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Colorectal Cancer: Causes, Symptoms, Diagnosis, Treatment, and Prevention

Cancer that begins in the colon or rectum, which are parts of the large intestine, is called colorectal cancer. Water and nutrients are absorbed from food and waste is eliminated from the body in the large intestine, the last part of the digestive system. The fourth most common form of cancer in the United States is colorectal cancer, which affects all racial, ethnic, and sexual groups. Some factors, however, can increase the risk of developing colorectal cancer, such as older age, family history, genetic conditions, inflammatory bowel diseases, and lifestyle habits.

Causes of Colorectal Cancer

A change in the DNA of the cells that line the colon or rectum is believed to be the cause of colorectal cancer, although its exact cause is unknown. Mutations can cause cells to grow faster and live longer than normal cells, which leads to the formation of tumors, a mass of abnormal cells. These tumors are not cancerous and do not spread to other parts of the body. Some of these tumors are benign. 

In a colonoscopy, polyps can be removed during a screening test. There are, however, some of these tumors that are malignant, causing damage or invasion of nearby tissues and organs, or spreading to other parts of the body. This is called metastasis, which can make the treatment and prognosis of colorectal cancer more difficult.

Symptoms of Colorectal Cancer

There are many people with colorectal cancer who have no symptoms in the early stages, which is why regular screening tests are recommended for those at higher risk. Symptoms may include:

• A change in bowel habits, such as diarrhea, constipation, or feeling that the bowel does not empty completely

• Blood in the stool, which may be bright red or very dark

• Stool that is narrower or thinner than usual

• Abdominal pain or discomfort, such as cramps, gas, bloating, or fullness

• Unexplained weight loss

• Fatigue or weakness

• Anemia or low iron levels

These symptoms are not specific to colorectal cancer, and they may be caused by other conditions, such as hemorrhoids, irritable bowel syndrome, or infections. As a result, you should consult a doctor if you experience any of these symptoms for more than a few weeks, or if they interfere with your daily activities or are severe.

Diagnosis of Colorectal Cancer

Your doctor will examine your medical history, family history, symptoms, and risk factors in order to diagnose colorectal cancer. In addition, the doctor may perform a physical examination, which includes feeling your abdomen for lumps or masses and checking your rectum for abnormalities. Some tests may also be ordered, such as:

• Blood tests, to check for anemia, liver function, and tumor markers

• Stool tests, to check for blood or DNA changes in the stool

• Colonoscopy, to examine the inside of the colon and rectum with a thin, flexible tube with a light and a camera at the end, and to remove any polyps or take tissue samples (biopsies) for further analysis

• Imaging tests, such as X-rays, CT scans, MRI scans, PET scans, or ultrasound, to check for the size, location, and spread of the tumor

According to the size and extent of the tumor, the involvement of nearby lymph nodes, and the presence of distant metastases, if colorectal cancer is diagnosed, the doctor will assign a stage to the cancer. Cancer stages range from 0 to IV, with higher stages indicating more advanced cancer. By determining the stage, the patient's treatment options and prognosis can be determined.

Treatment of Colorectal Cancer

A patient's treatment for colorectal cancer depends on several factors, including the stage of the cancer, the location of the tumor, their overall health and preferences, and the treatment's risks and benefits. Colorectal cancer is treated in a variety of ways:

• A surgery is performed to remove the tumor and some of the surrounding healthy tissue, and then to reconnect the remaining colon or rectum tissues. To allow waste to pass out of the body into a bag (colostomy or ileostomy), a temporary or permanent opening (stoma) may be created on the abdomen. The liver or lungs may be treated with surgery if they have metastases.

• If surgery is not possible or the cancer has spread widely, chemotherapy may be given alone. Chemotherapy can be given by mouth, by injection, or through a vein (intravenously).

• In radiation therapy, high-energy rays or particles are used to damage or shrink cancer cells. Radiation therapy can be given before or after surgery, or as a replacement for surgery if surgery is not possible. External beam radiation, which is given outside the body, or brachytherapy, which is given inside the body near the tumor, are two types of radiation therapy.

• Drugs that target specific characteristics of cancer cells that facilitate their growth and survival are known as targeted therapy. Chemotherapy may be given with targeted therapy or alone if it does not work or causes severe side effects. Targeted therapy can be given orally, intravenously, or by injection.

• Drugs that stimulate the immune system to recognize and attack cancer cells are known as immunotherapy. Injections of immunotherapy or intravenous administration (intravenously) may be given in conjunction with chemotherapy or alone if chemotherapy does not work or causes severe side effects.

Some side effects of colorectal cancer treatment include nausea, vomiting, diarrhea, constipation, hair loss, mouth sores, skin problems, infections, bleeding, fatigue, nerve damage, or fertility problems. As the patient's response to the treatment changes, the doctor will adjust the dose. Additionally, the doctor may prescribe some medications or suggest some lifestyle changes to help manage side effects and improve quality of life.

Prevention of Colorectal Cancer

There is no sure way to prevent colorectal cancer, but there are some steps that may lower the risk, such as:

• When you are 50 or older, or have a family history of colorectal cancer, a genetic condition, or an inflammatory bowel disease, you should get regular screening tests. Polyps can be found and removed by screening tests, or cancer can be detected at an early stage, when it is easier to treat.

• A healthy diet rich in fruits, vegetables, whole grains, and lean proteins can help prevent obesity, diabetes, and inflammation, which are risk factors for colorectal cancer.

• The benefits of physical activity include maintaining a healthy weight, improving digestion, and boosting the immune system, which can lower cancer risk. Physical activity is recommended at least 30 minutes a day, most days of the week.

• Women should limit their alcohol consumption to one drink a day, while men should limit it to two drinks a day. Alcohol damages the lining of the colon and rectum, and increases certain hormones that promote cancer growth.

• Smoking can damage the DNA of the cells in the colon and rectum, and increase levels of certain chemicals that can cause inflammation and cancer.

• Inflammation and polyp formation in the colon and rectum can be reduced by taking aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen, if prescribed by the doctor. However, these medications can also cause some side effects, such as stomach ulcers, bleeding, or kidney problems, so they should be used with caution.