Although the numbers of new colon and rectal cancers have been steadily declining in people over 50, the rate of newly diagnosed cancer is increasing in young adults from 20 to 49 in the United States.
The increase is primarily driven by rectal cancer in non-Hispanic whites where there was an average annual increase of 3.5 percent in men and 2.9 percent in women from 1992 through 2005. Overall, incidence of colorectal cancer in young adults rose during that time 1.5 percent in men and 1.6 percent in women each year, almost all of the new cancers diagnosed in the left colon (distal colon) or rectum.
Information about increasing rates of colon and rectal cancer were obtained by studying data from 13 Surveillance, Epidemiology, and End Results cancer registries from 1992 through 2006. Researchers analyzed information by sex, race and ethnicity, age, site of cancer, and stage at diagnosis.
In attempting to find a reason for increasing colorectal cancer rates in the younger group, who are not part of screening programs, the researchers looked at risk factors for colorectal cancer. Obesity is a major risk factor for colorectal cancer, and it is increasing in all age groups in the United States, as is Type 2 diabetes, which also increases chances for colon and rectal cancer.
Eating red meat increases colorectal cancer risk in the left colon and rectum, while consumption of calcium-rich foods decreases risk. Young adults’ consumption of fast food increased three-fold between the late 1970′s and the mid 1990′s. During that time calories from hamburgers and cheeseburgers increased by 30 percent while milk consumption went down by 42 percent. Young adults are eating more red meat, more calories, and less calcium-rich foods.
Two other risk factors, alcohol use and smoking, have been declining in young adults.
The study authors point out young people who may have inherited a gene for colon cancer or have inflammatory bowel disease should begin screening earlier than age 50 and that physicians need to know and follow the guidelines.
Clinical practice guidelines suggest that patients with inflammatory bowel disease, polyposis syndromes,a known genetic predisposition, or a personal or family history of adenomatous polyps or CRC begin screening before age 50 years. Early recognition of CRC in patients under age 50 without these risk factors requires clinical awareness and aggressive pursuit of symptoms.
Almost 9 out of 10 young adults had symptoms of colon or rectal cancer at the time of diagnosis. Half had rectal bleeding and a third had abdominal pain. Among those without symptoms, 14 percent had anemia.
Our findings of a recent increase in CRC among those under age 50 years suggests the importance of timely evaluation of the distal colorectum, at a minimum, in young adults who present with symptoms consistent with possible underlying cancer.
In conclusion, Rebecca L. Siegel and her team at the American Cancer Society wrote,
The increasing incidence of CRC in young adults is in contrast with the rapidly declining incidence among older individuals. The disparate increase in left-sided CRC suggests that particular attention be given to studies to elucidate the behavioral and environmental risk factors responsible for this trend and potential prevention and early detection strategies.
SOURCE: Siegel et al., Cancer Epidemiology, Biomarkers, and Prevention, Volume 18, Number 6, June 2009.