Neuroendocrine Tumors: Symptoms, Diagnosis & Treatment

Neuroendocrine tumours are complex and depict various rare tumour entities, which arise from neuroendocrine cells. These cells diffused through the different organs, have a very unique function in that they are both nerve and a hormone-producing cell. Common places where NETs would usually originate include the GI tract, lungs, and pancreas. Although a majority of NETs are malignant, improved diagnosis and treatment have made it possible for patients with NETs to live longer, and most of them have been living with the condition for several years.

What Are Neuroendocrine Tumors?

NETs are very heterogeneous tumors originating from neuroendocrine cells, which possess characteristics of nerve cells and hormone-secreting cells. This attribute enables them to synthesize, store, and release hormones into the bloodstream following stimulation by the nervous system. NETs vary considerably concerning growth rate, symptomatology, and treatment response; thus, an individualized approach becomes important for effective management.

Types of Neuroendocrine Tumors

NETs are categorized based on two main features:
Hormone Secretion:

Functional NETs manufacture and secrete hormones, which often become clinically evident through symptoms related to the hormone produced.

Non-functional NETs do not secrete active hormones but may lead to the development of symptoms by physically affecting organs and tissues.

Tumor Site:

• Gastrointestinal Neuroendocrine Tumors (GI-NETs): The majority of NETs arise in the GI tract. Common sites include the intestines, appendix, and rectum.
• Neuroendocrine Tumors of the Lung: These NETs are found in the lungs and bronchi and are the second most common type.
  Pancreatic Neuroendocrine Tumors (P-NETs): These NETs are found in the pancreas and are a different type of tumour than the usual forms of pancreatic cancers.
• NETs may less commonly begin in the thyroid gland, the adrenal glands, the parathyroid glands, the pituitary gland, and the thymus. These varying locations where NETs originate are one of the complicating features in diagnosing and treating them.

Incidence and Risk Factors

Although neuroendocrine tumours are uncommon, with an estimated incidence of approximately 6 per 100,000 persons, the incident rates have increased due to better diagnostic methods. NETs may occur at any age, but the most common age group in which the diagnosis is made is between 50 and 60 years.
Many congenital disorders are associated with the development of NETs, including:

• Multiple Endocrine Neoplasia (MEN): This is a type of cancer that affects your endocrine glands, which means tumours will occur on them.
• Von Hippel-Lindau Syndrome: This has been found to develop benign and malignant tumour growth in parts of the body.
• Neurofibromatosis Type 1: The nerves and other tissues develop tumours.
• Tuberous Sclerosis Complex: A medical condition that causes non-cancerous tumours in every part of your body but most especially in the brain. This increases the risk for certain cancers and also benign growths.

Symptoms and Causes of Neuroendocrine Tumors

Because early symptoms are often quite nonspecific and similar to other diseases, many NETs are not found until the tumour has grown large enough to press on nearby organs. Common Symptoms of NETs Symptoms of NETs depend on the tumour site and whether the tumour has spread and released excess amounts of hormones.

Common generalized symptoms may include the following: 

• Fatigue: Generalized fatigue is a common symptom and may be related to almost any chronic disease.
• Abdominal Pain: Pain often arises, and it may be persistent or intermittent, depending on the tumour of the GI tract or pancreas.
• Diarrhoea and Nausea: Symptoms in the gastrointestinal tract can result if the tumour stops some of the digestive processes. 
• Shortness of Breath and Coughing: These symptoms can arise if the NETs have spread to the lungs, and sometimes there may be blood in the sputum.
• Other symptoms may include changes in appetite, unexplained weight loss, and even flushing of the skin in cases where the NET secretes excess hormones. In light of this fact, medical intervention must be sought if these symptoms persist without a reasonable cause.

Understanding the Cause of Neuroendocrine Tumors

Neuroendocrine tumors arise because of uncontrolled neuroendocrine cell growth resulting in tumors. Though the exact cause of abnormal cell division is still not known, research concerning genetic factors and environmental triggers that can account for NET formation is still ongoing.

Neuroendocrine Tumors Complications

One of the most significant complications of NETs is carcinoid syndrome, seen when a neuroendocrine tumor secretes large quantities of hormones into the blood circulation.

 Symptoms of carcinoid syndrome may include:

• Flushing of the Face and Neck: The skin becomes red and hot because of sudden dilation of blood vessels.
• Wheezing and Difficulty Breathing: Respiratory symptoms can occur either when the tumour involves the lung or releases hormones.
• Diarrhoea: High levels of hormones can overstimulate the gut.
  If left inadequately treated, carcinoid syndrome may lead to other more serious health conditions and potentially life-threatening.

Diagnosis and Tests

Due to nonspecific symptoms of early NET, it may take several months to reach a correct diagnosis. If NET is suspected, healthcare providers may use one or more of the following diagnostic techniques depending on the suspected type of tumour.

Diagnostic Approaches for NETs

Biochemical tests: These tests detect the presence of high levels of a specific enzyme or protein in blood or urine that could indicate the presence of hormone-producing NETs (functional NETs).

• Imaging tests: Most providers use CT scans, MRIs, or X-rays to find the tumour. PET, which can show the spread of cancer, may also be used.
• Endoscopy and Endoscopic Ultrasound: These different endoscopic techniques allow direct tumour visualization in the GI tract and pancreas. Sometimes, this is coupled with ultrasound for excellent details.
• Biopsy: Looking at tissue samples under the microscope will enable a health professional to detect whether the tumour is malignant. It also gives additional information about its growth rate

Staging and Grading of Neuroendocrine Tumors

Staging of Cancer describes the extent of cancer's spread from where it started to other parts of the body. In NETs, the stages are described from 1 to 4; stage 4 describes metastatic cancer, which has spread distantly.

Grading of Cancer describes how much the tumour cells resemble normal cells

. NETs are graded as follows:

• Well-differentiated NET: Closely resemble the way normal cells appear and tend to grow slowly.
• Poorly Differentiated NETs: These are abnormal when viewed under a microscope and tend to grow quickly.

Treatment Options for Neuroendocrine Tumors

Surgery is still the main treatment for NETs when it is feasible to do so. But, of course, based on tumour location, size, and spread, other treatments may be necessary.

Types of Treatment for Neuroendocrine Tumors

• Surgery: For localized tumours, surgery often can cause a cure for NET. Sometimes when cancer has spread, surgery along with other treatments may alleviate symptoms.
• Somatostatin Analogs: These are drugs that halt the production of hormones and, to a large extent, alleviate the symptoms of functional NETs.
• Chemotherapy: The treatment entails the use of drugs to kill or inhibit cancer cell growth and is most useful in the case of aggressive NETs.
• Targeted Therapy: This destroys the tumours or slows down their growth by targeting genetic markers or proteins in the cancerous cells.

The techniques of internal radiation therapy, such as PRRT, involve the administration of small dosages of radioactive substances to hormone-secreting NETs.

Neuroendocrine Tumors Prevention

Because the causes of NETs are largely unknown, no specific preventive measures are possible. However, awareness of risk factors, particularly in cases of inherited genetic conditions, can enable people to make some realistic choices. Genetic counseling and regular health checks can also be helpful in early detection for people who have family histories of NET-associated syndromes.

Prognosis and Outlook

Prognosis can vary widely for NETs, based on tumor type and grade of disease as well as the extent of disease at diagnosis. Many NETs present at a late stage because of the indolent nature of these tumours. However, patients diagnosed with

localized NETs usually have a very favourable prognosis. Once NETs have spread, the goals of treatment are symptom management and slowing the progression of disease.

• Survival Rates: The five-year survival rate for patients with NETs is about 39%, but increases dramatically if the tumour is diagnosed at an early stage.
• Follow-up Care: Follow-up is very important since NETs may also recur many years after treatment. Continued follow-up could result in the early detection of any recurrence and so allow early intervention.

Living with Neuroendocrine Tumors

Living with a NET diagnosis can be challenging, as symptoms often recur over time. However, medical science and personalized treatments have greatly improved the lives of many patients with NETs. Generally, it is recommended that patients maintain close contact with their healthcare provider through follow-up programs and report immediately if they develop any new symptoms or concerns.

Conclusion

Neuroendocrine tumours are indeed infrequent, but diagnostics, management, and treatment need to be effectively tackled. Indeed, early diagnosis and new therapeutic interventions continue to advance the prognosis of patients with NETs. Knowledge and a proactive attitude give people a chance for better health and quality of life, even in those suffering from this very complex condition.