The present invention provides an SPR system and corresponding methods of use, for determining the presence or concentration of tumor-associated antigens in cancer patient samples. The SPR system may have multiple channels, with each channel having operably affixed thereto an antibody specific for a tumor-associated antigen, so as to allow detection of multiple tumor-associated antigens simultaneously. When a biological sample from a patient is applied to the SPR system, the presence of two or more tumor-associated antigens can be determined by measuring an SPR signal shift from each channel. The SPR system may detect the presence or concentration of a tumor-associated carbohydrate antigen, where the sensor surface contains affixed thereto an antibody specific for the glycosyl epitope, as well as an antibody specific for the polypeptide to which the carbohydrate antigen is naturally associated in cancer patients.