AOPEP and renal cell carcinoma: Apo-[3-methylcrotonoyl-CoA:carbon-dioxide ligase (ADP-forming)], dihydrouridine, acetone, pyruvate, hydroxyprolyl-asparagine, 7-aminomethyl-7-carbaguanine, and lys-gly/gly-lys, all increased when both RCC stages were compared to healthy controls, and they also increased when advanced RCC samples were compared to early RCC samples indicating that these metabolites are potential candidates for discriminating advanced RCC from early RCC, and both RCC stages from healthy controls.