Colorectal cancer (also known as bowel cancer) is a malignant tumor that develops in the colon or rectum, usually arising from polyps on the intestinal wall that slowly transform over many years. It is one of the most common cancers in Hong Kong and a leading cause of cancer death, yet it is also one of the most preventable cancers—because the progression from polyp to cancer often takes five to ten years, providing ample time to interrupt the process through screening.
The good news is that when colorectal cancer is detected early, the cure rate is quite high. Understanding its causes, symptoms, and screening methods is the first step to protecting yourself and your family.
Causes and Risk Factors
The exact causes of colorectal cancer are not fully understood, but research points to several important risk factors: age (risk rises significantly after age 50), dietary habits (high fat, high red and processed meat, low fiber), lack of exercise, obesity, smoking, and excessive alcohol consumption. In addition, people with chronic inflammatory bowel diseases such as ulcerative colitis are at higher risk.
Family history is also key. If a first-degree relative has had colorectal cancer, personal risk increases; a small number of people carry inherited genetic mutations (such as Lynch syndrome or familial adenomatous polyposis) that cause the disease at a younger age. Those with a family history should discuss earlier screening with their doctor.
Common Symptoms and Warning Signs
Early colorectal cancer often has no symptoms at all, which is exactly why screening is so important. As the tumor grows, possible warning signs include: changes in bowel habits (persistent diarrhea or constipation), blood in the stool or black stools, narrower stools, persistent abdominal pain or bloating, tenesmus (a frequent urge to have a bowel movement without being able to go), and unexplained weight loss and fatigue.
These symptoms can also be caused by benign conditions such as hemorrhoids or enteritis, so there is no need to panic excessively. However, if symptoms persist for more than two to four weeks, seek medical evaluation promptly and do not self-diagnose.
Diagnosis and Staging Concepts
For screening, a fecal occult blood test is a simple first-line tool; Hong Kong also has a public colorectal cancer screening program for people aged 50 and above. If screening is positive or symptoms are suspicious, the doctor will arrange a colonoscopy, which allows direct visualization of the colon and removal of polyps or tissue sampling for laboratory testing—this is the gold standard for diagnosis.
After diagnosis, the doctor will assess the extent of the tumor using computed tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET). Staging uses the TNM system: stage I tumors are confined to the intestinal wall, stages II and III progressively invade the outer layers or lymph nodes, and stage IV indicates metastasis to distant organs such as the liver or lungs. The earlier the stage, the more treatment options are available and the better the prognosis.
Overview of Treatment Approaches
Surgery is the primary curative treatment for colorectal cancer, and early-stage patients may even undergo minimally invasive laparoscopic resection. Because of its location, rectal cancer is often treated with preoperative radiation therapy and chemotherapy to shrink the tumor and improve the chance of preserving the anal sphincter.
Stage III patients usually need adjuvant chemotherapy after surgery to reduce recurrence; metastatic (stage IV) disease is treated mainly with chemotherapy, combined with targeted therapy (such as anti-angiogenic or anti-EGFR drugs, the latter effective only if there is no RAS gene mutation) and immunotherapy (for the MSI-H subtype). Genetic testing results play an increasingly important role in late-stage treatment decisions.
Clinical Trials: One More Treatment Option
Many new drugs and new combinations—such as targeted therapies for KRAS G12C and BRAF mutations, and novel immunotherapy combinations—are first made available to patients through clinical trials. Joining a clinical trial is not a "last resort" but an opportunity to access new treatments earlier.
The CancerLink platform can match patients with ongoing colorectal cancer clinical studies in Hong Kong based on cancer type, stage, and genetic mutations; once successfully matched and enrolled, all study-related treatment costs are covered. If standard treatments have limited effectiveness, consider including clinical trials as one of the options to discuss with your doctor.
If you or a family member is facing colorectal cancer, remember: this is one of the cancer types with the fastest treatment advances, with mature options from screening and surgery to new drugs. Actively cooperating with examinations and maintaining good communication with your medical team is the best path to recovery.