carbon-11-methionine and Lymphoma--Non-Hodgkin

The role for radiotherapy in patients with low-grade gliomas remains controversial. Two large prospective studies have failed to demonstrate a radiotherapeutic dose-response effect, and EORTC trial 22845 found no difference in survival between patients receiving adjuvant radiotherapy and those who received radiotherapy at tumour progression. The aim of this retrospective study was to analyse the patterns of carbon-11 methionine (MET) uptake on positron emission tomography (PET) in tumours treated with immediate radiotherapy and in those treated with delayed radiotherapy at the time of tumour progression. The 21 adult patients studied had histologically confirmed low-grade gliomas and had undergone a pre-treatment PET scan and a follow-up PET scan at the time of progression. Eleven of the patients had undergone initial radiotherapy a median of 5 weeks after the surgical procedure. The median time to progression was 3.5 years for this group, compared with 1.6 years for the group with delayed radiotherapy ( P=0.06). At the time of progression, non-irradiated tumours had a significantly higher MET uptake ( P=0.02) and a larger uptake volume ( P=0.008) compared with baseline, whereas irradiated tumours showed no statistically significant change. We observed a correlation between high pre-treatment uptake of MET and reduction in MET uptake in response to radiotherapy ( P=0.008). All irradiated tumours recurred within the radiation field. In conclusion, our results demonstrate signs of a residual radiation effect at the time of tumour progression in low-grade gliomas with high pre-treatment uptake of MET. Pre-treatment methionine uptake may be a marker for the radiosensitivity of low-grade gliomas.

Topics: Adult; Aged; Biomarkers, Tumor; Brain Neoplasms; Disease Progression; Disease-Free Survival; Dose Fractionation, Radiation; Female; Humans; Lymphoma, Non-Hodgkin; Male; Methionine; Middle Aged; Radiopharmaceuticals; Retrospective Studies; Sensitivity and Specificity; Tomography, Emission-Computed; Treatment Outcome

Our goal was to determine whether PET with 11C-methionine and/or 18FDG could predict malignancy grade in non-Hodgkin's lymphoma (NHL).. Twenty-three patients with high-grade, low-grade or transformed low-grade NHL were investigated. Standardized uptake values (SUV), transport rate and mass influx values were calculated both for the whole tumor [mean regions of interest, (ROI)] and for the tumor area with the highest levels of activity, comprising four contiguous pixels within each tumor and designated as a hot spot.. Both 11C-methionine and 18FDG detected all tumors. In addition, 18FDG discriminated between high- and low-grade NHL, whereas 11C-methionine did not. With 18FDG, three transformed low-grade NHLs behaved in an intermediate manner. All quantitative uptake values correlated well with each other for both tracers, except for the mean ROI SUV and transport rate of 11C-methionine. Quantifications of mean ROI uptake and hot spots were strongly correlated.. The results of this study together with previous findings from other studies indicate that 18FDG but not 11C-methionine can predict malignancy grade in NHL. Further studies with a larger series of patients are needed.

Topics: Adult; Aged; Deoxyglucose; Female; Fluorine Radioisotopes; Fluorodeoxyglucose F18; Humans; Image Processing, Computer-Assisted; Lymphoma, Non-Hodgkin; Magnetic Resonance Imaging; Male; Methionine; Middle Aged; Predictive Value of Tests; Tomography, Emission-Computed