Overview
Colorectal cancer is the third most common cancer diagnosed in both men and women. It typically starts as polyps (small growths) in the colon or rectum that can become cancerous over time. Screening is effective in detecting and removing polyps before they turn cancerous.
Colorectal cancer, also known as bowel cancer, develops when cells in the colon or rectum undergo genetic changes that cause them to grow uncontrollably. The colon and rectum are parts of the large intestine, which is the final section of the digestive tract. Most colorectal cancers begin as noncancerous (benign) polyps that form on the inner lining of the colon or rectum. Over time, some of these polyps can become cancerous. Regular screening can detect polyps early and remove them before they develop into cancer, making colorectal cancer one of the most preventable and treatable forms of cancer when caught early.
Symptoms
Symptoms can include changes in bowel habits (diarrhea or constipation), blood in the stool, persistent abdominal pain, unexplained weight loss, and fatigue.
Many people with colorectal cancer experience no symptoms in the early stages, which is why screening is so important. When symptoms do occur, they may vary depending on the location and size of the tumor. Common signs and symptoms include:
- A persistent change in bowel habits, including diarrhea, constipation, or a change in the consistency of your stool
- Rectal bleeding or blood in your stool (which may appear bright red or dark and tarry)
- Persistent abdominal discomfort, such as cramps, gas, or pain
- A feeling that your bowel doesn't empty completely
- Weakness or fatigue
- Unexplained weight loss
- Narrow stools
- Iron-deficiency anemia (low red blood cell count)
Causes
Risk factors include age (over 50), a family history of colorectal cancer, inflammatory bowel disease, a diet low in fiber, high in red or processed meats, smoking, and obesity.
Colorectal cancer occurs when healthy cells in the colon or rectum develop mutations in their DNA. These mutations cause cells to grow and divide uncontrollably, eventually forming a tumor. While the exact cause of these genetic changes is not always known, several factors can increase your risk:
- Age: Risk increases significantly after age 50, though rates are rising in younger adults.
- Family history: Having a close relative with colorectal cancer increases your risk.
- Inflammatory bowel disease: Conditions like ulcerative colitis and Crohn's disease increase risk.
- Diet: A diet low in fiber and high in red and processed meats may increase risk.
- Lifestyle factors: Smoking, heavy alcohol use, obesity, and a sedentary lifestyle are linked to higher risk.
- Genetic syndromes: Conditions like Lynch syndrome and familial adenomatous polyposis (FAP) greatly increase risk.
Treatment
Treatment depends on the stage and includes surgery, radiation therapy, chemotherapy, and targeted therapy.
The treatment plan for colorectal cancer is personalized based on the stage of the cancer, its location, the patient's overall health, and other factors. Common treatment options include:
- Surgery: The primary treatment for early-stage colorectal cancer, involving removal of the tumor and surrounding tissue. This may include polypectomy, local excision, or colectomy (removal of part or all of the colon).
- Radiation therapy: Uses high-energy beams to kill cancer cells, often used for rectal cancer or to shrink tumors before surgery.
- Chemotherapy: Uses drugs to kill cancer cells, often given after surgery to reduce the risk of recurrence or for advanced cancer.
- Targeted therapy: Uses drugs that target specific proteins or genes in cancer cells, such as bevacizumab or cetuximab.
- Immunotherapy: Helps the body's immune system fight cancer, particularly effective for some advanced colorectal cancers with certain genetic markers.
When to See a Doctor
If you are 45 or older, regular screening is recommended. See a doctor if you have any persistent changes in bowel habits or blood in your stool.
You should consult a healthcare professional if you experience any of the following:
- Blood in your stool or rectal bleeding
- Persistent changes in bowel habits lasting more than a few weeks
- Unexplained abdominal pain or cramping
- Unexpected weight loss or fatigue
- A family history of colorectal cancer or polyps
- Age 45 or older, even without symptoms — regular screening is essential
If you are at increased risk due to family history or other factors, your doctor may recommend starting screening earlier or more frequently. Early detection saves lives — don't delay your screening.
