Colorectal Cancer Rates Rise for First Time in Over 20 Years, New Study Finds

For years, colorectal cancer was considered one of preventive medicine's greatest success stories. Thanks largely to routine screening, the incidence of the disease in the United States had been steadily declining. Now, a new study published in the journal NEJM Evidence suggests that this encouraging trend may be reversing.

The study, led by Professor Caitlin Murphy of the University of Chicago, analyzed data from the US National Cancer Institute covering the years 2000 through 2023. In 2000, the incidence of colorectal cancer stood at 55.2 cases per 100,000 people. By 2022, that figure had fallen to 36.7. However, in 2023, it rose to 38.3 cases per 100,000, marking the first annual increase in more than two decades. According to the analysis, colorectal cancer rates increased across all age groups up to age 69, raising questions about the factors driving the changing pattern.

Why Colorectal Cancer Cases Are Increasing

The sharpest increase was observed among adults aged 45 to 49, with incidence rising by approximately 12.8% annually between 2019 and 2023. However, researchers point to one potentially encouraging explanation for this trend. In recent years, the United States lowered the recommended age for beginning routine colorectal cancer screening from 50 to 45. As a result, more people in their late 40s are being screened, leading to the detection of cancers that might previously have gone undiagnosed.

However, expanded screening does not fully explain the findings. Colorectal cancer rates have also increased among adults aged 65 to 69, while the previous decline has stalled among those aged 70 to 74, despite screening participation rates of approximately 80% in these older age groups. The researchers also examined whether disruptions caused by the COVID-19 pandemic could account for the apparent shift, but the trend remained even when data from 2020 and 2021 were excluded from the analysis.

Are Younger Generations at Greater Risk?

Murphy suggested that the findings may reflect a phenomenon known as the birth cohort effect, in which people born during a particular period experience different health risks from those born earlier. According to this explanation, individuals born in the 1960s and later may face a higher underlying risk of colorectal cancer. As these generations age, that increased risk becomes apparent in progressively older age groups.

The reasons for this potential generational shift remain unclear. Dr. Sonia Cooper, who directs the intestinal cancer prevention clinic at the University of Chicago Medical Center, emphasized the need to investigate the changing rates to identify potential risk factors and develop more effective prevention strategies.

The findings reinforce the importance of colorectal cancer screening. People with a first-degree relative who has been diagnosed with colorectal cancer should consult their physician about whether screening should begin earlier or involve additional testing. Certain symptoms also warrant medical attention regardless of age, including blood in the stool, persistent changes in bowel habits, unexplained weakness, and unintentional weight loss.

While the reasons behind the changing incidence rates remain uncertain, the findings highlight the importance of early detection and further research into the factors that may be increasing colorectal cancer risk across generations.