Diagnostic Accuracy of PET, SPECT, and Arterial Spin-Labeling in Differentiating Tumor Recurrence from Necrosis in Cerebral Metastasis after Stereotactic Radiosurgery

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The authors retrospectively reviewed patients treated between 2007–2010 and identified 14 patients with cerebral metastasis who had clinical or radiographic progression following stereotactic radiosurgery and were imaged with arterial spin-labeling (ASL), FDG-PET, and thallium SPECT before stereotactic biopsy. FDG-PET and ASL were equally sensitive in detecting tumor progression (83%). The specificity of ASL was superior to that of the other modalities (100%, 75%, and 50%, respectively). A combination of modalities did not augment the sensitivity, specificity, positive predictive value, or negative predictive value of ASL.

Abstract

CE-MR imaging, thallium SPECT, FDG-PET, and ASL-MR images from case 1 (A) with metastatic renal cell carcinoma to periventricular white matter of the posterior left lateral horn. CE-MR imaging shows new enhancement in the region treated. SPECT was positive while PET and ASL were negative for tumor recurrence. Biopsy of the target region indicated radiation necrosis in case 2 (B) with metastatic breast cancer to the right cerebellum. CE-MR imaging shows new enhancement in the region treated. PET (SUV = 6.6) and ASL were positive for tumor recurrence. Biopsy of the target region indicated tumor recurrence in case 3 (C) with metastatic melanoma to the right inferior frontal cortex. Only PET was positive for tumor recurrence (SUV = 10.7). Biopsy of the target region indicated tumor recurrence.
CE-MR imaging, thallium SPECT, FDG-PET, and ASL-MR images from case 1 (A) with metastatic renal cell carcinoma to periventricular white matter of the posterior left lateral horn. CE-MR imaging shows new enhancement in the region treated. SPECT was positive while PET and ASL were negative for tumor recurrence. Biopsy of the target region indicated radiation necrosis in case 2 (B) with metastatic breast cancer to the right cerebellum. CE-MR imaging shows new enhancement in the region treated. PET (SUV = 6.6) and ASL were positive for tumor recurrence. Biopsy of the target region indicated tumor recurrence in case 3 (C) with metastatic melanoma to the right inferior frontal cortex. Only PET was positive for tumor recurrence (SUV = 10.7). Biopsy of the target region indicated tumor recurrence.

BACKGROUND AND PURPOSE

Radiographic assessment of cerebral metastasis after stereotactic radiosurgery remains a major challenge in neuro-oncology. It is often difficult to distinguish tumor progression from radiation necrosis in this setting using conventional MR imaging. The objective of this study was to compare the diagnostic sensitivity and specificity of different functional imaging modalities for detecting tumor recurrence after stereotactic radiosurgery.

MATERIALS AND METHODS

We retrospectively reviewed patients treated between 2007 and 2010 and identified 14 patients with cerebral metastasis who had clinical or radiographic progression following stereotactic radiosurgery and were imaged with arterial spin-labeling, FDG-PET, and thallium SPECT before stereotactic biopsy. Diagnostic accuracy, specificity, sensitivity, positive predictive value, and negative predictive value were calculated for each imaging technique by using the pathologic diagnosis as the criterion standard.

RESULTS

Six patients (42%) had tumor progression, while 8 (58%) developed radiation necrosis. FDG-PET and arterial spin-labeling were equally sensitive in detecting tumor progression (83%). However, the specificity of arterial spin-labeling was superior to that of the other modalities (100%, 75%, and 50%, respectively). A combination of modalities did not augment the sensitivity, specificity, positive predictive value, or negative predictive value of arterial spin-labeling.

CONCLUSIONS

In our series, arterial spin-labeling positivity was closely associated with the pathologic diagnosis of tumor progression after stereotactic radiosurgery. Validation of this finding in a large series is warranted.

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Diagnostic Accuracy of PET, SPECT, and Arterial Spin-Labeling in Differentiating Tumor Recurrence from Necrosis in Cerebral Metastasis after Stereotactic Radiosurgery
Jeffrey Ross
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