Management Impact of 68Ga-DOTATATE PET/CT in Neuroendocrine Tumors

Abstract

Purpose: The goal of our retrospective single tertiary academic medical center investigation was to examine the added diagnostic value and clinical impact of ⁶⁸Ga-DOTATATE PET/CT in the therapeutic management of patients with neuroendocrine tumors (NETs).

Methods: Imaging database was queried for all "PET-DOTATATE" examinations performed at our tertiary care academic institution using MONTAGE™. The patient's clinical history and recent prior imaging were reviewed. The additional diagnostic value and clinical management impact of ⁶⁸Ga-DOTATATE were assessed through retrospective chart review.

Results: A total of 81 ⁶⁸Ga-DOTATATE PET/CT scans in 74 patients were found, and 11 patients were excluded from analysis as they had no prior imaging available for comparison, with resultant analysis cohort of 63 patients. Six patients had 2 or more ⁶⁸Ga-DOTATATE PET/CT examinations. The most common primary diagnosis was undifferentiated NET (63.5%), followed by carcinoid (27.0%), paraganglioma (4.8%), insulinoma (3.2%), and pheochromocytoma (1.6%). The primary sites of disease from the most to the least common were the pancreas (36.5%), small bowel (22.2%), unknown primary (15.9%), lung (6.3%), large bowel (6.3%), and mesentery (4.8%), and other locations accounted for 7.9%. In patients who had prior imaging available for comparison, there were new lesions identified on ⁶⁸Ga-DOTATATE PET/CT in 21 patients (33.3%) that were not identified on other prior imaging modalities. Of these patients, 5 underwent subsequent MRI and 1 had a repeat ⁶⁸Ga-DOTATATE PET/CT to further characterize new lesions seen. Moreover, 15 patients (23.8%) had a change in treatment plan, including altering medical therapy in 9 patients, change in planned extent of surgical management in 5 patients, and cancelation of a planned primary tumor resection in 1 patient with metastatic disease.

Conclusion: Our retrospective cohort demonstrated that ⁶⁸Ga-DOTATATE PET/CT improves lesion detection over conventional imaging in 33.3% and impacts the therapeutic management in 23.8% of patients with NET.

Keywords: 68Ga-DOTATATE; Neuroendocrine; PET; Somatostatin; Tumor.

Fig. 1

55-year-old male with a history of pancreatic NET with prior pancreatectomy who had planned surgical resection of a solitary peripancreatic lesion seen on surveillance CT. Representative pre-operative CT imaging showing only a 2.2 cm peripancreatic lesion but otherwise no additional sites of disease (a). Follow-up ⁶⁸Ga-DOTATATE PET/CT (b and c) examination revealed multiple osseous, and liver and nodal metastases which were also confirmed on an Octreoscan (d). The planned surgery was canceled, and the patients were treated medically

Fig. 2

59-year-old male with known pancreatic NET status post-distal pancreatectomy found to have liver metastases on surveillance CT but no suspicious pancreatic lesion. Subsequent ⁶⁸Ga-DOTATATE PET/CT revealed increased uptake in the mid pancreatic body (a). Follow-up T2 HASTE abdominal MRI showed a corresponding partly cystic mass in the mid pancreas (b)

Fig. 3

79-year-old female with a history of multiple liver masses suspicious for metastatic disease. Initial CT showed multiple liver lesions without a definite primary lesion (a). Follow-up ⁶⁸Ga-DOTATATE PET /CT revealed increased uptake in the distal pancreas compatible with primary NET and confirmed high radiotracer avidity in the multiple hepatic metastases (b). This patient was referred for PRRT with ¹⁷⁷Lu-DOTATATE

Fig. 4

59-year-old female with history of lung carcinoid undergoing routine surveillance imaging. Initial FDG PET/CT did not show evidence for metastatic disease (a). Follow-up ⁶⁸Ga-DOTATATE PET/CT revealed multiple hepatic lesions, suspicious for metastatic disease (b). Contrast-enhanced fat-saturated T1-weighted MRI of the abdomen confirmed enhancing hepatic lesions (c). Note that the smaller lesions seen on the ⁶⁸Ga-DOTATATE PET/CT are at ill-defined on the MRI