Colorectal cancer (CRC) refers to a malignant tumor arising from the epithelial lining of the colon or rectum. It is one of the most common cancers worldwide. According to the latest data from GLOBOCAN 2024, CRC ranks among the most frequently diagnosed cancers globally and is the second to third leading cause of cancer-related mortality worldwide. Its incidence continues to rise, particularly in economically developed countries and populations adopting a westernized lifestyle.
In Thailand, national cancer registry data indicate that colorectal cancer is the most common malignancy of the gastrointestinal tract, with a steadily increasing incidence. This trend parallels changes in dietary patterns, increased sedentary behavior, and rising rates of obesity within the population.
Pathogenesis and Etiology
The pathogenesis of most colorectal cancers follows the adenoma–carcinoma sequence. This process begins with the formation of an adenomatous polyp, accompanied by mutations in key genes, including:
- APC gene mutation
- KRAS mutation
- TP53 alteration
This multistep progression typically occurs over several years, making CRC a largely preventable cancer through appropriate screening and polypectomy before malignant transformation occurs.
Evidence-based risk factors include:
- Age ≥45 years (with increasing incidence now observed in younger individuals)
- Family history or hereditary syndromes such as Lynch syndrome
- High consumption of red and processed meats
- Obesity and physical inactivity
- Cigarette smoking and alcohol consumption
- Chronic inflammatory bowel disease
Clinical Presentation
In the early stages, most patients are asymptomatic, underscoring the critical importance of screening.
When symptoms develop, they may include:
- Changes in bowel habits (chronic constipation or diarrhea)
- Rectal bleeding or blood in the stool
- Abdominal pain, bloating, or discomfort
- Tenesmus (a persistent sensation of incomplete evacuation)
- Fatigue secondary to anemia
- Unexplained weight loss
Recent randomized controlled trials and meta-analyses confirm that colorectal cancer screening significantly reduces mortality.
International guidelines (USPSTF / NCCN 2024–2025) recommend:
- Annual Fecal Immunochemical Test (FIT)
- Colonoscopy every 10 years
- Stool DNA testing every 3 years
Lifestyle modifications—including increased dietary fiber intake, regular physical activity, weight control, and reduction of processed meat consumption—are supported by high-level evidence in reducing risk.
