Frequency of colorectal cancer in healthy individual's relatives: A cross-sectional population-based study

Family history of colorectal cancer has been shown to be related to the risk of developing colorectal cancer. This risk depends on the number of affected relatives and the age at diagnosis. In this study we aimed to estimate the frequency of a positive family history of colorectal cancer in a random sample from Tehran population. This study was a community-based cross-sectional survey conducted from May 2006 to December 2007 in Tehran province, Iran. A total of 5,500 peoples (age≥20 years) drawn up randomly by random sampling according to postal codes and invited to participate in the study. All participants completed a detailed health data registry form on family history status of colorectal cancer. The mean age of men with a positive family history was significantly different from men with negative family history. There was no significant difference between mean age of women responders with or without positive family history. Among all participants (n=5,500), 162 responders (2.9%) had a history of colorectal cancer. Of 162, 67 responders (1.22%) had one and 4(0.07%) had two or more first-degree relative with colorectal cancer. Of 5,500 participants, 18 subjects (0.33%) reported having two or more first-degree relative with colorectal cancer or one first-degree relative with colorectal cancer diagnosed at age <50 years. Four subjects (0.07%) had three or more first-degree relative with colorectal cancer. Based on the findings, we estimate that more than 570,000 subjects in the Iran in the age group≥20 years have at least two to three times increased risk of developing colorectal cancer which should be identified and encourage to participate in screening and surveillance protocols of colorectal cancer.