Prevalence of metastases outside the liver and abdominal lymph nodes on ⁶⁸Ga‐DOTATOC‐PET/CT in patients with small intestinal and pancreatic neuroendocrine tumours

Abstract

Metastases outside the liver and abdominal/retroperitoneal lymph nodes are nowadays detected frequently in patients with neuroendocrine tumours (NETs), owing to the high sensitivity of positron emission tomography (PET) with Gallium‐68‐DOTA‐somatostatin analogues (68Ga‐SSA) and concomitant diagnostic computed tomography (CT). Our aim was to determine the prevalence of extra‐abdominal metastases on 68Ga‐DOTATOC‐PET/CT in a cohort of patients with small intestinal (Si‐NET) and pancreatic NET (Pan‐NET), as well as that of pancreatic metastasis in patients with Si‐NET. Among 2090 patients examined by 68Ga‐DOTATOC‐PET/CT at two tertiary referral centres, a total of 1177 patients with a history of Si‐ or Pan‐NET, were identified. The most recent 68Ga‐DOTATOC‐PET/CT report for each patient was reviewed, and the location and number of metastases of interest were recorded. Lesions outside the liver and abdominal nodes were found in 26% of patients (n = 310/1177), of whom 21.5% (255/1177) were diagnosed with Si‐NET and 4.5% (55/1177) Pan‐NET. Bone metastases were found in 18.4% (215/1177), metastases to Virchow's lymph node in 7.1% (83/1177), and lung/pleura in 4.8% (56/1177). In the subset of 255 Si‐NET patients, 5.4% (41/255) manifested lesions in the pancreas, 1.5% in the breast (18/255), 1.3% in the heart (15/255) and 1% in the orbita (12/255). In Si‐NET patients, the Ki‐67 proliferation index was higher in those with ≥2 metastatic sites of interest, than with 1 metastatic site, (p <0.001). Overall, extra‐abdominal or pancreatic metastases were more often found in patients with Si‐NET (34%) than in those with Pan‐NET (13%) (p <0.001). Bone metastases were 2.6 times more frequent in patients with Si‐NET compared to Pan‐NET patients (p <0.001). Lesions to the breast and orbita were encountered in almost only Si‐NET patients. In conclusion, lesions outside the liver and abdominal nodes were detected in as many as 26% of the patients, with different prevalence and metastatic patterns in patients with Si‐NET compared to Pan‐NET. The impact of such metastases on overall survival and clinical decision‐making needs further evaluation.