From the Guidelines
The increasing incidence of colorectal cancer in younger individuals is likely caused by a combination of lifestyle factors, environmental changes, and genetic predispositions, with the most recent evidence suggesting that initiating screening at age 45 may be beneficial in reducing the burden of the disease. According to the most recent study 1, the incidence of colorectal cancer in people younger than 50 years has been increasing, and it is estimated that over the next decade, early-onset colorectal cancer will account for 10% of colon cancers and 25% of rectal cancers. The exact mechanisms driving this trend are complex and multifactorial, involving:
- Poor dietary habits, such as diets high in processed meats and low in fiber 1
- Obesity and sedentary lifestyles, which can create chronic inflammation and promote cancer development 1
- Environmental factors, such as increased exposure to certain chemicals and pollutants 1
- Changes in gut microbiome composition due to modern diets, antibiotic use, and other factors 1
- Genetic factors, including family history, which remains a strong predictor of colorectal cancer risk, even in younger people 1 Additionally, increased screening and awareness may be detecting more cases that previously went undiagnosed 1. The interplay between these factors creates a complex picture, with researchers still working to fully understand the exact mechanisms driving this concerning trend in younger populations. However, based on the most recent evidence, initiating screening at age 45 may be beneficial in reducing the burden of the disease, with some studies suggesting that starting screening at this age may result in the most optimal balance of burden to benefit of screening 1.
From the Research
Causes of Increasing Incidence of Colon Cancer in Younger Individuals
- The rising incidence of colon cancer in younger individuals is a concerning trend, with studies suggesting that the incidence has nearly doubled in younger adults since the early 1990s 2.
- The etiology of young-onset colon cancer is unexplained, and efforts to blame obesity or diabetes as causative factors are simplistic and inadequate 3.
- Generational differences in diet, environmental exposures, and lifestyle factors may contribute to the increasing incidence rates in younger people 2.
- Novel studies of the microbiome may elucidate bacterial causes of CRC carcinogenesis in younger individuals 3.
Epidemiologic Trends and Risk Factors
- Approximately 1 in 10 new diagnoses of CRC are now made in individuals 50 years or younger 2.
- Patients' risk of CRC has been calculated largely by age and family history, yet 3 of 4 patients with early-onset CRC have no family history of the disease 2.
- The majority of CRCs are sporadic rather than familial, and both environmental and genetic factors can increase the likelihood of developing CRC 4.
- Early-onset CRC is a truly heterogeneous disease, with mounting evidence to suggest that this patient population has a distinctive molecular profile, very different to late-onset CRC cases 4.
Screening and Treatment Options
- Moving up the colonoscopy screening to age 45 in normal-risk individuals may prove beneficial in detecting more patients with early-onset CRC 3.
- The development of risk-adaptive screening decision algorithms and flexible sigmoidoscopy screening at age 40 may be beneficial, given the predilection for left-sided primaries in this age group 3.
- Young adults with colon cancer received significantly more postoperative systemic chemotherapy at all stages, but they experienced only minimal gain in adjusted survival compared with their older counterparts who received less treatment 5.
- Attention should be given to long-term cancer survivorship in young adults with colon cancer because they likely face survivorship needs that are distinct from those of their older counterparts 5.