Testing the Effects of MK-3475 (Pembrolizumab) With or Without the Usual Chemotherapy Treatment for Patients 70 Years of Age and Older With Advanced Non-small Cell Lung Cancer

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