Large-scale research demonstrates that very small carcinoids exist in 1 out of 100 individuals throughout their lifespan, without causing any complications. They constitute only 1% of all the GI tract cancers, whilst malignant carcinoids make up approximately 50% of all cancers of the small intestine.
The size of a carcinoid tumor is directly related to its spread; tumors with a greater than 2 cm diameter are more likely to spread to other parts of the body. The carcinoid initiates in the lining of the intestinal wall and ultimately advances through its wall and into the adjacent lymphatic structures (nodes or channels), and blood vessels, before reaching sites such as the liver, brain, lungs, bones, skin, and even the heart.
Overview of Carcinoid Tumors
Most carcinoids are found in the small intestine. Statistics show that 20% of tumors in the small intestine will spread to other parts and become metastatic, and approximately one-third of them will have symptoms of carcinoid syndrome. Survey reveals that in the USA, every year 5 new carcinoid cancers are detected among 100,000 individuals; of these, approximately two-thirds originate in the digestive tract.
The other regions where clinically significant carcinoids occur are as follows:
- small intestine - 28.5%
- lungs (and associated bronchial structures) - 28%
- rectum - 14%
- colon - 5-7%
- appendix - 5%
- stomach - 4%
- pancreas - 1%
- liver - greater than 1%
- others - 8%
These tumors can also originate from or extend to some atypical areas such as the gallbladder, bile ducts, ovaries, testicles, urinary bladder, prostate gland, breast, kidneys, thymus gland and rarely in the eye or ear. Up to 25% of carcinoids of the digestive tract show correlation with a different kind of non-carcinoid tumor, such as in the colon, lung, breast, and prostate cancers.
Carcinoids of the appendix are the least cancerous and rarely metastatic forms. In fact, almost 87% of those found with appendix carcinoids undergo surgery to remove the appendix and are alive even after five years without any complications.
Video Credit: Carcinoid Cancer Foundation
Carcinoid Tumors in the GI Tract
In the USA, annually around 8,000 adults in their early sixties are identified with GI tract carcinoids. The rate of survival is impacted by the region where the tumor lies or originates, along with other factors. Patients with GI carcinoid tumors show a 5-year survival rate ranging from 65% to 90%, 46% to 78% when the carcinoid extends to adjacent tissues or other regional lymph nodes, and 14% to 54% when it has advanced to distant parts of the body.
Carcinoid Tumors in the Lung
About 4,000 adults in the USA are identified with lung carcinoids annually. Carcinoids constitute 1%–2% of all lung cancers, and are identified at an average age of 60 years. The survival rate for patients with a distinctive lung carcinoid varies from 85% to 90%. The rate varies from 50% to 70% for persons with more specific lung carcinoids.
It should be noted that data on rates of survival for people with carcinoids are approximate calculations. They are estimated results of the yearly collection of data based on the number of people with cancer. Specialists evaluate this survival data only every 5 years, therefore, the statistics may not exhibit the outcomes of findings that have been detected in a period of less than 5 years. The 5-year survival rate information does not provide data on recent progressive treatments. Patients must consult their physicians regarding the aptness of the statistics with their condition.
Over the past decade, a lot of progress has been seen in the prognosis for metastatic carcinoid patients. As a result of increased survival rates, problems related to CHD and new metastatic conditions (metastases of the skin and bone) have now become more essential features of carcinoids.
Nuclear scanning and CT scans are used for regular follow-up and tracking of the size of the tumor and on the development of metastases. Special attention should be given to unforeseen instances of bone metastases patterns. As persons with CHD have a low lifespan, therapeutic care should concentrate on lowering their increased hormonal secretions even when no signs of carcinoid syndrome are observed.
The hormones must be regularly supervised and followed up for their level of secretions. Regular check-ups every 6–12 months for identifying carcinoid-related heart disease at the initial level is essential to fine-tune the therapy and diagnosis procedure. Some combinations of drugs and new diagnostic and treatment procedures in metastatic carcinoids are known to improve the quality of life, extend the lifespan, and not only restrain but even reverse the development of tumors. Advancements in therapeutic care and cancer detection procedures involve a multidisciplinary approach with a team comprising an oncologist, surgeon, pathologist, gastroenterologist, cardiologist, radiologist, and nuclear medicine specialist. Such teams should work toward a “tailor-made therapy” for individual patients.
As a rare condition, patients with carcinoid tumors should be given treatment in specialized settings, and these centers should merge with multicenter studies for posterity.
Reviewed by Afsaneh Khetrapal BSc (Hons)