An experimental approach to relate a tumor-associated enzyme marker to tumor cell numbers.

Alkaline phosphatase was monitored in 17 mice with s.c.-implanted tumors to relate the total circulating alkaline phosphatase to the total number of tumor cells in each mouse. There was a semilogarithmic relationship between the alkaline phosphatase units and the number of tumor cells. A time-independent standard plot of alkaline phosphatase and the number of tumor cells was used to estimate the size of disseminated and localized tumors. In animals treated with cyclophosphamide, the alkaline phosphatase marker was used to monitor the regression and recurrence of the neoplasm in vivo.