Somatostatin Receptor Imaging in Mice with Difference Positive Rate of SSTR2.

Introduction: Imaging with [68Ga]Ga-DOTA-TATE, [68Ga]Ga-DOTA-JR11, and [18F]AlF-NOTA-JR11 was performed to analyze differences among the three probes and to analyze the correlation between the image and pathology parameters.

Method: Tumor-bearing mice with different positive rates of somatostatin receptor II (SSTR2) were established with HEK293-SSTR2 and HEK293 cells, and imaging was performed on the same mouse with [68Ga]Ga-DOTA-TATE, [68Ga]Ga-DOTA-JR11, and [18F]AlF-NOTA-JR11 at 20, 60, and 120 min. The image parameters were obtained, including the maximum standard uptake value (SUVmax), mean standard uptake value (SUVmean), standard deviation of SUVmean, tumor volume, and coefficient of variation (CoV). Immunohistochemistry (IHC) of the tumor was performed after imaging to obtain positive rate of SSTR2. Statistical analysis was performed to analyze the differences among the three imaging techniques and the correlations between the relative imaging parameter and IHC.

Result: The SUVmax of [18F]AlF-NOTA-JR11 at 20 min and 60 min was higher than that of [68Ga]Ga-DOTA-TATE (p = 0.0015, 0.0035) and [68Ga]Ga-DOTA-JR11 (p = 0.033, 0.019), and no significant difference was found in the other groups (p > 0.05). There was a significant positive correlation between the positive rate and SUVmean of tumors with three tracers (p < 0.05). However, a significant negative correlation between the positive rate and CoV was found only in the [68Ga]Ga-DOTA-TATE group at 60 min and 120 min (p = 0.048, 0.026).

Conclusion: [18F]AlF-NOTA-JR11 is more suitable for SSTR imaging within an hour than other two tracers. SUVmean of whole tumor can become an indicator for evaluating the positive rate of IHC, and the higher SUVmean of three tracers means a higher positive rate. However, the CoV is not applicable to the two antagonist tracers for evaluating the positive rate.