Our data indicate that investigations of anti-PD1 plus anti–cytotoxic T-lymphocyte–associated protein 4 (CTLA-4) therapies in any nonmelanoma advanced cancer should be conducted along with anti-PD1 monotherapy to ensure that the net effect of the addition of anti-CTLA-4 to anti-PD1 can be clearly established for that cancer and setting and that unnecessary CTLA-4 inhibition with related toxic effects (clinical and financial) can be avoided. This evidence concerns the gene CTLA4 and cancer.