Rectal Cancer Cases Surge Among Younger Adults in the US, Study Reveals
Rates of rectal cancer are increasing rapidly among American adults under the age of 65, according to a new study from the American Cancer Society. Federal data indicates that rectal cancer now constitutes nearly one-third of all colon and rectal cancer diagnoses, with diagnosis rates rising from 27 percent in the mid-2000s to 32 percent this year.
Distal Colon Tumours Drive the Increase
The rise in rectal cancer is primarily driven by tumours in the distal colon, the last section of the colon adjacent to the rectum. Located on the left side of the abdomen, the distal colon is where about 70 percent of colorectal cancers are diagnosed, as reported by the Texas-based MD Anderson Cancer Center. These left-sided cases are more easily detected during routine colonoscopies.
Overall colorectal cancer case numbers are also climbing. The new report reveals that 45 percent of new colorectal cancer cases occur in adults under 65, a significant increase from 27 percent in 1995. Colorectal cancer is now the second-most common cause of cancer deaths in the United States, with more than 158,000 new cases and 55,000 deaths projected for this year.
Mysterious Causes and Research Gaps
The reasons behind these alarming trends largely remain a mystery to oncologists. Most experts do not believe genetics are the primary cause, suggesting instead that environmental or lifestyle factors are at play. Rebecca Siegel, the society's senior scientific director, stated, "We need to redouble research efforts to understand the cause but also circumvent deaths through earlier detection by educating clinicians and the general public about symptoms and increasing screening in people 45-54 years."
Part of the increase in younger adults may be attributed to the lowering of the recommended screening age to 45 in 2021. However, this change does not fully explain the decades-long surge in cases.
Lifestyle Factors and Potential Toxins
Researchers have previously linked the rise in colorectal cancers to Americans' ultra-processed diets and sedentary lifestyles. Lifestyle factors are believed to contribute to more than half of all colorectal cancer cases, according to the society.
Past research has also identified a potential connection to colibactin, a toxin produced by harmful gut bacteria that can cause DNA damage in colon cells, potentially leading to cancer development.
Diagnosis Delays and Screening Shortfalls
Misdiagnosis exacerbates the issue, as younger patients often face delays when their symptoms are mistaken for benign conditions like haemorrhoids. Dr. Lynn O'Connor, chief of colon and rectal surgery at Mercy Medical Center in New York, explained, "There is significant misdiagnosis. These are young patients, it's not on the radar. They have to see at least two to three doctors before they get a diagnosis."
Early detection is crucial, as it dramatically improves survival rates and allows for the removal of precancerous growths. However, only 37 percent of Americans aged 45 to 49 are undergoing recommended screenings.
Dr. William Dahut, the society's chief scientific officer, emphasised, "These findings further underscore that colorectal cancer is worsening among younger generations and highlight the immediate need for eligible adults to begin screening at the recommended age of 45."
