Inclusion Criteria:  18 years of age or older Histologically confirmed stage 4 NSCLC or stage 3B/3C not able to receive chemoradiation with no sensitizing EGFR or ALK mutations. PDL-1 of 1%-49% No previous history of immunotherapy treatment ECOG PS 0-1 At least one measurable lesion according to RECIST version 1.1 Life expectancy of at least 3 months. Able to self-administer daily GM-CSF injections Eligible for treatment with 4 cycles of chemoimmunotherapy followed by maintenance therapy with pembrolizumab +/- pemetrexed.  Exclusion Criteria:  Receiving systemic glucocorticoids or other immunosuppressive treatment Untreated brain metastases Active autoimmune disease Active interstitial lung disease, pneumonitis Solid organ transplant recipients Subject may not participate in another drug research study while participating in this research study Pregnant patients Known hypersensitivity to GM-CSF (sargramostim)