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Nonfunctional tumors may delay diagnosis

Neuroendocrine tumors (NET) are broadly divided into 2 subgroups based on their symptoms1:

  • Nonfunctioning tumors—no specific clinical syndrome is observed
  • Functioning tumors—the tumors' secretions lead to clinical symptoms

In earlier stages of the disease, NET patients have nonfunctioning tumors or exhibit nonspecific symptoms.2

Nonfunctioning tumors may present with either no signs of the disease or only vague symptoms.3 This makes it difficult to diagnose NET at an early stage, and patients are often initially misdiagnosed with other gastrointestinal disorders, such as irritable bowel syndrome.2 Correct diagnosis is typically delayed by several years.4

Neuroendocrine Tumors often initially misdiagnosed with other gastrointestinal disorders

Adapted from Vinik & Moattari.2

NET can progress regardless of functional status. The tumors are slow growing and may be present for years without overt symptoms, and thus escape attention.2

Functional disease and diagnosis

Once NET have metastasized, they can release a large concentration of peptide hormones and bioactive substances into the bloodstream, leading to the distinct clinical symptoms associated with functioning NET.4

Correct diagnosis is often made after patients develop symptoms.2,4

50% of all patients have distant metastases at diagnosis.5

Carcinoid syndrome

The distinct set of symptoms caused by the secretions of functional gastrointestinal and pancreatic NET—the most common type of NET—is referred to as carcinoid syndrome.3,6 Patients with midgut gastrointestinal and pancreatic NET may present with carcinoid syndrome.2

Percentage of patients with symptoms of carcinoid syndrome7*

Percentage of patients with symptoms of carcinoid syndrome

*Numbers are based on 138 cases of patients with symptoms of carcinoid syndrome.

The most common symptoms of carcinoid syndrome are diarrhea and flushing. Additional symptoms may include abdominal pain, heart disease, and sweating.2

Flushing: red or purple coloring that appears suddenly on the face or neck; it may be accompanied by a feeling of warmth or a rapid heartbeat and is not typically associated with sweating.3

1. Fazio N, de Braud F, Delle Fave G, Oberg K. Interferon-α and somatostatin analog in patients with gastroenteropancreatic neuroendocrine carcinoma: single agent or combination? Ann Oncol. 2007;18:13-19. 2. Vinik A, Moattari AR. Use of somatostatin analog in management of carcinoid syndrome. Dig Dis Sci. 1989;34(suppl 3):14S-27S. 3. Jensen RT, Doherty GM. Carcinoid tumors and the carcinoid syndrome. In: DeVita VT Jr, Hellman S, Rosenberg SA, eds. Cancer: Principles and Practice of Oncology. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2004:1559-1574. 4. Modlin IM, Oberg K, Chung DC, et al. Gastroenteropancreatic neuroendocrine tumours. Lancet Oncol. 2008;9:61-72. 5. Yao JC, Hassan M, Phan A, et al. One hundred years after "carcinoid": epidemiology of and prognostic factors for neuroendocrine tumors in 35,825 cases in the United States. J Clin Oncol. 2008;26:3063-3072. 6. Caplin ME, Pavel M, Cwikla JB, et al; for the CLARINET Investigators. Lanreotide in metastatic enteropancreatic neuroendocrine tumors. N Engl J Med. 2014;371:224-233. 7. Creutzfeldt W. Carcinoid tumors: development of our knowledge. World J Surg. 1996;20:126-131.