What is colon cancer?


The colon is the longest part of the large intestine and the lowest part of the digestive system. The colon makes up the majority of the large intestine, approximately six feet in length. The colon is an important part of the digestive system, and as such, it has a major role in helping the body absorb nutrients, minerals, and water. 



The colon also helps rid the body of waste in the form of stool through rectum. The last six inches or so of the large intestine are the rectum and the anal canal (Anus). Colon cancer is a disease in which malignant (cancer) cells form in the tissues of the colon. 

Colon cancer is cancer of the large intestine (colon), the lower part of your digestive system. Rectal cancer is cancer of the last several inches of the colon. Together, they're often referred to as colorectal cancers.

Colon cancer is quite common, being the third most common cancer in men and women in the U.S. About 150,000 people in the U.S. are diagnosed with colon cancer and colorectal cancer each year. These are the second leading causes of cancer deaths in both men and women. According to the Centers for Disease Control (CDC), 53,196 Americans died from colon cancer in 2006 (the most recent year for available data).


What Exactly is colon cancer?

Cancer means out-of-control cell growth anywhere in your body, and colon cancer forms when this uncontrolled cell growth starts in the large intestine. At first some noncancerous (benign) clumps of cells called adenomatous polyps form on the inner walls of the large intestine. If these polyps left untreated, they may grow into malignant colon cancers over time. So it is better to get them removed during colonoscopy. Colon cancer cells will invade and damage healthy tissues near the tumor causing many health complications.

After malignant cancerous tumors form, the cancerous cells may travel through the blood and lymph systems, spreading to other parts of the body. These cancer cells can grow in several places, invading and destroying other healthy tissues throughout the body. This process itself is called metastasis, which is a very serious condition that is very difficult to treat.


What are the causes of colon cancer?

No specific causes are identified for colon cancer. When the cells uncontrollably grow and do not die, it results in cancer. There are certain factors which increase the risk of colon cancer. They include:


  • Genetics -20 % of colon cancers are caused by inherited mutations in the genes
  • Polyps- Adenomas and inflammatory polyps may become cancerous.
  • African-American race. African-Americans have a greater risk of colon cancer than do people of other races.
  • Inflammatory intestinal conditions. Chronic inflammatory diseases of the colon, such as ulcerative colitis and Crohn's disease, can increase your risk of colon cancer
  • Low-fiber, high-fat diet. Colon cancer and rectal cancer may be associated with a diet low in fiber and high in fat and calories. Research in this area has had mixed results. Some studies have found an increased risk of colon cancer in people who eat diets high in red meat.
  • A sedentary lifestyle. If you're inactive, you're more likely to develop colon cancer. Getting regular physical activity may reduce your risk of colon cancer.
  • Diabetes. People with diabetes and insulin resistance may have an increased risk of colon cancer.
  • Obesity. People who are obese have an increased risk of colon cancer and an increased risk of dying of colon cancer when compared with people considered normal weight.
  • Smoking. People who smoke cigarettes may have an increased risk of colon cancer.
  • Alcohol. Heavy use of alcohol may increase your risk of colon cancer.
  • Radiation therapy for cancer. Radiation therapy directed at the abdomen to treat previous cancers may increase the risk of colon cancer.
Symptoms of colon cancer?



Cancer symptoms are quite varied and depend on where the cancer is located, where it has spread, and how big the tumor is. It is common for people with colon cancer to experience no symptoms in the earliest stages of the disease. However, when the cancer grows, symptoms include:
  • A change in your bowel habits, including diarrhea or constipation or a change in the consistency of your stool
  • Rectal bleeding or blood in your stool
  • Persistent abdominal discomfort, such as cramps, gas or pain
  • A feeling that your bowel doesn't empty completely
  • Weakness or fatigue
  • Unexplained weight loss
  • Iron deficiency (Anemia)
Many people with colon cancer experience no symptoms in the early stages of the disease. When symptoms appear, they'll likely vary, depending on the cancer's size and location in your large intestine.

Are you at risk?

If you notice any symptoms of colon cancer, such as blood in your stool or a persistent change in bowel habits. Talk to your doctor about when you should begin screening for colon cancer. Your doctor may recommend more frequent or earlier screening if you have family history of the disease. Where as, guidelines generally recommend colon cancer screenings begin at age 50.

If your doctor suspects you may have colon cancer, you'll likely be referred to specialists who treat colon cancer.Those specialist physicians will request a complete physical exam as well as personal and family medical histories. 

Tests to detect (find) and diagnose colon cancer.

Fortunately colon cancer is both preventable and highly treatable when detected early. With screening colon cancer can be detected before symptoms develop. This is when the cancer is most curable. Physicians may conduct a series of tests such as, CBC and liver function test, digital rectal exam, fecal occult blood test, sigmodoscopy, biopsy, barium enema and colonoscopy. 


Diagnoses are usually made after the physician conducts a colonoscopy or a barium enema x-ray (lower G series). Only colonoscopy can see the entire colon. This is the best screening test for colon cancer.

Stages of colon cancer:
 If you are diagnosed with colorectal cancer, more tests will be done to see if the cancer has spread. This is called staging. CT or MRI scans of the abdomen, pelvic area, chest, or brain may be used to stage the cancer. Sometimes, PET scans are also used.

Stages of colon cancer are:
Stage 0: Very early cancer on the innermost layer of the intestine
Stage I: Cancer is in the inner layers of the colon
Stage II: Cancer has spread through the muscle wall of the colon
Stage III: Cancer has spread to the lymph nodes
Stage IV: Cancer has spread to other organs outside the colon

Blood tests to detect tumor markers, including carcinoembryonic antigen (CEA) and CA 19-9, may help your physician follow you during and after treatment.


How is colon cancer treated?

Cancer treatment depends on the type of cancer, the stage of the cancer (how much it has spread), age, health status, and additional personal characteristics. There is no single treatment for cancer, but the most common options for colon cancer are surgery, chemotherapy, and radiation therapy. Treatments seek to remove the cancer and/or relieve painful symptoms that the cancer is causing.

Surgery
Stage 0 colon cancer may be treated by removing the cancer cells. This is done using colonoscopy. For stages I, II, and III cancer, more extensive surgery is needed to remove the part of the colon that is cancerous. This surgery is called colon resection.

Chemotherapy
Almost all patients with stage III colon cancer should receive chemotherapy after surgery for 6 - 8 months. This is called adjuvant chemotherapy. The drug 5-fluorouracil can increase the chance of a cure in certain patients.

Chemotherapy is also used to improve symptoms and prolong survival in patients with stage IV colon cancer. Irinotecan, oxaliplatin, capecitabine, and 5-fluorouracil are the three most commonly used drugs. Monoclonal antibodies, including cetuximab (Erbitux), panitumumab (Vectibix), bevacizumab (Avastin), and other drugs have been used alone or in combination with chemotherapy.

You may receive just one type, or a combination of these drugs. There is some debate as to whether patients with stage II colon cancer should receive chemotherapy after surgery. You should discuss this with your oncologist.

Radiation therapy:
Radiation therapy is sometimes used in patients with colon cancer. It is usually used in combination with chemotherapy for patients with stage III rectal cancer. For patients with stage IV disease that has spread to the liver, treatments directed at the liver can be used. This may include: 

  • Burning the cancer (ablation) 
  • Delivering chemotherapy or radiation directly into the liver 
  • Freezing the cancer (cryotherapy) 
  • Surgery
Alternative Treatments

Although there is no scientific evidence to show that alternative treatments can treat or cure colon cancer, certain therapies can improve the quality of life of cancer patients. Activities such as art, dance and music can shift focus away from the disease and the treatment process, and help reduce stress. 

In addition, exercise and meditation can improve mood and appetite. Support groups are also a helpful resource for coping with colon cancer. Information on local groups can be found through organizations including the Colon Cancer Alliance, Cancer Care and the American Cancer Society.

Sources:
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