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Cancer of the colon and/or rectum is commonly referred to as colorectal cancer, the fourth most common cancer in the United States. More than 145,000 new cases of the disease are diagnosed each year. Only lung cancer accounts for more cancer deaths than colorectal cancer. Incidences of colorectal cancer have declined dramatically in recent decades. In 1995, 53 new cases of colorectal cancer were diagnosed for every 100,000 Americans. In 2015, that number dropped to 36. Colon cancer and rectal cancer are grouped together because they share many characteristics, symptoms and treatments. Two-thirds of colorectal cancers are colon cancers.
What causes colorectal cancer?
Together, the colon and rectum make up the large intestine. The colon, which is about four feet long, helps digest food and remove nutrients and water before sending the waste to the rectum, the final few inches of the intestine. Colorectal cancer may develop when:
- Polyps, mushroom-like growths inside the colon, grow and become cancerous
- Cells along the lining of the colon or rectum mutate and grow out of control, forming a tumor
Other risk factors for colorectal cancer include:
- Tobacco use
- Sedentary lifestyle
- Heavy alcohol use
- Poor diet, especially high in red and processed meats
- Family history, including inherited gene mutations or hereditary cancer syndrome
Who gets colorectal cancer?
The risk of colorectal cancer increases with age. According to the National Cancer Institute:
- The average age of a person diagnosed with colorectal cancer is 67.
- The average age of a person who dies from colorectal cancer is 73.
- Ninety-four percent of all new cases of colorectal cancer are diagnosed in people 45 and older.
- African American men and women are at a significantly higher risk of developing colorectal cancer than Caucasians or Hispanics.
- People of Ashkenazi Jewish descent have a higher risk of developing colorectal cancer.
Colorectal cancer types
More than 95 percent of all colorectal cancers are adenocarcinomas of the colon or rectum. Colorectal adenocarcinomas form in glands that secrete fluids to lubricate the colon and rectum. Adenocarcinomas are found in most common cancers, including breast, prostate and pancreatic. Other types of colorectal cancer include:
- Gastrointestinal carcinoid tumors
- Primary colorectal lymphomas
- Gastro intestinal stromal tumors
Recurrent colorectal cancer is cancer that returns to the same part of the colon or rectum where it was originally diagnosed.
Colorectal cancer that has spread to other parts of the body is called metastatic colorectal cancer. When it spreads, colorectal cancer is most often found in the liver, but may also spread to the lungs, bone and/or brain.
Colorectal cancer symptoms
Symptoms of colorectal cancer include:
- Diarrhea, constipation or both
- Thin, ribbon-like stools
- Abdominal bloating or cramps
- Feeling as if the bowel does not empty completely
- Rectal bleeding or blood in the stool
- Loose or watery stools
- Unexplained weight loss and/or loss of appetite
Colorectal cancer diagnostics and screening
Colorectal cancer may be detected and treated early with a proper screening regimen.
Facts about colorectal cancer screening:
- The American Cancer Society recommends that men and women of average or low risk have a colonoscopy beginning at age 45.
- African Americans have a higher risk of colorectal cancer and should begin screening at the age of 45.
- People with a family history of colorectal cancer should get screened 10 years earlier than when a family member was diagnosed. For example, talk to a doctor about getting a colonoscopy at 38 if your father was diagnosed with colon cancer at 48.
During a colonoscopy, a doctor may be able spot cancer in its early stages, perform a biopsy and remove polyps that may develop into cancer. For some patients who choose not to get a colonoscopy, less invasive stool tests may be an option.
Treating colorectal cancer
Surgery is most often the first-line treatment for colorectal cancer. Other treatments include:
- Radiation therapy
- Targeted therapy