Diagnostic performance of Ga-68 DOTATOC PET/CT in patients with Neuroendocrine tumors (NET)-Comparison with conventional imaging and impact on management

Objectives: The objective of this study was to evaluate the role of (68) Ga-DOTATOC PET/CT in the diagnosis and management of NET. Methods: 63 patients (median age 57, M/F=25/38) with known or clinical suscipicion of NETs, who were 6 weeks off sandostatin therapy, underwent (68)Ga-DOTA-TOC PET/CT imaging in this prospective trial (IND 123015;GCO 14-2008). 50/63(79%) had resection of primary malignancy before the PET/CT scan. 13/63 had rising tumor markers with a suspicion of NET. Images were evaluated for presence of Ga-68 DOTATOC avid disease sites. Results of (68)Ga-DOTA-TOC PET/CT were compared with those of conventional imaging (In-111Octreotide, MRI, CT) which was obtained within a median of 95 days. Histopathology results, when available, and follow-up PET/CT or conventional imaging with biochemical markers were considered as reference standards. Results: 68Ga-DOTATOC PET/CT was positive in 49/63 (78%) patients and negative in 14/63(22%) patients. 6/14patients who were negative on 68Ga-DOTATOC PET/CT were positive on conventional imaging. 3/6 patients had uptake in the pancreas and lymph node on In-111Octreotide scan which was considered false positive on follow up examinations. 1/6 had a biopsy proven renal cell carcinoma metastasis in the pancreas .1/6 had liver lesions on MRI which were proven to be benign adenomas. 1/6 had sub centimeter pancreatic lesions on MRI and showed progression on subsequent MRI's(False negative on PET/CT) .8/14 patients were considered disease free on subsequent imaging and follow-up. 6 patients did not have conventional imaging available for comparison. Sensitivity and specificity of PET/CT was 98 % and 100% respectively vs 65.9 % and 61.5 % respectively for conventional imaging. More lesions were detected by (68)Ga-DOTATOC PET/CT as compared to conventional imaging(Figure 1). (68)Ga-DOTATOC PET/CT also detected residual/recurrent malignancy in 2 patients who had surgery before and found primary site in 3 patients with an unknown primary. 68Ga-DOTATOC PET/CT significantly changed the management strategy in 14 patients (22%). Conclusion: Gallium-68-DOTA-TOC PET/CT is decidedly superior to existing conventional imaging methods for the evaluation of NETs and can have a significant impact on patient management. The impact of change in management on patients' quality of life and survival will be further evaluated.