Prospective evaluation of 68Ga-DOTANOC PET-CT in differentiated thyroid cancer patients with raised thyroglobulin and negative 131I-whole body scan: comparison with 18F-FDG PET-CT

The purpose of the study was to evaluate the role of 68Ga-DOTANOC PET-CT in differentiated thyroid cancer (DTC) patients with negative 131I-whole body scan (WBS) along with serially increasing serum thyroglobulin (Tg), and compare the same with 18F-FDG PET-CT. Sixty two DTC patients with serially rising Tg levels and negative 131I-WBS were prospectively enrolled. All patients underwent 68Ga-DOTANOC PET-CT and 18F-FDG PET-CT within an interval of two weeks. PET-CT analysis was done on a per-patient basis, location wise and lesion wise. All PET-CT lesions were divided into four categories-local, nodal, pulmonary and skeletal. Histopathology and/or serial serum Tg level, clinical and imaging follow up (minimum-1 year) were used as a reference standard. Ga-DOTANOC PET-CT demonstrated disease in 40/62 (65 %) patients and 18F-FDG PET-CT in 45/62 (72 %) patients, with no significant difference on McNemar analysis (p = 0.226). Per-patient sensitivity and specificity of 68Ga-DOTANOC PET-CT was 78.4 %, 100 %, and for 18F-FDG PET-CT was 86.3 %, 90.9 %, respectively. Out of 186 lesions detected by both PET-CTs, 121/186 (65 %) lesions were seen on 68Ga-DOTANOC PET-CT and 168/186 (90.3 %) lesions on 18F-FDG PET-CT (p < 0.0001). There were 103/186 (55 %) lesions concordant on both. Excellent agreement was noted between 68Ga-DOTANOC PET-CT and 18F-FDG PET-CT for detection of local disease (k = 0.92), while moderate agreement was noted for nodal and pulmonary disease (k = 0.67). 68Ga-DOTANOC PET-CT changed management in 21/62 (34 %) patients and 18F-FDG PET-CT in 17/62 (27 %) patients. Ga-DOTANOC PET-CT is inferior to 18F-FDG PET-CT on lesion based but not on patient based analysis for detection of recurrent/residual disease in DTC patients with negative WBS scan and elevated serum Tg levels. It can also help in selection of potential candidates for peptide receptor radionuclide therapy. (orig.)