By Miriam Komaromy, MD

Reviewed by Peggy Conrad, MS, CGC and Jonathan Terdiman, MD
Last updated August 11, 2000

If you have been diagnosed with the hereditary colon cancer syndrome hereditary nonpolyposis colorectal cancer (HNPCC), stopping cancer before it starts is probably on your mind. Although people with HNPCC are much more likely to develop colon cancer — and other cancers related to the syndrome — than members of the general population, screening guildelines have been developed by the Cancer Genetics Studies Constorium to give you the best chance at early detection.

Colon Cancer Screening

If you have been diagnosed with HNPCC, the single most important preventive action you can take is to undergo regular screening for colon cancer via colonoscopy. People with HNPCC should be screened every one to three years beginning between the ages of 20 and 25.

Both colonoscopy and sigmoidoscopy are procedures in which a physician inserts a thin, flexible tube with a light and viewing camera into the patient's rectum and then guides it along the colon so that he or she can detect — and remove — the polyps that are the precursors to developing colon cancer. Although doctors recommend screening via flexible sigmoidoscopy for the general population, this procedure is inadequate for HNPCC patients because their tumors are much more likely to develop in the upper half of the colon — which the sigmoidoscope can't reach.

By allowing doctors to detect and remove polyps before they become cancerous, this type of screening has proved to be extremely effective in preventing the development of colon cancer in HNPCC patients.

For news about colon cancer in people with HNPCC, see Related News below.

Endometrial Cancer Screening

If you are a woman with HNPCC, you should also undergo regular screening for endometrial cancer (cancer of the uterine lining) because women with HNPCC have a greatly increased risk for developing endometrial cancer when compared with members of the general population. Annual screening should begin with one (or both) of the following procedures between the ages of 25 and 35.

• Endometrial aspirate: In this procedure, your doctor would insert a small tube into your uterus (via your cervix) in order to collect a sample of your uterine lining. The sample is then examined for cancerous or pre-cancerous cells.
• Transvaginal ultrasound: In this procedure, your doctor would insert a thin monitor into your vagina so that he or she could perform an ultrasound to assess the thickness of your uterine lining. A thicker-than-average lining may indicate that cancer is present, and you would need to undergo a biopsy.

Ovarian Cancer Screening

Although it's clear that you can reduce your chances of getting colon cancer by following guidelines established by research organizations, and it appears that you can do the same for endometrial cancer, researchers have not yet discovered effective ways of doing this for all types of cancer that seem to be related to HNPCC. Such is the case for ovarian cancer.

Although ovarian cancer screening has not been shown to be effective in the general population, it may well be useful for women who are — for whatever reason — considered to be at high risk for ovarian cancer.

Screening for ovarian cancer is controversial, because existing methods are both insensitive (they can fail to detect a cancer when it, in fact, exists), and non-specific (they can detect an abnormality when none is really there.) However, this does not mean that you should forego screening. As one of the deadliest of gynecological disorders, ovarian cancer develops rapidly and is relatively difficult to treat. The bottom line is that if doctors fail to detect this type of malignancy before you begin feeling symptoms, the cancer has often become too advanced to cure.

If you have been diagnosed with HNPCC, you should consider undergoing one of the following screening procedures every six months (since the cancer develops so quickly):

• CA-125 blood testing: The chemical CA-125 is what's known as a tumor marker, meaning that ovarian tumors usually produce it. Thus, if ovarian cancer is present, you are likely to have an above-average amount of CA-125. However, a number of other conditions — including pregnancy, pelvic inflammatory disease, tuberculosis, and cirrhosis of the liver — can also lead to elevated CA-125 levels. Conversely, CA-125 levels can sometimes remain low even if cancer is present.
• Transvaginal ultrasound: Just like in the procedure for endometrial cancer, a thin monitor is inserted into the vagina. However, with this procedure the ultrasound is directed at the ovaries. As with C-125 testing, the results can be misleading. Sometimes the ultrasound misses ovarian cancer when it is present, and sometimes detects an abnormality when no cancer exists. Some data also suggest that using a procedure called color doppler (which measures blood flow) along with the ultrasound makes it easier to detect cancer, so you may want to request this as part of your ultrasound testing as well.

Often doctors will recommend performing both of the above tests to increase their chances of detecting cancer. If either test yields abnormal results, your doctor may recommend that you undergo yet another procedure — called a laparoscopy — to verify the results. In this surgical procedure, a physician inserts a thin, lighted tube through a small surgical cut made in the abdominal wall so that he or she can look directly at the ovaries.

Screening for Other HNPCC-Associated Cancers

Because HNPCC increases your risk for cancers of the urinary tract, stomach, and small bowel, you may also want to consider undergoing screening for these cancers. Before you undergo such testing, however, you should be aware that researchers do not yet know how effective such screening measures are. Nor has anyone determined how frequently you should be screened.

Physicians screen for cancer of the urinary tract via urine tests and/or ultrasound, and they screen for cancer in the stomach or small bowel via upper endoscopy, a procedure that's similar to colonoscopy except that the lighted tube is inserted through the mouth and guided down through the stomach.

References

Burke, W. et al. (1997). Recommendations for follow-up care of individuals with an inherited predisposition to cancer: Hereditary nonpolyposis colon cancer. JAMA 277(915-919).

Burt, R. (1997). Screening of patients with a positive family history of colorectal cancer. Gastrointestinal endoscopy clinics of North America 7(1): 65--79.

Jarvinen, H. et al. (2000). Controlled 15-year trial on screening for colorectal cancer in families with hereditary nonpolyposis colorectal cancer. Gastroenterology 118(5): 829-34.