The present pilot study tests the hypothesis that <i>SSAT-1</i> activity within the tumor, as measured by plasma acetylamantadine concentrations, can be used to monitor patient response to therapy.<h4>Results</h4>In cases with evidence of disease response, there was a reduction in the plasma acetylamantadine concentration at 4 h by approximately 32%. This evidence concerns the gene SAT1 and neoplasm.