Amino acid profile index for early detection of endometrial cancer: verification as a novel diagnostic marker.

BACKGROUND: Plasma amino acid profiles (PAAPs) vary in individual cancer patients, and it has been suggested that they may be useful for early detection of several types of cancer. We evaluated the diagnostic performance of a profile index for endometrial cancer composed of multiple plasma amino acids as a novel biomarker and compared its diagnostic performance with that of CA125. METHODS: Plasma amino acid levels of 80 patients with endometrial cancer, 122 with benign gynecological diseases, and 240 age- and body mass index-matched control subjects were measured using liquid chromatography and mass spectrometry. After univariate analysis, we applied a multiplex model based on the PAAP multivariate analysis to distinguish patients with endometrial cancer from control subjects. We compared the diagnostic performance of the multiple PAAP index (API) with that of CA125. RESULTS: The levels of several plasma amino acids were significantly different in patients with endometrial cancer. The area under the receiver operating characteristic curves (AUC) used to distinguish endometrial cancer patients from control subjects was 0.94. The AUC for API was significantly larger than that for CA125 (P = 0.0068). For the same specificity of 98.3 %, API showed a significantly higher sensitivity (60.0 %, 95 % CI, 43.3-75.1) than that of CA125 (22.5 %, 95 % CI, 10.1-38.5). In stage I cases, API showed significantly higher positivity than that of CA125 (P = 0.0002). CONCLUSIONS: The sensitivity and disease specificity of API for early-stage detection of endometrial cancer was superior to CA125. This novel plasma biomarker has the potential to become a diagnostic and screening marker for endometrial cancer.