Differentiation between recurrent brain tumour and post-radiation necrosis: The value of Tl-201 SPET versus (18)FDG PET using a dual-headed coincidence camera - a pilot study

The aim of this study was to determine whether it is possible to differenti ate between recurrent disease and post-treatment necrosis in patients treat ed for a primary brain tumour. This prospective study was designed to compa re the sensitivity and specificity of Tl-201 Single photon emission tomogra phy (SPET) and F-18-fluorodeoxyglucose (F-18-FDG) positron emission tomogra phy (PET) using a dual-headed coincidence camera. Sixteen patients suspecte d of having recurrent brain tumour (10 men, 6 women) (mean age 39.5 years, range 21-57 years) were studied. Tl-201 SPET and F-18-FDG PET studies were performed on the same day. An increase in activity was considered indicativ e of tumour recurrence. The images were also quantified using a thallium in dex and an FDG index. The F-18-FDG PET images were also assessed visually u sing a 5-point scale. The diagnosis of tumour recurrence was based on clini cal course and/or follow-up computed tomography or magnetic resonance imagi ng. The sensitivity of Tl-201 SPET and F-18-FDG PET was 92% (11/12) and 62% (7/12) respectively. One patient initially assessed as having necrosis sho wed a recurrence 9 months after both studies. McNemar's analysis of these r esults showed a statistically significant difference (P = 0.023) in the abi lity of the two methods to separate with accuracy tumour from radiation nec rosis. No correlation was found between the thallium index and the FDG inde x (r = 0.36). We conclude that Tl-201 SPET is a sensitive modality for the detection of brain tumour recurrence. F-18-FDG imaging using a dual-headed coincidence camera gave significantly poorer results compared to Tl-201 SPE T. Our results do not justify continuation of this prospective comparative study ((C) 1999 Lippincott Williams & Wilkins).