Colorectal Cancer

Colorectal cancer is a disease that starts in the colon or rectum, parts of your digestive system. While it’s the third most common cancer, regular screening and early detection can prevent it from developing or find it when treatment works best.

Table of contents

• What is Colorectal Cancer?
• Parts of the Body Affected
• How the Disease Develops
• Who Gets Colorectal Cancer?
• Risk Factors
• Signs and Symptoms
• Screening and Early Detection
• How Doctors Find Colorectal Cancer
• Stages of the Disease
• Treatment Options
• Reducing Your Risk
• Living After Treatment

What is Colorectal Cancer?

Colorectal cancer is a disease in which cells in the colon or rectum grow out of control^[1]. When cancer starts in the colon, it is called colon cancer, and when it begins in the rectum, it is called rectal cancer. Because these two types share many features, they are often grouped together as colorectal cancer^[3].

Cancer occurs when cells in the body begin to divide and grow in abnormal ways. In colorectal cancer, these abnormal cells develop in the tissues of the colon or rectum, which are important parts of your digestive system^[8].

Parts of the Body Affected

• Colon (large intestine)
• Rectum
• Anus

Your colon and rectum work together as part of your digestive system. The colon is the first and longest part of your large intestine, measuring about 5 feet long. Its main jobs are to absorb water and some nutrients from food and to change leftover waste into stool^[8]. The colon can be divided into different sections: the right colon (which includes the cecum, ascending colon, and part of the transverse colon) and the left colon (which includes the rest of the transverse colon, the descending colon, and the sigmoid colon)^[4].

The rectum is the lower part of your large intestine. It’s the passageway that connects the colon to the anus, where your body stores stool before it leaves your body^[8]. Together, the rectum and anal canal make up the last 6 to 8 inches of the large intestine^[12].

How the Disease Develops

Colorectal cancer usually doesn’t appear suddenly. It typically develops slowly over time, often starting with small clumps of cells called polyps that form inside the colon or rectum^[3]. Polyps are abnormal growths in the lining of your colon or rectum. Most polyps are not cancerous, but some types can turn into cancer over time^[1].

The process of a polyp becoming cancer usually takes about 10 to 15 years^[7]. This slow development is actually good news because it gives doctors time to find and remove polyps before they become cancerous. When colorectal cancer does form, it starts in the innermost lining of your colon or rectum, called the mucosa. This layer contains cells that make and release mucus and other fluids. If these cells change or mutate, they may create a polyp^[6].

If left undetected and untreated, the cancer can work its way through different layers of tissue and muscle in the colon wall. Eventually, it may spread to other parts of your body through your lymph nodes or blood vessels^[6].

Who Gets Colorectal Cancer?

Colorectal cancer is the third most common cancer diagnosed in people in the United States, excluding skin cancers^[6]. It is also the third leading cause of cancer deaths in both American women and men^[16].

The disease typically affects older adults, though it can happen at any age^[3]. According to experts, males are slightly more likely to develop colorectal cancer than females^[6]. Black people have an increased risk of colorectal cancer and death from the disease compared to other racial groups^[6].

Anyone can get colorectal cancer, regardless of gender, race, or nationality. Overall, the lifetime risk is about 1 in 23 for men and 1 in 25 for women^[3]. However, each person’s risk may be higher or lower depending on their individual risk factors.

While colorectal cancer typically affects people age 50 and older, the number of younger people getting this disease has been increasing. Over the past 15 years, the number of people age 20 to 49 with colon cancer has increased by about 1.5% each year^[6]. About 30% of colorectal cancer cases are now found in people under 55 years old^[7].

Risk Factors

A risk factor is anything that increases your chance of getting a disease. Some risk factors can be changed, while others cannot. Understanding your risk factors can help you take steps to lower your chances of developing colorectal cancer.

Age is one of the main risk factors. Your risk of getting colorectal cancer increases as you get older^[8].

Personal and family history plays an important role. If you have had colorectal cancer before, or if you have a parent, sibling, or child who has had it, your risk is 2 to 3 times higher than someone without this history. If a relative was diagnosed at a young age or if more than one relative has had colorectal cancer, the risk increases even more, to 3 to 6 times higher than average^[7].

Polyps can increase your risk. Having a personal history of high-risk adenomas—colorectal polyps that are 1 centimeter or larger or that have cells that look abnormal under a microscope—raises your risk^[8].

Genetic conditions can significantly increase risk. Having inherited changes in certain genes that cause conditions like familial adenomatous polyposis (FAP) or Lynch syndrome (also called hereditary nonpolyposis colorectal cancer) makes colorectal cancer much more likely^[8]. About 5% of people with colorectal cancer have these inherited conditions^[7].

Inflammatory bowel diseases are another risk factor. Having chronic ulcerative colitis or Crohn disease for 8 years or more increases your risk^[8].

Lifestyle factors that you can control include:

• Drinking three or more alcoholic drinks per day^[8]
• Smoking cigarettes^[8]
• Having obesity or being overweight^[8]
• Low physical activity^[4]
• Diet, particularly one high in red and processed meats^[4]

Signs and Symptoms

Many people with colorectal cancer don’t have symptoms at first, especially in the early stages^[3]. This is one reason why screening is so important. When symptoms do appear, they may include signs that could also be caused by less serious conditions, so it’s important to see a doctor if you notice any of these changes^[6].

Blood in or on your stool is an important warning sign. You might notice blood in the toilet after you use the bathroom, blood after wiping, or your stool may look dark or bright red. While blood in stool doesn’t always mean cancer—it can be caused by hemorrhoids or other conditions—it’s always important to have a healthcare provider check it out^[6].

Changes in bowel habits that last more than a few days should be evaluated. This includes having diarrhea, constipation, feeling that your bowel doesn’t empty completely, or noticing that your stool is narrower than usual^[8].

Abdominal pain or cramping with no known cause, especially if it doesn’t go away or hurts a lot, should be discussed with your doctor. Many things can cause belly pain, but it’s best to check with a healthcare provider if you have unusual or frequent pain^[6].

Other symptoms may include:

• Feeling bloated for more than a week or bloating that gets worse^[6]
• Frequent gas pains^[8]
• Weight loss for no known reason^[8]
• Feeling very tired or weak^[8]

Many people with colorectal cancer experience no symptoms at all, which is why screening is so important for catching the disease early^[7].

Screening and Early Detection

Screening means looking for signs of disease before you have any symptoms. For colorectal cancer, screening is especially powerful because it can actually prevent cancer from developing in the first place^[1].

The most effective way to reduce your risk of colorectal cancer is to get screened regularly, beginning at age 45^[23]. Most experts recommend that people at average risk start screenings at age 45 and continue until at least age 75. People over 75 and those at high risk should talk with their healthcare providers about how often they need screening and what type of test is best^[8].

An estimated 1 in 3 adults in the United States are not being screened as recommended^[7]. This is concerning because screening can find polyps so they can be removed before turning into cancer. Screening also helps find colorectal cancer at an early stage, when treatment works best^[1].

If you have certain risk factors—such as inflammatory bowel disease, a family history of colon polyps or cancer, or inherited genetic conditions—you may need to start screening at a younger age. Talk with your doctor about when to begin screening, which test is right for you, and how often to get tested^[1].

How Doctors Find Colorectal Cancer

If you have symptoms that could be caused by colorectal cancer, or if your screening test results are abnormal, you may need additional tests to find out if you have cancer^[8].

A colonoscopy is one of the main ways doctors examine the inside of the colon and rectum. During this procedure, a healthcare professional puts a long, flexible tube with a camera (called a colonoscope) into the rectum to check the entire colon. The doctor can pass surgical tools through the tube to take tissue samples and remove polyps^[10].

A biopsy involves removing a sample of tissue for testing in a laboratory. For colon cancer, the tissue sample is often collected during a colonoscopy. Sometimes surgery is needed to get the tissue sample. In the lab, tests can show whether the cells are cancerous and how quickly they’re growing^[10].

Other tests may include:

• A physical exam and digital rectal exam, where your provider inserts a gloved finger into the rectum to feel for abnormalities^[8]
• Blood tests to check overall health and look for low red blood cell counts, which might indicate bleeding. Blood tests can also track a protein called carcinoembryonic antigen (CEA) that some colon cancers make^[10]
• Imaging tests such as CT scans, which may be used to see if cancer has spread^[10]

Stages of the Disease

After colorectal cancer has been diagnosed, doctors do imaging tests to find out if cancer cells have spread within the colon or to other parts of the body. This process is called staging^[12]. Understanding the stage of cancer helps doctors and patients decide on the best treatment approach.

Colorectal cancer is divided into five stages, from Stage 0 to Stage 4:

Stage 0: Cancer cells are present but only in the inner lining of the colon or rectum. Surgery can remove the tumor and is the only treatment needed^[16].

Stage 1: Cancer grows in deeper layers of the colon or rectum wall but hasn’t grown beyond it. Surgery can remove the cancer tissue, and if any high-grade tumors are present nearby, healthy tissue is also removed^[16].

Stage 2: Cancer has grown through the wall of the intestine and started spreading to nearby tissue but not to lymph nodes. Surgery is standard, sometimes preceded by chemotherapy or immunotherapy if the tumor is aggressive^[16].

Stage 3: Cancer has spread to nearby organs and lymph nodes (small bean-shaped structures that are part of your immune system). Surgery followed by chemotherapy is used to eliminate remaining cancer cells. Radiation may be used if cancer has spread to nearby organs or if surgery isn’t an option^[16].

Stage 4: Cancer has spread (metastasized) to distant organs, often to the liver, lungs, brain, or the lining of the abdomen. Treatment options are more complex, and doctors primarily treat these tumors with chemotherapy. They may give chemotherapy before surgery to shrink tumors and follow it with surgery if possible^[16].

The five-year survival rate for colorectal cancer is approximately 91% for stages I and II but declines to 13% for stage IV. Only 1 in 3 cases are diagnosed at stage I or II^[7]. This shows how important early detection is for improving outcomes.

Treatment Options

When you’re diagnosed with colorectal cancer, your healthcare team will create a treatment plan specifically for you. This plan is based on your health and specific information about the cancer, including where the tumor is located, what stage the cancer is at, and what you prefer^[14].

Multiple treatment approaches are available, depending on the stage of the tumor and patient characteristics. These include surgery, chemotherapy, radiotherapy, targeted therapy, immunotherapy, and combinations of these treatments^[4].

Surgery is the most common treatment for colorectal cancer. For colon cancer, surgery and chemotherapy are the main treatments^[14]. The surgeon removes the part of the colon or rectum that contains cancer, along with some surrounding healthy tissue and nearby lymph nodes^[11].

Chemotherapy uses medicines to kill cancer cells or stop them from growing. It is commonly used to treat colorectal cancer, especially after surgery to kill any remaining cancer cells, or before surgery to shrink tumors^[14].

Radiation therapy uses high-energy rays to kill cancer cells. It is most often used to treat rectal cancer. For rectal cancer, radiation, a combination of chemotherapy and radiation (called chemoradiation), and surgery are the most common treatments^[14].

Targeted therapy uses drugs that target specific molecules or pathways that help colorectal cancer grow. Unlike traditional chemotherapy, which attacks all fast-dividing cells, targeted therapies focus on specific mechanisms. For example, some drugs work by preventing new blood vessels from forming, which tumors need to grow. Other drugs target special protein receptors to stop tumor cells from dividing^[13].

Immunotherapy helps strengthen your immune system to fight cancer. It is sometimes used to treat metastatic colorectal cancer—cancer that has spread to other parts of the body^[14]. This approach has been particularly effective for certain types of colorectal cancer, especially those with specific genetic characteristics^[16].

Thanks to these treatment options, early treatment, and new kinds of therapy, fewer people are dying from colon cancer^[6].

Reducing Your Risk

While you cannot control all risk factors for colorectal cancer, there are important steps you can take to reduce your risk.

Get screened regularly. Almost all colorectal cancers begin as precancerous polyps that can be present for years before cancer develops. Screening can find these polyps so they can be removed before they turn into cancer. This is actual cancer prevention^[23].

Maintain a healthy diet. Eating a diet rich in fruits, vegetables, and whole grains, and low in red and processed meats, may help reduce your risk. High intake of red and processed meats has been shown to increase the risk of colorectal cancer^[3]. Focus on eating more plant-based foods, increase your fiber intake with whole wheat bread, brown rice, beans, and legumes^[27].

Exercise regularly. An active lifestyle has been linked to a reduced risk of colorectal cancer^[3]. Research shows that patients who exercise don’t only face a healthier quality of life, but their treatment outcomes may also be improved^[24].

Keep a healthy weight. Being overweight or having obesity increases your risk. Eating healthfully and exercising regularly can help you maintain a healthy body weight^[3].

Limit alcohol. Heavy alcohol use may increase the risk of developing colorectal cancer. Alcohol turns into cancer-causing compounds in the body and can damage the cell lining of the colon. Doctors advise drinking alcohol in moderation only^[22].

Avoid tobacco. Smoking may increase colorectal cancer risk. If you smoke, quitting can help reduce your risk^[22].

Living After Treatment

For many people diagnosed with colorectal cancer, completing treatment is a significant milestone. While it brings relief, it can also bring uncertainty about the future and concern over the possibility of cancer coming back^[21].

Follow-up care is essential. Regular follow-ups monitor for recurrence, new cancers, or late effects of treatment. Depending on your cancer stage and treatment history, your doctor may recommend colonoscopies, imaging tests like CT scans, and blood tests to track tumor markers^[21]. Follow-up after colorectal cancer treatment varies from person to person^[14].

A survivorship care plan is a crucial tool for life after treatment. Work with your doctor to develop a plan that includes a schedule for follow-up exams and tests, awareness of potential long-term side effects and when to seek medical attention, recommendations for maintaining overall health such as nutrition and exercise, and guidelines for cancer screening and preventative care^[21].

Managing side effects is important. Since colon cancer treatments often affect the digestive system, many survivors experience bowel changes, including diarrhea, constipation, or loss of bowel control. Eating a balanced diet with fiber-rich foods, staying hydrated, and using medications as recommended by your doctor can help. Some people may need to experiment to find out which foods work best for their system. A dietitian—a healthcare professional who specializes in food and nutrition—can support you with diet problems^[26].

Some people have a colostomy or ileostomy after surgery, where the end of the bowel is brought out to an opening on the abdomen. This opening is called a stoma. While this requires adjustment, there are many resources and support groups available to help^[26].

Getting practical and emotional support can help you cope with cancer. This support can help with life during and after treatment. Many organizations, support groups, and other resources are available to help you cope with colorectal cancer and treatment^[26].