Overview of Colorectal Cancer
Colorectal cancer is a tumor resulting from the malignant proliferation of epithelial cells in the large bowel mucosa.The large bowel comprises the colon and rectum—the terminal section of the digestive tract—and functions primarily to absorb water and store feces.
Global overview of colorectal cancer
Colorectal cancer ranks among the most common malignancies worldwide. In recent years, its incidence in my country has risen significantly, making it the second most common new cancer diagnosis and posing a serious threat to public health.
Consult a doctor regarding cancer-related issues.
Individuals experiencing symptoms such as blood in the stool, changes in bowel habits, abdominal pain, an abdominal mass, or unexplained anemia—particularly those with a family history of colorectal cancer—should promptly consult a gastroenterologist or a colorectal surgeon.
Main types of colorectal cancer
1. Colon adenocarcinoma
It is the most common type of colorectal cancer, accounting for over 95% of cases; it includes well-differentiated, moderately differentiated, and poorly differentiated adenocarcinomas, with the degree of pathological differentiation influencing prognosis.
2. Rectal adenocarcinoma
An adenocarcinoma occurring in the rectum; due to its unique anatomical location, treatment must consider the preservation of anal function, making it a complex type of digestive tract tumor to treat.
3. Mucinous adenocarcinoma
Cancer cells secrete large amounts of mucus, forming "mucus lakes"; this subtype accounts for approximately 10% of colorectal cancers. It carries a poorer prognosis than ordinary adenocarcinoma and is commonly seen in young patients and those with hereditary colorectal cancer.
4. Signet-ring cell carcinoma
A special subtype of poorly differentiated adenocarcinoma characterized by signet-ring-shaped cancer cells; it is highly aggressive, carries a very poor prognosis, and is relatively common in young patients.
5. Neuroendocrine carcinoma
Originates in endocrine cells of the large intestine; highly malignant and rapidly growing. Prone to early metastasis; treatment strategies differ from those for adenocarcinoma.
Typical symptoms and signs of colorectal cancer
1. Blood in stool
Bloody stool is the most common symptom of colorectal cancer; the blood may be mixed with the stool (appearing dark red) or coat the surface (appearing bright red), often leading to a mistaken diagnosis of hemorrhoids and a delay in seeking medical attention.
2. Change in bowel habits
Increased or decreased bowel movement frequency, alternating diarrhea and constipation, and a marked sensation of tenesmus; symptoms persisting for more than three weeks warrant vigilance.
3. Abdominal pain and distension
Persistent dull or distending abdominal pain occurs, accompanied by an abdominal mass; intestinal obstruction may cause paroxysmal cramping, abdominal distension, and cessation of flatus and stool passage.
4. Anemia and weight loss
Chronic tumor bleeding leads to iron-deficiency anemia, manifesting as pallor, fatigue, and dizziness, accompanied by unexplained weight loss and loss of appetite.
5. Abdominal mass
Right-sided colon cancer often presents initially with an abdominal mass; a hard mass with an irregular surface can be palpated in the right lower quadrant.
6. Intestinal obstruction
Left-sided colon cancer frequently causes luminal narrowing leading to obstruction; clinical manifestations include abdominal distension, abdominal pain, vomiting, and cessation of passing gas and stool, requiring urgent management.
Diagnostic methods for colorectal cancer?
1. Colonoscopy
Colonoscopy is the gold standard for diagnosing colorectal cancer; it allows for direct visualization of the entire colon and rectal mucosa, the detection of lesions, and the performance of biopsies to obtain a pathological diagnosis.
2. Fecal occult blood test
The fecal occult blood test is a common method for colorectal cancer screening; a positive result indicates gastrointestinal bleeding, requiring further colonoscopy to determine the cause.
3. Contrast-enhanced CT scan
Contrast-enhanced abdominal CT allows for the assessment of tumor location, size, depth of invasion, lymph node metastasis, and distant organ metastasis; it is the primary modality for clinical staging.
4. Tumor marker
CEA and CA19-9 are commonly used serological markers; the extent of their elevation correlates with tumor burden, and they can be used for auxiliary diagnosis and postoperative monitoring for recurrence.
5. Digital rectal examination
Digital rectal examination is a simple and effective diagnostic method capable of detecting rectal tumors within 7–8 cm of the anal verge; it is a mandatory initial examination for suspected rectal cancer.
6. Pelvic MRI
Pelvic MRI clearly visualizes the relationship between rectal cancer and surrounding tissues and assesses the distance from the lower tumor margin to the anal verge, which is crucial for planning sphincter-sparing surgery.
Colorectal Cancer Treatment Methods?
1. Surgical treatment
Surgical resection is the primary treatment for colorectal cancer—including procedures such as right hemicolectomy, left hemicolectomy, and anterior resection—and requires regional lymph node dissection.
2. Laparoscopic surgery
Laparoscopic resection for colorectal cancer is minimally invasive and allows for rapid recovery; it has become a standard procedure and achieves oncological outcomes comparable to open surgery.
3. Chemotherapy
Postoperative adjuvant chemotherapy can reduce the risk of recurrence, while neoadjuvant chemotherapy can shrink locally advanced rectal cancer to facilitate surgery; oxaliplatin-based regimens are commonly used.
4. Targeted therapy
Targeted drugs such as bevacizumab and cetuximab can be used to treat advanced colorectal cancer; combining them with chemotherapy can prolong patient survival.
5. Immunotherapy
PD-1 inhibitors are suitable for patients with advanced colorectal cancer exhibiting high microsatellite instability (MSI-H), offering durable disease control.
6. Radiotherapy
Neoadjuvant chemoradiotherapy is the standard treatment for locally advanced rectal cancer; it reduces the rate of local recurrence and increases the success rate of anal-sphincter-preserving surgery.
7. Stoma care
Some patients require a temporary or permanent intestinal stoma postoperatively; proper stoma care is crucial for maintaining quality of life and preventing complications.
8. Follow-up monitoring
Postoperative follow-up involving regular colonoscopy, abdominal CT, and tumor marker testing is essential to monitor for recurrence and metachronous multiple primary cancers.
Conclusion
Colorectal cancer is a malignancy with a rapidly rising incidence rate in my country; early symptoms are often atypical and easily overlooked.Early detection via colonoscopy screening and comprehensive treatment—primarily surgery—help improve patient prognosis and quality of life.
