Isoenzyme pattern of alkaline phosphatase in the serum of children with leukaemia after long-term chemotherapy.

Chemotherapy was discontinued in thirteen children with acute lymphoblastic leukaemia after 2-3 years without relapse. In the following months, a continuous increase was observed in the serum alkaline phosphatase. A maximum was reached at different times but all patients had normal values again after 19 months. The rise in the total activity is due to an isolated increase of the bone isoenzyme. Increased enzyme activity in this post-therapy phase of the disease does not signify liver damage from the preceding chemotherapy, but rather is due to an increased osteoblast activity associated with a temporary increase in growth rate.