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Positron emission tomography (PET) and 11C-methionine (MET) are used for imaging amino acid metabolism in cancer. The aim was to study the potential of MET PET in assessing response to radiotherapy (RT) in primary squamous cell cancer (SCC) of the head and neck cancer. Seven patients had altogether 13 evaluable tumor sites. Six patients with SCC in the oral cavity and one with laryngeal SCC entered a MET PET study before and after preoperative RT (total tumor dose 62–73 Gy). All except one were operated, and the standardized uptake values (SUVs) of the tumor sites were compared with histology. The median SUV was significantly smaller (2.3; range 1.6–3.1; N = 4) in cases with complete response to RT than in those with persistent cancer (median 4.5; range 3.1–7.0, N = 7, P = 0.01). MET PET may distinguish persistent cancer from benign therapy-induced changes. High MET uptake in the tumor site after RT suggests the presence of persistent cancer.

Glucose metabolism has been demonstrated to be increased in neoplastic tissue, and to reflect the grade of malignancy of human cancer. We studied in vivo glucose metabolism in 22 pts with untreated non-Hodgkin's lymphoma with fluorine-18-fluorodeoxyglucose (FDG) and positron emission tomography (PET). FDG uptake in lymphoma deposits was measured as standardized uptake values (SUVs) of the tracer, and compared with histological classification and proliferative activity. Results The median SUV of the lymphomas was 8.5. A high FDG uptake in tumors was associated with high histological degree of malignancy by the Working Formulation (P = 0.005) or by the Kiel classification (P = 0.003). A high FDG accumulation was also associated with a high S-phase fraction (r = 0.786, P = 0.002). Conclusion FDG PET may find application in assessing the grade of aggressiveness of lymphoma in clinically problematic cases.