RB1 and urinary bladder cancer: Prior studies have found that CDKN1A mutations and CDKN2A loss are mutually exclusive in bladder cancer, a finding recapitulated in our small dataset.31 We did not see a correlation between alterations that we predicted to confer sensitivity to palbociclib (CDKN2A inactivation, CCND1 amplification, CDKN2B inactivation) or resistance to palbociclib (Rb loss, CDKN1A inactivation, CCNE1 amplification, or E2F amplifications) and efficacy of palbociclib in our patients.