TREATMENT

Surgery is the most common initial treatment for colorectal cancer. During surgery, the tumor, a small margin of the surrounding healthy intestine, and adjacent lymph nodes are removed. The surgeon then reconnects the healthy sections of the bowel. In patients with rectal cancer, the rectum sometimes is permanently removed if the cancer arises too low in the rectum. The surgeon then creates an opening (colostomy) on the abdominal wall through which solid waste from the colon is excreted. Specially trained nurses (enterostomal therapists) can help patients adjust to colostomies, and most patients with colostomies return to a normal lifestyle.

When a colorectal cancer is diagnosed, additional tests are performed to determine the extent of the disease. This process is called staging. Staging determines how advanced a colorectal cancer has become. The staging for colorectal cancer ranges from stage I, the least advanced cancer, to stage IV, the most advanced cancer. Stage I colorectal cancers involve only the innermost layers of the colon or rectum. The likelihood of cure (excellent prognosis) for stage I colorectal cancer is over 90%. Stage II cancers exhibit greater growth and extension of tumor through the wall of the colon or rectum into adjacent structures. Stage III colorectal cancers manifest spread of the cancer to local lymph nodes. Stage IV colorectal cancers have metastasized to distant organs or lymph nodes far from the original tumor. For more precise staging information, see colon cancer staging at www.cancer.gov.

With each subsequent stage of colon cancer, the risk for recurrent cancer and death rises. As noted, earlier cancers have lower risks of recurrence and death. By the time an individual has stage IV colorectal cancer, the prognosis is poor. However, even in stage IV colorectal cancer (depending on where the cancer has spread) the opportunity for cure exists.

For early colon cancers, the recommended treatment is surgical removal. For most people with early stage colon cancer (stage I and most stage II), surgery alone is the only treatment required. However, once a colon cancer has spread to local lymph nodes (Stage III), the risk of the cancer returning remains high even if all visible evidence of the cancer has been removed by the surgeon. This is due to an increased likelihood that tiny cancer cells may have escaped prior to surgery and are too small to detect at that time by blood tests, scans or even direct examination. Their presence is deduced from higher risk of recurrence of the colon cancer at a later date ( relapse). Medical cancer doctors (medical oncologists) recommend additional treatments with chemotherapy in this setting to lower the risk of the cancer's return. Drugs used for chemotherapy enter the bloodstream and attack any colon cancer cells that were shed into the blood or lymphatic systems prior to the operation, attempting to kill them before they set up shop in other organs. This strategy, called adjuvant chemotherapy, has been proven to lower the risk of cancer recurrence and is recommended for all patients with stage III colon cancer who are healthy enough to undergo it, as well as for the occasional higher risk stage II patient whose tumor may have been found to have obstructed or perforated the bowel wall prior to surgery.

There are several different options for adjuvant chemotherapy for the treatment of colon cancer. The treatments involve a combination of chemotherapy drugs given orally or into the veins. The treatments typically are given for a total of 6 months. It is important to meet with an oncologist who can explain adjuvant chemotherapy options as well as side effects to watch out for so that the right choice can be made for a patient as an individual.

Chemotherapy usually is given in a doctor's office, in the hospital as an outpatient, or at home. Chemotherapy usually is given in cycles of treatment followed by recovery periods without treatment. Side effects of chemotherapy vary from person to person and also depend on the agents given. Modern chemotherapy agents are usually well tolerated, and side effects for most people are manageable. In general, anticancer medications destroy cells that are rapidly growing and dividing. Therefore, normal red blood cells, platelets, and white blood cells that also are growing rapidly can be affected by chemotherapy. As a result, common side effects include anemia, loss of energy, and a low resistance to infections. Cells in the hair roots and intestines also divide rapidly. Therefore, chemotherapy can cause haiir loss, mouth sores, nausea, vomitting, and diarrhea, but these effects are transient.

Treatment of stage IV colorectal cancer.

Once colorectal cancer has spread distant from the primary tumor site, it is described as stage IV disease. These distant tumor deposits, shed from the primary tumor, have traveled through the blood or lymphatic system, forming new tumors in other organs. At that point, colorectal cancer is no longer a local problem but is instead a systemic problem with cancer cells likely present throughout the body. As a result, in most cases the best treatment is chemotherapy, which is a systemic therapy. Chemotherapy in metastatic colorectal cancer has been proven to extend life and improve the quality of life. If managed well, the side effects of chemotherapy are typically far less than the side effects of uncontrolled cancer. Chemotherapy alone cannot cure metastatic colon cancer, but it can more than double life expectancy and allow for good quality of life during the time of treatment.

Chemotherapy options for colorectal cancer treatment vary depending on other health issues that an individual faces. For fitter individuals, combinations of several chemotherapeutic drugs usually are recommended whereas for sicker people, simpler treatments may be best. Different multidrug combinations combine agents with proven activity in colorectal cancer such as oxaliplatin, 5-FU, irinotecan, cetuximab, panitumumab, and bevacizumab. Regimens often have acronyms to simplify their nomenclature (FOLFOX, FOLFIRI, FLOX). Oxaliplatin, irinotecan, and 5-FU are conventional chemotherapy drugs designed to block cell division non-selectively and typically have greater side effects. Bevacizumab, cetuximab, and panitumumab are newer treatments that target specific aspects of the cancer cell which may be more important to the tumor than the surrounding tissues, offering potentially effective treatments with fewer side effects than traditional chemotherapy. These newer chemotherapeutic agents most often are combined with standard chemotherapy to enhance their effectiveness.

If the first treatment is not effective, second- and third-line options are available that can confer benefit to people living with colorectal cancer. We now know that individuals who receive several different treatments survive longer than those who receive one or two types of treatment. Oncologists and researchers continue to work hard investigating new and better treatment options. New agents are becoming available with the potential to extend life even further. An agent called regorafenib has been approved by the Food and Drug Administration (FDA). Regorafenib has been shown to extend progression-free survival in some people with colorectal cancer who no longer are responding to other existing treatments.

Radiation theraphy in colorectal cancer has been limited to treating cancer of the rectum. As noted earlier, whereas parts of the colon move freely within the abdominal cavity, the rectum is fixed in place within the pelvis. It is in intimate relationship to many other structures and the pelvis is a more confined space. For these reasons, a tumor in the rectum often is harder to remove surgically because the space is smaller and other structures can be involved with cancer. As a result, for all but the earliest rectal cancers, initial chemotherapy and radiation treatments (a local treatment to a defined area) are recommended to try and shrink the cancer, allowing for easier removal and lowering the risk of the cancer returning locally. Radiation therapy is typically given under the guidance of a radiation specialist called a radiation oncologist. Initially, individuals undergo a planning session, a complicated visit as the doctors and technicians determine exactly where to give the radiation and which structures to avoid. Once the plan is formalized, radiation treatments for rectal cancer are typically (in the United States) delivered in daily treatments called "fractions" administered Monday through Friday for about 5 to 6 weeks. Treatment times are short but require many visits. Chemotherapy usually is administered daily while the radiation is delivered. Standard chemotherapy is 5-FU by injection into the vein or as a slow infusion or capecitabine, and an oral form of 5-FU is taken twice daily on the days of radiation. Side effects of radiation treatment include fatigue, temporary or permanent pelvic hair loss, and skin irritation in the treated areas

PREVENTION

The most effective prevention for colorectal cancer is early detection and removal of precancerous colorectal polyps before they turn cancerous. Even in cases where cancer has already developed, early detection still significantly improves the chances of a cure by surgically removing the cancer before the disease spreads to other organs. Multiple world health organizations have suggested general screening guidelines

Digital rectal examination and stool occult blood testing

It is recommended that all individuals over the age of 40 have yearly digital examinations of the rectum and their stool tested for hidden or "occult" blood. During digital examination of the rectum, the doctor inserts a gloved finger into the rectum to feel for abnormal growths. Stool samples can be obtained to test for occult blood (see below). The prostate gland can be examined at the same time for evidence of prostate cancer.

An important screening test for colorectal cancers and polyps is the stool occult blood test. Tumors of the colon and rectum tend to bleed slowly into the stool. The small amount of blood mixed into the stool usually is not visible to the naked eye. The commonly used stool occult blood tests rely on chemical color conversions to detect microscopic amounts of blood. These tests are both convenient and inexpensive. A small amount of stool is smeared on a special card for occult blood testing. Usually, three consecutive stool cards are collected. A person who tests positive for stool occult blood has a 30% to 45% chance of having a colon polyp and a 3% to 5% chance of having a colon cancer. Colon cancers found under these circumstances tend to be small and not to have spread and have a better long-term prognosis.

It is important to remember that having stool tested positive for occult blood does not necessarily mean a person has colon cancer. Many other conditions can cause occult blood in the stool. However, patients with a positive stool occult blood test should undergo further evaluations involving barium enema X-rays, colonoscopies, and other tests to exclude colon cancer and to explain the source of the bleeding. It is also important to realize that stool which has tested negative for occult blood does not mean that colorectal cancer or polyps do not exist. Even under ideal testing conditions, at significant percentage of colon cancers can be missed by stool occult blood screening. Many patients with colon polyps do not have positive stool occult blood. In patients suspected of having colon tumors and in those at higher risk for developing colorectal polyps and cancer, screening flexible sigmoidoscopies or colonoscopies are performed even if the stool occult blood tests are negative

Flexible sigmoidoscopy and colonoscopy

Beginning at age 50, a flexible sigmoidoscopy screening test is recommended every 3 to 5 years. Flexible sigmoidoscopy is an exam of the rectum and the lower colon (60 cm or about two feet in from the outside) using a viewing tube (a short version of colonoscopy). Recent studies have shown that the use of screening flexible sigmoidoscopy can reduce mortality from colon cancer. This is a result of the detection of polyps or early cancers in people with no symptoms. If a polyp or cancer is found, a complete colonoscopy is recommended. The majority of colon polyps can be completely removed at the time of colonoscopy without surgery. Recommendations now are that screening colonoscopies instead of screening flexible sigmoidoscopies should be done for healthy individuals starting at ages 50 to 55.

Colonoscopy uses a long ( 120 to 150 cm)  flexible tube which can examine the entire length of the colon. Through this tube the doctor can both view and take pictures of the entire colon, and also can take biopsies of colon masses and remove polyps.

Patients with a high risk of developing colorectal cancer may undergo screening colonoscopies starting at earlier ages than 50. For example, patients with family history of colon cancer are recommended to start screening colonoscopies at an age 10 years before the earliest colon cancer diagnosed in a first-degree relative or 5 years earlier than the earliest precancerous colon polyp discovered in a first-degree relative. Patients with hereditary colon cancer syndromes such as FAP, AFAP, HNPCC, and MYH are recommended to begin colonoscopies early. The recommendations differ depending on the genetic defect. For example, in FAP colonoscopies may begin during teenage years to look for the development of colon polyps. Patients with a prior history of polyps or colon cancer may also undergo colonoscopies to exclude recurrence. Patients with a long history (greater than 10 years) of chronic ulcerative colitis have an increased risk of colon cancer, and should have regular colonoscopies to look for precancerous changes in the colon lining.

Genetic counseling and testing

Blood tests are now available to test for FAP, AFAP, MYH, and HNPCC hereditary colon cancer syndromes. Families with multiple members having colon cancers, multiple colon polyps, cancers at young ages, and other cancers such as cancers of the ureters, uterus, duodenum, and more, should be referred for genetic counseling, followed possibly by genetic testing. Genetic testing without prior counseling is discouraged because of the extensive family education that is involved and the complicated nature of interpreting the test results.

The advantages of genetic counselling followed by genetic testing include: (1) identifying family members at high risk of developing colon cancer to begin colonoscopies early; (2) identifying high-risk members so that screening may begin to prevent other cancers such as ultrasound tests for uterine cancer, urine examinations for ureter cancer, and upper endoscopies for stomach and duodenal cancers; and (3) alleviating concern for members who test negative for the hereditary genetic defects.

Diet and colon cancer to prevent colon cancer

People can change their eating habits by reducing fat intake and increasing fiber (roughage) in their diet. Major sources of fat are meat, eggs, dairy products, salad dressings, and oils used in cooking. Fiber is the insoluble, nondigestible part of plant material present in fruits, vegetables, and whole-grain breads and cereals. It is postulated that high fiber in the diet leads to the creation of bulky stools which can rid the intestines of potential carcinogens. In addition, fiber leads to the more rapid transit of fecal material through the intestine, thus allowing less time for a potential carcinogen to react with the intestinal lining.

CAUSES OF COLON CANCER

Diet and colorectal cancer

Diets high in fat are believed to predispose people to colorectal cancer. In countries with high colorectal cancer rates, the fat intake by the population is much higher than in countries with low cancer rates. It is believed that the digestion of fat that occurs in the small intestine and the colon leads to the formation of cancer-causing chemicals (carcinogens). Diets high in vegetables and high-fiber foods such as whole-grain breads and cereals contain less fat that produces these carcinogens and may counter the effects of the carcinogens. Both effects would help reduce the risk of cancer.

Colon polyps and colorectal cancer

Doctors believe that most colorectal cancers develop in colorectal polyps. Therefore, removing benign (but precancerous) colorectal polyps can prevent colorectal cancer. Precancerous colorectal polyps develop when chromosomal damage occurs in cells of the inner lining of the colon. The damage produces abnormal cells, but the cells have not yet developed the ability to spread, the hallmark of cancer. Instead, the growing tissue remains localized within the polyp. When chromosomal damage increases further within the polyp, cell growth becomes uncontrolled, and the cells begin to spread, that is, they become cancer. Thus, colon polyps which are initially benign acquire additional chromosome damage to become cancerous

Ulcerative colitis and colorectal cancer

Chronic ulcerative colitis causes inflammation of the inner lining of the colon. For further information, please read the ulcerative colitis article. Colon cancer is a recognized complication of chronic ulcerative colitis. The risk for cancer begins to increase after 8 to 10 years of colitis. The risk of developing colon cancer in a patient with ulcerative colitis also is related to the location and the extent of his or her disease.

Patients at higher risk of cancer are those with a family history of colon cancer, a long duration of colitis, extensive colon involvement with colitis, and those with an associated liver disease, sclerosing cholangitis.

Since the cancers associated with ulcerative colitis have a more favorable outcome when caught at an earlier stage, yearly examinations of the colon often are recommended after 8 years of known extensive disease. During these examinations, samples of tissue (biopsies) are taken to search for precancerous changes in the cells lining the colon. When precancerous changes are found, removal of the colon may be necessary to prevent colon cancer

Genetics and colorectal cancer

A person's genetic background is an important factor in colon cancer risk. Among first-degree relatives of colon cancer patients, the lifetime risk of developing colon cancer is 18% (a threefold increase over the general population in the United States).

Even though a family history of colon cancer is an important risk factor, a majority (80%) of colon cancers occur sporadically in patients with no family history of colon cancer. Approximately 20% of cancers are associated with a family history of colon cancer.

Chromosomes contain genetic information, and chromosomal damage causes genetic defects that lead to the formation of colon polyps and later colon cancer. In sporadic polyps and cancers (polyps and cancers that develop in the absence of family history), the chromosome damages are acquired (develop in a cell during adult life). The damaged chromosomes can only be found in the polyps and the cancers that develop from that cell. But in hereditary colon cancer syndromes, the chromosomal defects are inherited at birth and are present in every cell in the body. Patients who have inherited the hereditary colon cancer syndrome genes are at risk of developing colon polyps, usually at young ages, and are at very high risk of developing colon cancer early in life; they also are at risk of developing cancers in other organs.

Familial adenomatous polyposis(FAP) is one hereditary colorectal cancer syndrome where the affected family members will develop countless numbers (hundreds, sometimes thousands) of colon polyps starting during their teens. Unless the condition is detected and treated early (treatment involves removal of the colon), a person affected by FAP is almost sure to develop colon cancer from these polyps. Cancers almost certainly develop by the time a person is in their 40s. These patients are also at risk of developing other cancers such as cancers in the thyroid gland, stomach, and the ampulla (part of the bile duct that drains into the small intestine from the liver) as well as benign tumors called desmoid tumors. FAP arises from a mutation in a specific gene called the APC gene. The specific mutation can be identified in most people with appropriate testing, and such testing is recommended for individuals diagnosed with FAP as well as their family members.

Attenuated familial adenomatous polyposis (AFAP) is a milder version of FAP. Affected members develop fewer than 100 colon polyps. Nevertheless, they are still at very high risk of developing colon cancers at a young age. They are also at risk of having gastric polyps and duodenal polyps.

Hereditary nonpolyposis colon cancer (also known as Lynch Syndrome or HNPCC) is a hereditary colorectal cancer syndrome where affected family members can develop colon polyps and cancers, usually in the right colon, in their 30s to 40s. Patients with HNPCC are also at risk of developing uterine cancer, stomach cancer, ovarian cancer, and cancers of the ureters (the tubes that connect the kidneys to the bladder), and the bile ducts. Ironically, it appears that while colon cancer occurs more frequently in patients with HNPCC, these cancers may be more easily cured than "sporadic" colon cancers. The specific genetic abnormalities associated with HNPCC have been identified, and patients and family members can be tested to determine if HNPCC is present and if family members carry the abnormality and are likely to develop cancer.

MYH polyposis syndrome is a recently discovered hereditary colorectal cancer syndrome. Affected members typically develop 10 to 100 polyps occurring at around 40 years of age and are at high risk of developing colon cancer. Here, too, the genetic abnormality has been identified.

As time goes by, it is likely that additional hereditary syndromes leading to colon cancer will be identified. Nevertheless, it is important to remember that the overwhelming majority of colorectal cancers do not have a single, identifiable chromosomal abnormality that can be looked for in relatives in order to identify individuals at risk for colorectal cance

Colon cancer facts

• Colorectal cancer is a malignant tumor arising from the inner wall of the large intestine.
• Colorectal cancer is the third leading cause of cancer in males and fourth in females in the U.S.
• Risk factors for colorectal cancer include a family history of colorectal cancer, colon polyps, and long-standing ulcerative colitis.
• Most colorectal cancers develop from polyps. Removal of colon polyps can prevent colorectal cancer.
• Colon polyps and early cancer may have no symptoms. Therefore regular screening is important.
• Diagnosis of colorectal cancer can be made by barium enema or by colonoscopy with biopsy confirmation of cancer tissue.
• Treatment of colorectal cancer depends on the location, size, and extent of cancer spread, as well as the health of the patient.
• Surgery is the most common treatment for colorectal cancer.
• Chemotheraphy can extend life and improve quality of life for those who have had or are living with colorectal cancer.

References :http://www.medicinenet.com/colon_cancer/article.htm