Predicting neuroendocrine neoplasm grade with dual tracer positron emission tomography/computed tomography (PET/CT)...

The aim of this study was to investigate the ability of dual tracer positron emission tomography/computed tomography (PET/CT) using ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) and ¹⁸F-AlF-NOTA-octreotide (¹⁸F-OC) in predicting neuroendocrine neoplasm (NEN) grade. The lesions that have been histologically confirmed were accurately located using both ¹⁸F-FDG and ¹⁸F-OC PET/CT.

For each lesion, the standardized uptake value (SUV)_max was measured, and tumor-to-background ratio was calculated by dividing the SUV_max by the SUV_mean of background tissue at the two scans. SUVR was calculated by dividing the SUV_max of the lesion at ¹⁸F-OC PET/CT by the SUV_max at ¹⁸F-FDG PET/CT. For evaluating the correlation between continuous variables and lesion grade, the Spearman rank correlation test was used. Receiver operating characteristic (ROC) curve was used to evaluate the performance of PET/CT parameter in discriminating lesions of different grades.

A total of 49 patients (22 males, 27 females; mean age: 56.5 ± 14.3 years; range: 14-85 years) and 65 lesions were included in this study. A substantial correlation was observed between SUVR and lesion grade (rho = -0.655, p < 0.001), better than other PET/CT parameters. For discriminating G1/2 neuroendocrine tumor (NET) from G3 NET and neuroendocrine carcinoma (NEC), SUVR had the largest area under ROC curve (AUC) of 0.88. With the cut-off value of 2.217, we got the best Youden's index, 0.668. For discriminating G1/2/3 NET from NEC, SUVR and OC SUV_max had the largest AUC of 0.923. With the cut-off value of OC SUV_max of 4.35, we got the best Youden's index, 0.805.

This study suggests that ¹⁸F-FDG and ¹⁸F-OC PET/CT are complementary in evaluating the grade of NEN and that SUVR is a promising tool for predicting NEN grade.