The analysis showed an additional 18% of new mutations outside the KRAS
exon 2 gene. Further analysis showed that if a patient has a mutated tumor, there is no benefit but there is also no harm when a patient is treated with panitumumab plus FOLFIRI. If patients have a wild-type RAS
tumor, the analysis showed that there is a clear benefit in progression-free survival and overall survival when panitumumab is combined with FOLFIRI, Peeters says.