Use of carbon-11 methionine positron emission tomography to assess malignancy grade and predict survival in patients with lymphomas

The aim of this study was to investigate whether uptake of carbon-11 methionine (MET) is associated with histological grade of malignancy and survival in patients with newly diagnosed or recurrent lymphoma. Thirty-two patients with histologically confirmed lymphoma participated in the study. Twenty-six (81%) were studied before any therapy and six before treatment for recurrent disease. Twenty-eight patients had non-Hodgkin's lymphoma and four had Hodgkin's disease. An ECAT 931/08-12 positron emission tomography (PET) scanner was used for PET imaging. After the transmission scan, a median dose of 293 MBq of MET was injected intravenously and dynamic images were acquired for 40 min. The uptake of MET in tumour was measured as the standardized uptake value (SUV) and influx constant (Ki). The SUV formula was also adjusted to the predicted value of lean body mass (SUVlean) and body surface area (SUVBSA). The PET results were correlated with the clinical follow-up data. The median SUV in 32 malignant lesions was 6.6 (range, 1.9-12.4) and the median Ki was 0. 116 min-1 (range, 0.025-0.201, n=23). The median SUV was 7.0 (range, 5.4-12.4, n=9) in high, 6.2 (range, 1.9-10.4, n=11) in intermediate and 5.7 (range, 3.8-8.3, n=8) in low grade lymphomas. One intermediate grade lymphoma of the skin was visually negative (SUV 1. 9). In Hodgkin's disease the median SUV was 7.0 (range, 3.2-7.9, n=4). The median Ki value was 0.162 min-1 (range, 0.147-0.197, n=7) in high, 0.099 (range, 0.025-0.152, n=10) in intermediate, and 0.078 (range, 0.056-0.152, n=4) in low grade lymphomas and 0.149 (range, 0. 096-0.201, n=2) in Hodgkin's disease. The difference between high and other grade non-Hodgkin's lymphomas was significant when using Ki (P