68Ga-DOTATATE PET/CT Interobserver Agreement for Neuroendocrine Tumor Assessment: Results of a Prospective Study on 50 Patients

We evaluated observer agreement for Ga-68-DOTATATE PET/CT interpretations in patients with neuroendocrine tumor (NET). Methods: Ga-68-DOTATATE PET/CT was performed on 50 patients with known or suspected NET of the small bowel (n = 19), pancreas (n = 14), lung (n = 4), or other location (n = 13). The images were reviewed by 7 observers, who used a standardized interpretation approach. The observers were classified as having a low level of experience (<500 scans or <5 y experience with Ga-68-DOTATATE PET/CT; n = 4) or a high level of experience (500 scans or y experience with Ga-68-DOTATATE PET/CT; n = 3). Interpretation by the primary nuclear medicine physician, who had access to all clinical and imaging data, served as the reference standard. Interobserver agreement was determined by the Cohen K statistic and intraclass correlation coefficient (ICC) with corresponding 95% confidence interval (95%Cl). Results: Interobserver agreement was substantial, and the median number of false findings was low for the overall scan result: that is, positive versus negative scan result (K = 0.80; 95%Cl, 0.74-0.86; false findings, 3), organ involvement (K = 0.70; 95%Cl, 0.64-0.76; false findings, 5), and lymph node involvement (K = 0.71; 95%Cl, 0.65-0.78; false findings, 6). Interobserver agreement was substantial to almost perfect, and the average absolute difference (A) from the reference observer was low for number of organ and lymph node metastases (organ: ICC, 0.84; 95%Cl, 0.77-0.89; Delta = 0.45; lymph node: ICC, 0.77; 95%Cl, 0.69-0.84; Delta = 0.45), tumor SUVmax (ICC, 0.99; 95%Cl, 0.97-0.99; Delta = 0.44), and reference SUV (spleen: ICC, 0.81; Delta = 1.10; liver: ICC, 0.79; Delta = 0.62). Interpretations of appropriateness for peptide-receptor radionuclide therapy varied more significantly among observers (K = 0.64; 95%Cl, 0.57-0.70), and a higher frequency of false-positive recommendations for peptide-receptor radionuclide therapy occurred in observers with low experience than in those with high experience (range, 7-12 vs. 4-8). Conclusion: The interpretation of Ga-68-DOTATATE PET/CT images for NET staging is consistent among observers with low and high levels of experience. However, image-based recommendations for or against peptide-receptor radionuclide therapy require experience and training.