Colorectal cancer is the third most common form of cancer in the United States, with approximately 130,000 cases diagnosed each year. It is also the second leading cause of cancer deaths in the United States; yet, when discovered early, this is disease is 90% curable.
Primarily, colorectal cancer occurs because of abnormalities in some of the genes in colon cells that control cell growth and death. In about 5% of people with colorectal cancer, a mutation in an important gene is passed from parent to child, which means it is inherited.
Below, you will find answers to some frequently asked questions about Hereditary Non-polyposis Colorectal Cancer or HNPCC. If you have additional questions, we encourage you to write them down and ask your doctor, genetics counselor, or registry coordinator.
What is HNPCC?
HNPCC is an inherited colorectal cancer syndrome that accounts for 5% of all cases of colorectal cancer. The "H" stands for hereditary, meaning it is inherited or can be passed from parent to child. "NP" stands for non-polyposis, which distinguishes HNPCC from familial adenomatous polyposis (FAP), another inherited syndrome with hundreds to thousands of polyps. The "CC" stands for colorectal cancer, the most frequent cancer that develops in HNPCC families.
How is HNPCC inherited?
HNPCC is caused by an inherited mutation or abnormality in a gene that normally repairs our body's DNA. There are at least five of these genes known as mismatch repair genes that are known to be associated with HNPCC. If genetic damage is not repaired, cancer can occur. When an individual has an inherited gene mutation, it is present in the cells of all organs of the body. This makes it easier for other cancers to develop, such as cancer of the uterus or ovaries, gastrointestinal tract (stomach, small intestine and pancreas), urinary tract, or kidneys.
HNPCC and the risk of cancer by age 70
Cancers associated with HNPCC
Lifetime risk of cancer in HNPCC
Risk in general population
Less than 1%
Less than 1%
Although the risk of developing cancer if you have HNPCC is high, becoming more informed about the syndrome, getting the recommended screenings and check ups, and receiving treatment by experts can help prevent cancer and save lives.
How is HNPCC diagnosed?
detailed family history is the first step in determining if your family may be affected with HNPCC or an inherited colon cancer syndrome. There are several criteria that alert your health care provider to a possible diagnosis of HNPCC. The strictest include:
3 relatives with colorectal cancer
1 colorectal cancer diagnosed in a relative at or before age 50
1 relative with colorectal cancer should be a first-degree (parent, child, sibling) to the other 2 with colorectal cancer
colorectal cancer occurs in 2 successive generations
Less strict criteria include:
families with 2 colorectal cancers and 1 uterine cancer, or 2 relatives with colorectal cancer and advanced precancerous polyps
1 colorectal cancer or uterine cancer diagnosed at or before age 50
1 relative with cancer should be first-degree to the other 2 with cancer or polyps
cancers occurring in 2 successive generations
2 HNPCC-associated cancers*
1 relative with cancer should be first-degree to the other 2 with cancers
cancers occurring in 2 successive generations
1 relative with cancer should be diagnosed before age 50
*HNPCC associated cancers: colorectal, uterine/endometrial, small bowel, ureter, renal pelvis
Other clues used in the diagnosis of HNPCC in a family include multiple relatives with colorectal cancer, especially at a young age, persons who have had more than one colorectal cancer, or clusters of colorectal and other HNPCC associated cancers.
If the family history is suggestive of HNPCC, genetic counseling is recommended prior to genetic testing. A genetic counselor will review your family history and will also discuss the important issues regarding testing, including your emotional well-being.
If there is a high likelihood that your family has an inherited colon cancer syndrome DNA sequencing (blood testing) for the gene mutations known to cause HNPCC may be recommended. Approximately 50% of HNPCC families have a mutation detected. If it is detected in the family, other relatives may subsequently be tested. Importantly, a positive gene test in someone only confirms that the gene mutation has been inherited, it does not detect polyps or cancer.
Sometimes, an alternative method of testing, called microsatellite instability (MSI), is done on cancerous tissue or polyps. A positive MSI test, along with a strong family history, is highly suggestive of HNPCC. However, genetic testing with direct DNA sequencing should follow.
In patients with a positive DNA test, regular colorectal and gynecologic surveillance is required to prevent or detect cancer in its early, curable stages. If a family chooses not to undergo genetic testing, or the mutation cannot be found, regular surveillance is also needed.
How can cancer be prevented in an HNPCC family?
In order to prevent colorectal cancer, regular colonoscopies are required. In the majority of cases, cancer develops from adenomatous polyps that can be removed during the colonoscopy.
Besides regular screening, a healthy diet and lifestyle can aid in colorectal cancer prevention. Be sure to consult with your doctor before making any lifestyle changes.
If cancer is found, surgical removal of the entire colon is the only definite way to prevent colon cancer from recurring. Following surgery, most patients are able to eat normal diets and lead normal lives.
HNPCC families can be followed in a registry, such as the David G. Jagelman Inherited Colorectal Cancer Registries at The Cleveland Clinic, whose main purpose is to prevent needless deaths from colon cancer by providing the best care, promoting knowledge of the risks, and conducting research.
What is recommended screening for HNPCC patients? Method: colonoscopy
Age to Begin: At 21 years, or 10 years younger than the youngest person diagnosed with colorectal cancer in the family, whichever is earlier.
Interval: Every 2 years until age 40 and then every year thereafter
Method: Pelvic exam, transvaginal ultrasound and CA-125 (blood test for ovarian cancer)
Age to Begin: 25-35 years
Interval: Every year
Method: Endometrial biopsy
Age to Begin: As symptoms arise, such as persistent, unusual vaginal bleeding
Method: Urine cytology (especially for families who have someone diagnosed with transitional cell carcinoma of the ureter or renal pelvis)
Age to Begin: At 30 years
Interval: Every 1-2 years
Other cancers that occur in the family may require specialized testing beyond these basic recommendations.