Abstract LB-149: Serum thymidine kinase 1 levels predict prostate cancer-specific survival

Abstract

Abstract Background: Thymidine kinase 1 (TK1) is an enzyme involved in DNA synthesis. Thymidine kinases phosphorylate thymidine as part of the DNA synthetic pathway. TK1 expression is a marker of active cellular proliferation; intracellular concentrations are low during the G0/G1 phases of the cell cycle, increasing during the S/G2 phases. Previous studies have suggested that serum TK1 levels could be used as marker for presence of prostate cancer (PCa). Here, we evaluated whether serum TK1 levels could predict risk of PCa prognosis. Materials and Methods: The study population included 40 men with clinically defined T1/T2NxM0 PCa and 43 men with de novo metastatic cancer (M1) at diagnosis confirmed by bone scan imaging. All men were diagnosed and treated at the Tampere University Hospital between 2000-2010. All men provided a serum sample at the time of diagnosis. Information on deaths and causes of death were obtained from national causes of death registry. Serum TK1 concentrations were determined using the AroCell TK210 ELISA kit. Cox regression and Kaplan-Meier Curves with adjustment for tumor risk group (Gleason-grade, TNM stage and PSA level) were used to evaluate the risk of PCa death in relation to TK1 levels (median or below vs. above median). ROC analyses were used to evaluate the predictive accuracy of PSA, TK1 and their combination. Results: M1 cases were older than M0 cases; median age 72 vs 62 years, respectively. M1 cases were mainly managed with androgen deprivation therapy, whereas M0 cases were most often managed with radical prostatectomy. Median serum TK1 levels were significantly higher among M1 cases compared to M0 cases (p for difference 0.001). In the combined study population, serum TK1 levels were a significant predictor of PCa-specific (HR 8.33, 95% CI 2.05-33.88) and overall mortality (HR 5.53, 95% CI 1.93-15.85) after adjustment for established prognostic factors including tumor risk group. Kaplan-Meier survival curves defined by TK1 level started to differ within 24 months from PCa diagnosis. In ROC analyses TK1 alone or in combination with PSA was no more accurate than PSA alone in predicting PCa death. Conclusion: The proliferation biomarker TK1 in serum predicted survival after PCa diagnosis, demonstrating independent predictive value over established clinical risk factors. If confirmed in further and larger studies, this biomarker could be incorporated in PCa risk stratification when selecting optimal treatment and surveillance schedule. Citation Format: Teemu J. Murtola, Paavo Raittinen, Teuvo Tammela. Serum thymidine kinase 1 levels predict prostate cancer-specific survival [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-149.