This study evaluated the clinical utility of serum thymidine kinase 1 (STK1) in following the progression of pre-malignancies and malignancies and in monitoring the response of common carcinomas to therapy within a routine clinical setting. The STK1 concentration levels of patients with malignancies (n=224), pre-malignancies (n=10), non-tumor/non-proliferating diseases (systemic lupus erythematosus, SLE) (n=53), benign tumors (n=20) and healthy volunteers (n=761) were determined by enhanced chemoluminescence dot blot assay. Prior to treatment, STK1 levels in the pre-malignant group alone (3.1±2.3) or in the pre-malignant and malignant groups together (2.3±1.9) were significantly higher than in the benign (1.4±0.8), SLE (1.1±0.8) or healthy volunteer (0.6±0.4) groups (p<0.01). According to ROC analysis, the STK1 assay provided a high degree of discrimination between STK1-positive pre-malignant (0.978) or pre-malignant + malignant (0.941) patients and STK1-negative healthy individuals. After varying treatments (surgery, chemotherapy, X-ray), STK1 levels increased by 40-50% during the first month, then decreased back to normal values or even lower. Following treatment, STK1 levels were significantly increased in squamous cell carcinoma (SCC) as compared to adenocarcinoma (AC) patients. In other types of malignancies, STK1 levels decreased from as early as the first month. The STK1 levels of relapsed treated patients were significantly higher (50-60%) than those of mid/long-term treated patients. In conclusion, the STK1 assay discriminated between patients with malignancies and healthy individuals very well, and is therefore potentially useful for a broad range of clinical applications. For example, it could be used for the evaluation of early tumor progression or of tumor progression during therapy in routine clinical settings, as well as for the screening of healthy individuals.

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