Pembrolizumab for Advanced NSCLC and PS 2-3

Inclusion Criteria: * Men and women, aged 18 years and older, with locally advanced NSCLC who are ineligible for definitive surgical resection or concurrent chemoradiation, or metastatic NSCLC * Patients must not have received any systemic therapy for metastatic cancer * Patients must not have received any PD-1 or PD-L1 inhibitor * ECOG performance status of 2 or 3 at the time of consent and on the first day of therapy * Patients may not have a molecular alteration in ALK, ROS1, EGFR, BRAF, NTRK, RET, MET, or any other gene for which first-line FDA approved targeted therapy exists. * Patients with treated brain metastases are eligible if there is no evidence of progression for at least 4 weeks after CNS-directed treatment, as ascertained by clinical examination and brain imaging (MRI or CT) during the screening period. * Patients with new or progressive brain metastases (active brain metastases) or leptomeningeal disease are eligible if the treating physician determines that immediate CNS directed therapy is not required and is unlikely to be required during the first cycle of therapy. * Patients with HIV on effective anti-retroviral therapy with an undetectable viral load within 6 months are eligible for this trial. * Adequate organ and marrow function as defined below: * Leukocytes ≥ 3,000/mcL * Absolute neutrophil count ≥ 1,000/mcL * Platelets ≥ 100,000/mcl * Total bilirubin ≤ 1.5 x ULN * AST (SGOT)/ALT (SPGT) ≤ 3 x ULN or ≤5 x ULN if liver metastases present * GFR (Cockroft-Gault) ≥ 30 mL/min * Women of childbearing potential (WOCBP) must have a negative serum or urine pregnancy test within 3 days prior to C1D1 of pembrolizumab therapy. For the purposes of this trial, WOCBP are defined as women who have had a menstrual period within the last 48 months. * Provision of signed and dated informed consent form * Ability to take the study medication, and complete the study questionnaires * Stated willingness to comply with all study procedures for the duration of the study * For women of reproductive potential, agreement to use highly effective contraception during study treatment and for at least 4 months after the final dose * For men of reproductive potential, agreement to use condoms or other methods to ensure effective contraception with female partners of reproductive potential Exclusion Criteria: * Autoimmune conditions requiring \>10mg prednisone (or its equivalent) of daily therapy or other systemic immunosuppressive therapy. * Patients who are receiving other investigational agents * Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements * Patients with known leptomeningeal disease for which CNS therapy is required * Pregnant or lactating patients