Serum mucin antigens CASA and MSA in tumors of the breast, ovary, lung, pancreas, bladder, colon, and prostate. A blind trial with 420 patients.

BACKGROUND

The tumor markers CASA (cancer-associated serum antigen) and MSA (mammary serum antigen) have previously been shown to be useful in the clinical management of ovarian and breast carcinoma, respectively, but have not been assessed in other types of cancer. These assays were compared with carcinoembryonic antigen (CEA) and prostate-specific antigen (PSA) in a blind trial using sera from the Mayo Clinic-National Cancer Institute (NCI) Diagnostic Serum Bank.

METHODS

CASA and MSA were assessed retrospectively in a blind trial using 465 serum samples from the Mayo Clinic-NCI Diagnostic Serum Bank representing malignant and benign disease of the breast, ovary, lung, pancreas, bladder, colon, and prostate and age-matched and gender-matched healthy control donors. CASA, MSA, and PSA levels were determined using commercially available kits, and CEA values and clinical details were later provided by the Mayo Clinic.

RESULTS

CASA and MSA showed good reproducibility in 45 duplicate samples. CASA values were significantly elevated in the serum of patients with malignant tumors of the breast (44%), ovary (58%), lung (56%), prostate (48%), and bladder (54%), but not in those with benign conditions of these organs or pancreatic or colon cancer. MSA levels were only elevated significantly in cancers of the breast (52%) and ovary (58%). CASA showed significantly better sensitivity than either CEA (20%) or MSA (25%) in the detection of lung cancer, whereas CEA showed significantly superior detection of colon cancers (78%). CASA was not as sensitive as PSA in prostate cancer (48% versus 96%), but gave superior specificity in nonmalignant conditions of the prostate (93% versus 70%), although this was not statistically significant.

CONCLUSIONS

The commercial CASA and MSA assays are reliable and reproducible tests for these tumor markers. In addition to ovarian cancer, CASA is also elevated significantly in many patients with breast, lung, prostate, and bladder cancer and has potential clinical use in patients with these tumors. The use of the MSA assay appears restricted to breast cancer.