Comparison of ⁶⁸Ga-DOTATOC PET and ¹¹¹In-DTPAOC (Octreoscan) SPECT in patients with neuroendocrine tumours

Purpose: Neuroendocrine tumours (NETs) can be imaged with scintigraphy using radiolabelled somatostatin analogues. The aim of our study was to compare the value of ⁶⁸Ga-DOTATOC PET and ¹¹¹In-DTPAOC SPECT (Octreoscan) in the detection of NET manifestations. Methods: Twenty-seven NET patients were prospectively examined. ⁶⁸Ga-DOTATOC PET and ¹¹¹In-DTPAOC SPECT were performed using standard techniques. Treatment was not applied in between. Mean and maximum standardised uptake values (SUVs) were calculated for PET findings. Tumour/non-tumour ratios were calculated for SPECT findings. Findings were compared by a region-by-region analysis and verified with histopathology, CT and MRI within 21 days. Results: SUVs of positive lesions on ⁶⁸Ga-DOTATOC PET ranged from 0.7 to 29.3 (mean SUV) and from 0.9 to 34.4 (maximum SUV). Tumour/non-tumour ratios on ¹¹¹In-DTPAOC SPECT ranged from 1.8 to 7.3. In imaging lung and skeletal manifestations, ⁶⁸Ga-DOTATOC PET was more efficient than ¹¹¹In-DTPAOC SPECT. All discrepant lung findings and 77.8% of discrepant osseous findings were verified as true positive PET interpretations. In regional comparison of liver and brain, ⁶⁸Ga-DOTATOC PET and ¹¹¹In-DTPAOC SPECT were identical. In lymph nodes, the pancreas and the gastro-intestinal system, different values of the two techniques were not indicated in regional analyses. In a single patient, surgical interventions were changed on the basis of ⁶⁸Ga-DOTATOC PET findings. Conclusion: ⁶⁸Ga-DOTATOC PET is superior to ¹¹¹In-DTPAOC SPECT in the detection of NET manifestations in the lung and skeleton and similar for the detection of NET manifestations in the liver and brain. ⁶⁸Ga-DOTATOC PET is advantageous in guiding the clinical management.