AFP and neoplasm: Then the significant changes derived from raw and second derivative (SD) FTIR signatures related to different DTCs, were extracted and mutually confirmed by clinical tumor markers, including alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), carcinoembryonic antigen 125 (CA-125), carcinoembryonic antigen 15-3 (CA-15-3), carcinoembryonic antigen 19-9 (CA-19-9) and carcinoembryonic antigen 724 (CA-724).