Labile disulfide bonds and free thiol groups in human IgG. V. Association of postoperative mean 'sigma S' course and tumor recurrence in ovarian cancer.

Sigma S comprises both free thiol groups and labile S-S-bonds of the total IgG that react with dithionitrobenzoate. Previous investigations have shown that this parameter was significantly decreased in malignant diseases of various organ systems as compared with benign disorders of the respective organs. The present study on patients with ovarian cancer investigated whether a significant correlation exists between the post-operative course of sigma S and the clinical evidence. For this purpose, on the basis of former results, a value of sigma S of 1.25 was determined as a criterion between malignant and benign ovarian diseases. For each investigated case, the post-operative temporal average of sigma S was calculated (sigma S) and a value of 1.25 was used as discriminating threshold. A four-fold table was set up containing the frequencies of tumor recurrences and tumor free cases with sigma S less or greater than 1.25. In a total of 40 patients of ovarian cancer an association between sigma S less than 1.25 and increased frequency of recurrences was confirmed, with a probability of error of 1%. The total predictive value of the sigma S level was about 70% and is herewith comparable to the leading tumor marker CA 125 in ovarian cancer.