The measurement of total lactic dehydrogenase and its isoenzymes in solid tumours.

The routine practice of making enzymatic assessments for the purposes of cancer diagnosis, including the determination of total amount of LDH provides only limited information. However, the total amount of LDH may be used to monitor the effect of chemotherapy or radiotherapy in certain tumours, such as epithelial tumours and germ-cell tumours of the ovaries, non Hodgkin's lymphomas or malignant tumours of the testicles. The differentiation of LDH isoenzymes, with a view to linking their pattern to precise localizations has been studied. In germ-cell testicular tumours, there is a marked increase in LDH 1. In liver metastases, LDH 5 and/or LDH 4 are disturbed in 90% of the cases, while the total amount of LDH is raised in only 72% of the cases. In many cases, the association of a disturbance in the serum ratio of the total amount of LDH and a disturbance in the isoenzymes of LDH 4 and LDH 5 associated with a high level of GGT indicate the presence of liver metastases.