Rectal cancer is on the rise in American men and women under 40 -- although it remains uncommon, researchers said.
Using data from the Surveillance, Epidemiology, and End Results (SEER) cancer registry, Dr. Joshua E. Meyer of New York Presbyterian Hospital in New York City and colleagues found that the incidence of colon cancer among this group has remained stable over the past three decades, suggesting that the bump in rectal cancer diagnoses among young adults is not due to increased screening. The study was published online in the journal Cancer.
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The SEER database includes population-based cancer registries covering roughly 26 percent of the U.S. population. Myer and colleagues searched data obtained between 1973 through 2005 for cancer in individuals under age 40. Roughly half of the cases found were in those aged 35 to 39; roughly three quarters of the patients were white.
The incidence of colon cancer excluding the rectum was stable at 1.11 per 100,000 over this period. Rectal cancer occurred at a rate of 0.42 per 100,000 over the study period, but rose at a rate of 2.6 percent per year. Cancer of the rectosigmoid junction before age 40 was even less common with an incidence of 0.13 per 100,000, but also 2.2 percent per year.
Together, rectal and rectosigmoid cancers appeared to have started to climb in incidence starting in 1984. The rate of increase was identical between males and females and was seen in both black and white populations.
Although uncommon, cancer of the rectum and anus gained significant attention with the death of American actress Farrah Fawcett in 2009 after a three-year battle with anal cancer. Anal cancer is rare compared to rectal cancer; the American Cancer Society estimates 39,670 new cases of rectal cancer and 5,260 new cases of anal cancer in 2010.
Current guidelines for colorectal cancer screening from the American College of Gastroenterology recommend that screening begin at age 50 for average-risk individuals and at age 45 years for African Americans, who are at higher risk. An earlier start for screening is suggested only for those with a positive family history of colorectal cancer or certain types of polyps.
Although the researchers offered no clear explanation for the changing incidence of rectal cancers and didn't recommend a change to screening guidelines, they warned physicians to take symptoms seriously in younger patients.
"Patients presenting with rectal bleeding or other alarming signs or symptoms should be evaluated with this finding in mind," they wrote. "Although colonoscopy may not be warranted, we suggest that flexible sigmoidoscopy, at a minimum, should be performed in this setting to rule out rectal or rectosigmoid cancer."