In the next 15 years, more than one in 10 colon cancers and nearly one in four rectal cancers will be diagnosed in patients younger than the traditional screening age, according to researchers at The University of Texas MD Anderson Cancer Center. This growing public health problem is underscored by data trends among 20- to 34-year-olds in the USA, among whom the incidence of colorectal cancer (CRC) is expected to increase by 90% and 124.2%, respectively, by 2030.
Published in the JAMA Surgery, the findings build on prior studies of CRC trends but go a step further by providing quantitative estimates of exponentially increasing risk for CRC among patients who fall under 50, the age at which CRC screening becomes recommended for the general public. The authors point to lifestyle and behavioral factors such as obesity, lack of physical activity and a Western diet as major risk factors for CRC, though the exact causes of the predicted increases are not known.
"This is an important moment in cancer prevention," said principal investigator Dr George Chang, associate professor, Departments of Surgical Oncology and Health Services Research. "We're observing the potential real impact of CRC among young people if no changes are made in public education and prevention efforts. This is the moment to reverse this alarming trend."
The retrospective cohort study analysed Surveillance, Epidemiology, and End Results (SEER) data on more than 393,000 patients with histologically confirmed CRC between 1975 and 2010, examining age at diagnosis in 15-year intervals starting at age 20.
Researchers observed that the annual incidence rate for CRC diagnosed in patients under age 34 is increasing across all stages of disease: localised, regional and distant. The trends indicate that:
- By 2020 and 2030, the incidence rate of colon cancer will increase by 37.8% and 90%, respectively, for patients 20-34. By 2030, this represents a 131.1% incidence rate change of colon cancer in younger patients compared to patients older than 50 years of age.
- Similarly, by 2020 and 2030, the incidence rates for rectosigmoid and rectal cancers are expected to increase by 49.7% and 124.2%, respectively, for the same age group – a 165% incidence rate change compared to patients older than 50 years for these cancers by 2030.
- Among patients 35-49, incidence rates are anticipated to increase 27.7% for colon cancer and 46% for rectal cancer in the same timeframe.
An opposite trend was observed in older patients largely thanks to screening and prevention efforts. There has been a steady decline in the incidence rate of CRC in patients 50 and older, with the most notable declines in regional and distant disease. Based on the predictive model, the researchers anticipate this trend will continue, with incidence declining by 21.2% and 37.8% in 2020 and 2030 for colon, respectively; and 19.0% and 34.3% in 2020 and 2030 for rectum, respectively. The largest decrease is expected for patients older than 75 years.
Lack of screening and risk factors such as obesity and physical inactivity are known contributors to CRC. The authors encourage reduced consumption of processed and fast food and more vegetables and fruits to reduce risk. While the researchers note that the findings do not suggest revisiting screening guidelines at this time, Dr Christina Bailey, surgical oncology fellow and the study's first author, added that physicians should be on the lookout for CRC symptoms that might otherwise be dismissed in younger people and only identified as cancer after the disease has progressed.
"While our study observations are limited to CRC, similar concerns are being raised about breast cancer, as we see incidence increasing among younger women," said Chang. "Identifying these patterns is a crucial first step toward initiating important shifts in cancer prevention."
The authors concluded that further studies are needed to determine the cause for trends observed and identify potential preventive and early detection strategies.
Bailey CE, Hu C-Y, You N, et al. Increasing Disparities in the Age-Related Incidences of Colon and Rectal Cancers in the United States, 1975-2010. JAMA Surg 2014; Published online November 5. doi:10.1001/jamasurg.2014.1756