Large intestine (colon) and rectum form the final part of the digestive system. The sigmoid colon - the last part of the large intestine that measures 1.5 meters in total length – continues with rectum that is the 20-cm segment of the colon before anus. When the foods digested in the stomach and the small intestine reach the large intestine, the nutrients, water and minerals that the body need are absorbed and the remaining part is stored to be excreted from the anus.
Colon cancer is a type of cancer that originates from cells of the colon, while rectal cancer develops in cells of the rectum. These two types of cancer are usually referred to as colorectal cancers.
It is among the most common cancers both in our country and worldwide. Most cases occur in people older than 50 and the incidence does not significantly vary between men and women.
Colorectal cancers usually occur in the form of polyp, a growth of colonic mucosa into lumen of colon. Even though not all polyps transform into cancer, they should be removed or followed due to the risk of converting into cancer.
If it is diagnosed in the early stage, the disease can be successfully treated.
There are many factors that determine the risk of colon cancer. The major ones are listed below:
- Age (incidence increase at or above 50),
- History of colorectal cancer or polyp,
- Inflammatory bowel diseases (Ulcerative Colitis, Crohn’s Disease),
- Family history of colon cancer and genetic predisposition,
- Eating red meat and processed meats too much,
- Diet low in fiber and rich in fat,
- Diabetes, obesity,
- Inactive life (sedentary lifestyle)
Most patients cannot recognize symptoms of the early stage colon cancer. However, various symptoms may occur in advanced stages depending on stage, size and location of the cancer. Common symptoms of the colon cancer are as follows:
- Rectal bleeding or blood in stool
- Changes in bowel habits (diarrhea or constipation)
- Changes in consistency of the stool
- Stool thinner than usual
- Unexplained weight loss
- Feeling that bowel does not empty completely
- Abdominal cramp, gas or pain
- Chronic tiredness and fatigue
- Nausea, vomiting
As is the case for all other cancers, prevention of colon cancer is also to eliminate or minimize manageable risks. Studies revealed out that healthy eating (fibrous foods, fresh fruits and vegetables with green leaves) plays an important role in the prevention of the colon cancer. The principle components of a healthy life, including but not limited to avoiding tobacco and tobacco products, regular exercise, avoiding consumption of alcohol and maintenance of optimal body weight are important in preventing colon cancer as well as all other cancers.
However, an important prevention strategy is to determine the best personalized screening method for high-risk people in a doctor visit.
Regular screening should be started at a particular age (50 years) to diagnose colon cancer in the early stage. Chance of treatment is very high in early stage colon cancer. Therefore, the principal objective should be discovering the disease before onset or in early stage.
Mucosa of colon can be examined with colonoscopy due to presence of symptoms that lead to colon cancer suspect and suspicious areas can be biopsied in the examination. In a colonoscopy, your doctor can visualize the entire colon, ranging from the distal end of the small intestines to the rectum, and the rectum using the colonoscope, a flexible tube equipped with a camera, on a screen that is available in the colonoscopy room. If a lump or polyp is visualized, provisional diagnosis is made. At the same time, polyps can be removed in the colonoscopy.
There is no blood test that definitely points to colon cancer, excluding tumor marker assays that are used to quantify the risk of colon cancer. However, blood tests can be ordered to clarify the underlying cause of complaints, such as chronic fatigue and tiredness. Again, a positive fecal occult blood test that is ordered to investigate cause of anemia will necessitate colonoscopy.
Barium enema examination is an imaging method that is used for diagnosis, although it is not as reliable as colonoscopy.
After the diagnosis of colonc cancer is made, the next step is to determine the stage. Your doctor will determine stage (I to IV) of your cancer based on a set of very strict criteria. You may think that colonc cancer is very broadly staged as local, limited or regional and distant.
Cancer stages are usually symbolized with Roman numbers I to IV. Stage IV is the most advanced stage of cancer. A personalized treatment is planned for each patient by considering stage, age, general health status and personal preferences.
Among the treatment options of the colon cancer are chemotherapy, targeted treatment, radiotherapy and surgery. These treatments can directly be used to treat the tumor or they are instituted to increase quality of life and relieve symptoms in advanced stage cancers. Moreover, treatment options can be used alone or in combination.
Chemotherapy uses drugs to treat the cancer. The active substances of drugs kill the cancerous cells. Chemotherapeutic agents can be given into a vein or be taken by mouth. In case of intravenous administration, a thin tube, called catheter, is inserted into a great vein and the chemotherapeutic agent is administered through this catheter throughout the treatment period.
One or more than one chemotherapeutic agent can be administered depending on the type of cancer and response to treatment. Active chemotherapy maintained for a particular time is followed by an “off” period. After the “off” period expires, the treatment resumes. Each of these sequential active and “off” periods is called a cycle.
In the early stage colon cancers, chemotherapy may be started before or after the surgery in order to both improve outcomes of surgery and enhance the survival rates.
Side effects of the chemotherapy are a function of the chemotherapeutic agent and the dose. Most common side effects of chemotherapeutics include; fatigue, nausea, vomiting, mouth sores, hair loss and inflammation of the digestive system. Side effects caused by chemotherapy will also be treated by your doctor. If these side effects are severe enough to threaten your health, your doctor may advise to suspend the treatment or to switch you to another chemotherapeutic agent.
Targeted therapies are newer anti-cancer treatments compared to chemotherapy. These medicines target specific abnormalities that are present in cancerous cells. Before these medicines are started, cancer cells are first analyzed in laboratories to determine whether they have particular mutations or not.
Radiation therapy aims to kill cancer cells by using high-powered energy beams.
If the radiation source is out of the body and the beams are directed to cancer, this treatment is called external radiotherapy. On the other hand, if the radioactive agent is placed at the locus of the tumor through a needle or a catheter, method is called internal radiotherapy (brachytheraphy).
Although radiation therapy can be the first-line treatment, it is usually used to kill cells that cannot be removed operatively. In the first-line treatment, radiotherapy is mostly combined with chemotherapy and this modality is also called chemoradiotherapy.
Radiotherapy has a very wide spectrum of side effects depending on the body part irradiated. The risks that apply to you will be explained by your doctor.
Minimally invasive surgery is the first choice for small tumors like polyps.
On a routine colonoscopy or colonoscopy performed on a suspicion, very small and early stage tumors and polyps may be removed.
Endoscopic mucosa resection is performed for larger tumors that are limited to the mucosa. A part of the colonic mucosa is removed along with the polyp or the tumor.
Minimally invasive surgery is the modality that is preferred after colonoscopic interventions. Small incisions are made on the abdominal skin. While a tube equipped with a light source and a camera is inserted through one of these incisions, other incisions are reserved for insertion of surgical instruments into the abdominal cavity and the removal of the operative material.
For colon tumors that involve longer segments, a small amount of the surrounding healthy tissue is removed along with the tumor. Next, the non-diseases two ends are anastomosed to each other to ensure continuum of the large intestine (subtotal colectomy). If it is not possible to stitch two ends to each other, one end is closed and left in the abdominal cavity, while the other end is anastomosed to the abdominal skin. This procedure is called colostomy. Colostomy is usually required for a particular time and it enables complete healing of surgical wounds. However, if the tumor is located in rectum very close to the anus, the patient may require to live with a colostomy at the rest of the life.
If tumor involves a very substantial part of the colon or it is present in both right and left colon, the option is total colectomy – removal of entire colon- and the distal end of the small intestine is stitched to the rectum (ileorectal anastomosis).
A surgical procedure can be planned for colon cancer that already spread to other organs in order to relieve symptoms.
Even if a part of the colon is operatively removed due to colon cancer, development of a polyp in the remaining colonic segments is always likely. Therefore, you need to visit your doctor at pre-determined intervals in order to have postoperative development of new colorectal polyps be followed up.
Asking your questions about the treatment of colon and rectum cancer, your life after treatment, rehabilitation, pain management, clinical studies and all the questions in your mind about the colon and rectum cancer to your doctor will help you for an informed participation to your treatment and alleviating your concerns.
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