Quantitative scanning of soft-tissue sarcomas with nitrogen-13-labeled L-glutamate

Nitrogen-13-L-glutamate, a labeled amino acid enzymatically synthesized from cyclotron-produced N-13 ammonia and alpha-ketoglutaric acid, was used as an imaging agent in 14 patients with soft-tissue sarcomas. Concentration of nitrogen-13 label within the sarcoma was seen in 11 of the 14 patients; in some cases, clinically inapparent metastatic tumor lesions could also be detected. In eight patients, the tumor response to chemotherapy was evaluated by serial studies with this agent. In each case, the change in uptake of N-13 label by the sarcoma after therapy paralleled the clinical response to treatment. N-13-labeled L-glutamate may thus be of value as an imaging agent in the management of patients with soft-tissue sarcomas.