Spotlight on colorectal cancer

Studies this month looked at colorectal cancer screening, risk associated with dietary patterns, and estimated U.S. incidence.

Colorectal cancer was the focus of several recent studies, which assessed the impact of primary care clinicians on screening, linked dietary patterns to cancer risk, and estimated incidence in the U.S.

To determine the effect of practice-based strategies on colorectal cancer screening uptake, researchers surveyed 717 primary care clinicians in Canada (family physicians and general practitioners) and followed their patients for two years. Results were published online on Feb. 28 by the American Journal of Gastroenterology.

Overall, 38.8% of patients underwent screening during the follow-up period. Those who were more than five years overdue were less likely to undergo screening than those who were less than one year overdue (25.3% vs. 53.5%; hazard ratio [HR], 0.31; P<0.0001).

Clinicians reported using several different strategies to increase screening uptake (e.g., systematic reminder prompts during patient encounters). The only strategy that was modestly associated with screening uptake was use of a systematic process to generate lists for patients overdue for screening (HR, 1.09; P=0.03).No single strategy majorly affected screening uptake, but clinician use of multiple strategies, compared to one or fewer strategies, was associated with increased screening participation (HR, 1.19 for two to three strategies and 1.27 for four to five strategies). One limitation of the study is that clinicians' strategies were self-reported.

Another study, published online on Feb. 26 by Gastroenterology, assessed associations between Western and prudent dietary patterns and colorectal cancer risk. The Western dietary pattern included red and processed meats, high-fat dairy products, refined grains, and desserts, whereas the prudent dietary pattern included high intakes of vegetables, fruits, whole grains, and fish.

Researchers used the Health Professionals Follow-up Study and Nurses' Health Study to document 3,260 cases of colorectal cancer among 137,217 men and women over 32 years of follow-up. Higher long-term Western dietary pattern scores were directly associated with overall incidence of colorectal cancer (P<0.0001 for trend; P=0.04 for trend in men and 0.002 for trend in women). The association was significant for tumors of the distal colon (P=0.0004 for trend) and rectum (P=0.01 for trend) but not of the proximal colon.

Although higher prudent dietary pattern scores appeared to be inversely associated with overall risk of colorectal cancer, tests for linear trend were significant in men but not women (P=0.03 and 0.24 for trend, respectively), and the lower risk did not vary by anatomic subsite. A limitation of the study is that the diet data were obtained from questionnaires.

Finally, a retrospective cohort study published online on Feb. 28 by the Journal of the National Cancer Institute reported that the incidence of colorectal cancer in the U.S. is increasing among young adults. Using data from the nine oldest Surveillance, Epidemiology, and End Results (SEER) Program areas, researchers determined the cancer incidence among patients ages 20 and older diagnosed with invasive colorectal cancer from 1974 through 2013.

They determined that, compared with people born circa 1950, those born circa 1990 have double the risk of colon cancer (incidence rate ratio [IRR], 2.40; 95% CI, 1.11 to 5.19) and quadruple the risk of rectal cancer (IRR, 4.32; 95% CI,2.19 to 8.51). Thus, age-specific risk of colorectal cancer for contemporary birth cohorts has risen back to the level of those born circa 1890.