Most people don’t associate diarrhea with cancer, the former especially being a common symptom of an infection of the gastrointestinal tract. While considered an uncommon symptom, diarrhea can occur as a consequence of the cancer itself or as a side effect of the various cancer treatments.
A consequence of cancer
According to Dr. Roel Tolentino, treatment for diarrhea in cancer and treatment for infectious diarrhea are the same
According to Dr. Roel Tolentino, surgical oncologist, “Most of the time, we see diarrhea after surgery. But with regards to diarrhea during cancer, it’s very rare, although we do see it in patients with carcinoid syndrome, pancreatic cancer, gallbladder cancer, and especially those with biliary tract cancer.
“In these patients, there is a disturbance in the enterohepatic circulation [bile circulation from the liver to the small intestine] caused by an obstruction of the bile ducts by the tumor. If these patients eat fatty foods, these foods will not be absorbed by the small intestine. The fats will act as osmotic particles that will attract water into the lumen of the colon, thereby producing diarrhea.”
Dr. Tolentino explains that diarrhea can also happen when the small intestine fails to absorb the bile and it ends up in the colon. “It becomes an irritant, producing watery diarrhea.”
A consequence of treatment
In patients undergoing treatment for cancer, diarrhea is one of the most common side effects of therapy.
Chemotherapy. “The highest incidence of diarrhea is found in patients undergoing chemotherapy,” states Dr. Tolentino. “The chemotherapeutic agents affect the rapidly dividing cells in the body, which include the cells in the gastrointestinal tract. These cells become atrophic and irritate the lining of the intestines. The thickness of the intestinal lining would be affected and there would be diarrhea because of inflammation.”
He explains that diarrhea rates as high as 50 to 80 percent have been documented in chemotherapeutic regimens containing fluoropyrimidines (for instance, 5-fluorouracil) or irinotecan. In fact, reviews of several clinical trials involving a combination of irinotecan, high-dose fluorouracil and leucoverin in colorectal cancer have shown early death rates of 2.2 to 4.8 percent because of gastrointestinal toxicity.
Other drugs can cause diarrhea. Says Dr. Tolentino, “Cisplatin can also produce diarrhea, as well as cyclophosphamide, methotrexate and oxaloplatin. Almost all of the major chemotherapeutic drugs can cause diarrhea.”
Targeted therapy. With targeted therapy, diarrhea, as with other common side effects of cancer treatment, is less than what occurs under chemotherapy. “Targeted therapies are a different kind of therapy,” says Dr. Tolentino. “These drugs target a specific metabolic pathway. These monoclonal antibodies are different from the usual chemotherapeutic drugs.”
Radiotherapy. According to Dr. Tolentino radiotherapy-induced diarrhea depends on the radiation dose and the irradiated site in the abdomen. “Usually, a dose of 4,500 to 5,500 rads would produce minimal diarrhea, but as you go higher, the diarrhea becomes a great problem for the patient.”
Changes in normal bowel functions can also be expected in radiation therapy to the abdominal, pelvic, lumbar (back) or para-aortic fields. Aside from diarrhea, common side effects of radiation include cramping, gas, bloating, and malabsorption.
Surgery. Postsurgical complications of gastrointestinal surgery that may lead to the development of diarrhea include increased transit time, fat malabsorption, gastroparesis (partial stomach paralysis), fluid and electrolyte imbalance, and dumping syndrome.
“When we do resection of the small intestine or colon,” explains Dr. Tolentino, “the length of the gastrointestinal tract becomes shorter. Because of the faster transit time, food goes down immediately to the distal gastrointestinal tract. Surgery might alter your intestines’ ability to absorb nutrients or fat and may result in diarrhea.”
Infectious diarrhea vs. diarrhea in cancer
The term diarrhea per se means that there is bowel movement that is more frequent than normal. But how would you differentiate diarrhea as caused by an infectious agent from diarrhea in cancer?
“The clinical presentation is the same,” says Dr. Tolentino. “The patients would present with abdominal colic, the same crampy symptoms. The differentiating factor, however, is fever, which is more common in infectious diarrhea. Fever is not common in patients with cancer. Also, if there is colon or rectal cancer, the first symptom is constipation, not diarrhea, because the stools cannot pass beyond the obstruction.
However, when there is an increase in pressure in the partially obstructed intestinal lumen because of trapped digested food, the stools will just come out, producing bloody, explosive diarrhea.”
Treatment
According to Dr. Tolentino, the treatment for diarrhea in cancer is the same as the treatment for infectious diarrhea. Oral rehydration preparations are given to prevent dehydration and to correct fluid and electrolyte imbalance. Antidiarrheal drugs such as loperamide and diphenoxylate HCl are not contraindicated.
However, Dr. Tolentino advises that all cancer patients should seek medical advice for their ailments, especially because they already are immunocompromised. In cases where antibiotics are needed, the regimen for infectious diarrhea is different from that prescribed for diarrhea in cancer. “In infection, we can give metronidazole, but in cancer patients, we may give neomycin, which is not absorbed by the intestine. Plus, antidiarrheal agents might not be adequate. It may be necessary to decrease dosage or temporarily stop chemotherapy, allowing a window of healing of about two to three weeks. After the diarrhea has been resolved, treatment can be continued.”
Prevention
Predicting which patients will develop diarrhea depends on the person’s immune system and overall state of health, says Dr. Tolentino. “If the patient has a good immune system, he/she can resist the side effects of the various therapies. If the patient is healthy, the side effects, including diarrhea, is less severe.”
Dr. Tolentino believes that the old adage about an ounce of prevention being worth a pound of cure, is more than relevant for cancer patients. “Instead of eating three big meals a day, we advise patients with diarrhea to eat six small meals.
Patients should avoid spicy foods and foods with lactose [such as milk and dairy products], and those that are rich in carbohydrates and fats. In those patients with mild diarrhea, they should eat more bulk-forming foods, especially the BRAT [bananas, rice, apples, toast] diet to reduce frequency of stools. Fluid intake should also be increased to at least three liters per day. Avoid alcohol and caffeine-containing drinks. From my clinical experience, probiotic foods such as yogurt help modify harmful gut microorganisms that have been implicated in the development of diarrhea.”
Diarrhea need not be a life-threatening side effect of a treatment that is meant to save or prolong a life. With the right diet and strict medical supervision, cancer patients will not have diarrhea to add to their physical and emotional distress.