Researcher Rebecca Siegel of the American Cancer Society has published a puzzling report which indicates that the incidence of colon and rectal cancer is increasing in millennials and Generation X, while decreasing in older people. Colon cancer remains the third most common malignancy diagnosed in both women and men in the US. According to the American Cancer Society in 2017, there will be 95,520 new colon cancers and about 39,000 cases of rectal cancer. Overall the lifetime risk of developing colorectal cancer for American men is 4.7% (1 in 21) and for women it is 4.4% (1 in 23). The risk in men is slightly higher than women.
Rebecca Siegel and her co-researchers explain these findings in the Journal of the American Medical Association (JAMA) as to why colorectal cancer was increasing among white millennials.
Their data reveal that the mortality rate for colorectal cancer in the US for individuals between ages 20-54 dropped from 6.3 per 100,000 in 1970 to 3.9 per 100,000 in 2004. However, during the next decade, the rates went up by 1 percent each year. At the end of 2014, the rate for colorectal cancer was 4.3 per 100,000. The researchers then broke down the trend based on race. While the outlook for young and middle aged whites was not great, the outlook in African Americans was better than all other races.
For the past few decades, the mortality rate from colorectal cancer for Caucasians was dropping but after 2004, the rates started to climb going from 3.6 per 100,000 to 4.1 per 100,000 in 2014. At the same time the mortality rates for African Americans dropped to 6.1 per 100,000 in 2014. While this is still a high rate compared to Caucasians, the researchers believe that the trend is headed in the right direction. For all other races, the mortality rates also started to drop until 2006 and remain stable throughout 2014.
As to why the rates of colon cancer have started to rise, Dr. Siegel feels that obesity may be one factor that explains it. Obesity rates have been increasing in all races over the past 3 decades and is a known factor for cancer. But this does not explain the drop in colon cancer in African Americans, who also have very high rates of obesity. The data for this study were obtained from the National Center for Health Statistics and Information and involved 250,000 people.
These data have now raised more questions regarding screening tests which currently recommend colonoscopy starting at age 50.