The main issues addressed in our study were: (i) whether smokers and never-smokers differ in the associations of APM polymorphisms with NSCLC risk and clinical outcome, (ii) whether ERAP2 influences the ERAP1 effect, if any, as we observed it in other diseases—psoriasis (50), and ankylosing spondylitis (51). Here, ANPEP is linked to ankylosing spondylitis.