What exactly causes colorectal cancer?

Colorectal cancer is a malignant tumor of the colon (large intestine) or the rectum (the lower part of the colon). Despite significant advancements in diagnosis and treatment, colorectal cancer remains the second leading cause of cancer-related deaths for Americans. Fortunately, colorectal cancer is often preventable and highly treatable—especially when caught early. 

What Causes Colorectal Cancer?

Colorectal cancer usually begins as small growths called polyps on the inner lining of the colon or rectum. Over time, some polyps can mutate into invasive cancer. While not all polyps become cancerous, removing them during a colonoscopy can stop cancer from developing.

Certain factors can raise your risk:

  • Age: Most people diagnosed are over age 50, though it can occur in younger adults too.
  • Family history: Having a parent or sibling with colorectal cancer increases your risk.
  • Lifestyle: Diets high in red or processed meats, diets low in fiber are the largest lifestyle-related risk factors. Also lack of exercise, smoking, and heavy alcohol use are linked to higher risk.
  • Chronic conditions: Inflammatory bowel diseases like Crohn’s disease and ulcerative colitis also raise your risk.

Symptoms to Watch For

In early stages, colorectal cancer may not cause any symptoms, which is why screening is so important. When symptoms do appear, they may include:

  • Blood in your stool 
  • A change in bowel habits, particularly narrowing of stool, constipation and/or diarrhea
  • Feeling like you can't completely empty your bowels
  • Stomach pain or cramping that doesn’t go away
  • Unexplained weight loss
  • Fatigue or weakness

If you experience any of these symptoms, especially if they last more than a few days, talk to your doctor right away.

The Importance of Screening

Screening helps find colorectal cancer early, when it's easier to treat—and can even prevent cancer by removing polyps before they become invasive.

Doctors recommend starting screening for colorectal cancer at age 45 if you're at average risk. There are several screening options:

  • Colonoscopy: The Gold Standard for screening: A physician examines the inner lining of your rectum and colon with a camera attached to a flexible scope. The doctor will often remove polyps (if present) during the examination, potentially preventing the progression of benign polyps to invasive cancer.
  • Stool tests: These look for hidden blood or abnormal DNA in your stool and are done at home.
  • CT colonography: A type of imaging that takes pictures of your colon using Computed Tomography (an advanced form of X-Ray imaging).

Ask your doctor which screening method is right for you.

How to Reduce Your Risk

There’s a lot you can do to lower your risk of colorectal cancer:

  • Eat more fruits, vegetables, and whole grains
  • Limit red and processed meats
  • Get regular exercise
  • Don’t smoke
  • Drink alcohol in moderation
  • Keep a healthy weight

Treatment Options

If you're diagnosed with colorectal cancer, your treatment will depend on the stage and location of the cancer. Common treatments include:

  • Surgery: To remove the cancerous part of the colon or rectum as well as any involved lymph nodes.
  • Chemotherapy: Kills cancer cells and shrinks tumors with medicine that can treat throughout the body
  • Radiation therapy: Uses Focused high energy X-rays targeting the tumor and lymph nodes at risk to improve local control.

For most cases, surgery is the mainstay of treatment, with chemotherapy and radiation therapy being added for special circumstances or higher risk disease. 

Radiation Therapy and New Approaches for Rectal Cancer

For rectal cancer, radiation therapy is often used before surgery to shrink the tumor. This makes it easier to remove and reduces the chance of the cancer coming back.

In some cases, if the tumor responds well to chemoradiation (a combination of chemotherapy and radiation), surgery may not be needed right away. This is called a non-operative or “watch-and-wait” approach. Instead of surgery, patients are closely monitored with regular scans, exams, and colonoscopies. This can help preserve bowel function and avoid a permanent colostomy.

The Bottom Line

Colorectal cancer is serious, but it’s also highly preventable and treatable. Knowing the symptoms, getting screened, and living a healthy lifestyle can go a long way in protecting your health. Colorectal cancer requires management by a team of Gastroenterologists, Surgeons, Medical Oncologists, and Radiation Oncologists. At Mission Hope, our physicians collaborate closely, and we have strong working relationships with the other cancer treatment specialists on the Central Coast. We are dedicated to providing outstanding and tailored colorectal cancer prevention and treatment. 

Jonathan Van Wickle, MD
Board Certified Radiation Oncologist
Mission Hope Cancer Center