EGFR mutated- NSCLC or NSCLC among never-smokers (regardless of EGFR or ALK mutation status) have inferior responses to anti-PD-1 antibody therapies compared to NSCLC with KRAS mutation or smoking-associated NSCLC.[1,2] We hypothesized that tumor immune microenvironment (IME) differences between smokers vs non- smokers, KRAS mutants vs EGFR mutants may explain this clinical association. The gene discussed is KRAS; the disease is non-small cell lung carcinoma.