Colorectal Cancer: Side Effects


Common side effects of colorectal cancer and/or colorectal cancer treatment include the following.


Constipation is the infrequent or difficult passage of stool. About 40% of patients in palliative care (care given to improve a patient’s quality of life) experience constipation, and about 90% of patients taking opioid medications (narcotics) experience constipation. Constipation includes fewer bowel movements, stools that are abnormally hard, discomfort or a feeling of incomplete rectal emptying. Patients with constipation can experience pain, swelling in the abdomen, loss of appetite, nausea and/or vomiting, inability to urinate and confusion.


Diarrhea is frequent, loose or watery bowel movements. It is a common side effect of certain chemotherapeutic drugs or of radiation therapy. Medications are available to manage diarrhea if it occurs. In some cases, diarrhea can lead to dehydration and needs to be managed in the hospital or clinic with intravenous fluids and replacement of minerals that can be lost when diarrhea occurs.


Fatigue is extreme exhaustion or tiredness and is the most common problem patients with cancer experience. More than half of patients experience fatigue during chemotherapy or radiation therapy, and up to 70% of patients with advanced cancer experience fatigue. Patients who feel fatigue often say that even a small effort, such as walking across a room, can seem like too much. Fatigue can seriously affect family and other daily activities and can make patients avoid or skip cancer treatments.

Fluid in the Abdomen (Ascites)

Ascites is the buildup of fluid in the abdomen, in the area around the organs known as the peritoneal cavity. Ten percent of all ascites is caused by cancer and is called malignant ascites. Most cancer-related ascites appear in patients with cancers of the ovary, endometrium (lining of the uterus), breast, colon, GI system or pancreas. These cancers can cause fluid to build up in the body. People with ascites may experience weight gain, abdominal swelling, a sense of fullness or bloating, a sense of heaviness, indigestion, nausea and/or vomiting, changes to the navel, hemorrhoids (a condition that causes) painful swelling near the anus) or ankle swelling.

Mouse Sores (Mucositis)

Mucositis is an inflammation of the inside of the mouth and throat, leading to painful ulcers and mouth sores. It occurs in up to 40% of patients receiving chemotherapy treatments. Mucositis can be caused by a chemotherapeutic drug directly or the reduced immunity brought on by chemotherapy.

Nausea and Vomiting

Vomiting is the act of expelling the contents of the stomach through the mouth. It is a natural way for the body to rid itself of harmful substances. Nausea is the urge to vomit. Nausea and vomiting are common in patients receiving chemotherapy for cancer and in some patients receiving radiation therapy. Many patients with cancer say they fear nausea and vomiting more than any other side effects of treatment. When it is minor and treated quickly, nausea and vomiting can be quite uncomfortable but cause no serious problems. Persistent vomiting can cause dehydration, electrolyte imbalance, weight loss, depression and avoidance of chemotherapy.


Depending on the stage of the disease, 30% to 75% of all patients experience pain from cancer. About 85% to 95% of cancer pain can be treated successfully. Pain can make other aspects of cancer seem worse, such as fatigue, weakness, sleep disturbance and confusion. Pain can come from the tumor itself or may be a result of cancer treatment. Pain from a tumor can be a result of the tumor growing and spreading to the bones or other organs and putting pressure on and damaging nerves. Pain from surgery is normal and may persist for months or years. Pain may develop after radiation therapy and go away on its own. It can also develop months or years after treatment, especially after radiation therapy to the chest, breast or spinal cord. Certain chemotherapeutic drugs can cause pain along with numbness in the fingers and toes.

Sexual Dysfunction

Sexual dysfunction is common in all people, affecting up to 43% of women and 31% of men without cancer. It may be even more common in patients with cancer, as a result of treatments, the tumor or stress. Many people, with or without cancer, find it intimidating to discuss sexual problems with their doctors. Sexual problems are most commonly caused by body changes from cancer surgery, chemotherapy or radiation therapy, hormone changes, fatigue, pain, nausea and/or vomiting, medications that reduce libido (desire for sex), fear of recurrence, stress, depression and anxiety. Symptoms of sexual dysfunction generally fall into four categories: desire disorders, arousal disorders, orgasmic disorders and pain disorders.

Hand-Feet Syndrome

Hand-feet syndrome is a side effect of some types of chemotherapy. It occurs when small amounts of chemotherapy leak out of the capillaries (small blood vessels) in the hands and feet. Once out of the blood vessels, the chemotherapy damages the surrounding tissues. Symptoms include redness, swelling, burning, tenderness and rash. In more severe cases, people may also experience cracked or peeling skin, blisters, pain and difficulty walking or using the hands.


Anemia is common in patients with cancer, especially those receiving chemotherapy. Anemia is an abnormally low level of red blood cells (RBCs). RBCs contain hemoglobin (an iron protein) that carries oxygen to all parts of the body. If the level of RBCs is too low, parts of the body do not get enough oxygen and cannot work properly. Most patients with anemia feel tired or weak. The fatigue (tiredness) associated with anemia can seriously affect quality of life and make it more difficult for patients to cope with cancer and treatment side effects

Blocked Intestine (Gastrointestinal, or GI, Obstruction)

In some patients with colorectal cancer, the tumor can grow so it blocks the path that food and fluids take when they travel through the bowels. Scar tissue (commonly called adhesions) may also cause an obstruction of the bowel in patients who have previously had surgery. Normally, the intestines move food and fluids through the GI tract, and enzymes, fluid and electrolytes help the body to absorb nutrients. In a GI obstruction, the food and fluids cannot move through the system, and the normal contraction the intestines make to move the food (called peristalsis) can cause intense pain. If left untreated, a GI obstruction is a very serious and even life-threatening problem. Patients with a GI obstruction may experience nausea and/or vomiting, pain from the obstruction and cramping from the movement of the intestine as it tries to move food along.


Neutropenia is an abnormally low level of neutrophils, a type of white blood cell. All white blood cells help the body to fight infection. Neutrophils fight infection by destroying bacteria. Patients who have neutropenia are at increased risk for developing serious bacterial infections because there are not enough neutrophils to destroy harmful bacteria. Neutropenia occurs in about 50% of patients receiving chemotherapy and is common in patients with leukemia. Tell your doctor right away if you are experiencing these symptoms:

High blood Pressure

Peripheral sensory neuropathy (numbness and tingling of the fingers and toes)