Background and aim: This study aimed to examine the expression of RGD binding integrins in patients of elevated serum thyroglobulin (Tg) level with negative radioiodine scintigraphy (TENIS) employing 68 Ga-NODAGA-RGD PET-CT.
Material and methods: This was a prospective study involving 30 proven cases of TENIS with histopathological diagnosis of differentiated thyroid carcinoma post-surgery. In addition to observing the lesional concentration on 68 Ga-NODAGA-RGD PET-CT, a 4-point visual grading system (grade I-IV), was undertaken to estimate the degree of radiotracer avidity, for potential of theranostics.
Results: On 18 F-FDG-PET/CT, the uptake was seen in 182 lesions out of a total of 200 (91%). 68 Ga-NODAGA-RGD PET-CT showed expression in a total of 110/200 (55%) lesions. On patient-specific analysis, 68 Ga-NODAGA-RGD PET-CT was positive for the disease in 21/30 patients (70%) and negative in 9/30 (30%) patients. The overall patient-specific sensitivity and specificity of 68 Ga-NODAGA-RGDPET-CT were 75% and 100%, respectively. 18 F-FDG PET-CT was positive for the disease in 26/30 patients (86.66%) and negative in 4/30 (13.33%) patients. The overall patient-specific sensitivity and specificity of 18 F-FDG-PET/CT were 92.86% and 100%, respectively. The 4-point visual grading system revealed 14/200 (7%) lesions demonstrating Grade I uptake, 49/200 (24.5%) lesions grade II uptake, 17/200 (8.5%) lesions grade III uptake and 40/200 (20%) lesions grade IV uptake.
Conclusion: The results suggested that RGD-binding integrin is expressed in a sizeable fraction of metastatic lesions of TENIS cases, albeit demonstrating a varying degree of uptake. Out of the soft tissue, lung, and bone lesions, metastatic bone lesions showed more RGD affinity than other sites. The patients with substantial RGD uptake on a 4-point visual grading system may be potential targets for RGD-based therapy.
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