- Patients must have histologically or cytologically confirmed incurable gastrointestinal tract, head and neck, or non-small cell lung cancers that are KRAS wild type; if KRAS mutational status cannot be determined on archived tumor tissue from the patient, a needle or excisional biopsy of a malignant site may be performed prior to enrollment; mutational status may be determined either by polymerase chain reaction (PCR) assay (e.g., DxS KRAS mutation kit) or by direct sequencing of KRAS exon 2, codons 12 and 13; the result must detect no mutations at these sites