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Colorectal cancer (CRC), also known as colon cancer, is a cancer that occurs in the large intestine (colon) or rectum and is the third most diagnosed cancer in the U.S., appearing more frequently in older men and women over the age of 50.
Colorectal cancer often begins with appearance of small, non-cancerous (benign) growths (polyps) in the lining of the colon that are without symptoms. Some of these polyps can eventually develop into tumors and become colorectal cancer. Not all polyps become cancerous. The risk of polyps developing into cancer depends on the type of polyps, of which there are two main types:
1) Adenomas are considered pre-cancerous because they sometimes become adenocarcinomas, which represent 96% of colorectal cancers.
2) Hyperplastic and inflammatory polyps occur more often and are usually non-cancerous.
Additional risks for polyps becoming cancerous include their size, number, or whether they have abnormal cells. If a polyp does become cancerous, the cancer can spread into the lining of the colon or rectum, and eventually through other layers. Once inside the wall of the colon or rectum, the cancer can then spread into the blood vessels and lymph system (nodes) or other, distant parts of the body (metastasis).
A few other, less common colorectal cancers include:
Carcinoid Tumors that arise from hormone-producing cells in the colon.
Gastrointestinal Stromal Tumors (GISTs) that arise from special cells in the lining of the colon, and which can be either cancerous or non-cancerous (benign); however, GISTs do not commonly appear in the colon.
Lymphomas, which are cancers that begin in lymph nodes.
Sarcomas, which begin in the blood vessels, muscles, or connective tissues, and rarely appear as colorectal cancers.
Colorectal cancer is classified based on the following stages:
Stage 0 – Carcinoma in Situ: abnormal cells may be found in the lining (mucosa) of the colon or rectum.
Stage I – Cancer has formed in the lining (mucosa) of the colon or rectal wall and has spread to the submucosa (outer layer) or the muscle layer.
Stage II (IIA, IIB, IIC) – Cancer has spread through the muscle of the colon or rectum to the outer layer (serosa); Cancer has spread through the outer layer (serosa) to the lining of the abdomen (peritoneum); Cancer has spread through the outer layer (serosa) to other organs.
Stage III (IIA, IIIB, IIIC) – Cancer has spread through the mucosa (inner layer), submucosa (outer layer), or muscle layer of colon or rectum, or through the colon or rectal wall to four-to-six lymph nodes; Cancer has spread through the mucosa (inner layer), submucosa (outer layer), or muscle layer of colon or rectum, or through the colon or rectal wall to the mucosa that lines the abdomen (peritoneum) and one-to-three lymph nodes, or four-to six lymph nodes, or seven or more lymph nodes; Cancer has spread to the mucosa lining the abdomen (peritoneum) and four-to six lymph nodes, or seven or more lymph nodes, or to nearby organs.
Stage IV (IVA, IVB, IVC) – Cancer has spread to one area or organ not near the colon or rectum, such as liver, lung, ovary, or distant lymph node; Cancer has spread to more than one area or organ, such as liver, lung, ovary, or distant lymph node; Cancer has spread to the lining of the wall of the abdomen (peritoneum) and may have spread to other organs.
The level of staging for colorectal cancer determines its treatment and outcomes (prognosis).
What type of doctors treat colorectal cancer?
Colorectal cancer is treated by a team of specialists who collaborate to create the best care plan. Key doctors include:
- Colorectal surgeons: These specialists perform surgeries to remove cancerous tissues from the colon or rectum. They also handle complications or follow-up surgeries if needed.
- Medical oncologists: These doctors use treatments like chemotherapy, targeted therapy, or immunotherapy to manage cancer, especially if it has spread.
- Radiation oncologists: They use radiation therapy to shrink tumors or destroy cancer cells. Radiation is often used for rectal cancer.
- Gastroenterologists: These doctors focus on diagnosing and treating digestive system disorders. While they perform colonoscopies to detect cancer, they do not treat it.
A colorectal doctor typically refers to a colorectal surgeon, while a gastroenterologist focuses on diagnosing and managing digestive disorders.
What are the symptoms of colorectal cancer?
Colorectal cancer can cause different symptoms that vary from person to person. Common symptoms include:
- Persistent changes in bowel habits, like diarrhea, constipation, or stools that are narrower than usual
- Blood in the stool, which may appear bright red or dark
- Abdominal pain, cramping, or discomfort that doesn’t go away
- A feeling that the bowel doesn’t empty completely after a bowel movement
- Unexplained weight loss or loss of appetite
- Fatigue or weakness
Blood in the stool or subtle changes in bowel habits may be early warning signs of colorectal cancer. However, most people do not notice their symptoms until the cancer has progressed. That’s why regular screenings, such as colonoscopies starting at age 45 or earlier for high-risk individuals, are important for early detection.
How is colorectal cancer diagnosed?
Colorectal cancer diagnosis involves a combination of screening tools and diagnostic tests:
- Colonoscopy: A thin, flexible tube with a camera is inserted into the colon to check for abnormalities. If polyps or suspicious areas are found, a biopsy can be taken for testing.
- Stool-based tests: These include fecal occult blood tests (FOBT) or fecal immunochemical tests (FIT), which check for hidden blood, and stool DNA tests, which look for abnormal DNA changes.
- CT colonography (virtual colonoscopy): A less invasive imaging test that uses CT scans to create detailed pictures of the colon and rectum.
- Blood tests: While blood work, such as a carcinoembryonic antigen (CEA) test, can suggest cancer, it cannot confirm the diagnosis. Blood tests are often used to monitor the cancer’s progress or recurrence.
What can colorectal cancer be mistaken for?
Colorectal cancer can develop over many years without obvious symptoms. Some patients were misdiagnosed in the early stages of their cancer because their symptoms were similar to those of common health conditions, such as:
- Irritable bowel syndrome (IBS): A disorder causing abdominal discomfort, bloating, and changes in bowel habits.
- Hemorrhoids: Swollen blood vessels in the rectum or anus that can cause rectal bleeding.
- Diverticulitis: Inflammation or infection of small pouches in the colon.
- Infections: Intestinal infections can mimic symptoms like diarrhea or abdominal pain.
What is the life expectancy for someone with colorectal cancer?
The life expectancy for colorectal cancer depends on several factors, including the stage at diagnosis, overall health, and response to treatment.
The survival rates based on cancer stages are:
- Localized (early stage): If the cancer is confined to the colon or rectum, the 5-year survival rate is about 91%. Early detection offers the best chance for successful treatment.
- Regional spread: When cancer has spread to nearby lymph nodes or tissues, the 5-year survival rate drops to about 72%.
- Distant spread (metastatic cancer): If the cancer has spread to distant organs, such as the liver or lungs, the 5-year survival rate is approximately 15%.
These survival rates are averages, and outcomes will vary from person to person. Advances in treatment options, including targeted therapies and immunotherapy, continue to improve prognosis for many patients.