Rectal cancer rates are increasing in people under 40, although rates of colon cancer have remained stable in younger people.
It isn’t clear why, but rectal cancer rates in this young group of men and women began increasing in 1984, rising about 3.8 percent a year.
Increases were similar for both sexes and all races.
A research team found 7,661 patients under 40 with colon or rectal cancer, including 1,922 with rectal cancer in the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) cancer registry database between 1973 and 2005.
More than half of the cases, 52 percent, were in patients from 35 to 39, with 28 percent from 30 to 34, and 20 percent under 30.
Looking through the medical literature,the study authors couldn’t find an explanation for why rectal cancer was going up while colon cancer wasn’t. Screening or lifestyle issues couldn’t be identified as a possible reason.
Both rectal and colon cancer are rare in people under 40 with slightly over 1 case of colon cancer for every 100,000 people in the United States and less than 0.5 cases of rectal cancer. This compares to 34.5 new colon cancer cases per 100,000 people and 13.4 new rectal cancer cases in the overall US population of all ages.
Because the overall incidence of rectal cancer in this age group is so low, the authors do not recommend changes in screening guidelines. However, they do urge that symptoms of rectal cancer, including rectal bleeding, be followed up.
Dr. Jeffrey Meyer, lead author of the study, recommends,
We suggest that in young people presenting with rectal bleeding or other common signs of rectal cancer, endoscopic evaluation should be considered in order to rule out a malignancy. This is in contrast to what is frequently done, which is to attribute these findings to hemorrhoids. More frequent endoscopic evaluation may be able to decrease the documented delay in diagnosis among young people.
Concluding, Dr. Meyer and his team wrote,
The incidence of rectal and rectosigmoid cancer appears to be increasing in patients aged less than 40 years. Patients presenting with rectal bleeding or other alarming signs or symptoms should be evaluated with this finding in mind.