Role of [99mTc]Tc-Galacto-RGD2 SPECT/CT in identifying metastatic differentiated thyroid carcinoma after thyroidectomy and radioactive iodine therapy

Abstract

PurposeIntegrin αvβ3, a member of the arginine-glycine-aspartate (RGD)-binding subfamily, is associated with tumor angiogenesis and metastasis. The aim of study is to investigate the clinical role of [99mTc]Tc-Galacto-RGD2 SPECT/CT in high-risk differentiated thyroid carcinoma (DTC) after thyroidectomy and radioactive iodine (RAI) therapy. MethodsThirty-six patients with high-risk DTC (20 males, 16 females; mean age: 59.9 ± 16.6 y) who underwent thyroidectomy and RAI therapy were consecutively enrolled in this study. All patients underwent [99mTc]Tc-Galacto-RGD2 SPECT/CT and diagnostic 131I whole-body scan 6 months after the last RAI treatment. A region of interest (ROI) was drawn and the ratio of tumor/non-target (T/NT) was calculated. Per-patient and per-lesion analysis was performed to evaluate the diagnostic efficacy. The final diagnosis was confirmed by histopathology and follow-up. Integrin αvβ3, CD31, and Ki-67 expression in the tumor were also analyzed for evaluation of angiogenesis and proliferation. ResultsOut of 36 patients, twenty-two had metastatic disease. By per-patient analysis, the area under the curve of [99mTc]Tc-Galacto-RGD2 SPECT/CT was marginally significantly higher than that of 131I whole-body scan and morphological imaging (P = 0.0034 and 0.0006). For per-lesion analysis, [99mTc]Tc-Galacto-RGD2 SPECT/CT identified 67 metastatic lymph nodes in 14 patients, 12 lung metastases in four patients, and 12 bone metastases in six patients; its sensitivity was significantly higher than that of 131I whole-body scan in detection of lymphatic (90.54% vs. 55.41%, P = 0.0124) and bone metastasis (92.31% vs. 30.77%, P = 0.046). The ratio of T/NT in metastatic lesions increased with the DTC upstaging. Conclusions[99mTc]Tc-Galacto-RGD2 SPECT/CT has high sensitivity in the detection of metastasis in high-risk DTC and further contributes to evaluation of tumor angiogenesis and radio‑iodine refractory status.