Colon Cancer

Overview

The 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 the rectum, which is the 20-cm segment of the colon before the anus. When the foods are digested in the stomach and the small intestine reaches the large intestine, the nutrients, water, and minerals that the body need is 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 a polyp, a growth of colonic mucosa into the lumen of the 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.

Risk Factors:

• Many factors 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,
• A diet low in fiber and rich in fat,
• Diabetes, obesity,
• Inactive life (sedentary lifestyle)
• Smoking,
• Alcohol

Symptoms:

Most patients cannot recognize symptoms of early-stage colon cancer. However, various symptoms may occur in advanced stages depending on the tumor's stage, size, and location. Common symptoms of colon cancer are as follows:

Prevention:

As is the case for all other cancers, prevention of colon cancer is also to eliminate or minimize manageable risks. Studies revealed that healthy eating (fibrous foods, fresh fruits, and vegetables with green leaves) plays a vital role in preventing 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 essential in preventing colon cancer as well as all other cancers. However, determining the best-personalized screening method for high-risk people during a doctor's visit is an important prevention strategy.

Diagnosis:

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 the colon can be examined with colonoscopy due to the 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, a provisional diagnosis is made. Polyps can be removed in the colonoscopy at the same time.

No blood test 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 called to investigate the cause of anemia will necessitate a colonoscopy. Barium enema examination is an imaging method used for diagnosis, although it is less reliable than colonoscopy..

Treatment:

After the diagnosis of colon cancer is made, the next step is to determine the stage. Your doctor will evaluate the stage (I to IV) of your cancer based on a set of stringent criteria. You may think colon cancer is very broadly staged as local, limited, regional, and distant. Cancer stages are usually symbolized by the Roman numbers I to IV. Stage IV is the most advanced stage of cancer. Each patient's treatment is planned by considering stage, age, general health status, and personal preferences.

Among the treatment options for colon cancer are chemotherapy, targeted treatment, radiotherapy, and surgery. These treatments can be used directly 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

Chemotherapy uses drugs to treat the cancer. The active substances of medicines kill the cancerous cells. Chemotherapeutic agents can be given into a vein or be taken by mouth. In the case of intravenous administration, a thin tube, called a 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 agents can be issued 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 sequential active and "off" period is called a cycle. In the early stage colon cancers, chemotherapy may be started before or after the surgery to both improve the outcomes of surgery and enhance the survival rates. Side effects of the chemotherapy are a function of the chemotherapeutic agent and the dose.

The most common side effects of chemotherapeutics include fatigue, nausea, vomiting, mouth sores, hair loss, and inflammation of the digestive system. Your doctor will also treat side effects caused by chemotherapy. If these side effects are severe enough to threaten your health, your doctor may advise you to suspend the treatment or to switch you to another chemotherapeutic agent.

Targeted Therapy

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.

Radiotherapy

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 mainly combined with chemotherapy, and this modality is also called chemoradiotherapy. Radiotherapy has a vast spectrum of side effects depending on the body part irradiated. Your doctor will explain the risks that apply to you.

Surgery

Minimally invasive surgery is the first choice for small tumors like polyps. A routine colonoscopy or colonoscopy performed on suspicion may remove tiny and early-stage tumors and polyps. Endoscopic mucosa resection is performed for more extensive tumors limited to the mucosa. A part of the colonic mucosa and the polyp or the tumor are removed. 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 inserting surgical instruments into the abdominal cavity and removing the operative material for colon tumors that involve longer segments, a small amount of the surrounding healthy tissue is removed along with the cancer.

Next, the non-disease two ends are anastomosed to each other to ensure a continuum of the large intestine (subtotal colectomy). If it is impossible to stitch two ends to each other, one end is closed and left in the abdominal cavity, while the other is anastomosed to the abdominal skin. This procedure is called colostomy.

A colostomy is usually required for a particular time, enabling complete healing of surgical wounds. However, if the tumor is located in the rectum very close to the anus, the patient may require to live with a colostomy for the rest of their life. Suppose the tumor involves a very substantial part of the colon, or it is present in both the right and left colon. In that case, the option is total colectomy – removal of the 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 to relieve symptoms. Even if a part of the colon is operatively removed due to colon cancer, the development of a polyp in the remaining colonic segments is always likely. Therefore, you need to visit your doctor at pre-determined intervals to have postoperative development of new colorectal polyps 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 colon and rectum cancer to your doctor will help you participate in your treatment and alleviate your concerns.