Inclusion Criteria:

          -  Documentation of Disease: Histologic or cytologic diagnosis of non-small cell lung
             cancer (adenocarcinoma). Stage IV or recurrent metastatic non-small cell lung cancer.
             No planned initiation of definitive (potentially curative) concurrent chemo-radiation

          -  Planning to begin MK-3475 (pembrolizumab) treatment within 14 days of registration,
             with or without combination chemotherapy. Treating physician considers pembrolizumab
             as appropriate and plans to proceed with one of the following treatment schedules:

               -  MK-3475 (pembrolizumab) 200 mg IV flat dose every 21 days or 400 mg IV every 42
                  days.

               -  MK-3475 (pembrolizumab) 200 mg IV or 400 mg IV + carboplatin area under the curve
                  (AUC) = 5 + pemetrexed 500 mg/m^2 (20% chemotherapy dose reduction is permitted
                  per the discretion of the treating physician)

          -  Patients will be ineligible if they have an autoimmune disorder, are post-organ
             transplantation, or are receiving ongoing immunosuppression treatment

          -  Prior adjuvant therapy is allowed and must have been completed at least 6 months prior
             to registration

          -  No planned radiation or other cancer treatment in the 3 months following registration

          -  No untreated brain metastases. Patients must be off corticosteroids and asymptomatic
             at registration

          -  Absolute neutrophil count (ANC) >= 1500/mm^3 (1.5 x 10^9/L)

          -  Platelet count: >= 100,000/mm^3 (100 x 10^9/L)

          -  Creatinine >= 30 mL/min* for patients enrolled to pembrolizumab alone and > 45 mL/min
             for patients enrolled to chemotherapy + pembrolizumab

             * Calculated using the Cockcroft-Gault formula

          -  Total serum bilirubin =< 1.5 upper limit of normal (ULN) (< 3 ULN if Gilbert's
             disease)

          -  Aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) =< 3 x ULN (=<
             5.0 x ULN if liver metastases present)

          -  Alkaline phosphatase =< 2.5 x ULN (=< 5 x ULN if bone or liver metastases present)
             Language: Patients must be able to speak and comprehend English in order to complete
             the mandatory patient-completed measures