Colorectal cancer is a common yet potentially life-threatening condition that begins in the colon or rectum—key parts of the large intestine. It often starts as small, noncancerous growths called polyps that can turn cancerous over time. While it is most often diagnosed in older adults, the rate of colorectal cancer is steadily rising among younger individuals, making early awareness and screening more important than ever.

Types

There are several types of colorectal cancer, each defined by the type of cell where the cancer begins:

  • Adenocarcinoma: This is the most common type, accounting for over 90% of cases. It begins in the mucus-producing glands that line the colon and rectum.
  • Carcinoid tumors: These originate in hormone-producing cells in the intestines and grow slowly.
  • Gastrointestinal stromal tumors (GISTs): Rare in the colon, these start in the interstitial cells of Cajal found in the GI tract wall.
  • Lymphoma: A rare type that typically starts in the lymph nodes but may appear in the colon.
  • Sarcoma: Another rare form that arises in the muscle layer or connective tissues of the colon or rectum.

Symptoms

Colorectal cancer may not produce symptoms in its early stages, which is why routine screening is crucial. As the disease progresses, the following signs may occur:

  • Changes in bowel habits (diarrhea, constipation, or narrow stools)
  • Blood in the stool (bright red, dark brown, or black)
  • Persistent abdominal discomfort (cramping, gas, or pain)
  • A feeling that the bowel doesn’t empty completely
  • Weakness or fatigue
  • Unexplained weight loss

If you experience any of these symptoms, consult a healthcare provider promptly.

Causes

Colorectal cancer typically develops when mutations occur in the DNA of cells in the colon or rectum. These genetic changes can cause normal cells to grow uncontrollably, forming tumors. Most often, the disease starts as small polyps—benign growths on the lining of the colon or rectum—that can gradually become cancerous if left untreated.

The exact cause of these mutations is still being studied, but certain biological and environmental factors play a role. Long-term exposure to inflammation (such as with inflammatory bowel diseases), lifestyle habits, and inherited genetic syndromes (like Lynch syndrome) can all increase the likelihood of these changes occurring. Some mutations may be spontaneous, while others are passed down from parents.

Diet and gut health also appear to contribute. A lack of fiber and an excess of red and processed meats may lead to changes in the gut microbiome, fostering an environment more favorable to cancer development. Meanwhile, oxidative stress, chronic inflammation, and exposure to carcinogens in tobacco or alcohol can further damage DNA in cells.

Although we don’t fully understand why certain individuals develop colorectal cancer and others don’t, a combination of genetic predisposition, lifestyle factors, and environmental exposures are likely at play. Understanding these factors may eventually help develop more personalized prevention strategies.

Risk Factors

Several factors may increase your risk of developing colorectal cancer:

  • Age: Risk increases after age 45
  • Diet: High intake of red or processed meats and low consumption of fiber, fruits, and vegetables
  • Personal or family history of colorectal cancer or polyps
  • Inflammatory bowel disease (such as Crohn’s disease or ulcerative colitis)
  • Genetic conditions: Lynch syndrome, familial adenomatous polyposis (FAP)
  • Obesity
  • Sedentary lifestyle
  • Smoking and heavy alcohol use

Identifying and managing these risks can aid in early detection and prevention.

Diagnosis

Diagnosis typically starts with a review of your medical history and a physical exam, often followed by a digital rectal exam to check for abnormalities.

Key diagnostic tools include:

  • Colonoscopy: A flexible tube with a camera is inserted through the rectum to examine the entire colon and remove any suspicious polyps.
  • Biopsy: Samples of tissue are collected during colonoscopy for laboratory analysis.
  • Stool tests: These may detect hidden blood or altered DNA in stool samples.
  • Imaging scans: CT, MRI, and ultrasound help determine the location and extent of cancer.
  • Blood tests: A complete blood count (CBC), liver function tests, and tumor markers like CEA (carcinoembryonic antigen) can help assess overall health and detect signs of cancer.

Staging

Staging is a crucial part of understanding how far colorectal cancer has progressed and planning the appropriate treatment. It describes the size of the tumor, how deeply it has invaded the intestinal wall, and whether it has spread to lymph nodes or distant organs.

  • Stage 0: This is the earliest stage, also known as carcinoma in situ. Cancer is confined to the innermost lining of the colon and hasn’t grown beyond it.
  • Stage I: The cancer has grown into the inner layers of the colon or rectum but hasn’t spread outside the wall.
  • Stage II: Cancer has spread through the wall of the colon or rectum but hasn’t reached nearby lymph nodes.
  • Stage III: The cancer has moved to nearby lymph nodes but not to distant organs.
  • Stage IV: Cancer has metastasized to distant organs such as the liver, lungs, or peritoneum.

In addition to stages, doctors may use the TNM classification system:

  • T (Tumor): Describes the size and extent of the main tumor.
  • N (Node): Describes the number and location of lymph nodes involved.
  • M (Metastasis): Indicates whether the cancer has spread to other parts of the body.

Staging is essential for choosing the best treatment plan, estimating prognosis, and comparing results across clinical studies. Advanced imaging and biopsy results are often combined to assign a final stage.

Treatment

Treatment depends on the stage, location, and overall health of the patient. Common options include:

Surgery

  • Polypectomy or local excision: For early-stage cancer within polyps
  • Colectomy: Removal of part or all of the colon
  • Colostomy or ileostomy: Creating an opening in the abdomen to divert waste, used in some cases

Chemotherapy

Used before or after surgery to shrink tumors or kill remaining cancer cells.

Radiation Therapy

Often used for rectal cancer, either before surgery to reduce tumor size or after surgery to prevent recurrence.

Targeted Therapy

Medications that specifically target cancer cell mechanisms such as VEGF or EGFR.

Immunotherapy

Helps boost the immune system’s ability to attack cancer cells, particularly in advanced stages or in cases involving genetic mutations.

A multidisciplinary approach combining these treatments may provide the best results.

Prevention

Colorectal cancer is one of the most preventable cancers when detected early. You can lower your risk by:

  • Getting regular screenings starting at age 45 (or earlier with risk factors)
  • Eating a diet rich in fruits, vegetables, and whole grains
  • Limiting red and processed meats
  • Maintaining a healthy weight
  • Exercising regularly
  • Avoiding tobacco and limiting alcohol
  • Discussing genetic testing if you have a family history

Talk to your healthcare provider about which screening tests—such as colonoscopy, fecal occult blood tests, or sigmoidoscopy—are right for you.

Related Conditions

Colorectal cancer is often interconnected with other medical conditions, either as a consequence of the disease or due to shared risk factors.

  • Bowel obstruction: A tumor can grow large enough to block the passage of stool, leading to bloating, pain, constipation, and even vomiting. Severe obstructions may require emergency surgery.
  • Anemia: Chronic bleeding from the colon or rectum may cause a slow drop in red blood cell count, resulting in fatigue, weakness, and pale skin. This type of anemia is often a clue in diagnosing colorectal cancer.
  • Type 2 diabetes: Individuals with diabetes may face a higher risk of colorectal cancer, likely due to overlapping factors like obesity and inflammation. Also, insulin resistance may fuel tumor growth.
  • Hypertension: High blood pressure has been associated with a higher likelihood of colorectal cancer recurrence, though the mechanisms are still under investigation.
  • Liver dysfunction: If colorectal cancer spreads to the liver, it can impair liver function, which is vital for metabolism and detoxification.

Recognizing and managing these related conditions is essential for comprehensive cancer care. Treating them in tandem with colorectal cancer may improve outcomes and quality of life.

Living With Colorectal Cancer

A diagnosis of colorectal cancer can bring emotional and physical challenges, but many people live long and meaningful lives with proper care.

Coping Strategies

  • Journaling and emotional expression
  • Engaging in relaxation techniques like meditation or yoga
  • Staying active and maintaining routines
  • Seeking support from family, friends, or cancer groups

Survival Rates

  • For localized colon cancer: 5-year survival is ~91%
  • For localized rectal cancer: 5-year survival is ~90%
  • When cancer spreads to distant organs: survival drops to 13–17%

These statistics highlight the importance of early detection and continued care.

Disclaimer: This article is for educational purposes only and does not replace professional medical advice. Please consult a licensed healthcare provider for diagnosis or treatment.