18 F-Alfatide II for the evaluation of axillary lymph nodes in breast cancer patients: comparison with 18 F-FDG

Purpose 18 F-Alfatide II has been translated into clinical use and been proven to have good performance in identifying breast cancer. In this study, we investigated 18 F-Alfatide II for evaluation of axillary lymph nodes (ALN) in breast cancer patients and compared the performance with 18 F-FDG. Methods A total of 44 female patients with clinically suspected breast cancer were enrolled and underwent 18 F-Alfatide II and 18 F-FDG PET/CT within a week. Tracer uptakes in ALN were evaluated by visual analysis, semi-quantitative analysis with maximum standardized uptake value (SUV max ), mean standardized uptake value (SUV mean ), and SUV max ratio of target/non-target (T/NT). Results Among 44 patients, 37 patients were pathologically diagnosed with breast cancer with metastatic (17 cases) or non-metastatic (20 cases) ALN. The sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) of visual analysis were 70.6%, 90%, 81.1%, 85.7%, and 78.3% for 18 F-Alfatide II, 64.7%, 90%, 78.4%, 84.6%, and 75% for 18 F-FDG, respectively. By combining 18 F-Alfatide II and 18 F-FDG, the sensitivity significantly increased to 82.4%, the specificity was 85%, the accuracy increased to 83.8%, the PPV was 82.4%, and the NPV significantly increased to 85.0%. Three cases of luminal B subtype were false negative for both 18 F-Alfatide II and 18 F-FDG. The other 2 false negative cases of 18 F-Alfatide II were triple-negative subtype and 3 false negative cases of 18 F-FDG were luminal B subtype too. The AUCs of three semi-quantitative parameters (SUV max , SUV mean , T/NT) for 18 F-Alfatide II were between 0.8 and 0.9, whereas those for 18 F-FDG were more than 0.9. 18 F-Alfatide II T/NT had the highest Youden index (76.5%), specificity (100%), accuracy (89.2%), and PPV (100%) among these semi-quantitative parameters. 18 F-Alfatide II uptake as well as 18 F-FDG uptake in metastatic axillary lymph nodes (MALN) was significantly higher than that in benign axillary lymph nodes (BALN). Both 18 F-Alfatide II and 18 F-FDG did not show difference in primary tumor uptake irrespective of ALN status. Conclusion 18 F-Alfatide II can be used in breast cancer patients to detect metastatic ALN, however, like 18 F-FDG, with high specificity but relatively low sensitivity. The combination of 18 F-Alfatide II and 18 F-FDG can significantly improve sensitivity and NPV. 18 F-Alfatide II T/NT may serve as the most important semi-quantitative parameter to evaluate ALN.