Concentration of cholesteryl 14-methylhexadecanoate was determined by high-performance liquid chromatography in serum of 123 healthy individuals, 83 of patients with other diseases than cancer, and of 394 patients with cancer. A mean level of 22.89 nmol/ml in healthy persons was not significantly different from 23.22 nmol/ml found in other diseases than cancer. With a cut-off value of 40.0 nmol/ml, there were 2 falsely positive results in the former and 4 in the later group. Significantly elevated mean concentrations (60-80 nmol/ml) were demonstrated in most patients with cancer irrespective of the clinical stage. No differences were found in this respect between males and females, and in different age groups. The sensitivity of the test was 81.8% for the whole population tested, if progressive and stable diseases as well as partial remissions were evaluated. Lower sensitivities were found in females and in patients more than 60 years old (down to 70.6%). The test showed a significantly greater sensitivity in less advanced stages of the disease (T1 and T2). Considering the type of cancer, highest sensitivity was observed for testicular cancer (86.2%), lower for prostatic (77.8%), mammary (76.5%), ovarian (75.8%), and colorectal tumors (73.3%) as well as for lymphomas (70%). Follow-up of patients with all these types of cancer revealed that changes in their clinical condition are accompanied with significant alterations in the cholesteryl 14-methylhexadecanoate level. When this ester was determined in 807 sera with a known level of other markers (irrespective of diagnosis), a significant correlation was demonstrated with carcinoembryonic antigen and nearly a significant one with prostatic specific antigen. There was no correlation with CA 15-3, CA 19-9, CA 125, or TPA. Because of its sound theoretical basis, absolutely specific method of determination, high specificity (97.1%), and predictive value (94.7%), the cholesteryl 14-methylhexadecanoate level determination may be useful as an alternate procedure supplementing the spectrum of tumor markers generally used.

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