Serum deoxythymidine kinase in small cell carcinoma of the lung: Relation to clinical features, prognosis, and other biochemical markers

Thymidine kinase (s‐TK), lactate dehydrogenase (LDH), and carcinoembryonic antigen (CEA) were determined in pretreatment serum from 125 patients with small cell carcinoma of the lung. The distribution of marker levels into three ranges, when including all patients were as follows: s‐TK <5 units 49%, 5‐<10 units 25%, ⩾10 units 26%; LDH < 6.7 μkat 31%, 6.7‐<13.4 μkat 48%, ⩾13.4 μkat 21%; CEA < 7.5 μg/l 51%, 7.5‐<15 μg/l 25%, ⩾15 μg/l 24%. The percentages of patients with limited and with extensive disease within each range were s‐TK <5 82/18, 5‐<10 29/71, ⩾10 9/91; LDH < 6.7 76/24, 6.7‐<13.4 51/49, ⩾13.4 21/79; CEA < 7.5 70/30, 7.5‐<15 39/61, ⩾15 23/77. Analyses in relation to metastases present showed that patients with skeletal and bone marrow metastases had significantly higher s‐TK and LDH than those without, while this was not the case for CEA. A strong correlation between s‐TK and LDH level, a weaker correlation between CEA and s‐TK, and no correlation between CEA and LDH level, was found. Both the level of s‐TK and LDH correlated to the patients' performance, as defined by the Karnofsky index. These correlations were mainly confined to the patients with extensive disease. Analyses of the prognostic capacity of variables showed that s‐TK, stage, and Karnofsky index could divide the patients into groups with highly significant difference in survival time, while LDH and CEA were of less value. Longitudinal studies showed that the serum markers mirrored the disease activity, with the exception that highly increased s‐TK was found during remission induction for some patients. It was concluded that the expression of pathologic levels for the serum markers were dependent on different biological parameters. Of the serum markers, only s‐TK was judged useful for estimation of disease spread and prognosis of the individual patient. Cancer 58:111–118, 1986.