What Is Colorectal Cancer?

Colorectal cancer starts in the colon or rectum. Symptoms include blood in the stool, changes in bowel habits, abdominal pain, and unexplained weight loss.

Anyone can develop colorectal cancer, but it's most common in men. The risk of developing colorectal cancer increases as you age. Other risk factors include smoking, drinking alcohol, or having a family history of the disease.

The earlier colorectal cancer is detected and treated, the better the outcome. Experts recommend routine screening for colorectal cancer starting at age 45 or even sooner for those with risk factors. The earlier colorectal cancer is detected and treated, the better the outcome.

Colorectal cancer is the third most common cancer diagnosed in men and women in the U.S. The rate of colorectal cancer cases in the U.S. has been on the rise among younger adults.

Types of Colorectal Cancer

There are different types of colorectal cancers, including:

• Adenocarcinoma: This type makes up more than 90% of all colorectal cancer diagnoses. Cancer begins in mucus-making cells lining the colon and rectum.
• Carcinoid tumor: This starts in hormone-producing cells in the intestines.
• Gastrointestinal stromal tumor (GIST): Cancer cells develop in interstitial cells of Cajal, located in the wall of the gastrointestinal (GI) tract. These tumors are rarely found in the colon.
• Lymphoma: This immune system cancer usually begins in the lymph nodes. Lymphoma is a rare type of GI tumor.
• Sarcoma: This rare type of colorectal cancer often arises from smooth muscle cells.

Colorectal Cancer Symptoms

Colorectal cancer may not cause symptoms, especially early in the disease. This is why routine screening is so important.

It's important to see a healthcare provider right away if you have colorectal cancer symptoms. These include:

• A change in bowel habits (e.g., diarrhea or constipation)
• A feeling that your bowel has not emptied completely
• Abdominal pain
• Blood on or in your stool that appears bright red, dark brown, or black
• Unexplained weight loss
• Weakness or fatigue

What Causes Colorectal Cancer?

Colorectal cancer is a cancer of the colon or rectum. The colon (large intestine) absorbs water from undigested food, and the rectum collects and holds stool. Colorectal cancer often begins as a polyp, or growth, on the inner lining of the colon or rectum.

Not all polyps are cancerous. If cancer develops, the growth can spread to the wall of the colon or rectum and beyond. This happens if DNA changes cause cells to grow out of control. Exactly why the cells that make up these growths begin to mutate and divide isn't clear.

Risk Factors

Certain factors can increase your risk of colorectal cancer, such as:

• A diet high in red or processed meats or low in fruits and vegetables
• A personal or family history of colorectal cancer or polyps
• Age (i.e., older than 45)
• Alcohol or tobacco use
• Certain genetic disorders (e.g., Lynch syndrome)
• Inflammatory bowel disease (IBD), which causes inflammation of the colon (ulcerative colitis) or small intestine (Crohn's disease)
• Overweight or obesity

How Is Colorectal Cancer Diagnosed?

A healthcare provider will collect your health history and perform a physical exam. This might include a digital rectal exam, in which they insert a gloved finger into the rectum to feel for abnormalities.

Other diagnostic tests include:

• Biopsy: A healthcare provider will examine a suspicious tissue sample for cancer cells
• Blood tests: These include a complete blood count (CBC), liver function tests, and tumor markers. Blood tests can show different cell types and markers in your blood that might signal cancer.
• Colonoscopy: A healthcare provider inserts a thin tube with a light into the rectum to examine the entire colon and rectum and remove polyps.
• Proctoscopy: This test checks for rectal cancer. A healthcare provider inserts a thin tube with a light through the anus to look closely at the rectum.
• Imaging tests: A CT, MRI, or ultrasound can create detailed images of the inside of your body to see how much cancer has spread.
• Stool test: Looks for hidden blood in the stool or other markers of cancer

Stages of Colorectal Cancer

A healthcare provider will stage colorectal cancer based on whether the cancer is localized or has spread to lymph nodes and distant organs. Stage 0 cancer means it's in its earliest stage, and stage IV cancer is advanced, meaning it has metastasized (spread).

The stages of colorectal cancer include:

• Stage 0: Cancer is confined to the innermost layer of the tissue that lines the intestine.
• Stage I: A healthcare provider detects cancer cells in the inner layers of the colon.
• Stage II: Cancer is still localized but has spread through the muscular layer of the colon.
• Stage III: Cancer cells have spread to the lymph nodes.
• Stage IV: A healthcare provider has found cancer cells in distant organs like the liver and lungs.

Treatments for Colorectal Cancer

Treatment for colorectal cancer depends on several factors, such as the cancer's location and stage. Surgery is usually the main treatment.

The type of surgery depends on the size of the polyp and whether the cancer has spread. Treatment for early-stage cancer contained within a polyp involves removing the polyp during colonoscopy. More advanced cancer might require a colectomy. This procedure involves cutting out all or part of the colon.

A healthcare provider might perform a colostomy or ileostomy if the colon or rectum are diseased. These surgeries create an opening in the abdomen so waste collects in an external pouch.

Other treatments include chemotherapy, radiation, targeted drug therapy, or immunotherapy. A healthcare provider might advise a combination of these therapies.

How To Prevent Colorectal Cancer

Screenings are essential for reducing your risk of colorectal cancer. Several tests can look for possible colorectal cancer, including a colonoscopy and stool tests. A flexible sigmoidoscopy also examines the rectum and lower part of the colon.

Talk to a healthcare provider about what test is best for you. People with a family history of colorectal cancer may also consider genetic counseling to assess their risk.

You may be able to reduce your risk of colorectal cancer by:

• Eating more fruits, vegetables, and whole grains 
• Exercising regularly
• Limiting your red or processed meat intake
• Maintaining a healthy weight
• Quitting smoking

Related Conditions

Colorectal cancer may be associated with or increase your risk of other health problems. Related conditions include:

• Bowel obstruction: This happens if stool cannot move through the intestines. A cancerous tumor may cause a blockage, leading to bloating, constipation, and severe abdominal pain. A severe bowel obstruction is a medical emergency and requires surgery.
• Hypertension (high blood pressure): This is common among people with colorectal cancer, but the exact cause is unclear. Colorectal and hypertension have many of the same risk factors, such as a high intake of red meat.
• Type 2 diabetes: People with colorectal cancer might have an increased risk of type 2 diabetes, and vice versa. Both health problems share several risk factors, including being overweight or having obesity.

Living With Colorectal Cancer

Colorectal cancer is highly treatable if diagnosed and treated early. Colon cancer has a five-year survival rate of 91% if it's localized and 13% if it's distant, with an overall survival rate of 63%. Rectal cancer has a five-year survival rate of 90% if it's localized and 17% if it's distant, with an overall survival rate of 68%.

Colorectal cancer may lead to strong emotions, including anger, fear, and sadness. Here are some ways to cope with a diagnosis:

• Journaling
• Making time for things you enjoy
• Talking about your feelings with others
• Trying relaxation techniques (e.g., meditation and yoga)

Research has shown that colorectal disproportionally impacts Black Americans. Black adults with colorectal cancer are more likely to receive early diagnosis and treatment than White adults. This is likely due to several factors, including socioeconomic status and systemic racism. Public health policies aimed at expanding access to screenings and treatment among Black Americans are essential.