The role of thallium-201 uptake and retention in intracranial tumors after radiotherapy

Mordechai Lorberboym, Lynda R. Mandell, Roger E. Mosesson, Isabelle Germano, Wendy Lou, Maria DaCosta, Debra G. Linzer, Josef Machac

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42 Scopus citations

Abstract

This study prospectively assessed the diagnostic accuracy and prognostic value of 201Tl uptake and retention in primary and metastatic intracranial tumors treated by conventional radiotherapy and/or radiosurgery. Methods: An initial 201Tl study (early and delayed images), was obtained in 60 postsurgical patients, 6-12 wk after radiotherapy or radiosurgery. Repeat imaging was performed as clinically warranted. Tumor-to-background count ratios and a retention index (RI) were calculated for all lesions. Results: Abnormally increased 201Tl uptake was observed in 40 of 60 patients. In all patients with positive results, the diagnosis of residual tumor was confirmed at biopsy or by clinical follow-up. In 20 of 60 patients, no abnormal 201Tl uptake was observed, despite findings on CT and/or MRI scans that were suspicious for tumor. Ten of the negative 201Tl studies were confirmed as true-negatives by the clinical course and by resolution of CT/MRI abnormalities. The remaining 10 negative SPECT studies ultimately proved to be false-negatives: six of these patients had lesions <1 cm in maximum diameter; one patient had a large metastatic choriocarcinoma; and three patients had low-grade astrocytomas >2 cm in minimum diameter. Tumor- to-background ratio of 201Tl uptake did not distinguish between tumor type, or predict clinical outcome. The RI of 201Tl was significantly higher for metastatic melanoma than for other tumor metastases. It demonstrated reasonably good correlation with clinical outcome: 6/7 patients with eventual tumor regression showed a decrease in RI on follow-up examination, and 4/5 patients with eventual tumor progression had an increase in RI. Conclusion: Thallium-201 brain SPECT appears to be a useful noninvasive imaging technique in patients irradiated for intracranial tumors. Thallium-201 scintigraphy has very high specificity (100% in this cohort) for detecting viable residual tumor. False-negative findings may occur. Quantitative analysis of 201Tl uptake has limited diagnostic and prognostic significance, but changes in 201Tl retention after radiation therapy seems to have prognostic value.

Original languageEnglish
Pages (from-to)223-226
Number of pages4
JournalJournal of Nuclear Medicine
Volume38
Issue number2
StatePublished - Feb 1997
Externally publishedYes

Keywords

  • intracranial tumors
  • radiation therapy
  • retention index
  • thallium-201

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