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Colon Cancer Overview
Generally speaking, colon and rectal cancers usually begins as polyps. Most colorectal polyps are benign (non-cancerous) growths, but some will develop into cancer. Symptoms of colorectal cancer include change in bowel habits, and blood in stool. Unfortunately, most colorectal cancer cases at early stage do not present any obvious symptoms. Therefore regular screenings are highly recommended, especially a colonoscopy. If there is any abnormality found, doctors can remove it with surgery, radiation therapy and chemotherapy.
Cancer is a group of more than 100 different diseases. They affect the body's basic unit, the cell. Cancer occurs when cells become abnormal and divide without control or order. Like all other organs of the body, the colon and rectum are made up of many types of cells. Normally, cells divide to produce more cells only when the body needs them. This orderly process helps keep us healthy.
If cells keep dividing when new cells are not needed, a mass of tissue forms. This mass of extra tissue, called a growth or tumor, can be benign or malignant.
Benign tumors are not cancer. They can usually be removed and, in most cases, they do not come back. Most important, cells from benign tumors do not spread to other parts of the body. Benign tumors are rarely a threat to life.
Malignant tumors are cancer. Cancer cells can invade and damage tissues and organs near the tumor. Also, cancer cells can break away from a malignant tumor and enter the bloodstream or lymphatic system. This is how cancer spreads from the original (primary) tumor to form new tumors in other parts of the body. The spread of cancer is called metastasis.
When cancer spreads to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if colon cancer spreads to the liver, the cancer cells in the liver are colon cancer cells. The disease is metastatic colon cancer
The Symptoms of Colon Canccer
Symptoms of colon cancer are numerous and nonspecific. They include fatigue, weakness, shortness of breath, change in bowel habits, narrow stools, diarrhea or constipation, red or dark blood in stool, weight loss, abdominal pain, cramps, or bloating. Other conditions such as irritable bowel syndrome (spastic colon), ulcerative colitis, Crohn's disease, diverticulosis, and peptic ulcer disease can have symptoms that mimic colorectal cancer. For more information on these conditions, please read the following articles: Irritable Bowel Syndrome, Ulcerative Colitis, Crohn's Disease, Diverticulosis, and Peptic Ulcer Disease.
http://www.medicinenet.com/colon_cancer/page3.htm
Staging of Colon Cancer:
- Stage 0:
Since these cancers have not grown beyond the inner lining of the colon, surgery to take out the cancer is all that is needed. This may be done in most cases by polypectomy (removing the polyp) or local excision through a colonoscope. Colon resection (colectomy) may occasionally be needed if a tumor is too big to be removed by local excision.
- Stage I:
These cancers have grown through several layers of the colon, but they have not spread outside the colon wall itself (or into the nearby lymph nodes). Partial colectomy -- surgery to remove the section of colon that has cancer and nearby lymph nodes -- is the standard treatment. You do not need any additional therapy.
- Stage II:
Many of these cancers have grown through the wall of the colon and may extend into nearby tissue. They have not yet spread to the lymph nodes.
Surgery (colectomy) may be the only treatment needed. But your doctor may recommend adjuvant chemotherapy (chemo) if your cancer has a higher risk of coming back because of certain factors, such as:
- The cancer looks very abnormal (is high grade) when viewed under a microscope.
- The cancer shows microsatellite instability (MSI)
- The cancer has grown into nearby organs.
- The surgeon did not remove at least 12 lymph nodes.
- Cancer was found in or near the margin (edge) of the surgical specimen, meaning that some cancer may have been left behind.
- The cancer had blocked off (obstructed) the colon.
- The cancer caused a perforation (hole) in the wall of the colon.
Not all doctors agree on when chemo should be used for stage II colon cancers. It is important to discuss the pros and cons of chemotherapy with your doctor, including how much it might reduce your risk of recurrence and what the likely side effects will be.
Most often, the chemo given will be FOLFOX (5-FU, leucovorin, and oxaliplatin). For patients who have too many side effects, 5-FU and leucovorin alone or capecitabine may be used instead. Your doctor may recommend a particular one of these if it is better suited to your health needs.
If your surgeon is not sure he or she was able to remove all of the cancer because it was growing into other tissues, radiation therapy may be advised to try to kill any remaining cancer cells. Radiation therapy can be given to the area of your abdomen where the cancer was growing.
- Stage III:
In this stage, the cancer has spread to nearby lymph nodes, but it has not yet spread to other parts of the body.
Surgery (partial colectomy) followed by adjuvant chemo is the standard treatment for this stage. The FOLFOX regimen is the most common chemotherapy combination, although some doctors may prefer 5-FU and leucovorin, or capecitabine alone if they are better suited to your health needs.
Your doctors may also advise radiation therapy if your surgeon thinks some cancer cells might have been left behind after surgery. In people who aren't healthy enough for surgery, radiation therapy and/or chemotherapy may be options.
- Stage IV:
The cancer has spread from the colon to distant organs and tissues such as the liver, lungs, peritoneum, or ovaries.
In most cases surgery is unlikely to cure these cancers. However, if only a few small areas of cancer spread (metastases) are present in the liver or lungs and they can be completely removed along with the colon cancer, surgery may help you live longer and may even cure you. Chemotherapy is typically given as well, before and/or after surgery. In some cases, hepatic artery infusion may be used if the cancer has spread to the liver.
If the metastases cannot be surgically removed because they are too large or there are too many of them, chemotherapy may be tried first to shrink the tumors to allow for surgery. Chemotherapy would then be given again after surgery. Another option may be to destroy tumors in the liver with cryosurgery, radiofrequency ablation, or other non-surgical methods.
If the cancer is too widespread to try to cure it with surgery, operations such as a colectomy or diverting colostomy (cutting the colon above the level of the cancer and attaching the end to an opening in the skin on the abdomen to allow waste out) may still be needed in some cases. This can relieve or prevent blockage of the colon and so may prevent certain problems. Sometimes, such surgery can be avoided by inserting a stent (a hollow metal or plastic tube) into the colon during colonoscopy to keep it open.
If you have stage IV cancer and your doctor recommends surgery, it is very important to understand what the goal of the surgery is -- whether it is to try to cure the cancer or to prevent or relieve symptoms of the disease.Most patients with stage IV cancer will get chemotherapy and/or targeted therapies to control the cancer. The most commonly used regimens include:
- FOLFOX (leucovorin [folinic acid], 5-FU, and oxaliplatin)
- FOLFIRI (leucovorin, 5-FU, and irinotecan)
- CapeOX (capecitabine and oxaliplatin)
- Any of the above combinations plus either bevacizumab or cetuximab
(but not both)
- 5-FU and leucovorin, with or without bevacizumab
- Capecitabine, with or without bevacizumab
- FOLFOXIRI (leucovorin, 5-FU, oxaliplatin, and irinotecan)
- Irinotecan, with or without cetuximab
- Cetuximab alone
- Panitumumab alone
The choice of regimens may depend on several factors, including any previous treatments you've had and your overall health. If one of these regimens is no longer effective, another may be tried.
For advanced cancers, radiation therapy may also be used to help prevent or relieve symptoms such as pain. While it may shrink tumors for a time, it is very unlikely to result in a cure. If your doctor recommends radiation therapy, it is important that you understand the goal of treatment.
Recurrent colon cancerRecurrent cancer means that the cancer has returned after treatment. The recurrence may be local (near the area of the initial tumor), or it may affect distant organs.
If the cancer comes back locally, surgery (followed by chemotherapy) can sometimes help you live longer and may even cure you. If the cancer can't be removed surgically, chemotherapy may be tried first. If it shrinks the tumor enough, surgery may be an option. This would again be followed by more chemotherapy.
If the cancer comes back in a distant site, it is most likely to appear first in the liver. Surgerymay be an option in some cases. If not, chemotherapy may be tried first to shrink the tumor(s), which may then be followed by surgery. If the cancer is too widespread to be treated surgically, chemotherapy and/or targeted therapies may be used. Possible regimens are the same as for stage IV disease. The options depend on which, if any, drugs you received before the cancer came back and how long ago you received them, as well as on your health. Surgery may still be needed at some point to relieve or prevent blockage of the colon and to prevent other local complications. Radiation therapy may be an option to relieve symptoms in some cases as well.
As these cancers can often be difficult to treat, you may also want to speak with your doctor about clinical trials of newer treatments you might be eligible for.
Early diagnosis of colorectal cancer
All adults should undergo colon cancer screening beginning at age 50 or earlier, depending upon their risk of developing colorectal cancer. Several tests are currently available, each of which has advantages and disadvantages. The optimal screening test depends upon your preferences and your risk of developing colon cancer.
Colon cancer screening tests work by detecting polyps or by finding early stage cancers. Regular screening for and removal of polyps reduces your risk of developing colorectal cancer - by up to 90 percent with colonoscopy. Early detection of cancers that are already present in the colon increases the chances of successful treatment and decreases the chance of dying as a result of the cancer.
http://www.cancer.org/Cancer/ColonandRectumCancer/DetailedGuide/colorectal-cancer-diagnosed
Oncare's News Article about Colon Cancer： (to be updated)
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