Colorectal Cancer - Early Signs, Risk Factors, Diagnosis, and Treatment Explained

Overview: What Is Colorectal Cancer?

Colorectal cancer starts in the large intestine (colon) or the rectum, which are the final parts of the digestive system. Together, these cancers are referred to as colorectal cancer.

This cancer is one of the most common types worldwide. In the United States, colorectal cancer is the third most common cancer diagnosed in both men and women. Colorectal cancer is serious, but the good news is that with regular screening and timely treatment, it is highly preventable and often curable.

Screening tests such as colonoscopy can find precancerous growths (polyps) before they turn into cancer. Early detection improves survival rates significantly, making regular screening a key part of prevention.

What Are the Types of Colorectal Cancer?

Colorectal cancer is not a single disease. There are several subtypes, but most cases fall into these categories:

• Adenocarcinoma: The most common type, making up about 95% of cases. It starts in the glandular cells that produce mucus in the colon or rectum.
• Mucinous adenocarcinoma: A subtype of adenocarcinoma where the tumor contains mucus, which can make it harder to treat.
• Signet-ring cell carcinoma: A rare and aggressive form that grows and spreads quickly.
• Gastrointestinal stromal tumors (GISTs): Rare tumors that begin in the connective tissue of the digestive tract.
• Carcinoid tumors: Begin in hormone-producing cells of the intestine.
• Lymphomas: Very rare; start in the immune cells of the colon or rectum.

Most patients are diagnosed with adenocarcinoma, but knowing the subtype helps doctors tailor treatment.

What Are the Causes of Colorectal Cancer?

Doctors do not always know the exact cause of colorectal cancer, but certain changes in DNA (mutations) make cells grow uncontrollably. These changes may be inherited or acquired during life.

Possible causes include:

• Genetic mutations that activate oncogenes or disable tumor-suppressor genes.
• Chronic inflammation in the colon (from conditions like ulcerative colitis or Crohn’s disease).
• Polyps that develop into cancer if left untreated.

What Are the Risk Factors for Colorectal Cancer?

Certain factors increase the risk of colorectal cancer:

Lifestyle Risk Factors

• Unhealthy diet – High in red meat, processed meat, and low in fiber.
• Lack of physical activity – Sedentary lifestyle raises risk.
• Obesity – Increases the likelihood of cancer and worsens outcomes.
• Smoking – Linked to higher risk of polyps and cancer.
• Alcohol consumption – Heavy drinking contributes to risk.

Medical Risk Factors

• Personal history of colorectal polyps or previous cancer.
• Inflammatory bowel disease (Crohn’s or ulcerative colitis).
• Type 2 diabetes – Associated with increased risk.

Genetic and Family History

• Hereditary syndromes like Lynch syndrome or Familial Adenomatous Polyposis (FAP).
• Family history – Having close relatives with colorectal cancer raises risk.

Age and Other Factors

• Age over 50 (though cases in younger adults are rising).
• African American ethnicity – Higher incidence and worse outcomes.

What Are the Symptoms of Colorectal Cancer?

Colorectal cancer often develops silently at first. Early signs may be mild and easy to overlook.

Common early symptoms include:

• Changes in bowel habits (diarrhea, constipation, or narrower stools).
• Blood in the stool (bright red or dark).
• Unexplained abdominal discomfort, cramps, or gas.
• Feeling that the bowel does not empty completely.
• Fatigue and weakness.

Advanced symptoms may include:

• Unexplained weight loss.
• Persistent abdominal pain.
• Severe anemia (low red blood cells).
• Bowel obstruction (blockage).

Many of these symptoms can also be caused by non-cancer conditions like piles or infections. But if they persist, it’s best to get checked early. If you notice these symptoms, seek medical advice promptly. Early treatment offers the best chance of cure.

How Is Colorectal Cancer Diagnosed?

Doctors use a series of tests to confirm colorectal cancer:

• Colonoscopy: A long, flexible tube with a camera, called a colonoscope, is inserted through the anus to examine the entire colon and rectum for polyps or cancerous growths.
• Sigmoidoscopy: A shorter, flexible tube is used to examine the lower part of the colon (sigmoid colon) and rectum.
• Biopsy: A tissue sample, or biopsy, is removed during a colonoscopy or sigmoidoscopy for laboratory examination to confirm the presence of cancer cells.
• Stool Tests: Tests that check stool for hidden blood (fecal occult blood test) or altered DNA (stool DNA test) can indicate potential problems.
• Digital Rectal Exam: A doctor inserts a gloved, lubricated finger into the rectum to feel for lumps or other abnormalities.
• Imaging Tests: CT / MRI creates detailed cross-sectional images of the body to help detect the extent of the cancer and if it has spread. PET Scan uses a radioactive tracer to identify areas of increased metabolic activity, often combined with a CT scan (PET-CT) to help determine if the cancer has spread.
• Molecular Testing: After a biopsy, tests may be done to identify specific gene mutations, such as microsatellite instability (MSI) or changes in mismatch repair (MMR) genes, which can help determine the best treatment. These tests can help doctors choose targeted medicines or immunotherapy, which may be more effective in certain patients.
• Blood Tests: While not used for diagnosis, blood tests can check for anemia (low red blood cell count), which is common in bowel cancer, and evaluate liver and kidney function.

These tests help doctors confirm diagnosis, assess the stage, and plan treatment.

Staging of Colorectal Cancer

Staging describes how advanced the cancer is, while grading describes how abnormal the cells look under a microscope.

Stages of Colorectal Cancer

• Stage 0 (Carcinoma in situ): Abnormal cells limited to the inner lining.
• Stage I: Cancer has grown into the colon wall but not spread.
• Stage II: Cancer has grown through the colon wall but not reached lymph nodes.
• Stage III: Cancer has spread to nearby lymph nodes.
• Stage IV: Cancer has spread (metastasized) to distant organs such as the liver or lungs.

Staging is critical because it guides treatment decisions and helps predict prognosis. Staging helps doctors decide whether surgery alone is enough, or whether chemotherapy, radiation, or advanced therapies should also be used.

What Are the Treatment Options for Colorectal Cancer?

Treatment depends on the stage, location, and type of cancer, as well as overall health.

Surgery:

• Polypectomy and Endoscopic Mucosal Resection (EMR): For very small cancers contained within polyps, these minimally invasive procedures can remove the entire cancerous polyp during a colonoscopy.
• Laparoscopic Surgery: A minimally invasive approach that uses small incisions to remove polyps or tumors, often including nearby lymph nodes.
• Bowel Resection: The removal of the cancerous part of the colon or rectum along with a portion of the surrounding healthy tissue and lymph nodes. A colostomy or ileostomy (an opening to the outside of the body for stool) may be performed, which can be temporary.

Medical Treatments:

• Chemotherapy: Uses powerful drugs to kill cancer cells, often after surgery.
• Targeted therapy: Blocks specific proteins or genes that fuel cancer growth (e.g., bevacizumab, cetuximab).
• Immunotherapy: Boosts the immune system to fight cancer, effective in some advanced cases.

Radiation Therapy: 

• Used especially in rectal cancer to shrink tumors before surgery or destroy remaining cancer cells afterward.

What Is the Prognosis for Colorectal Cancer?

The prognosis for colorectal cancer depends on the stage, age, general health, and how well the cancer responds to treatment.

5-year survival rates (US data):

• Stage I: about 90%
• Stage II: about 70–80%
• Stage III: about 50–70%
• Stage IV: about 15%

Early detection greatly improves survival. Advances in surgery, targeted therapy, and immunotherapy continue to improve outcomes.

Screening and Prevention of Colorectal Cancer

Screening is one of the most effective ways to prevent colorectal cancer.

Guidelines (American Cancer Society):

• Begin regular screening at age 45 for people at average risk.
• Continue until at least age 75.
• Screening methods: colonoscopy (every 10 years), stool tests (FIT, FOBT), sigmoidoscopy, or CT colonography.
• People at higher risk (family history, genetic conditions, inflammatory bowel disease) may need screening earlier and more frequently.

Think of a colonoscopy as a ‘preventive repair.’ It can remove polyps before they turn into cancer, which is why it’s such a powerful tool.

For International Patients

People from around the world come to Apollo Hospitals for the treatment of colorectal cancer. Our international patient services team will guide you all the way from seeking the first virtual connect all the way to treatment in India and then returning home post treatment.

Services include:

• Medical opinions and scheduling
  • Pre-arrival medical review of reports and imaging.
• Travel and logistics
  • Assistance with visa invitation letters, airport transfers, and nearby accommodation options.
  • Dedicated international patient coordinators to guide through each step.
• Language and cultural support
  • Interpreter services in multiple languages.
  • Clear, simple explanations at every stage with written care plans.
• Financial coordination
  • Transparent treatment estimates and packages when possible.
  • Support with international payment methods and insurance coordination.
• Continuity of care
  • Shared records, imaging, and treatment summaries for home doctors.
  • Telemedicine follow-ups for convenience after returning home.

Frequently Asked Questions (FAQs)

1. What is the survival rate of colorectal cancer?

Survival depends on the stage. Early-stage colorectal cancer has a 5-year survival rate above 90%, while advanced stages have lower rates. Early screening is key.

2. What are the side effects of treatment?

Side effects vary by treatment. Surgery may cause pain or bowel changes. Chemotherapy can cause fatigue, nausea, and hair loss. Targeted and immunotherapy may cause skin changes or immune-related side effects. Radiation can cause diarrhea or irritation. Most side effects improve after treatment. Doctors now use supportive medicines to make these side effects much more manageable than in the past.

3. Can colorectal cancer come back after treatment?

Yes. Recurrence can happen months or years later. Regular follow-up appointments, blood tests, and scans help detect it early if it returns.

4. How long is recovery after colorectal cancer surgery?

Recovery depends on the type of surgery. Minimally invasive surgery may require 2–4 weeks, while major surgery may take 6–8 weeks. Full recovery also depends on overall health.

5. Is colorectal cancer curable?

Yes, especially if detected early. Surgery can often cure stage I and II cancers. Even advanced cases may be controlled with modern treatments. Even if cure isn’t possible, modern treatments can help many patients live longer and with a better quality of life.

6. What is the cost of colorectal cancer treatment?

Costs vary by country, hospital, and treatment type. In India at Apollo, treatment may be significantly more affordable compared to the US or Europe, while still offering advanced care. International patients can request detailed cost estimates before travel.

7. Can lifestyle changes reduce the risk?

Yes. Eating a high-fiber diet, exercising regularly, limiting alcohol, quitting smoking, and maintaining a healthy weight can lower your risk.