What is Colorectal Cancer?
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Understanding the Disease — and How to Take Action
Colorectal cancer (CRC) begins in the colon or rectum, the final parts of the digestive system. It is the second leading cause of cancer deaths in the United States — but it doesn’t have to be. CRC is also one of the most preventable and treatable cancers when found early (CDC, 2025). Screening, awareness, and timely care save lives every day.
CRC grows slowly, often starting as a small, noncancerous polyp. Over time, some polyps can turn into cancer. This long growth period is why screening is such a powerful tool: it allows clinicians to find and remove polyps before they become life-threatening.
Symptoms and Warning Signs
Colorectal cancer doesn’t always make itself known right away. Many people feel fine until the disease is more advanced. When symptoms do appear, they may include:
- Blood in the stool (bright red or dark)
- Persistent changes in bowel habits (diarrhea, constipation, or narrowing of the stool)
- Ongoing abdominal pain, discomfort, or cramping
- Unexplained weight loss
- Fatigue or weakness
- Feeling like you cannot fully empty your bowels
These symptoms don’t always mean cancer, but they always deserve attention. If you notice changes that feel unusual for you, talk to your healthcare provider.
Stages of Colorectal Cancer
Doctors use stages (0 through IV) to describe how far CRC has grown or spread:
- Stage 0: Cancer is only in the inner lining of the colon or rectum.
- Stage I: Cancer has grown slightly into the colon or rectal wall.
- Stage II: Cancer has grown deeper through the wall.
- Stage III: Cancer has spread to nearby lymph nodes.
- Stage IV: Cancer has spread to distant organs (metastatic disease).
Staging helps guide treatment decisions and gives patients and caregivers clarity about what comes next.
Treatment by Stage
Most oncologists will follow the NCCN Guidelines when designing your treatment plan. Learn more about how oncologists design treatments by stage and the NCCN Guidelines.
Why Early Detection Matters
Colorectal cancer is highly preventable and more treatable when caught early. Screening tests can:
- Find and remove precancerous polyps before they turn into cancer.
- Detect cancer at an early stage, when treatment is most effective.
The U.S. Preventive Services Task Force (USPSTF) recommends screening for:
- Adults ages 45–75
- Adults ages 76–85, based on personal health history and provider guidance (USPSTF, 2021)
Since lowering the recommended age from 50 to 45, research shows a sharp rise in early-stage diagnoses among people ages 45–49 — clear proof that screening is saving lives (Stat News, 2025).
Colorectal Cancer Screening
Several safe and effective screening tests are available, including:
- Colonoscopy
- Stool-based tests
- Flexible sigmoidoscopy or CT colonography
Talk with your healthcare provider about which test is right for you based on your age, risk factors, and medical history.
Colon Cancer vs Rectal Cancer
Although grouped together as colorectal cancer, colon cancer and rectal cancer have important differences.
Where They Start
- Colon cancer begins in the large intestine (colon).
- Rectal cancer begins in the rectum, the final segment of the digestive tract.
How They Differ
Rectal cancer often requires a more complex treatment pathway because of its location in a confined space surrounded by critical structures. Treatment may include a combination of:
- Chemotherapy
- Radiation therapy
- Surgery
- Targeted or precision approaches
What They Share
- Many of the same risk factors
- Similar warning signs
- Screening pathways that detect both
- Strong prevention potential through polyp removal
Understanding these distinctions empowers patients to ask informed questions and pursue the best treatment plan.
Common Questions About Colorectal Cancer
What causes colorectal cancer?
CRC develops from a mix of genetic, environmental, and lifestyle factors. Family history, inflammatory bowel disease, diet, smoking, obesity, and age all influence risk — but CRC can affect anyone.
Is colorectal cancer rising in young adults?
Yes. Early-age onset CRC (diagnosed before age 50) is increasing at an alarming rate. Researchers are actively studying contributing factors, including microbiome changes, diet, and environmental exposures.
How often should I get screened?
Frequency depends on your chosen test and your risk level. Colonoscopies are often repeated every 10 years, while stool tests may be done annually. High-risk patients may need earlier or more frequent screening.
Is colorectal cancer hereditary?
About one-third of cases involve family history of CRC or polyps. Around 5–10% are linked to inherited syndromes such as Lynch syndrome or FAP. Genetic counseling can help clarify your risk.
What are polyps?
Polyps are growths on the lining of the colon or rectum. Most are harmless, but some can turn into cancer over time. Removing polyps prevents cancer before it starts.
Can colorectal cancer be cured?
When caught early, many colorectal cancers are highly curable. Even advanced CRC has expanding treatment options, including precision medicine, immunotherapies, and clinical trials.
What are the survival rates of colorectal cancer?
One of the first questions many patients ask after receiving a colon or rectal cancer diagnosis is, “How long will I live?” This question is getting at something called the colorectal cancer survival rate.