Objectives
The objective of this study was to assess receptor expression in metastatic differentiated thyroid carcinoma patients with progressive elevated thyroglobulin and negative iodine scintigraphy, we used 68Ga-DOTATATE [Gallium-68 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA)–octreotate (DOTATATE)] (Krenning’s score) and 68Ga-PSMA-11 (Gallium-68 prostate‐specific membrane antigen‐11) PET-computed tomography (CT) [molecular imaging prostate‐specific membrane antigen (miPSMA) score]. Patients with Krenning’s score 3 and above and miPSMA score 2 and above were considered to determine the incidence of patients, who would qualify for treatment with 177Lu-DOTATATE/PSMA [Lutetium-177 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA)–octreotate (DOTATATE)/prostate‐specific membrane antigen]-based therapy. In addition, we compared 68Ga-DOTATATE and 68Ga-PSMA-11 PET-CT with 2-deoxy-2-[F-18]fluoroglucose (18F-FDG) PET-CT (using maximum standardized uptake value).
Materials and methods
A total of 74 patients with histopathologically proven metastatic differentiated thyroid carcinoma with thyroglobulin elevation and negative iodine scintigraphy syndrome were studied retrospectively. They all had 18F-FDG, 68Ga-DOTATATE, and 68Ga-PSMA-11 PET-CT scans available for undertaking this analysis. The lesions detected by 68Ga-DOTATATE and 68Ga-PSMA-11 were evaluated using Krenning’s and miPSMA scores. In addition, quantitative comparisons of maximum standardized uptake values for 68Ga-DOTATATE and 68Ga-PSMA-11, as well as with 18F-FDG, were conducted.
Results
Patient-wise analysis revealed positivity rates of 40.5% for 68Ga-DOTATATE, 41.89% for 68Ga-PSMA-11, and 75.67% for 18F-FDG. Among the 74 patients, 14 (18.91%) were deemed eligible for 177Lu-DOTATATE/PSMA-617 therapy based on Krenning’s score of 3 and above both/either miPSMA score of 2 and above on 68Ga-DOTATATE or 68Ga-PSMA-11 PET-CT. Within this subgroup, seven out of 74 patients (9.45%) were eligible for 177Lu-DOTATATE therapy, and nine out of 74 patients (12.16%) were eligible for 177Lu-PSMA-targeted therapy. Four patients were eligible for both therapies.
Conclusion
Among thyroglobulin elevation and negative iodine scintigraphy patient’s subgroup, 9.45% could qualify for 177Lu-DOTATATE and 12.16% for 177Lu-PSMA-617. Four were eligible for both therapies. Given the lack of effective therapies, this subset of patients warrants consideration for radionuclide therapy exploration.