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Carcinoid Tumor Diagnosis and Treatment - A Detailed Guide

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Carcinoid tumors are slow-growing and rare neuroendocrine tumors. The clinicians experience diagnostic challenges, as most patients do not have any symptoms in the early stages. If the symptoms do exist, they overlap with other, less serious conditions. A multidisciplinary approach is required for optimal carcinoid tumor treatment, with surgery being the only curative option. Carcinoid syndrome diagnostic tests may also be performed in patients with carcinoid tumors, especially those with advanced stages.

Carcinoid Tumor Diagnostic Tests

A carcinoid tumor diagnosis begins with a physical examination and a medical history assessment. The doctor will initially try to understand the causes of the symptoms experienced by the patient. If the doctor suspects carcinoid tumors, additional tests will be recommended. The following are the different tests recommended for carcinoid tumor diagnosis:

Biochemical Tests

The carcinoid tumors secrete several hormones and other chemicals. Carcinoid tumor blood tests involve measuring the levels of these chemicals or byproducts of these chemicals in the blood, which may indicate carcinoid tumors.

The chemicals predominantly secreted by carcinoid tumors include 5-hydroxytryptamine, dopamine, histamine, atrial natriuretic peptide, neurotensin, α1-antitrypsin, somatostatin, pancreatic polypeptide, substance P, kallikrein, and prostaglandins. Chromogranin A is probably the most specific carcinoid disease biomarker. As chromogranin testing does not depend on the secretion of serotonin, it is better when compared with the urine 5-HIAA test for non-secreting tumors and atypical carcinoids.

Urine Test

Patients suspected of carcinoid tumors may undergo a 24-hour urine collection to detect levels of 5-hydroxyindoleacetic acid (5-HIAA), a serotonin metabolite. However, this test is highly specific (100%) for carcinoid disease diagnosis but has less specificity (73%). The low specificity of this test is because of non-secreting carcinoid tumors present in several patients.

The levels of 5-HIAA can also be elevated in Whipple's disease, celiac disease, and small bowel obstruction. Certain medications and foods, such as bananas, avocados, and walnuts, may alter the test results and should be avoided before the test.

Colonoscopy

A colonoscopy is performed to diagnose and manage carcinoid tumors of the rectum and colon. During the colonoscopy, the doctor inserts a flexible tube with a camera at the end into the rectum and guides it to the colon. The camera transmits images of the internal structures that can be clearly seen on the monitor. The abnormal tissues are detected and can be obtained for further analysis.

As gastrointestinal carcinoid tumors are slow-growing and do not cause symptoms at the initial stages, they should be routinely monitored through methods such as colonoscopy, especially in people who are at risk or have a history of carcinoid tumors.

Appendicitis

Some carcinoid tumors are slow-growing and non-aggressive and do not present symptoms during the early stages. These are diagnosed by chance while diagnosing or treating other conditions. In some patients, carcinoid tumors are detected when they undergo surgery for appendicitis.

Upper Endoscopy

Upper endoscopy, or esophagogastroduodenoscopy, is a technique that involves the insertion of a tube with light and a camera at the end into the mouth and being guided to the esophagus, stomach, and initial section of the small intestine. The technique is used to diagnose carcinoid tumors in the stomach and the small intestine in patients suspected of having the tumors. If carcinoid tumors are detected, the samples can be obtained for further analysis.

Imaging Tests

Once the patients are suspected of having carcinoid tumors through biochemical tests or urine analysis, the doctor advises them to undergo imaging tests to confirm the exact site of carcinoid tumors. Conventionally, computed tomography is one of the most common tests for carcinoid tumor diagnosis and the extent of metastasis. However, conventional CT has poor sensitivity (44% to 55%). The advanced CT techniques involving multiplanar reconstructions have relatively higher sensitivity.

Abdominal CT assists in diagnosing the liver metastasis of carcinoid tumors. Sometimes, in patients with diarrhea or abdominal pain, small intestine and colon tumors may be detected through barium studies. However, the barium studies are often non-specific and may result in missing tumors.

Radionuclide Scanning

Radiolabeled receptor-binding peptides and scintigraphy provide valuable information about carcinoid tumor diagnosis. Studies have reported the superiority of the indium-111 (In-111) labeled octreotide (octreoscan) to localize the primary tumor compared with magnetic resonance imaging, or CT. In asymptomatic patients with gastrointestinal carcinoid tumors, the diagnostic sensitivity is between 80% and 90%, and it is greater than 90% in symptomatic patients. Metaiodobenzylguanidine scintigraphy is an alternative method for detecting carcinoid tumors. As carcinoid tumors have low proliferating activity, the FDG-PET scan is not generally useful.

Removing Tissue for Laboratory Testing

The method involving the removal of the sample tissues for the abnormal site and sending them to the laboratory for carcinoid tumor diagnosis is known as carcinoid tumor biopsy. A biopsy can be performed using different methods. One method is to insert the needle under imaging guidance (image-guided percutaneous biopsy) to obtain the sample from the tumor. In some cases, biopsy may be assisted by endoscopy and colonoscopy. Surgery may also be performed to obtain the tissue samples.

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Treatment for carcinoid tumor

Effective carcinoid tumor treatment involves a multidisciplinary approach that includes surgical resection, debulking, medical therapy, and hepatic chemoembolization. The different options available for carcinoid tumor treatment include:

Surgery

Surgical resection is the preferred carcinoid tumor treatment. The extent of removal of the malignant tissue is based on the size and location of the tumor. In patients suffering from bronchopulmonary carcinoid tumors and having adequate pulmonary reserve, carcinoid tumor lung surgery is the preferred treatment.

Radical gastrectomy is the mainstay of treatment, irrespective of the tumor size, in patients with type III gastric carcinoid tumors. The surgical management of small intestinal carcinoids depends on the tumor location, size, and extent of metastasis. Small carcinoid tumors of the appendix require a simple appendectomy. However, more extensive surgery is required in cases of tumor size >2 cm, involvement of lymph nodes, and lymphatic invasion of the tumor. It has been reported that 55% of the patients with carcinoid tumors of the colon have nodal or liver metastasis. Thus, formal hemicolectomy with a mesenteric resection is considered the ideal treatment for colon carcinoid tumors.

Medications to control excess hormones

Patients with carcinoid tumors may also have symptoms due to the secretion of excess hormones by the malignant cells. Oncologists may prescribe medications that block the secretion of hormones, resulting in the management of symptoms and the delay of tumor growth. These drugs have good efficacy in lowering levels of neuroendocrine tumor markers.

Chemotherapy

Chemotherapy for carcinoid tumors includes the administration of drugs that kill or delay the growth of cancer cells. These drugs are administered systemically, either orally or through injections. These drugs inhibit the synthesis of hormones and proteins in cancer cells, stimulate the immune system, and inhibit angiogenesis. In patients with malignant gastrointestinal neuroendocrine tumors with high proliferation indices, cytotoxic drugs are considered first-line therapy.

Targeted drug therapy

Several molecules, such as enzymes and proteins, and various pathways are essential for the growth and proliferation of carcinoid tumor cells. Targeted drug therapy works by targeting these molecules and pathways and killing or delaying the growth of carcinoid tumor cells. As the targeted therapy targets only the processes within the cancer cells, this therapy has relatively fewer side effects compared with conventional chemotherapy.

Radiation Therapy

Drugs that deliver the radiation into the cancer cells are also used for the treatment of carcinoid tumors. Peptide receptor radionuclide therapy (PRRT) involves the combination of the drug with radioactive substances to kill cancer cells. Once the drug is injected into the blood, it travels to the cancer cells, binds with them, and delivers radiation to kill them. It is usually used in patients with advanced carcinoid tumors.

Somatostatin analogs

Carcinoid tumors are also treated with a somatostatin analog. Somatostatin is a peptide that occurs naturally and blocks several processes, such as cell growth, hormonal secretion, and smooth muscle contraction. The daily subcutaneous injection of the somatostatin analog may significantly reduce the symptoms; however, the duration of response to standard treatment of the somatostatin analog is 12 months.

Immunotherapy

Malignant carcinoid tumor cells escape the destructive effects of the immune system through certain processes. Immunotherapy interferes with these processes and makes these carcinoid cancer cells vulnerable to being attacked and killed by the immune system. Immunotherapy drugs also strengthen the patient's immune system and increase their ability to fight against cancer cells.


Why Choose HCG for Carcinoid Tumor Diagnosis and Treatment?

Carcinoid tumor diagnosis and treatment are challenging, especially in patients who are diagnosed in advanced stages. It requires advanced facilities for diagnosis and treatment, a team to perform complex surgeries, state-of-the-art operating theaters, and experienced paramedical staff to take care before and after the treatment. HCG is one of the highly recommended cancer hospitals in India for carcinoid tumor diagnosis and treatment and is equipped with all facilities that increase the chances of a favorable prognosis and improve the overall quality of life of the patients.

Conclusion

Methods for carcinoid tumor diagnosis include blood tests, urine tests, colonoscopy, appendicitis, upper endoscopy, biochemical tests, imaging tests, biopsy, and radionuclide scanning. The options for carcinoid tumor treatment include surgery, medications to control excess hormones, chemotherapy, radiation therapy, targeted drug therapy, somatostatin analogs, and immunotherapy.

Frequently Asked Questions

What is the new treatment for carcinoid tumors?

Several new carcinoid tumor treatments have been approved, and several are under clinical research. Targeted therapy, such as peptide receptor radionuclide therapy, is one of the most advanced treatments for carcinoid tumors.

Several carcinoid tumor diagnosis methods are available to detect the spread of carcinoid tumors. These include imaging methods such as CT scans and MRI scans.

It is a carcinoid tumor test. 5-hydroxyindoleacetic acid (5-HIAA) is a serotonin metabolite. Patients with carcinoid tumors have increased levels of serotonin. The levels of 5-HIAA are also increased in the urine of such patients. In the 5-HIAA test, the levels of 5-HIAA are measured in the urine.

The biomarkers for carcinoid tumor investigation include 5-hydroxytryptamine, dopamine, histamine, atrial natriuretic peptide, neurotensin, α1-antitrypsin, somatostatin, pancreatic polypeptide, substance P, kallikrein, chromogranin, and prostaglandins.

The 24-hour urine collection is done to detect the presence of 5-HIAA in patients suspected of having carcinoid tumors.