['Pyruvate kinase type M2 (TuM2-PK) and thymidine kinase 1 (TK1) are the key enzymes involved in tumor cells metabolism and proliferation. We explored the association of their preoperative circulating levels with disease recurrence in patients with renal cell carcinoma (RCC).', 'We measured the plasma levels of TuM2-PK levels and serum TK1 activity preoperatively in patients with RCC, using a quantitative ELISA, and correlated the results with clinicopathological parameters.', 'Significantly higher levels of TuM2-PK and TK1 were found in 116 patients with RCC compared with 20 healthy participants (P < .001 and P = .03), but not compared with 27 patients with benign kidney tumors (P = .13 and P = .72). There was a significant association between the level of TuM2-PK and of TK1 activity with T stage (P = .01 and P = .04). Of 2 markers only TuM2-PK was significantly associated with tumor grade (P = .001). The presence of extensive tumor necrosis (> 50%) was associated with high TuM2-PK (P = .001) and low TK1 (P = .03). The 5-year recurrence-free survival for patients with elevated TuM2-PK or TK1 was significantly lower compared with those for patients with normal marker levels (55% vs 94%, P < .001 and 21% vs 90%, P = .002). Multivariate Cox Proportional Hazard analysis demonstrated that TuM2-PK and TK1, adjusted for stage, grade and tumor necrosis were retained as independent predictors of disease recurrence (HR = 7.3, P = .04 and HR = 3.8, P = .03).'] Are circulating tumor M2 pyruvate kinase and thymidine kinase 1 potential predictors for disease recurrence in renal cell carcinoma after nephrectomy?