Pharmacokinetics of positron-labeled 1,3-bis(2-chloroethyl)nitrosourea in human brain tumors using positron emission tomography.

The nitrosoureas are widely used in the chemotherapy of brain tumors, two of the most common being 1,3-bis(2-chloroethyl)nitrosourea and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea. However, we do not understand how these compounds work, nor do we know which part of the molecule has antitumor activity. In six patients with brain tumor, we measured the kinetic behavior of positron-labeled 1,3-bis(2-chloroethyl)nitrosourea in both the tumor and the normal brain with the aid of positron emission tomography; we also analyzed the distribution of radioactivity in plasma. We found the clearance of total radioactivity from the tumor to be significantly slower than from the contralateral brain and plasma, indicating a different rate of 1,3-bis(2-chloroethyl)nitrosourea decomposition in the tumor than in normal brain.