ALTERNATIVE METHOD FOR THE DIAGNOSIS OF EARLY CANCER USING PLASMA FREE AMINO ACID PROFILES

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The amino-acid balance is altered in patients with various diseases, due to metabolic changes. The metabolism in cancer cells is also known to be notably altered. Amino-acid profiles could therefore be useful biomarkers of various cancers. In this study, significant changes of amino-acid profiles were detected in the plasma of colorectal and breast cancer patients through multivariate analysis.Venous blood samples were taken from colorectal cancer patients, breast cancer patients, and healthy controls. Plasma free amino acids were measured by liquid chromatography(LC)/mass spectrometry(MS). Based on the amino-acid profiles, multiple logistic-regression models were used to discriminate between colorectal or breast cancer patients and control subjects. Diagnostic performance was evaluated as the area under the curve(AOC) of the receiver operating characteristic(ROC) curve, and was validated with randomly divided test data.The plasma amino-acid profiles differed between colorectal and breast cancer patients and healthy controls. No weight loss was observed in any of the cancer patients. The AUC of the discriminant ROC curve for each discriminant score was calculated as 0.863 for colorectal cancer and 0.856 for breast cancer. Reproducible performance was observed using split test data. Moreover, the performance of these discriminants was independent of the cancer stage.The occurrence of cancer alters plasma amino-acid profiles without cachexia or weight loss, and the pattern of change differs between cancers. Plasma amino-acid profiling might therefore be useful for the low-cost early detection of several kinds of cancer.