Inclusion Criteria:  18 years or older Stage IV histologically proven Non Small Cell Lung Cancer (NSCLC) Monotherapy with nivolumab or pembrolizumab. Patients were required to have measurable disease per the Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1.  Exclusion Criteria:  Active malignancy other than NSCLC, ALK or EGFR mutated NSCLC Anticancer therapy or surgery within the past 2 weeks or inability to breathe under the calorimetry.