Intestinal Cancer

Overview

Intestinal cancer refers to malignant tumors that develop in the intestines, including both the small intestine and large intestine (colon and rectum). This group of cancers represents some of the most common malignancies worldwide, with colorectal cancer being the third most commonly diagnosed cancer globally. The term encompasses various types of cancer that can occur throughout the digestive tract beyond the stomach.

The intestines are crucial parts of the digestive system responsible for nutrient absorption and waste elimination. The small intestine, approximately 20 feet long, is where most nutrient absorption occurs, while the large intestine (colon and rectum) processes waste and absorbs water. Cancer can develop in any part of these structures, though colorectal cancer is far more common than small intestine cancer.

Intestinal cancers typically develop from polyps (abnormal growths) that become malignant over time. Early detection through screening programs has significantly improved outcomes, as these cancers are often curable when caught in early stages. However, symptoms may not appear until the cancer has advanced, making awareness of risk factors and regular screening crucial for prevention and early treatment.

Symptoms

The symptoms of intestinal cancer can vary depending on the location, size, and stage of the tumor. Many symptoms are subtle and may be attributed to less serious conditions, which can delay diagnosis. Early-stage intestinal cancer may produce no symptoms at all.

Primary Symptoms

• Abdominal pain - Persistent cramping or discomfort
• Changes in bowel habits - Diarrhea, constipation, or alternating patterns
• Blood in stool - Bright red or dark, tarry stools
• Unintentional weight loss - Significant loss without trying
• Fatigue - Persistent tiredness and weakness
• Nausea and vomiting

Additional Symptoms

• Changes in stool consistency or appearance
• Feeling that bowel doesn't empty completely
• Iron deficiency anemia
• Bloating and abdominal distension
• Loss of appetite
• Pelvic pain (in rectal cancer)
• Jaundice (if liver involvement)
• Ascites (fluid accumulation in abdomen)
• Bowel obstruction symptoms
• Unexplained fever

Location-Specific Symptoms

• Right-sided colon cancer: Iron deficiency anemia, fatigue, occult bleeding
• Left-sided colon cancer: Changes in bowel habits, blood in stool, cramping
• Rectal cancer: Rectal bleeding, tenesmus, pelvic pain
• Small intestine cancer: Abdominal pain, nausea, vomiting, weight loss

Causes

Intestinal cancer develops through a complex process involving genetic mutations that cause normal cells to become cancerous. While the exact cause is often unknown, several factors contribute to cancer development.

Genetic Factors

• Hereditary syndromes: Lynch syndrome, familial adenomatous polyposis (FAP)
• Gene mutations: APC, KRAS, p53, PIK3CA mutations
• DNA mismatch repair defects: Microsatellite instability
• Tumor suppressor gene loss: Loss of protective genetic mechanisms

Precancerous Conditions

• Adenomatous polyps: Benign growths that can become malignant
• Inflammatory bowel disease: Crohn's disease and ulcerative colitis
• Previous colorectal cancer: History increases risk of new cancers
• Radiation exposure: Previous radiation therapy to abdomen/pelvis

Environmental and Lifestyle Factors

• Diet: High red meat, processed meat, low fiber intake
• Obesity: Increased risk, particularly for colon cancer
• Smoking: Increases risk of colorectal cancer
• Alcohol consumption: Moderate to heavy drinking
• Physical inactivity: Sedentary lifestyle

Other Contributing Factors

• Age: Risk increases significantly after age 50
• Diabetes: Type 2 diabetes increases risk
• Hormonal factors: Some hormonal influences in women
• Infection: Certain bacterial or viral infections

Risk Factors

Understanding risk factors helps identify individuals who may benefit from enhanced screening or preventive measures:

High-Risk Factors

• Age over 50: Risk doubles every decade after 50
• Family history: First-degree relative with colorectal cancer
• Personal history: Previous colorectal cancer or adenomatous polyps
• Hereditary syndromes: FAP, Lynch syndrome, Peutz-Jeghers syndrome
• Inflammatory bowel disease: Ulcerative colitis, Crohn's disease

Moderate Risk Factors

• Diet high in red/processed meat: Daily consumption increases risk
• Obesity: BMI >30, particularly abdominal obesity
• Smoking: Current or former smokers
• Heavy alcohol use: More than 3 drinks per day
• Type 2 diabetes: 30-40% increased risk

Lower Risk Factors

• Physical inactivity: Sedentary lifestyle
• Low fiber diet: Insufficient fruits and vegetables
• Low calcium intake: Inadequate dietary calcium
• Vitamin D deficiency: Low levels may increase risk

Diagnosis

Diagnosing intestinal cancer involves multiple steps, from initial assessment to staging studies. Early detection through screening is crucial for optimal outcomes.

Initial Assessment

• Medical history: Symptoms, family history, risk factors
• Physical examination: Abdominal examination, digital rectal exam
• Laboratory tests: Complete blood count, liver function tests
• Tumor markers: CEA (carcinoembryonic antigen), CA 19-9

Screening Tests

• Colonoscopy: Gold standard for colorectal cancer screening
• Flexible sigmoidoscopy: Examines lower portion of colon
• CT colonography: Virtual colonoscopy using CT imaging
• Fecal occult blood test: Detects hidden blood in stool
• Fecal immunochemical test (FIT): More specific than FOBT
• Stool DNA test: Detects genetic changes in stool samples

Diagnostic Imaging

• CT scan: Abdomen and pelvis with contrast
• MRI: Particularly useful for rectal cancer staging
• PET scan: Detects metabolically active cancer cells
• Chest X-ray/CT: Screen for lung metastases
• Ultrasound: Endorectal ultrasound for rectal cancer

Tissue Diagnosis

• Biopsy: Tissue sample obtained during colonoscopy
• Histopathology: Microscopic examination of tissue
• Immunohistochemistry: Protein expression analysis
• Molecular testing: Genetic analysis for targeted therapy

Treatment Options

Treatment of intestinal cancer depends on the type, location, stage, and patient factors. A multidisciplinary approach involving surgeons, oncologists, and radiation oncologists is typically employed.

Surgical Treatment

• Polypectomy: Removal of polyps during colonoscopy
• Local excision: Removal of small, early-stage tumors
• Segmental resection: Removal of affected intestinal segment
• Hemicolectomy: Removal of right or left half of colon
• Low anterior resection: Rectal cancer surgery preserving sphincter
• Abdominoperineal resection: Removal of rectum and anus
• Liver resection: For isolated liver metastases

Chemotherapy

• Adjuvant chemotherapy: After surgery to prevent recurrence
• Neoadjuvant chemotherapy: Before surgery to shrink tumors
• Palliative chemotherapy: For advanced disease symptom control
• Common regimens: FOLFOX, FOLFIRI, CAPOX
• Agents: 5-fluorouracil, oxaliplatin, irinotecan, capecitabine

Targeted Therapy

• Anti-EGFR therapy: Cetuximab, panitumumab (for KRAS wild-type)
• Anti-VEGF therapy: Bevacizumab, ziv-aflibercept
• Multi-kinase inhibitors: Regorafenib for refractory disease
• BRAF inhibitors: For BRAF-mutated tumors

Radiation Therapy

• Neoadjuvant radiation: For rectal cancer before surgery
• Adjuvant radiation: After surgery for high-risk cases
• Palliative radiation: For pain relief and symptom control
• Stereotactic radiation: Precise radiation for oligometastatic disease

Immunotherapy

• Checkpoint inhibitors: For microsatellite instability-high tumors
• Pembrolizumab: FDA-approved for MSI-H colorectal cancer
• Nivolumab: Alternative checkpoint inhibitor option

Supportive Care

• Nutritional support: Dietary counseling and supplements
• Pain management: Multimodal approach to pain control
• Ostomy care: Education and support for colostomy patients
• Psychological support: Counseling and support groups

Prevention

While not all intestinal cancers can be prevented, many cases can be avoided through lifestyle modifications and screening programs:

Primary Prevention

• Healthy diet: High fiber, fruits, vegetables; limit red/processed meat
• Regular exercise: At least 150 minutes moderate activity weekly
• Maintain healthy weight: BMI 18.5-24.9
• Limit alcohol: No more than 1-2 drinks per day
• Don't smoke: Smoking cessation reduces risk
• Calcium and vitamin D: Adequate intake may be protective

Secondary Prevention (Screening)

• Average risk: Begin screening at age 45-50
• High risk: Earlier and more frequent screening
• Family history: Start 10 years before youngest affected relative
• Regular colonoscopy: Every 10 years if normal
• Annual FIT testing: Alternative to colonoscopy

Chemoprevention

• Aspirin: May reduce risk in some high-risk individuals
• NSAIDs: Potential protective effect, but with risks
• Statins: Some evidence of protective benefit
• Hormone replacement: May affect risk in women

When to See a Doctor

Seek Immediate Medical Attention If:

• Severe abdominal pain with vomiting
• Signs of bowel obstruction
• Significant rectal bleeding
• Signs of perforation (severe pain, fever, rigid abdomen)
• Severe dehydration or electrolyte imbalance

Schedule Medical Consultation For:

• Screening: Age-appropriate cancer screening
• Persistent symptoms: Changes in bowel habits >2 weeks
• Blood in stool: Any visible or occult blood
• Unexplained weight loss: >5% body weight in 6 months
• Family history: Genetic counseling and early screening
• Iron deficiency anemia: Unexplained anemia in adults

Related Conditions

• Colorectal Polyps
• Inflammatory Bowel Disease
• Lynch Syndrome
• Familial Adenomatous Polyposis
• Iron Deficiency Anemia
• Bowel Obstruction
• Liver Metastases

References

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4. Bray F, Ferlay J, Soerjomataram I, et al. Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin. 2018;68(6):394-424.
5. Wolf AMD, Fontham ETH, Church TR, et al. Colorectal cancer screening for average-risk adults: 2018 guideline update from the American Cancer Society. CA Cancer J Clin. 2018;68(4):250-281.