“Having a first-degree relative with colorectal cancer approximately doubles the risk, and the risk increases with the proportion of relatives affected, particularly if they are diagnosed at an early age (61).”
Colon Cancer in the United States
Colorectal cancer (CRC) is the second leading cause of cancer death in the US and is one of the most commonly diagnosed cancers. It is the third most common cancer in men and in women. “An estimated 56,290 deaths due to colon cancer are expected to occur in 2005, accounting for about 10 percent of cancer deaths this year in the United States (68).”
It is believed that CRC is caused by a complex interaction of inherited susceptibility and environmental factors. Within the large intestine, genetic changes alter the growth of normal cells to form polyps (adenomas). Adenomas are common, are found in approximately 25% of people by age 50, and the prevalence increases with age. Seventy to ninety percent of CRC is believed to arise from these adenomatous polyps (62). Overall, about 10.5% will progress to CRC; however, as many as 50% of large adenomas (over 2 centimeters) will progress to cancer. The average time between the development of a polyp and its progression to CRC is 10-15 years (63).