To study the possible association of neutrophil defensin 1, 2 and 3 expression with an anti-PD-(L)1 immunotherapy response, we have applied the newly developed MALDI MSI method to pretreatment biopsies of responding and nonresponding NSCLC patients to anti-PD-(L)1 immunotherapy. Here, DEFA1 is linked to non-small cell lung carcinoma.