Deoxythymidine kinase in the tumour cells and serum of patients with non-Hodgkin lymphomas.

The levels of deoxythymidine kinase in tumour cells (C-TK) and in serum (S-TK) were investigated and the tumour volume calculated in 89 patients with non-Hodgkin lymphoma (NHL), in order to ascertain the importance of C-TK and tumour burden as regards the S-TK levels. Among all patients, a correlation was seen between S-TK and tumour volume but not between S-TK and C-TK. However, within different tumour volume categories (small, medium-sized and large), there was a correlation between S-TK and C-TK. Multiple regression analysis supported this notion. C-TK correlated with the proliferation-associated parameters, S-phase fraction and mitotic index. As already known, S-TK was found to have a strong prognostic value. C-TK and tumour burden were also of prognostic value. In multivariate analyses, C-TK and tumour volume did not provide prognostic information in addition to S-TK, whereas, in the absence of S-TK, C-TK and tumour volume did provide additional information. It is concluded that the serum level of TK depends on both the tumour burden and the tumour cell proliferation rate. Based upon estimations of S-TK in patients assessed shortly after chemotherapy, we also suggest that S-TK reflects the number of proliferating cells that have died during the period immediately before sampling.