Utility of I-124 PET/CT in identifying radioiodine avid lesions in differentiated thyroid cancer: a systematic review and meta-analysis.

INTRODUCTION: Diagnostic I-123 scans have been shown to underestimate the disease burden in differentiated thyroid cancer (DTC) when compared to I-131 post-treatment scans, especially in children and patients who have had prior radioiodine (RAI) therapy and/or distant metastasis. I-124 PET/CT has been shown to be highly effective in imaging DTC-related metastatic disease.

METHODS: We performed a systematic review and meta-analysis of studies investigating the sensitivity and specificity of I-124 PET/CT in identifying lesions amenable to RAI therapy as confirmed by I-131 post-treatment scanning.

RESULTS: There were 141 patients and 415 lesions of DTC identified altogether. There was significant heterogeneity in the individual studies. The pooled sensitivity of the I-124 PET/CT in detecting lesions of differentiated thyroid cancer amenable to I-131 therapy was 94·2% (91·3-96·4% CI, P < 0·01), and the pooled specificity was 49·0% (34·8-63·4% CI, P < 0·01). The pooled positive likelihood ratio (LR) was 1·43 (1·05-1·94 CI), and the pooled negative LR was 0·28 (0·15-0·53 CI). Overall, the diagnostic odds ratio was 7·90 (3·39-18·48 CI). There were a small but increased number of lesions identified by I-124 PET/CT that was not detected on post-treatment scan.

CONCLUSION: I-124 PET/CT is a sensitive tool to diagnose RAI avid DTC lesions, but also detects some new lesions that are not visualized on the post-treatment I-131 scan. Further, carefully designed dosimetric studies may be required to fully establish the role of I-124 PET CT for identifying potential lesions for I-131 therapy. I-124 PET/CT in patients with DTC may have other applications in specific clinical situations.