Colorectal cancer (CRC) is a major global health issue, with the third highest incidence of cancer and the second most common cause of cancer death. CRC has traditionally been regarded as an age-related cancer, with a peak incidence in those above 50 years. This was largely determined by lifestyle influences and the institution of mass screening programs, leading to reduced incidence in older persons in most high-income nations.
However, the last half-century has witnessed an alarming trend, with the prevalence of CRC on the rise among young adults (less than 50 years). This is predominantly seen in high-income nations like the U.S., Australia, and parts of Europe but is increasingly also rising in Asian and Latin American countries.
The evolving epidemiology of CRC also calls for additional research into potential risk factors such as diet, lifestyle, and genetic susceptibility. Elucidation of these patterns is important to enable the development of targeted prevention and early detection efforts to combat the increasing burden of early-onset CRC.1
This article discusses the increased rate of CRC in young adults, examining plausible causes, risk factors, and prevention.
The increasing trend
CRC is increasingly a growing concern among youth populations in the United States. The American Cancer Society states that while overall mortality due to CRC has declined, incidence is still on the rise among individuals younger than 50 years.
In 2023, around 19,550 individuals below the age of 50 were diagnosed with CRC, and there were 3,750 fatalities in this age bracket. The ratio of CRC in cases of individuals below 55 years has come close to doubling from 11% in 1995 to 20% in 2019.
Subsequent to this, increasing diagnoses at subsequent stages also take this pattern. Regional-stage diagnoses increased by 2%-3% annually among those less than 65 and distant-stage by 0.5%-3% starting 2010. The trend contradicts the earlier increases in the detection of early stages due to mass screening. Rectal cancer cases, in particular, have increased, their share of all CRC diagnoses elevating from 27% in 1995 to 31% in 2019.2
Despite the overall mortality rate to slow down, an increasing number of young adults are experiencing an increase in CRC-related mortality by 0.5%-3% annually. The reason behind the increase remains uncertain but may include lifestyle, diet, obesity, and hereditary elements.
Better early detection strategies and improved access to screenings and treatment must be employed to address the mounting crisis.
Colorectal Cancer Symptoms
Potential causes
Epidemiological data show that Western-type diets high in red and processed meats but low in fiber- make significant contributions to the risk of CRC. High consumption of red meat increases concentrations of gut microbiota-derived metabolites such as trimethylamine-N-oxide (TMAO) and secondary bile acids that trigger inflammation and carcinogenesis. Fiber intake, however, enhances production of short-chain fatty acid (SCFA), reducing inflammation and enhancing the gut barrier and thus diminishing CRC risk.
Gut microbiota is vital for pathogenesis of CRC. Dysbiosis, or disruption of balance in gut microbiota, correlates with CRC. Certain bacterial strains, including Fusobacterium nucleatum and Bacteroides fragilis, have been implicated in causing tumorigenesis by stimulating inflammatory cascades and immune evasion. Conversely, probiotic microorganisms like Faecalibacterium prausnitzii and Bifidobacterium promote intestinal homeostasis and may impart protection against CRC.
Risk factors for lifestyle CRC are firmly established and include obesity, physical inactivity, tobacco smoking, and excessive alcohol consumption. Obesity alters the balance of the gut microbiota and increases systemic inflammation, which encourages a pro-carcinogenic state.
Physical activity, nonetheless, has also been reported to modulate the microbiome in a positive way and reduce the risk of CRC. Environmental exposures, such as excessive antibiotic use, may also disrupt microbial diversity and increase the risk of CRC.
While environmental and lifestyle determinants contribute the most, genetic susceptibility is also involved in CRC risk. Individuals with Lynch syndrome or familial adenomatous polyposis (FAP) are at a greatly increased lifetime risk for CRC.
Additionally, genome-wide association studies identified many genetic variants at high risk for CRC, typically in combination with dietary and microbial determinants.
Screening and early detection
CRC is affecting younger patients more and more, but they are typically diagnosed later and have poorer outcomes. CRC incidence among patients under 55 has been rising 1%-2% annually since the mid-1990s, and death rates have risen similarly, based on the American Cancer Society.
This diagnostic delay can mainly be blamed on decreased screening rates, incorrectly interpreted symptoms, and inadequate patient as well as doctor awareness.
There are various factors responsible for late diagnosis of CRC in youths. Firstly, recommendations for CRC screening have been predominantly focused on adults, and only routine screening was recommended after age 45.
Therefore, younger patients with rectal bleeding or abdominal pain do not undergo immediate medical evaluation, and doctors also do not prioritize CRC screening highest among them. Misdiagnoses, typically attributing symptoms to milder conditions like hemorrhoids or irritable bowel syndrome, cause further delay in detection.
Early diagnosis significantly improves rates of survival, with stage I CRC having a 91% five-year survival rate compared to just 14% for stage IV. Advances in recent screening tests, including fecal immunochemical tests (FIT), multi-target stool Deoxyribonucleic acid (DNA) tests, and colonoscopies, improve early detection. Future technologies such as liquid biopsies and artificial intelligence (AI)-facilitated diagnostics hold immense potential for improving detection access and accuracy.
Despite the benefits, screening compliance is low due to cost, apprehension, and lack of information. Expansion in the scope of screening programs, the number of physician referrals, and marketing for non-invasive tests can make a difference in compliance. Policy changes that eliminate cost-sharing barriers to preventive services can also bring about change.
Cancer Screening Considerations: Balancing the Benefits and Risks
Future directions
Long considered a disease of old age, CRC now more and more frequently afflicts individuals younger than age 50. Studies point to genetic vulnerabilities, microbiome dysregulation, and eating habits as being accountable for the trend.
Technological innovations, including liquid biopsy and artificial intelligence (AI)-boosted imaging, are revolutionizing early detection. For instance, blood tests analyzing circulating tumor DNA (ctDNA) hold promise as non-invasive screening. Furthermore, AI is also improving the reliability of colonoscopy screening, reducing the number of false negatives, and streamlining early intervention programs.
A multi-prong prevention strategy is necessary in the treatment of CRC and other chronic diseases. Lifestyle modification remains the cornerstone of prevention. Research emphasizes the contribution of diet, exercise, and environmental exposures to CRC risk.
Consumption of processed meat, low fiber intake, and physical inactivity are large contributors to higher cancer rates. Conversely, a whole grain, lean protein, and vegetable diet with exercise reduces risk.
Environmental exposures also play an important role. Higher exposure to microplastics, endocrine disruptors, and processed food alter the composition of the gut microbiota and lead to chronic inflammation. Public health measures that promote gut health and microbiome diversity with probiotic and prebiotic-rich diets may minimize risk.
Healthcare organizations and governments worldwide are modifying policies to address these rising health concerns. To address the growing number of cases of CRC in young adults, age guidelines for screening have been lowered from 50 to 45 in many countries.
The implementation of public screening programs using non-invasive modalities, such as FIT, is likely to increase coverage rates. Policy changes also focus on reducing differentials in healthcare access. Telemedicine and mobile health applications are expanding preventive care reach, particularly among vulnerable groups. Governments are also making regulatory efforts in food labeling, restricting carcinogenic food additives, and promoting healthier food environments.
Prevention of disease in the future depends on incorporating scientific evidence with evidence-based policy-making and effective interventions in public health, along with good policy reforms that are inclusive. Combining technological enhancements, changes in lifestyle, and wide-ranging policy reforms, it is possible to reduce significantly the incidence of CRC and overall wellbeing.
Increasing early detection mechanisms, encouraging preventive healthcare, and providing medical resources to everyone are essential in building a healthier future.
