Annual colonoscopies for people with Lynch syndrome (HNPCC or hereditary nonpolyposis colon cancer) successfully find cancers at an early stage.
A recent study by the German HNPCC Consortium confirmed the effectiveness of annual colonoscopies to find colorectal cancers at a curable stage. Regular colonoscopies found early cancers more often than did patient symptoms.
Current recommendations are for surveillance colonoscopies to begin by age 25, be repeated every 1 to 2 years until age 40, and then annually.
Over 1,100 individuals from families with HNPCC were scheduled for annual colonoscopies, and more than 80 percent were completed in less than 15 months. Ninety-nine colorectal cancers were found in ninety patients.
Of those cancers:
- 17 (17 percent) were identified by symptoms: 8 before the first baseline colonoscopy, 8 when the time between colonoscopies was more than 15 months, and 1 in an interval between tests less than 15 months.
- 43 were found during follow-up colonoscopies, only 2 of which regionally advanced (stage III)
Tumor stages were significantly lower among those whose cancers were found by colonoscopy compared to those identified after patients experienced symptoms.
The researchers divided the study patients into three groups:
- Those with an identified inherited genetic mutation for one of the Lynch mismatch repair genes (MUT group)
- Those without a mutation but with microsatellite instability (MSI group)
- Those with a strong family history that met the Amsterdam criteria but did not have MSI (MSS group)
By the age of 60, the mutation and MSI group combined had a 23 percent risk of getting colorectal cancer. However, risk for the MSS group was only 1.8 percent.
Patients who had an adenomatous polyp removed during the first colonoscopy had a risk of another polyp that was two and a half times as great as those without that first polyp. Their risk of subsequent colorectal cancer was almost four times as high.
The Amsterdam II criteria is used to detect families at risk for Lynch-related mutations. Each of the following criteria must be fulfilled:
- 3 or more relatives with an associated cancer (colorectal cancer, or cancer of the endometrium, small intestine, ureter or renal pelvis)
- 2 or more successive generations affected
- 1 or more relatives diagnosed before the age of 50 years
- 1 should be a first-degree relative of the other two (first degree relatives are parents, siblings, or children)
- Familial adenomatous polyposis (FAP) should be excluded in cases of colorectal carcinoma
However, genetic testing is necessary to confirm a mutation.
Christoph Engel and his colleagues in the German HNPCC Consortium concluded,
Annual colonoscopic surveillance is recommended for individuals with HNPCC. Less intense surveillance might be appropriate for MSS families.