Rectal cancer

Disease Description (Causes and Symptoms)

• Definition summary: Rectal cancer is a malignant tumor (mostly adenocarcinoma) that mainly arises from the mucosa of the rectum (the last approximately 15 cm of the large intestine).
• Main causes/risk factors: A high-fat diet (especially red meat) and low-fiber diet, calcium and vitamin D deficiency, smoking, heavy alcohol consumption, obesity, lack of exercise, inflammatory bowel disease (ulcerative colitis and Crohn’s disease), colorectal polyps (adenomas), family history (familial adenomatous polyposis and Lynch syndrome), and age (mainly 50 years or older).
• Pathophysiology summary: Dysplasia arising in glandular cells of the mucosa gradually becomes invasive, progressing from the mucosal layer → submucosa → muscular layer → serosa, and may spread to surrounding organs (bladder, vagina, and nerves) and distant organs such as the liver and lungs through local invasion and lymphatic or hematogenous metastasis.
• Main symptoms: Asymptomatic (early stage) or bloody stool, changes in bowel habits (constipation, diarrhea, or narrow stools), a feeling of incomplete evacuation, pain during bowel movements, abdominal pain, weight loss, and symptoms related to anemia (fatigue). It is difficult to distinguish it from conditions such as hemorrhoids based on symptoms alone.

Treatment Methods

• Diagnostic evaluation: Digital rectal examination, colonoscopy (confirmation by biopsy), pelvic MRI (local staging), abdominal and chest CT (distant metastasis), PET/CT (selectively), and blood tumor markers (CEA), which are used for treatment follow-up rather than as an aid to diagnosis. If hereditary disease is suspected, genetic testing (e.g., MMR genes and APC) may be considered.
• Surgery: Radical resection is the basic treatment. Depending on the tumor location and stage, anus-preserving surgery (such as low anterior resection) may be performed; when anal preservation is not possible, abdominoperineal resection with a permanent stoma may be required. Minimally invasive surgery (laparoscopic or robotic) is possible.
• Chemotherapy:
  • Adjuvant therapy: Intended to prevent recurrence after surgery (used according to the stage and pathological findings). Common regimens include 5-FU-based regimens (such as FOLFOX and CAPOX).
  • Systemic therapy (metastatic disease): 5-FU-based therapy ± targeted therapy (anti-VEGF agents such as bevacizumab; anti-EGFR agents such as cetuximab or panitumumab in patients with RAS wild-type tumors), immune checkpoint inhibitors (in patients with microsatellite instability-high (MSI-H)/dMMR tumors), and others.
• Radiation therapy:
  • Locally advanced rectal cancer (e.g., T3–4 or lymph-node-positive): Preoperative (neoadjuvant) radiation or concurrent chemoradiation therapy can reduce the tumor and improve the possibility of preserving anal function. It is rarely used alone.
• Endoscopic resection: Early lesions limited to the mucosa or submucosa (when there is no vascular or lymphatic invasion) can be treated with endoscopic resection.
• Lifestyle management during/after treatment: Eat a balanced diet (increase fiber intake and limit animal fat), stop smoking and limit alcohol, exercise regularly, and manage weight. Education on temporary or permanent stoma care is necessary after surgery.
• Prognosis and follow-up: Even after radical resection, recurrence is possible in 20–50% of cases (mostly within 3–5 years after surgery). Surveillance is performed through regular imaging tests, CEA testing, colonoscopy, and other examinations.

Checklist Before an Outpatient Visit (Including Example Questions)

• Items/documents to bring:
  • List of currently used medications and supplements (including doses and dosing times)
  • History of allergies (including medications and anesthesia)
  • Records of previous surgeries and medical history (especially colorectal diagnoses and surgeries)
  • Previous test results (colonoscopy findings and biopsy reports, CT/MRI/PET images or radiology reports)
  • Family history (colorectal cancer, colorectal polyps, and hereditary cancers)
  • Symptom records (dates and amount of bleeding, when changes in bowel habits began, weight changes, pain, etc.)
• Examples of questions to prepare for the outpatient visit (useful for patients to check in advance):
  • Recent weight change (kg) and whether anemia symptoms (dizziness or fatigue) are present
  • Frequency and form of bowel movements, characteristics of blood, and time of day
  • Changes in urination or sexual function (important for preoperative counseling)
• Other: The hospital will provide separate instructions regarding fasting or stopping medications before possible tests.

General Example Questions to Ask the Doctor

• "What is my current stage and prognosis (survival rate and risk of recurrence)?"
• "What is the recommended treatment sequence (surgery → adjuvant therapy / neoadjuvant chemotherapy and radiation therapy → surgery, etc.)?"
• "What are the main side effects of each treatment, and what precautions should I take in daily life?"
• "Is it possible to preserve the anus (sphincter) during surgery, and how likely is a permanent stoma?"
• "What schedule will be used for follow-up tests (CEA, imaging, and colonoscopy)?"

Examples of Disease-Specific Questions

• "Given the stage of my rectal cancer, do you recommend radiation and chemotherapy before surgery (neoadjuvant concurrent therapy), and can this increase the possibility of preserving anal function?"
• "I have a family history. Do you recommend genetic testing for hereditary colorectal cancer (Lynch syndrome or familial adenomatous polyposis)? When should the test be performed, and what does it mean?"