Multinational, randomized, multicenter, open-label, Phase III study of 1093 participants (age ≥ 18 years) with histologically- or cytologically-confirmed, stage IV squamous-cell NSCLC, who have received no prior therapy for metastatic disease, will be randomized on a 1:1 basis to receive first-line necitumumab plus chemotherapy consisting of gemcitabine and cisplatin in study Arm A, or gemcitabine-cisplatin chemotherapy alone in study Arm B. Baseline radiographic assessment of disease will be performed within 21 days prior to randomization (first treatment will be administered within 7 days following randomization). Participants will undergo radiographic assessment of disease status (computed tomography or magnetic resonance imaging) every 6 weeks (± 3 days), until there is radiographic documentation of progressive disease (PD). Chemotherapy will continue for a maximum of six cycles in each arm (or until there is radiographic documentation of PD, toxicity requiring cessation, protocol noncompliance or withdrawal of consent); participants in Arm A only will continue to receive necitumumab until there is radiographic documentation of PD, toxicity requiring cessation, protocol noncompliance, or withdrawal of consent.