The SNP rs1790834 on CYB5A showed significant association with PSA response in CRPC patients treated with AA/P (P < 0.05), but rs743572, rs10883783 and rs1790858 did not. The rs1790834 variant significantly decreased both PFS and OS (P < 0.05)….The CYB5A rs790834 genotype is a novel SNP related to CRPC and may be used as a biomarker for CRPC treatment.