Racial differences in colorectal cancer incidence not due to biology

Advanced precancerous polyps are the precursor lesions for most colorectal cancers, the third most common cancer and the second-leading cause of cancer death in the United States among all racial and ethnic groups. However, according to the U.S. Centers for Disease Control, millions of people in the U.S. are not getting screened for colon cancer.

Given that differences in colorectal cancers incidence and mortality are not due to biological factors, differences in access to or uptake of screening for the disease appears to account for the higher incidence and death rates in blacks.

"Our findings support eliminating the current age difference by race and beginning average-risk screening at age 50 regardless of race," said Thomas F. Imperiale, M.D., the Regenstrief Institute who led the study. "We need to ensure that screening is readily accessible for all persons 50 years and older, and that it considers their individual risk factors and preferences.

"By identifying the similarity of risk between blacks and whites this study highlights the importance of improving education about access to and uptake of colon cancer screening in the black community."

Because of the higher incidence and mortality rates in blacks, the current recommendation of the American College of Gastroenterology and the U.S. Multi-Society Task Force on Colorectal Cancer recommend colorectal cancer screening beginning at 45 years for average-risk blacks, while the American College of Physicians recommends starting at age 40, five to ten years earlier than for non-blacks.

"The recent American Cancer Society recommendation to lower the age to begin screening to 45 years may affect the impact of our study findings, although whether this new recommendation will be followed is uncertain," Dr. Imperiale said. "If the ACS recommendation is not well accepted by providers and patients, our study has the potential to change practice for the better by providing the evidence needed to make screening guidelines more uniform.

"I also see the potential of our study contributing to the improvement of both screening efficiency and the balance of benefits and risks of screening for blacks."

The new study reviewed and analyzed data of more than 300,000 average risk for colorectal cancers in men and women as reported in studies published between 2010 and 2017.

"Prevalence of Advanced, Precancerous Colorectal Neoplasms in Black and White Populations: A Systematic Review and Meta-analysis" will be published in the December 2018 issue of Gastroenterology.

Authors, in addition to Regenstrief Institute investigator Thomas Imperiale, M.D., who is the Lawrence Lumeng Professor of Gastroenterology and Hepatology at IU School of Medicine and a core investigator at the Richard Roudebush Veterans Affairs Medical Center, are IU School of Medicine student Priya R. Abhyankar, B.S.; Timothy E. Stump, M.A. of the IU School of Medicine's Department of Biostatistics, and Thomas W. Emmett, M.D., M.L.S. of the Ruth Lilly Medical Library.

The project was supported by Indiana Clinical and Translational Sciences Institute Collaboration in Translational Research grant UL1TR001108.