An insight into Neuroendocrine Tumours (NETs)
The term neuroendocrine tumour (NET) refers to a group of low-grade cancers that develop from neuroendocrine cells scattered throughout the body. As these secretory cells have traits of both nerve cells and hormone -producing cells, and release hormones into the blood, NETs can also produce hormones. We spoke to Professor Anthony Gill, Professor of Surgical Pathology at University of Sydney and Senior Staff Specialist, Department of Anatomical Pathology at Royal North Shore Hospital to discuss these tumours which arise most commonly in the gastrointestinal tract or lung.
“NETs are uncommon but not rare. They account for less than 0.5% of all malignancies, and the estimated incidence is 3 to 4 per 100 000 each year, which is about as common as testicular cancer or Hodgkin Lymphoma. NETs are being diagnosed more commonly, but this is probably not due to a true increase in incidence, rather it is due to better detection and more accurate diagnosis,” said Prof Gill.
Unlike most cancers, NETs are normally slow growing tumours but can spread to other parts of the body. Some patients will develop symptoms due to the hormones secreted by the NET’s such as flushing, wheezing or diarrhoea, but most patients will present like other cancers with vague symptoms, perhaps due to a mass which may involve and damage organs.
“There are some rare syndromes including hereditary syndromes, which place people at an increased risk of developing NETs, including multiple endocrine neoplasia (MEN) or von Hippel Lindau syndrome (VHL), but the overwhelming majority of NETs occur sporadically for no known reason. Like all tumours they are more common in the elderly, but they can occur at any age and, compared to other cancers, are relatively more common in young people.
“The main role of the pathologist is to diagnose NETs on a biopsy and to separate them from high grade cancers which are much more common but require very different treatment. Importantly, the pathologist can also try to predict how quickly a neuroendocrine tumour will grow, and one way of doing this is to perform a Ki67 index – a test which estimates how quickly the cancer cells are growing,” said Prof Gill.
A multidisciplinary team is important for those people with NETs, working together to create an overall treatment plan for a patient by combining different types of treatments. These care teams generally consist of doctors (surgeons, oncologists, endocrinologists, pathologists, radiologists) and allied health professionals (nurses, dieticians, physiotherapists). Treatment options can depend on a number of different factors, including the type of NET, the stage and grade, possible side effects, and the patient’s preferences and overall health.
“The prognosis depends on the grade, i.e. how quickly the pathologist thinks the tumour is growing, and the stage i.e. how big the tumour is and whether it has spread. For example, almost all patients with microscopic tumours in the appendix will be cured by simple appendicectomy with no further treatment. However, once the tumour has spread widely it is difficult to cure but could be controlled by treatments for many years - much longer than most tumours - and many patients live longer than 5 years even when the tumour has spread throughout the body.
“It is important that patients with NETs are treated in specialty units so they can access new treatments. For example, there are a lot of new treatments available for those tumours which have spread, including a class of drugs known as ‘somatostatin analogues’ which work by stopping the tumour cells excreting hormones and slowing their growth. Another new treatment becoming available for NETs is peptide receptor radionuclide therapy (PRRT), where radioactive tracer material is injected into the blood stream. This radioactive material binds to the tumour (but not normal cells) and can either kill the tumour cells or slow their growth,” said Prof Gill.
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This article appeared in the June 2019 Edition of ePathWay which is an online magazine produced by the Royal College of Pathologists of Australasia (http://www.rcpa.edu.au/Library/Publications/ePathway).
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