Julia Draznin Maltzman, MD
The Abramson Cancer Center of the University of Pennsylvania
Ultima Vez Modificado: 11 de julio del 2006
March is the National Colorectal Cancer Awareness month. Colorectal cancer is the third most common diagnosis of cancer in the United States. The American Cancer Society estimates that there will be 146,940 new cases of colorectal cancer diagnosed in the US in the year 2004. The Colon Cancer Alliance translates these statistics into harsh terms: one person is diagnosed with colorectal cancer every four minutes. Approximately 56,730 patients with colorectal cancer will die from their disease. Put in another way, in the US, a person dies of colon cancer every 9.3 minutes. This means that one out of eighteen people in this country will develop colorectal cancer at some point in their lifetimes. Most of the people diagnosed with colon cancer are over the age of 50 and are Caucasian. However, African Americans are 30% more likely to die of the disease should they have it develop.
If colon cancer is present in one or more members of the same family, there is a small but real possibility that there is a genetic component to the disease. Although only a small percentage of all newly diagnosed colon cancer is genetic (10%), it is important to identify these people as the implications on their lives and on the lives of their families are tremendous. Identifying the population at risk for developing this often deadly disease may increase these patients' preventive and screening practices. Much research has gone into identifying people with genetic susceptibility to colon cancer so that we may be able to target this population for various prevention strategies. In the long-term, this research may lead to a better understanding of the biology of colorectal cancer and may even result in new therapeutics and prevention techniques.
David E. Loren, MD is a gastroenterologist specially trained endoscopist (a doctor who spends most of his time performing endoscopies such as a colonoscopy) who currently serves as the Director of Endoscopic Research in the Division of Gastroenterology and Hepatology at Jefferson Medical College of Thomas Jefferson University in Philadelphia. In addition to completing his Gastroenterology fellowship at the University of Pennsylvania, Dr. Loren completed an additional Advanced Endoscopy fellowship. Among the patients that Dr. Loren cares for are those with genetic colorectal syndromes. He is currently an Assistant Professor of Medicine at Jefferson Medical College in Philadelphia. OncoLink has asked Dr. Loren to help us understand the various genetic colorectal syndromes and how one should find out if they are at risk.
OncoLink: What is a hereditary colon cancer syndrome, and what types are there?
Dr. Loren: A syndrome is a set of signs or a series of events occurring together that make up a single disease or disease process. A hereditary colon cancer syndrome is a set of signs that identify a genetic condition that predisposes people to colon cancer.
There are two main categories of hereditary colon cancer syndromes. The main difference between the two is the number of polyps that grow in the colon. In Familial Adenomatous Polyposis (FAP), patients grow hundreds of polyps, any of which may turn into cancer at any time. The growth of these polyps starts at an early age. Because of the early age of onset and the many polyps that develop, nearly all patients with this syndrome will develop cancer at some point in their lives.
In contrast, Hereditary Non-Polyposis Colon Cancer (HNPCC) patients develop many fewer polyps. However, the polyps that do grow are very aggressive with up to 80% of these patients developing colon cancer. HNPCC-affected individuals are typically older than the FAP patients at the time that they are diagnoses with colon cancer, but younger than those without a genetic predisposition (those who develop colon cancer sporadically)-It is important to identify patients with familial colon cancer syndromes as early intervention with a screening program can save their lives and the lives of family members.
OncoLink: How would I know if there is a familial colon cancer syndrome in my family?
Dr. Loren: Because colon cancer develops at a young age in both FAP and HNPCC, anyone younger than age 50 that has been diagnosed with a colon cancer or has a family member younger than age 50 who was diagnosed with colon cancer should think about the possibility of a familial colon cancer syndrome. Also, because the cancers arise from polyps, anyone younger than age 40 that has been diagnosed with a polyp or has a family member under the age of 40 with a polyp should be considered for possibly having a genetic syndrome. In these cases, patients should speak with their primary care doctor, gastroenterologist, or a genetic counselor to find out more information and better clarify their risk.
In addition, other types of cancers are also associated with the familial colon cancer syndromes. The most common of these are endometrial cancer (uterus), cancer of the urinary tract (renal pelvis or ureters), cancer of the pancreas, cancer of the ovaries, and cancer of the small intestine. If anyone who is younger than age 50 is diagnosed with one of these cancers, the patient and their family members should discuss the possibility of a familial colon cancer syndrome with a physician and/or genetic counselor.
OncoLink: Are there any genetic tests that can be done to identify patients at risk of familial colon cancer syndromes?
Dr. Loren: Yes, there are a number of tests that can be done. These range from simple blood tests to analysis of tissue samples of the polyps and/or cancers themselves. Any of these tests should be performed only after speaking with a physician and/or a genetic counselor.
OncoLink: What can be done when a person is diagnosed with a colon cancer syndrome?
Dr. Loren: Fortunately, if a familial colon cancer syndrome is found, patients can undergo screening and surveillance procedures to detect the pre-cancerous polyps before they grow and develop into invasive cancer. This is usually done with colonoscopy. A colonoscopy is a procedure where a flexible tube is used to look inside the colon and find polyps and remove them before they grow into cancer. Patients with familial colon cancer syndromes should have this done at a much younger age than people who do not have an increased risk of the cancer. Such screening modalities and close follow up has been shown to save lives by preventing cancers before they develop. In the case of patients with FAP, patients may require removal of their colons entirely to prevent colon cancer. The hundreds of polyps that grow in this condition make it impossible to remove or biopsy each and every polyp.
OncoLink: What resources are available for someone who is at risk for colon cancer?
Dr. Loren: There are many places to turn to for more information. The American Gastroenterologic Association, National Cancer Institute, and American Cancer Society all have general information available on the familial colon cancer syndromes. I encourage concerned people to speak with their physicians, as every family should be considered individually.
It is also important to speak with a genetic counselor to evaluate the risks posed to the patients', families, and children, both existing and future.
OncoLink: If a colon cancer syndrome is diagnosed in an individual, how does that affect that person's family?
Dr. Loren: In many cases, the genetic abnormality causing the cancer can be found. Family members can then be tested to see if they are affected. They should be screened for cancer at an early age, about ten years before the onset of the youngest cancer in their family. This may be as early as their teen years. Care should be taken to note that if a genetic cause is not found in the person who has cancer, it does not mean that there is no genetic etiology. Our genetic tests are limited, and it simply means that the genetic abnormality was not identified by standard methods. In those cases, further discussions of testing need to be considered by the patient, their families, and their doctors.
If you have any further questions, you may contact Dr. Loren through the OncoLink Comments form.
OncoLink has joined forces with the National Colorectal Research Alliance to help their scientists study the risk factors associated with colorectal cancer and identify potential preventive and treatment therapies. This confidential survey was developed by cancer experts as an interactive way to help our leading scientists study families with a history of colorectal cancer. OncoLink/National Colorectal Cancer Research Alliance prevention database.