Tests for monitoring NET disease progression
Various imaging techniques and biochemical tests are available for characterizing, localizing, and monitoring changes in primary NET and their metastases.
Changes in symptom severity or the appearance of new symptoms may be indicators of progressive disease.10
- Computed tomography
Widely available, computed tomography (CT) may be ordered for surgical candidates as part of preoperative planning, and may help identify the spread of disease.19,20 Triple-phase CT, in particular, offers good resolution for intrahepatic and extrahepatic metastases, and may help identify bone metastases.21,22
Note that venous-phase imaging provides optimal resolution of hepatic metastases.
- Magnetic resonance imaging
Magnetic resonance imaging (MRI) has been shown to be effective in the detection of hepatic and bone metastases.19,23-25
- Octreoscan™ (somatostatin receptor scintigraphy)
Octreoscan is a whole-body imaging technique that may be particularly helpful in identifying previously unsuspected extrahepatic and lymph node metastases.23,25,26 The technique is also useful for identifying patients who may be candidates for peptide receptor radionuclide therapy (PRRT).12
Octreoscan is a trademark of Curium.
- Positron emission tomography
Positron emission tomography (PET) can be used with chemical tracers to detect metastases, and with [11C]-labeled and [18F]-labeled amine precursors, such as serotonin and levodopa. PET with [68Ga]-labeled somatostatin analog (SSA) may identify metastatic NET; however, [68Ga] generators are not widely available.10
- Chromogranin A
Chromogranin A (CgA) levels are typically highest in metastatic disease, particularly in patients with multiple liver metastases.27,28 Serum CgA levels may also be associated with tumor burden and may be correlated with survival.29,30 Importantly, CgA levels may start to increase before changes in tumor size can be seen on CT or MRI.31
- 5-Hydroxyindoleacetic acid
In patients with serotonin-producing NET who exhibit symptoms of carcinoid syndrome, elevated levels of 5-hydroxyindoleacetic acid (5-HIAA) are associated with increased tumor mass and poor outcomes.26,32,33 Very high elevations have been linked to carcinoid heart disease.33,34
Additionally, specific biochemical tests can be used to monitor symptoms, response to treatment, and extent of disease.13
Certain medications, such as antacids and proton pump inhibitors, can alter tumor biomarker levels.11