5HIAA Urine Tests and Blood Tests for Neuroendocrine Tumours
Blood tests are a vital part of diagnosing and managing neuroendocrine tumours (NETs). While imaging and biopsy remain central to assessing NETs, blood tests offer additional insights that can help in early detection, monitoring, and evaluating treatment response.
This article explores:
- The role of these tests in treating NETs
- Key biomarkers to be aware of
- Recent advances in diagnostics
Neuroendocrine Cancer Australia (NECA), is dedicated to supporting individuals diagnosed with NETs, and their families. NECA offers a wealth of resources, educational programs, and advocacy efforts aimed at deepening the understanding of NETs, improving patient care, and encouraging research advancements. Patients diagnosed with NETs can engage with NECA’s comprehensive support and information by calling the NET nurse line.
Role of blood tests in neuroendocrine tumour (NET) diagnosis
Blood tests play a crucial role in the diagnosis and ongoing monitoring of neuroendocrine tumours. They help detect and track specific biomarkers produced by NET cells, providing valuable information about tumour activity and disease progression.
Importantly, these tests can guide treatment planning and predict patient outcomes, supplementing imaging studies for a more comprehensive understanding of the disease.
Blood tests are often used alongside imaging techniques like PET/CT scans to offer a fuller picture of a patient’s condition. They are especially useful for tracking tumour markers over time, which can help in assessing whether a treatment is effective or if there are signs of recurrence.
However, blood tests alone are not sufficient for a complete diagnosis and should always be interpreted in conjunction with imaging and clinical findings. Some biomarkers lack specificity, meaning they can be elevated in conditions other than NETs.
False positives and false negatives can also occur, potentially complicating the diagnostic process. As a result, blood tests are often used as a complementary tool rather than a standalone diagnostic method.
Imaging and biopsy remain the gold standard for confirming a NET diagnosis and planning treatment.
Key biomarkers in NET tests
Several biomarkers can aid in the detection and monitoring of neuroendocrine tumours. These markers provide clues about the presence and activity of NETs, though their levels can vary based on the tumour type and location.
Chromogranin A (CgA)
Chromogranin A (CgA) is one of the most commonly tested biomarkers for neuroendocrine tumours. It is a protein released by NET cells and is particularly useful for diagnosing and monitoring disease activity. Elevated levels of CgA are often seen in patients with NETs, making it a valuable marker for clinicians.
While CgA is a useful marker, it is not perfect. Its sensitivity and specificity can be affected by various factors, including:
- Certain medications like proton pump inhibitors
- Other medical conditions, such as chronic kidney disease
False positives make it essential to interpret results in the context of other diagnostic findings.
5-Hydroxyindoleacetic acid (5-HIAA)
5-Hydroxyindoleacetic acid (5-HIAA) is a breakdown product of serotonin and is commonly measured in patients with carcinoid tumours that produce serotonin.
Elevated levels of 5-HIAA can indicate the presence of serotonin-secreting NETs, particularly those in the gastrointestinal tract.
Traditionally, 5-HIAA levels are measured using a 24-hour urine collection. Urine testing remains the gold standard for 5-HIAA, as it may provide more reliable results in some cases.
Pancreatic polypeptide
Pancreatic polypeptide is another biomarker that can be elevated in patients with pancreatic neuroendocrine tumours (pNETs). While it is not as widely used as CgA or 5-HIAA, it can provide additional information, especially in cases where other markers are inconclusive.
Pancreatic polypeptide levels can also be influenced by non-tumour-related factors, and must not be taken in isolation.
Gastrin and insulin
In addition to the more common biomarkers, there are others like gastrin and insulin that are relevant in specific types of functional NETs.
- Elevated gastrin levels may indicate a gastrinoma
- High insulin levels can be a sign of an insulinoma
These biomarkers are crucial for diagnosing and managing functional NETs that produce hormones, as they directly reflect tumour activity.
Genetic and molecular testing
Genetic and molecular testing can provide insights into the hereditary aspects of neuroendocrine tumours. Understanding the genetic basis of NETs is essential for patients who may have a hereditary form of the disease.
There are several genetic mutations that can contribute to the risk of developing NETs, including:
- Multiple Endocrine Neoplasia Type 1 (MEN1)
- Multiple Endocrine Neoplasia Type 2 (MEN2)
- Neurofibromatosis Type 1 (NF1)
- Tuberous Sclerosis Complex
- Von Hippel-Lindau (VHL) syndrome
Identifying these genetic mutations can help in early detection and inform treatment strategies, especially for patients with a family history of NETs.
Genetic testing not only aids in diagnosis but also helps in screening family members who might be at risk, leading to earlier detection and better outcomes for high-risk individuals.
Test interpretation
Interpreting the results of NET tests is complex and requires a thorough understanding of the patient’s overall health and medical history. Biomarker levels can fluctuate for reasons unrelated to cancer, and false positives are not uncommon.
False positives and negatives can pose significant challenges in NET diagnosis and monitoring. Factors such as medication use, food substances, other medical conditions, and the natural variability of biomarkers can affect test accuracy.
This variability underscores the need for a multifaceted approach that includes:
- Imaging
- Biopsy
- Clinical assessment
Blood tests in treatment monitoring and recurrence detection
One of the primary uses of blood tests in NET management is tracking biomarker trends over time. By monitoring how levels of markers like CgA or 5-HIAA change, doctors can evaluate how well a treatment is working or identify early signs of disease progression. Consistent trends are often more informative than a single test result.
Blood tests are also valuable for detecting disease recurrence. A sudden rise in biomarker levels can signal that the cancer has returned or is spreading. Early detection of recurrence allows for prompt intervention, which can be critical in managing NETs and improving patient outcomes.
Advances in blood-based diagnostics
Recent advances in blood-based diagnostics, such as liquid biopsy, are changing how NETs are monitored. Liquid biopsy involves detecting circulating tumour DNA (ctDNA) in the blood, providing a less invasive way to assess tumour genetics. This technology holds promise for early detection, monitoring treatment response, and identifying genetic mutations that could inform personalised therapy.
The future of blood tests in NET management looks promising. With ongoing research, new biomarkers and technologies are being developed to make diagnostics more accurate and personalised. These advancements could lead to more targeted treatments, better monitoring of disease progression, and improved overall outcomes for patients with neuroendocrine tumours.
Further information and support for people diagnosed with NETs is available by calling the NECAÂ NET nurse line.
