Lactate dehydrogenase levels during MACOP-B chemotherapy for non-Hodgkin's lymphoma.

Lactate dehydrogenase (LD) levels rose consistently during MACOP-B chemotherapy for intermediate and high-grade non-Hodgkin's lymphoma (NHL). Levels peaked at week nine and fell to normal within six weeks of completion of therapy. Isoenzyme patterns, studied prospectively in seven patients, showed a parallel rise in LD1 and LD2 suggesting a source other than tumour tissue for the rise in total LD. In the absence of evidence of myocardial or renal damage, haematopoietic tissue was the most likely source. With no evidence of haemolysis, normal serum levels of vitamin B12 and folate and normal red cell folate, dyserythropoiesis was considered to be the underlying mechanism. A rising mean corpuscular volume further reinforced this suggestion. Intensive use of methotrexate along with co-trimoxazole as prophylaxis against pneumoycystis carinii is considered the most likely cause of marrow dysfunction. Failure to recognise that rising LD levels during such therapy is treatment-related, rather than of tumour origin, may lead to inappropriate change or abandonment of therapy.