Murff_Harvey-headshotGuest blogger, Dr. Harvey Murff from Vanderbilt University School of Medicine discusses the increased incidence in colorectal cancer diagnosis in people under age 50. In individuals over the age of 50, the number of new colorectal cancer cases has decreased by 30% over the last 10 years. This is likely due to increases in colorectal cancer screening rates. Also during this time, deaths associated with colorectal cancer decreased by 30%. These are encouraging numbers and additional reductions could be seen by improving overall adherence with recommended screening guidelines. Of concern is that over this same time period, rates of new colorectal cancers in individuals younger than 50 has increased. The steepest increase has been seen in rectal cancer. It is estimated that 10-11% of colon cancers and 18% of rectal cancers are diagnosed in individuals under the age of 50. The consistency of this evidence suggests this increase in colorectal cancer diagnosis in younger individuals is a real phenomenon. This rise could be related to an upsurge in colorectal cancer risk factors in younger individuals or perhaps some unidentified factor.

Explaining the Risks

Although it is unclear why this increase in colorectal cancers in people under 50 has occurred, it is important to comment on what these risk estimates mean. Risks can be presented in several different formats. The most common formats include relative risk and absolute risk. Determining relative risks is important as it helps us describe how trends in a condition might have changed over time. Absolute risk is helpful when considering an individual’s chance of developing a disease. Remember that even if you’re doubling how often a rare event occurs (relative risk), it will still be a rare event (absolute risk). For example, if a diagnosis which used to occur one time in a million suddenly occurs two times in a million, the relative risk is double. However, in absolute terms there is only one additional case per million. Colorectal cancer is rarer in individuals under 50. Relative rates have increased by 20% from 2002 to 2012, which is an increase from 6 cases for every 100,000 people to 7.2 cases per 100,000 people. The absolute increase is 1.2 cases per 100,000 people. Over this same period, relative rates have decreased by 32% in individuals older than 50, going from 177 cases per 100,000 people to 120 cases per 100,000 people for an absolute decrease of 53 cases per 100,000. So overall, because of the decrease in colorectal cancer rates in the age range that is most likely to get colorectal cancer, overall rates have decreased. The earlier numbers I presented include all age ranges. If we just look at individuals around the median age of the U.S. populations (ages 40-44), we see that the rate of colorectal cancer increased from 13.5 cases in 100,000 to 17.9 in 100,000 from 2000-2006. This is a relative increase of 33% with an absolute increase of 4.4 cases per 100,000 people. If we look at individuals around the median age of colorectal cancer diagnosis (65-69) the rates went from 200 cases per 100,000 to 160.9 cases per 100,000 for a relative decrease of 20% and an absolute decrease of 39.1 cases per 100,000. An additional number worth considering is the percent of colorectal cancers that are diagnosed in individuals under the age of 50, which is 1 in 10. While 10% is a significant proportion, it is important to place this within the context of the population structure of the United States. The median age of colorectal cancer diagnosis is 69 years old but the median age in the US is around 40. Only a third of the population is over the age of 50. So even though the diagnosis is much less common in younger adults, because there are many more young adults than older adults, the total contribution to colorectal cancers is significant.

Screening Recommendations and Importance of Family History

Increases in colorectal cancers for individuals under age 50 represent very important increases, but it is not at all certain at this time how this might impact current screening guidelines. Current guidelines recommend beginning screening for all average risk individuals at age 50. A change in recommendations to screen all individuals between ages 40 to 49 could represent a very large increase in screening procedures to detect a limited number of cases. Given the costs, labor issues and complications associated with screening, health policy experts have to carefully weigh when routine screening seems to offer the best advantage. While additional data and careful deliberations are needed to determine what ages are best to initiate colorectal screening in average risk individuals under age of 50, not everyone under 50 is considered average risk. Up to 22% of colorectal cancer cases diagnosed before the age of 50 are associated hereditary cancer syndromes while additional cases are related to inflammatory bowel disease. Your family history can have major impact on when colorectal cancer screening should begin. Colorectal cancers in individuals under 50 are also more likely associated with symptoms, so it is very important to take any unexplained persistent rectal bleeding seriously and seek medical care. Do not ignore the symptoms or try to blame on hemorrhoids. Colorectal cancer in individuals under age 50 is beginning to receive more attention and research focus. As research progresses we may begin to understand risk factors and diagnose these cancers earlier. It is important to know your family history and to report any symptoms to your health care provider. Fight Colorectal Cancer is committed to understanding CRC in the under 50. Join us in Nashville on April 1st (live stream or in person) as Dr. Murff and other experts discuss this important topic.

Video Recording of the Under 50 Panel from Nashville

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2 thoughts on “The Under 50 Phenomenon

  1. so if you aren’t familiar with the genetics as much with the younger tumors would the Cologuard not be as effective a test for younger people? in that it might not be testing for the particular DNA prevalent in it?

  2. Reply to Dr. Harvey Murff,

    Thank you so much for detailing the increasing incidence of colon cancer patients under 50! I was diagnosed this past October at 45, after having intermittent bleeding on and off for months. For someone under fifty going through the extensive prep and painful procedure for something that is most likely to be hemorrhoids is not insignificant. So my decision to do an early colonoscopy wasn’t as simple as “just get it done.” We need to consider adding something like ultrasound diagnosis or improve the blood detection markers to make a colonoscopy confirmatory rather than a first-line screening for younger patients.

    I’m troubled by the term “phenomenon” used to describe the increasing incidence of those under 50. Since my diagnosis, I’ve only been asked about family history ten thousand times. But when I researched another possible cause (detailed in my book The Colon Cancer Diet), I found that the majority of colon cancer patients do not have a documented family history. Some experts I read (on medline, not the general internet) went so far as to say that 95% of colon cancer is the result of diet and lifestyle.

    By continually focusing on family history, I feel that cancer awareness groups are giving under 50s without a family history a false sense of security. Prevention isn’t just getting a colonoscopy. Prevention is a process of recognizing possible risk factors and changing them. While we may not have definitive studies about which lifestyle choices are the riskiest for colon cancer, we know that many of the same lifestyle changes help prevent a host of chronic diseases. My hope is that we’ll see large, definitive studies as we go forward, in the same way we have with other cancers.

    Thank you again for detailing both the absolute and relative risk increases for the under 50 crowd!

    Christopher Maloney, too cool for : cancer.

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