A new study finds colorectal cancer patients with Lynch syndrome (hereditary non-polyposis colon cancer or HNPCC) have better survival than patients without the inherited form of the disease. Overall, 94 percent of Lynch syndrome patients were alive five years after their diagnosis compared to 75 percent of those with sporadic cancer.
Italian researchers studied all patients with colorectal cancer treated at a cancer institute in Rome between 1970 and 1993. Patients who met the Amsterdam I criteria were diagnosed as having Lynch syndrome (HNPCC). During that time 40 patients, 25 women and 15 men, had Lynch syndrome. 573 patients, 312 women and 261 men had sporadic colon or rectal cancer.
The average age at diagnosis for sporadic cancer patients was 61, while Lynch syndrome patients were diagnosed younger at an average age of 47. Lynch patients were more likely to have right-sided tumors than sporadic colorectal cancer patients (85 percent versus 57 percent.)
Stage at diagnosis did not differ significantly with 70 percent of Lynch patients and 62 percent of sporadic patients diagnosed with stage I or II cancers.
- For early stage I and II cancers, 96 percent of Lynch and 84 percent of sporadic patients survived five years.
- At stage III, 93 percent of Lynch and 64 percent of sporadic patients were alive five years later
Vittoria Stigliano and her colleagues concluded,
Our results show that overall survival of colorectal cancer in patients with HNPCC is better than sporadic CRC patients. The different outcome probably relates to the specific tumorigenesis involving DNA mismatch repair dysfunction.
Lynch syndrome is an inherited cancer syndrome, passed directly from parent to child, and caused by mutations in the genes that repair damaged DNA. It is responsible for 3 to 5 percent of colorectal cancer, as well as some uterine, ovarian, and other associated cancers. Lynch syndrome colon cancers are usually diagnosed in younger people, in the right side of the colon, and have high microsatellite instability. Genetic testing can identify the genes that cause them to make a definite diagnosis.
In the Italian study, the Amsterdam I criteria (below) based on family history was used to select patients with Lynch syndrome. However, some patients whose families meet Amsterdam criteria do not, in fact, test positive for known mismatch repair genes.
Amsterdam I Criteria
- Three or more family members with a confirmed diagnosis of colorectal cancer, one of whom is a first degree (parent, child, sibling) relative of the other two
- Two successive affected generations
- One or more colon cancers diagnosed under the age of 50
- Familial adenomatous polyposis (FAP) has been excluded
Source: Stigliano et al., Journal of Experimental and Clinical Cancer Research, September 19, 2008.