Comparison of 68Ga-DOTA-JR11 and 68Ga-DOTA-TATE PET/CT in patients with metastatic neuroendocrine tumors: a preliminary study

440 Objectives: 68Ga-DOTA-JR11 is a novel radiolabeled somatostatin receptor (SST) antagonist for neuroendocrine tumor imaging. Preclinical data showed that sst antagonist may perform better than sst agonists. The clinical data, however, remains limited. In this study, we present the preliminary data of 68Ga-DOTA-JR11 PET/CT in metastatic neuroendocrine tumors with comparison to 68Ga-DOTA-TATE PET/CT. Methods: Eight patients with biopsy-proven neuroendocrine tumors (G1 or G2) were prospectively recruited in this study. All participants received an intravenous injection of 68Ga-DOTA-JR11 (80ug peptide) and 68Ga-DOTA-TATE (40ug peptide) on two consecutive days. Torso PET/CT scans were acquired 40-60 min post-injection on the same scanner (Polestar m660, SinoUnion Healthcare Inc.). The images were reviewed by an experienced nuclear medicine physician. The biodistribution and physiological uptake of organs were compared between the two tracers. The number, SUVmax, and tumor-to-background ratio (TBR) of focal lesions were recorded. Results: The clinical characteristics are summarized in Table 1. Unlike 68Ga-DOTA-TATE, 68Ga-DOTA-JR11 demonstrated minimal or mild uptake in almost all organs except for urinary tract (Figure 1). A total of 174 focal lesions were depicted on both 68Ga-DOTA-JR11 PET/CT and 68Ga-DOTA-TATE PET/CT (Table 2). In 5 out of 7 patients with liver metastasis, 68Ga-DOTA-JR11 demonstrated more liver lesions than 68Ga-DOTA-TATE (27±17 versus 20±18, P=0.034, Figure 1). In patient 6, 68Ga-DOTA-JR11 showed fewer liver lesions than 68Ga-DOTA-TATE. SUVmax of matched liver lesions was significantly lower for 68Ga-DOTA-JR11 than for 68Ga-DOTA-TATE (14.9±9.3 versus 21.3±9.8, P<0.001; Table 3). Nevertheless, 68Ga-DOTA-JR11 showed a much higher TBR than 68Ga-DOTA-TATE (7.4±6.0 versus 2.9±1.7, P<0.001). It was probably due to a lower liver background for 68Ga-DOTA-JR11 than for 68Ga-DOTA-TATE (SUVmax: 3.2±1.7 versus 9.2±1.9, P<0.001). By contrast, 68Ga-DOTA-JR11 showed a significantly lower detection ability for bone metastasis (Table 1, Figure 2). In 3 patients with bone metastasis, 68Ga-DOTA-TATE revealed 20 bone lesions, while 68Ga-DOTA-JR11 only showed 3 lesions. The two tracers showed comparable sensitivity for primary tumors and metastatic lymph nodes. SUVmax of metastatic lymph nodes were significantly lower for 68Ga-DOTA-JR11 than for 68Ga-DOTA-TATE (8.9±4.2 versus 19.4±4.6, P=0.011) Conclusions: 68Ga-DOTA-JR11 performs better in the detection rate and TBR of liver metastasis. However, 68Ga-DOTA-TATE outperforms 68Ga-DOTA-JR11 in the detection of bone metastasis. The sensitivity differences in different metastatic sites provide key information for alternative peptide choice in peptide receptor radionuclide therapy (PRRT). Figure Captions Figure 1. The PET images of 68Ga-DOTA-TATE and 68Ga-DOTA-JR11 in patient 4 with a rectum G2 neuroendocrine tumor (not shown) and liver metastasis. Physiological uptake was seen at pituitary gland, parotid glands, submandibular glands, thyroids, adrenal glands, spleen, and bowel (arrows) in 68Ga-DOTA-TATE MIP images (A). Nevertheless, only spleen showed mild uptake in 68Ga-DOTA-JR11 MIP images (B). Representative axial images of the live were demonstrated (68Ga-DOTA-TATE, C; 68Ga-DOTA-JR11, D). 68Ga-DOTA-JR11 depicted more liver lesions than 68Ga-DOTA-TATE, with a lower liver background. Figure 2. The PET/CT images of 68Ga-DOTA-TATE and 68Ga-DOTA-JR11 in patient 8 with a recurrent neuroendocrine tumor (para-prosthetic soft tissue in the right arm, arrowhead in A) and multiple bone metastasis. 68Ga-DOTA-TATE MIP image (A) and axial fusion images (C-G) showed multiple bone lesions (red arrow) in the pelvis (C-F) and right 3rd rib (G). All these lesions were negative in 68Ga-DOTA-JR11 images (MIP, B; axial, H-L). The blue arrows in A represent urinary activity.