Colorectal cancer starts in the colon or the rectum (the intestinal tract of the digestive system). Colorectal cancer can also be referred to separately as colon cancer or rectal cancer, depending on where it starts. Colon cancer and rectal cancer have many features in common. Excluding skin cancers, colorectal cancer is the third most common cancer diagnosed in both men and women in the United States.
The American Cancer Society estimates that 93,090 new cases of colon cancer, and 39,610 new cases of rectal cancer were diagnosed in the United States in 2015. Overall, the risk for colorectal cancer is about 5% in men and slightly less in women.
Colorectal cancer is the second leading cause of cancer related deaths in the United States when both sexes are considered and the third leading cause when men and women are considered separately.
Colorectal cancer was estimated to cause 49,700 deaths in 2015.
Types of Colorectal Cancer
Colorectal cancer is classified into several types. Adenocarcinomas are the most common type and include about 95% of all colorectal cancers. The other cancer types are not common in the colon or the rectum.
Carcinoid tumors start from specialized hormone-producing cells in the intestine.
Gastrointestinal stromal tumors (also known as GISTs) start in cells in the wall of the colon; some GISTs are benign (noncancerous) and others are malignant. These tumors can be found anywhere in the digestive tract, but they are not typically found in the colon.
Lymphomas are cancers of the immune system cells that typically start in lymph nodes but may also start in the colon or the rectum.
Sarcomas can start in the blood vessels and in the wall of the colon and rectum; sarcomas of the colon or rectum are rare.
Risk Factors
Several lifestyle-related factors have been linked to colorectal cancer. The links between diet, weight, and exercise and colorectal cancer risk are some of the strongest for any type of cancer.
The risk factors for colorectal cancer include:
- Age: risk increases after age 50
- Diet and lifestyle: a diet high in red meats and processed meats increases the risk; by contrast, a diet high in vegetables, fruits, and whole grains has been linked to a reduced risk for this cancer (fiber supplements do not seem to help); lack of physical activity also increases the risk
- Obesity: stronger in men
- Smoking is a well-known cause of lung cancer but is also linked to colorectal cancer
- Heavy use of alcohol, in part because it lowers folic acid levels: limit alcohol intake to 2 drinks a day for men, 1 drink a day for women
- Family history of colorectal cancer in 1 or more first-degree relatives: parents, siblings, or children
- Familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer
- A history of certain medical conditions: adenomatous polyps (adenomas); irritable bowel disorder
- A personal history of colorectal cancer, even after it has been completely removed, increases the risk for new cancer around the colon and rectum
- African Americans are at greatest risk in the United States
- Ashkenazi Jews are the ethnic group with the highest risk worldwide; several genetic mutations (changes) are common in this group: the 11307K APC mutation is present in 5% of American Jews
Symptoms
If you have any of the following symptoms, consult with your physician to check for colorectal cancer:
- A change in bowel habits (diarrhea, constipation, or narrowing of the stool lasting more than a few days)
- A feeling that you need to have a bowel movement that is not relieved by doing so
- Rectal bleeding
- Blood in the stool, which may make it appear dark
- Cramping or stomach pain
- Weakness and fatigue
- Unintended weight loss
Diagnosis and Screening
A physical exam, medical history, and many tests are used to diagnose colorectal cancer including:
- Guaiac-based fecal occult blood test and fecal immunochemical test: samples of stool (feces) are checked for blood, which may be a sign of a polyp or cancer
- Stool DNA test: a sample of stool is checked for certain abnormalities from cancer or polyp cells
- Sigmoidoscopy: a flexible tube is put into the rectum and lower colon to check for polyps and cancer
- Colonoscopy: a longer flexible tube is used to look at the entire colon and rectum
- Double-contrast barium enema: an x-ray test of the colon and rectum
- CT colonography (virtual colonoscopy): a type of CT scan of the colon and rectum
Treatment
The treatment of patients with colorectal cancer is based on the specific type of the cancer, the disease stage, and the patient’s age and overall health. Depending on the stage of the cancer, 2 or more treatments may be combined or used in sequence.
Surgery is the most common treatment for colorectal cancer, and is usually the primary treatment. Colectomy is the removal of a portion of or the entire colon and can be performed as an open surgery or a laparoscopic surgery.
Radiation therapy is used mainly when the colon cancer has attached to an internal organ or the lining of the abdomen, or when it has spread, especially to the bones or the brain. For rectal cancer, radiation therapy is usually used before or after surgery to help prevent cancer recurrence. Radiation therapy is often used with chemotherapy.
Chemotherapy for colorectal cancer usually involves 2 or more drugs. Several effective regimens are available as initial therapy and for later treatments for stage IV (advanced) disease. The most common chemotherapy drugs include 5-FU (fluorouracil), Camptosar (irinotecan), Eloxatin (oxaliplatin), and Xeloda (capecitabine). Leucovorin (folinic acid) or Fusilev (levoleucovorin) is often given with fluorouracil.
Targeted therapy involves the use of drugs to stop cancer cell growth by interfering with the way cells communicate. For colorectal cancer, targeted therapy involves drugs called EGFR inhibitors and antiangiogenic drugs. EGFR inhibitors include Erbitux (cetuximab) and Vectibix (panitumumab). Antiangiogenic agents stop the growth of blood vessels to the tumor, and are often combined with chemotherapy to treat metastatic cancer; these drugs include Avastin (bevacizumab), Stivarga (regorafenib), and Zaltrap (ziv-aflibercept).
New Drugs for Advanced Colorectal Cancer
Cyramza (ramucirumab) was approved by the FDA in April 2015 for use in combination with Fusilev, 5-FU, and Camptosar for patients with metastatic colorectal cancer that progresses with first-line therapies.
Lonsurf (trifluridine + tipiracil) is a combination of 2 oral drugs. It was approved by the FDA in September 2015 for patients with metastatic colorectal cancer that no longer responds to other chemotherapies.
