SELECTIVE DECREASE OF SERUM IMMUNOGLOBULIN G1 AS A MARKER OF MALIGNANT TRANSFORMATION IN COLORECTAL TISSUE

BACKGROUND. Malignant diseases of various origins were previously show n to be associated with a characteristic and highly significant change in the serum pattern of immunoglobulin (Ig)G subclasses, comprised of a decrease in %IgG1 and an increase in %IgG2 relative to and independ ent of the absolute concentration of total IgG. The goal of the curren t study was to evaluate this phenomenon as an indirect marker in the p rimary diagnosis of colorectal carcinoma. METHODS. Using affinity chro matography, IgG1, IgG2, and total IgG were determined in 36 patients w ith colorectal carcinoma of different stages and compared with 162 app arently healthy controls. RESULTS. It was found that: 1) the mean valu es for %IgG1 and %IgG2 of all carcinoma patients differed significantl y from those of the controls; 2) no quantitative association was found with tumor stages, and four of five patients with incipient adenocarc inoma within a polyp exhibited the characteristic shift in IgG subclas ses; 3) based on a calculated cutoff, the specificity and sensitivity of %IgG1 to discriminate between controls and carcinoma patients was f ound to be 88% and 74%, respectively; and 4) a quantitative correlatio n between individual %IgG1 values and the probability of correct assig nment to carcinoma patients or controls was established. CONCLUSIONS. The significant decrease in %IgG1 accompanied by an increase in %IgG2 in total serum IgG represents an indirect, tissue nonspecific, and ear ly marker of malignant proliferation that distinguishes colorectal car cinoma patients from healthy controls with a specificity of 88% and se nsitivity of 74%. (C) 1997 American Cancer Society.