Survival Comparison Between Sporadic, Familial Polyposis, and Nonpolyposis Colon Cancer
abstract & commentary
Source: Bertario L, et al. Int J Cancer 1999;80:183-187.
Colorectal cancer is projected to be diagnosed in 129,400 people in the United States this year and will be responsible for the deaths of about 56,600 people. It is estimated that about 10% of the cases of colorectal cancer occur in familial aggregations. The two hereditary forms of colorectal cancer that are best characterized are familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC), both autosomal dominant traits. A number of studies have suggested that the familial forms of colorectal cancer have a better natural history than sporadic colorectal cancer.1-4 However, such studies may involve a selection bias.
In an effort to assess the natural history of FAP, HNPCC, and sporadic colon cancer, researchers at the National Cancer Institute of Milan examined 144 patients with HNPCC, 161 patients with FAP, and 2035 patients with sporadic colorectal cancer and compared their clinical characteristics and survival. Patients with hereditary cancers were significantly younger at diagnosis than those with sporadic cancers (FAP, 43 years; HNPCC, 49 years; sporadic, 60 years). Furthermore, 40% of those in the HNPCC group had right-sided tumors compared with 13% of the sporadic group and 14% of the FAP group. The stage distribution was not greatly different; Dukes A or B was n oted in 51% of the sporadic group, 48% of the FAP group, and 52% of the HNPCC group. The overall five-year survival was 57% for the HNPCC group, 54% for the FAP group, and 51% for the sporadic group. After adjustments for stage, age, location, and sex, there were no significant differences among the three groups.
Commentary
HNPCC is related to a mutation in a DNA mismatch repair gene that leads to genetic instability in the colonic epithelium and an increased risk of colorectal cancer. FAP is a mutation in the adenomatous polyposis coli (APC) gene that leads to multiple adenomatous polyps, some of which undergo progression to invasive carcinoma. Both of these forms of hereditary cancer can be prevented with adequate efforts to screen families based upon the detection of an index case.
Suspicion of a familial pattern should be high in young patients and those with first degree relatives who also have colorectal cancer. In such a setting, screening asymptomatic family members can be life-saving.
It is important to note that similar benefits are noted in the general population not affected by genetic susceptibility through the screening of men and women age 50 years or older with fecal occult blood testing and colonoscopy every two years.
References
1. Fujita S, et al. Jap J Clin Oncol 1996;26:351-355.
2. Percesepe A, et al. Int J Cancer 1997;71:373-376.
3. Sankila R, et al. Gastroenterology 1996;110:682-687.
4. Myrhoj T, et al. Scand J Gastroenterol 1997; 32:572-576.
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