Background: Family history of colon cancer has been shown to be related to the risk of developing colon cancer. The impact that a comprehensive family history of colon or other cancers has on the risk of colon cancer has not been thoroughly studied. Purpose: The purpose of this study was to assess the risk of developing colon cancer associated with having a family history of colon, rectal, breast, ovarian, endometrial, or prostate cancer. Methods: A case-control study was conducted using data from the Utah Population Database. Case patients had first primary colon cancers (n = 2543). Three control subjects per case were individually matched to case patients on year of birth, place of birth, marital status, and sex. Results: Those case patients with the highest familial standardized incidence ratio were at an increased risk of developing colon cancer (for men, odds ratio [OR] = 2.51 and 95% confidence interval [CI] = 1.88-3.29; for women, OR = 2.90 and 95% CI = 2.17-3.82). A second- or third-degree relative with colon cancer increased risk from 25% to 52%. Risk associated with family history was greater in those patients diagnosed before age 50 (for men, OR = 3.61 and for women, OR = 7.18) than in those diagnosed at 50 or more years of age (for men, OR = 2.44 and for women, OR = 2.73). The risk associated with a family history of colon cancer was greatest for the distal segment of the colon. Women were at an increased risk of colon cancer if they had a first-degree relative with breast (OR = 1.59; 95% CI = 1.25-2.03), uterine (OR = 1.50; 95% CI = 0.99-2.26), ovarian (OR = 1.63; 95% CI = 1.41-1.89), or prostate (OR = 1.49; 95% CI = 1.21-1.82) cancer; men were at increased risk of colon cancer if they had a first-degree relative with breast (OR = 1.30; 95% CI = 1.02-1.66), uterine (OR = 1.96; 95% CI = 1.34-2.87), or ovarian (OR = 1.59; 95% CI = 0.90-2.81) cancer. Conclusions: These findings support previous observations that people with a family history of colon cancer are at increased risk of colon cancer. Those with a second- or third-degree relative with colon cancer or a first-degree relative with breast, ovarian, uterine, or prostate cancer also have an increased risk of developing colon cancer. Implications: These data support the recommendations that individuals who have a first-degree, and possibly a second- or third-degree, relative with colon cancer should have regular screening for colon cancer.
