[11C]methionine PET, histopathology, and survival in primary brain tumors and recurrence

BACKGROUND AND PURPOSE

[(11)C]Methionine (MET) PET imaging is a sensitive technique for visualizing primary brain tumors and recurrence/progression after therapy. The aim of this study was to evaluate the relationship between the uptake of MET and histopathologic grading and to investigate the prognostic value of the tracer, in both settings.

METHODS

Cerebral uptake of MET was determined in 52 patients: in 26 patients for primary staging (group A) and 26 patients with suspected brain tumor recurrence/progression after therapy (group B). Semiquantitative methionine uptake indices (UI) defined by the tumor (maximum)-to-background ratio was correlated with tumor grade and final outcome.

RESULTS

Overall median survival was 34.9 months. MET showed pathologically increased uptake in 41 of 52 scans. Although a weak linear correlation between MET uptake and grading was observed (R = 0.38, P = .028), analysis of variance showed no significant differences in MET UI between tumor grades for either group A or B. Benign and grade I lesions showed significant difference in MET uptake in comparison with higher grade lesions (P = .006). Using Kaplan-Meier survival analysis, no thresholds could be found at which MET was predictive for survival. Proportional hazard regression showed that only WHO grading class (low versus high) was predictive of survival (P = .015).

CONCLUSION

Interindividual MET uptake variability does not allow noninvasive grading on an individual patient basis. Moreover, there is no significant prognostic value in studying maximal methionine UI in brain tumors. The clinical use of MET should therefore be primarily focused on questions such as detection of recurrence, biopsy guidance, and radiation therapy target volume delineation.

Additional value of PET-CT in the staging of lung cancer: comparison with CT alone, PET alone and visual correlation of PET and CT

Integrated positron emission tomography (PET) and computed tomography (CT) is a new imaging modality offering anatomic and metabolic information. The purpose was to evaluate retrospectively the accuracy of integrated PET-CT in the staging of a suggestive lung lesion, comparing this with the accuracy of CT alone, PET alone and visually correlated PET-CT. Fifty patients undergoing integrated PET-CT for staging of a suggestive lung lesion were studied. Their tumor, node, metastasis (TNM) statuses were determined with CT, PET, visually correlated PET-CT and integrated PET-CT. These TNM stages were compared with the surgical TNM status. Integrated PET-CT was the most accurate imaging technique in the assessment of the TNM status. Integrated PET-CT predicted correctly the T status, N status, M status and TNM status in, respectively, 86%, 80%, 98%, 70% versus 68%, 66%,88%, 46% with CT, 46%, 70%, 96%, 30% with PET and 72%, 68%, 96%, 54% with visually correlated PET-CT. T status and N status were overstaged, respectively, in 8% and 16% with integrated PET-CT, in 20% and 28% with CT, in 16% and 20% with PET, in 12% and 20% with visually correlated PET-CT and understaged in 6% and 4% with integrated PET-CT, versus 12% and 6% with CT, 38% and 10% with PET and 12% with visually correlated PET-CT. Integrated PET-CT improves the staging of lung cancer through a better anatomic localization and characterization of lesions and is superior to CT alone and PET alone. If this technique is not available, visual correlation of PET and CT can be a valuable alternative.

Parathyroid imaging: basic principles and KU Leuven experience: MIBI-dual phase versus MIBI/I-123

OBJECTIVE

The aim of our study was to evaluate and compare retrospectively MIBI-dual phase and MIBI/I-123 subtraction scintigraphy for preoperative localisation of hyperfunctioning parathyroid glands. In our department we also attempted to improve the results of the latter method by altering the subtraction technique.

SUBJECTS AND METHODOLOGY

Fifty-one patients with hyperparathyroidism underwent preoperative evaluation with radionuclide scanning for the localisation of abnormal parathyroid glands. MIBI-dual phase and MIBI/I-123 subtraction scintigraphy were carried out respectively in fourteen and thirty-seven patients. Anatomopathological findings were used as the gold standard.

RESULTS

Topographic identification of the pathological parathyroid glands was correct in 28% for MIBI-dual phase, in 46% for MIBI/I-123 ('old' method) and in 67.5% for MIBI/I-123 ('new' method). Relying on a normal histology of the normal parathyroid glands, there's a specificity of respectively 82.7%, 99% and 96%.

CONCLUSION

MIBI/I-123 subtraction scintigraphy is superior to MIBI-dual phase for the preoperative detection and localisation of hyperfunctioning parathyroid tissue, especially when using a gradual subtraction.