 Patients with squamous non-small cell lung cancer and an ECOG of 0-1 who received a first-line therapy with Cis-Carboplatin for at least 2 cycles that had at least Complete Response CR Partial Response PR Stable Disease SD according to Response Evaluation Criteria in Solid Tumors RECIST v 1.1 will be randomized either to Arm A Pembrolizumab or to Arm B Placebo for a maximum of 2 years or until progressive disease or unacceptable toxicity. 