In terms of EGFR mutational status, the chemotherapy cohort had 18 (56%) of the cases confirmed negative for mutations, and 14 (44%) cases indeterminate; whereas the erlotinib cohort had 50 (63%) of the cases confirmed negative for mutations and 29 (37%) cases indeterminate due to a lack of evaluable specimens (tumor or plasma). Here, EGFR is linked to neoplasm.