Researchers have demonstrated a possible connection between colorectal polyps in close relatives and the risk of developing colorectal cancer. The study, which was published by Song et al in the British Medical Journal, is of potential consequence for cancer screening procedures.

Colorectal cancer is the second-deadliest form of cancer in the world, according to the World Health Organization. Although lifestyle factors, such as being overweight or sedentary, increase the risk for developing the disease, there is also a known hereditary factor. Most people diagnosed with colorectal cancer are over age 65, but in a growing number of countries, the proportion of younger people being affected by the malignancy is increasing.

Researchers at Karolinska Institutet and Harvard University have now conducted the largest registry study to date on the relationship between colorectal cancer and having a first-degree relative (ie, parents and siblings) with a colorectal polyp.

Study Details

The study included 68,060 patients with colorectal cancer and 333,753 healthy controls matched for parameters such as age and sex. Data on colorectal cancer and polyps were sourced from the ESPRESSO (Epidemiology Strengthened by Histopathology Reports in Sweden) cohort.

All other patient data were drawn from Swedish health-care registries. The researchers also took the hereditary nature of colorectal cancer into account.

Results

The team found that approximately 8.4% of the participants with colorectal cancer had a sibling or parent with colorectal polyps, as opposed to 5.7% of the control group.

According to the report, “The increase in risk was attenuated to 40% after adjusting for family history of colorectal cancer, but increased to 70% to 77% when more than one first-degree relative had a polyp or when a polyp was first diagnosed in a first-degree relative before age 50 years.” The researchers found what appear to be several hereditary risk relationships.

"The risk was double in people with at least two first-degree relatives with polyps or a first-degree relative who had a colorectal polyp diagnosed before the age of 60," said the study's first author Mingyang Song, MD, ScD, of Harvard University.

A weakness of the study is the lack of information on other risk factors of colorectal cancer, such as lifestyle factors as well as the size and spread of the polyps. More research is now needed to corroborate the results.

"If additional studies reveal a link between a family history of polyps and the risk of colorectal cancer, it is something to take into account in the screening recommendations, especially for younger adults," said senior study author Jonas F. Ludvigsson, MD, PhD, a pediatrician at Orebro University Hospital and Professor in the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet. "I really hope that this study can help doctors…identify patients at a higher risk of colorectal cancer."

Disclosure: The study was financed by the National Institutes of Health and the American Cancer Society. For full disclosures of the study authors, visit bmj.com.