Overview
Colon cancer is a type of cancer that begins in the large intestine (colon). The colon is the final part of the digestive tract.
Although it can occur at any age, colon cancer mainly affects older persons. On the inside of the colon, it typically starts as tiny polyps—clumps of cells that aren’t malignant (benign). Some of these polyps may develop into colon cancer in the future.
Small polyps could not even cause any symptoms. In order to identify and remove polyps before they develop into cancer, doctors advise routine screening tests to help prevent colon cancer.
There are numerous therapies available to help control colon cancer, such as surgery, radiation therapy, and medication such as chemotherapy, targeted therapy, and immunotherapy.
The term colorectal cancer, which combines the terms colon cancer and rectal cancer (which starts in the rectum), is often used to refer to colon cancer.
Symptoms
Signs and symptoms of colon cancer include:
- A persistent 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
Early on in the disease, colon cancer is often symptomless in many patients. Depending on the size and location of the cancer in your large intestine, symptoms may differ when they do.
Causes
Most colon cancers are unknown causes, according to doctors.
Colon cancer typically starts when normal colonic cells experience DNA abnormalities (mutations). A set of instructions that inform a cell what to do can be found in its DNA.
Your body’s healthy cells divide and grow in an organized fashion to maintain regular physiological function. However, when a cell’s DNA is harmed and it becomes cancer, it continues to divide even though new cells are not required. A tumor is created as the cells assemble.
The cancer cells may spread over time and engulf neighboring healthy tissue, causing it to be destroyed. Additionally, malignant cells might go to other body regions and deposit themselves there (metastasis).
Risk factors
Factors that may increase your risk of colon cancer include:
- Older age. Colon cancer can be diagnosed at any age, but a majority of people with colon cancer are older than 50. The rates of colon cancer in people younger than 50 have been increasing, but doctors aren’t sure why.
- African-American race. African-Americans have a greater risk of colon cancer than do people of other races.
- A personal history of colorectal cancer or polyps. If you’ve already had colon cancer or noncancerous colon polyps, you have a greater risk of colon cancer in the future.
- Inflammatory intestinal conditions. Chronic inflammatory diseases of the colon, such as ulcerative colitis and Crohn’s disease, can increase your risk of colon cancer.
- Inherited syndromes that increase colon cancer risk. Some gene mutations passed through generations of your family can increase your risk of colon cancer significantly. Only a small percentage of colon cancers are linked to inherited genes. The most common inherited syndromes that increase colon cancer risk are familial adenomatous polyposis (FAP) and Lynch syndrome, which is also known as hereditary nonpolyposis colorectal cancer (HNPCC).
- Family history of colon cancer. You’re more likely to develop colon cancer if you have a blood relative who has had the disease. If more than one family member has colon cancer or rectal cancer, your risk is even greater.
- Low-fiber, high-fat diet. Colon cancer and rectal cancer may be associated with a typical Western diet, which is 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 and processed meat.
- A sedentary lifestyle. People who are inactive are more likely to develop colon cancer. Getting regular physical activity may reduce your risk of colon cancer.
- Diabetes. People with diabetes or insulin resistance 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 may have an increased risk of colon cancer.
- Alcohol. Heavy use of alcohol increases your risk of colon cancer.
- Radiation therapy for cancer. Radiation therapy directed at the abdomen to treat previous cancers increases the risk of colon cancer.
Prevention
Screening colon cancer
Around the age of 45, doctors advise persons with an average risk of colon cancer to think about getting screened. However, those at higher risk, such as those with a family history of colon cancer, have to think about screening earlier.
There are several screening options, each having advantages and disadvantages of its own. Together, you can select which tests are right for you after discussing your options with your doctor.
Lifestyle changes to reduce your risk of colon cancer
You can take steps to reduce your risk of colon cancer by making changes in your everyday life. Take steps to:
- Eat a variety of fruits, vegetables and whole grains. Fruits, vegetables and whole grains contain vitamins, minerals, fiber and antioxidants, which may play a role in cancer prevention. Choose a variety of fruits and vegetables so that you get an array of vitamins and nutrients.
- Drink alcohol in moderation, if at all. If you choose to drink alcohol, limit the amount of alcohol you drink to no more than one drink a day for women and two for men.
- Stop smoking. Talk to your doctor about ways to quit that may work for you.
- Exercise most days of the week. Try to get at least 30 minutes of exercise on most days. If you’ve been inactive, start slowly and build up gradually to 30 minutes. Also, talk to your doctor before starting any exercise program.
- Maintain a healthy weight. If you are at a healthy weight, work to maintain your weight by combining a healthy diet with daily exercise. If you need to lose weight, ask your doctor about healthy ways to achieve your goal. Aim to lose weight slowly by increasing the amount of exercise you get and reducing the number of calories you eat.
Colon cancer prevention for people with a high risk
It has been discovered that several drugs lower the risk of colon cancer or precancerous polyps. For instance, some data suggests that regular aspirin or aspirin-like medication use lowers the incidence of polyps and colon cancer. However, it is unclear what dosage and how long would be required to lower the risk of colon cancer. Daily aspirin use carries some dangers, such as ulcers and gastrointestinal bleeding.
Those at a high risk of colon cancer are typically the only ones who should consider these choices. To advise these drugs to those with a typical risk of colon cancer would require more research.
If you are more likely to develop colon cancer, talk to your doctor about your risk factors to find out if taking preventive medicine is safe for you.
Diagnosis
Screening for colon cancer
For healthy individuals who do not exhibit any symptoms, doctors advise a number of screening tests to look for non-cancerous colon polyps or indicators of colon cancer. The probability of curing colon cancer is highest when it is discovered in its earliest stages. It has been demonstrated that screening lowers your risk of dying from colon cancer.
Doctors typically advise starting colon cancer screenings around age 45 for persons with an average risk of the disease. However, those who are at a higher risk, such as those who have a family history of colon cancer or are of African-American background, ought to think about screening earlier.There are several screening options, each having advantages and disadvantages of its own. Together, you can select which tests are right for you after discussing your options with your doctor. Polyps can be removed during a colonoscopy if it is performed for screening in order to catch them early before they develop into cancer.
Diagnosing colon cancer
If your signs and symptoms indicate that you could have colon cancer, your doctor may recommend one or more tests and procedures, including:
- Using a scope to examine the inside of your colon (colonoscopy). Colonoscopy uses a long, flexible and slender tube attached to a video camera and monitor to view your entire colon and rectum. If any suspicious areas are found, your doctor can pass surgical tools through the tube to take tissue samples (biopsies) for analysis and remove polyps.
- Blood tests. No blood test can tell you if you have colon cancer. But your doctor may test your blood for clues about your overall health, such as kidney and liver function tests.Your doctor may also test your blood for a chemical sometimes produced by colon cancers (carcinoembryonic antigen, or CEA). Tracked over time, the level of CEA in your blood may help your doctor understand your prognosis and whether your cancer is responding to treatment.
Staging Colorectal Cancer
| Stage | Tumor (Maximum Penetration) | Regional Lymph Node Metastasis | Distant Metastasis |
|---|---|---|---|
| 0 | Tis | N0 | M0 |
| I | T1 or T2 | N0 | M0 |
| II | T3 | N0 | M0 |
| III | Any T or | Any N | M0 |
| T4 | N0 | M0 | |
| IV | Any T | Any N | M1 |
| * TNM classification: Tis =carcinoma in situ; T1 = submucosa; T2 = muscularis propria; T3 = penetrates all layers (for rectal cancer, includes perirectal tissue); T4 = adjacent organs or peritoneum. N0 = none; N1 = 1–3 regional nodes; N2 = ≥ 4 regional nodes; N3 = apical or vascular trunk nodes. M0 = none; M1 = present. |
Treatment
Your specific situation, including the location and stage of your cancer as well as any additional health issues you may have, will determine which treatments are most likely to benefit you. Surgery to remove the tumour is typically the first step in treating colon cancer. There may also be a recommendation for additional therapies like chemotherapy and radiation therapy.
Surgery for colon cancer in its early stages
If your colon cancer is very small, your doctor may recommend a minimally invasive approach to surgery, such as:
- Removing polyps during a colonoscopy (polypectomy). If your cancer is small, localized, completely contained within a polyp and in a very early stage, your doctor may be able to remove it completely during a colonoscopy.
- Endoscopic mucosal resection. Larger polyps might be removed during colonoscopy using special tools to remove the polyp and a small amount of the inner lining of the colon in a procedure called an endoscopic mucosal resection.
- Minimally invasive surgery (laparoscopic surgery). Polyps that can’t be removed during a colonoscopy may be removed using laparoscopic surgery. In this procedure, your surgeon performs the operation through several small incisions in your abdominal wall, inserting instruments with attached cameras that display your colon on a video monitor. The surgeon may also take samples from lymph nodes in the area where the cancer is located.
Surgery for colon cancer that is more advanced
If the cancer has grown into or through your colon, your surgeon may recommend:
- Partial colectomy. During this procedure, the surgeon removes the part of your colon that contains the cancer, along with a margin of normal tissue on either side of the cancer. Your surgeon is often able to reconnect the healthy portions of your colon or rectum. This procedure can commonly be done by a minimally invasive approach (laparoscopy).
- Surgery to create a way for waste to leave your body. When it’s not possible to reconnect the healthy portions of your colon or rectum, you may need an ostomy. This involves creating an opening in the wall of your abdomen from a portion of the remaining bowel for the elimination of stool into a bag that fits securely over the opening.Sometimes the ostomy is only temporary, allowing your colon or rectum time to heal after surgery. In some cases, however, the colostomy may be permanent.
- Lymph node removal. Nearby lymph nodes are usually also removed during colon cancer surgery and tested for cancer.
Surgery for advanced cancer
In order to relieve a blockage in your colon or treat other issues, your surgeon may advise surgery if your cancer is very advanced or if your general health is very bad. This surgery is performed to treat the signs and symptoms of cancer rather than to treat the disease itself, such as a blockage, bleeding, or pain.
Your doctor might advise surgery or other localized therapies to eradicate the cancer if it has only spread to your liver or lung and your general health is otherwise good. This sort of operation may be preceded or followed by chemotherapy. The long-term possibility of becoming cancer-free is offered by this method.
Chemotherapy
Chemotherapy uses drugs to destroy cancer cells. Chemotherapy for colon cancer is usually given after surgery if the cancer is larger or has spread to the lymph nodes. In this way, chemotherapy may kill any cancer cells that remain in the body and help reduce the risk of cancer recurrence.
Chemotherapy might also be used before an operation to shrink a large cancer so that it’s easier to remove with surgery.
Chemotherapy can also be used to relieve symptoms of colon cancer that can’t be removed with surgery or that has spread to other areas of the body. Sometimes it’s combined with radiation therapy.
For some people with low-risk stage III colon cancer, a shorter course of chemotherapy after surgery may be possible. This approach may reduce the side effects compared with the traditional course of chemotherapy, and may be just as effective.
Radiation therapy
To kill cancer cells, radiation therapy makes use of potent energy sources like protons and X-rays. Before surgery, it could be used to reduce the size of a large cancer to make removal easier.
Radiation therapy may be used to treat symptoms, such as pain, when surgery is not an option. Chemotherapy and radiation are occasionally combined.
Targeted drug therapy
Targeted drug treatments focus on specific abnormalities present within cancer cells. By blocking these abnormalities, targeted drug treatments can cause cancer cells to die.
Targeted drugs are usually combined with chemotherapy. Targeted drugs are typically reserved for people with advanced colon cancer.
Immunotherapy
An anti-cancer medicine therapy called immunotherapy makes use of your immune system. Because cancer cells create proteins that prevent immune system cells from detecting the cancer cells, your body’s immune system may not attack your cancer. Immunotherapy affects that process in order to work.
Advanced colon cancer patients typically receive immunotherapy. To determine whether your cancer cells are likely to respond to this treatment, your doctor may test them.
Supportive (palliative) care
Palliative care is a type of specialist medical treatment that concentrates on relieving pain and other severe sickness symptoms. A group of medical professionals—including doctors, nurses, and other specialists—who specialize in providing palliative care collaborate with you, your family, and your other medical professionals to add an extra layer of support to your ongoing treatment.
Teams providing palliative care work to enhance the quality of life for cancer patients and their families. Along with any curative or other therapies you might be receiving, this type of care is available.
People with cancer may feel better and live longer when palliative care is utilized in addition to all other necessary therapies.