Radioimmunotherapy of human lymphoma in athymic, nude mice as monitored by ³¹P nuclear magnetic resonance

Human B cell lymphoma (Raji) growing in athymic, nude mice has been successfully treated with a single pulse dose of ¹³¹I-labeled monoclonal antibody (Lym-1) specific for this tumor. Sequential in vivo measurements of phosphate metabolites in the tumors by ³¹P surface coil nuclear magnetic resonance showed a significant initial decrease of phosphocreatine following radioimmunotherapy. Diminution of relative ATP to Pi peak area ratio suggesting tissue damage occurred within 3-4 days. The contribution from metabolites resonating at ca 3.8 ppm (putative sugar phosphate region) increased. There was no significant change in pH either as a function of tumor volume or treatment. The sequence of alterations of nuclear magnetic resonance spectra from tumors of treated mice were strikingly different from sequential nuclear magnetic resonance spectra obtained from tumors of control mice. These observations lead us to conclude that ³¹P surface coil nuclear magnetic resonance is a promising non-invasive method for assessing and predicting the efficacy of radioimmunotherapy. Further spatial discrimination of the region of tissue observed by the surface coil nuclear magnetic resonance experiment is under exploration in an effort to increase the utility of these methods.