A familial component to human rectal cancer, independent of colon cancer risk.

BACKGROUND & AIMS: The Utah Population Database (UPDB) is unique; it links genealogy for over 2 million Utah individuals to a statewide Cancer Registry. We have investigated the familial nature of rectal cancer, considered independently from colon cancer.

METHODS

We estimated relative risks in relatives, and average relatedness among rectal cancer patients using matched controls from the UPDB.

RESULTS

There is a significant increased risk for rectal cancer in first-degree relatives of rectal cancer patients (relative risk [RR], 1.97), equivalent to the risk for colon cancer (RR, 2.11). The significant increased risk for rectal cancer extends to second- and third-degree relatives. The RR for rectal cancer among first-degree relatives of young-onset rectal cancer patients (<55 y), is equivalent (RR, 3.34) to their risk of colon cancer (RR, 3.35).

CONCLUSIONS

The UPDB provides strong evidence for a familial component to rectal cancer that may include a genetic component in addition to shared environment. There is a significant increased risk of rectal cancer in the close and distant relatives of rectal cancer patients, which is even higher among relatives of young-onset patients. Although it has been reported that relatives of colon cancer probands are at increased risk for colorectal cancer, the risk of large-bowel cancer among relatives of rectal cancer patients has been less clear. Relatives of rectal cancer probands experience a risk of cancer of the large bowel that is at least as high as the risk previously reported for relatives of individuals with colon cancer.