68ga-dotanoc and Insulinoma

Localization of primary tumor in insulinoma is often difficult. We evaluated the role of 68Ga-DOTA-Nal3-Octreotide (DOTANOC) PET/CT for localization of primary tumor in patients with clinical and biochemical suspicion of insulinoma.. Data of 35 patients (age: 38.4±16.5 years) who underwent 68Ga-DOTANOC PET/CT for clinical and biochemical suspicion of insulinoma (hypoglycemia, raised serum insulin and C-peptide levels) were retrospectively analyzed. PET/CT images were evaluated visually and semiquantitatively (SUV) by two experienced nuclear medicine physicians. A definite lesion in pancreas on non contrast CT showing increased 68Ga-DOTANOC was taken as positive. In the absence of CT lesion focal 68Ga-DOTANOC uptake in the pancreas more than liver was taken as positive. All patients had also undergone conventional imaging (CIM) (CT/MRI/endosonography) and their reports were retrieved for comparison. Histopathology and/or imaging/clinical/biochemical follow up (minimum 6 months) was used as reference standard.. The mean serum insulin levels was 51.6±54 µIU/mL and C-peptide level was 6.9±7.3 ng/mL. 68Ga-DOTANOC PET/CT was interpreted as positive in 11 patients (31.5%) and negative in 24 (68.5%). PET/CT demonstrated total 16 pancreatic lesions in 11 patients. In two patients it also showed both liver and lymph nodal metastases. 68Ga-DOTANOC PET/CT was true positive in 8, true negative in 1, false positive in 3 and false negative in 23 patients. Per patient based sensitivity of PET/CT was 25.8% (95% CI: 11.8-44.6), specificity was 25% (95% CI: 0.6-80.5) and accuracy was 25.7%. The mean SUVmax of pancreatic lesions was 13.8±11.1. On comparison no significant difference was seen between CIM and PET/CT on patient based (P=1.00) or lesion based comparison (P=0.790).. 68Ga-DOTANOC PET/CT has limited utility for localizing the primary tumor in patients with clinical and biochemical suspicion of insulinoma. However, it might be useful for differentiating benign and malignant insulinoma. Further prospective comparative studies are warranted.

Topics: Adolescent; Adult; Child; Female; Humans; Insulinoma; Male; Middle Aged; Organometallic Compounds; Pancreatic Neoplasms; Positron Emission Tomography Computed Tomography; Receptors, Somatostatin; Young Adult

Malignant insulinoma is an extremely rare pancreatic tumor variant characterized by an aggressive clinical behavior with local and distant spread. Delays in the diagnosis are common because symptoms usually precede tumor detection and may be misattributed. Aggressive surgical resection is the primary treatment option; therefore accurate tumor localization is important for appropriate management. Although somatostatin receptor imaging has a limited role in the visualization of benign insulinoma (characterized by a low expression of somatostatin receptors), it can still have a role in the detection of malignant forms.

Topics: Female; Humans; Insulinoma; Middle Aged; Multimodal Imaging; Organometallic Compounds; Pancreatic Neoplasms; Positron-Emission Tomography; Radiopharmaceuticals; Tomography, X-Ray Computed

Hypoglycemia secondary to ectopic insulin secretion of non-pancreatic tumors is rare.. We describe a middle aged woman with recurrent hypoglycemia. On evaluation, she was detected to have hyperinsulinemic hypoglycemia and right sided renal mass lesion. 68Ga-Dotanoc and 99mTc-HYNICTOC scans confirmed the intrarenal mass to be of neuroendocrine origin. Right nephrectomy was done and it turned out to be an insulin secreting neuroendocrine tumour. Neuroendocrine nature of this tumour was further confirmed by ultra-structural examination. Her hypoglycemia did not recur after resection of this tumour.. Few cases of ectopic insulin secretion have been reported though some are not proven convincingly. This case addresses all the issues raised in previous case reports and proves by clinical, laboratory, functional imaging and immunohistochemical analysis that ectopic origin of insulin by non-pancreatic tumors does occur. To our knowledge, this is the first reported case of ectopic insulinoma arising from the kidney.

Topics: Female; Humans; Hyperinsulinism; Hypoglycemia; Insulin; Insulin Secretion; Insulinoma; Kidney Neoplasms; Middle Aged; Nephrectomy; Neuroendocrine Tumors; Organometallic Compounds; Positron-Emission Tomography; Prognosis

A 65-year-old woman with suspected insulinoma on the basis of clinical, biochemical, and conventional imaging data underwent F-dihydroxyphenylalanine (DOPA) PET/CT and Ga-DOTANOC PET/CT. F-DOPA PET/CT did not show any focal uptake in the pancreas, whereas Ga-DOTANOC PET/CT showed a focal area of intense uptake in the pancreatic tail. The patient underwent surgery and an insulinoma of about 20 mm in diameter was detected in the pancreatic tail. F-DOPA PET may fail in localizing insulin secreting tumors in adults; in these cases, the use of Ga-somatostatin analogs may lead to the correct diagnosis.

Topics: Aged; Dihydroxyphenylalanine; Female; Fluorine Radioisotopes; Humans; Insulinoma; Multimodal Imaging; Organometallic Compounds; Radiography; Radionuclide Imaging; Whole Body Imaging