Assessing and treating 
radiotherapy-associated 
diarrhea

PDF of Radiation 0213

Cancer treatment-related disruptions of normal gastrointestinal function are a common clinical challenge and usually include constipation or diarrhea.^1,2 Treatment-related diarrhea can lead to patient dehydration and nutritional and electrolyte imbalances and hypokalemia; rapid dehydration can lead to shock.^1,3 In severe cases, reductions in therapeutic radiation doses or even the discontinuation of radiotherapy are necessary.^1,3 Untreated, severe cases of treatment-related diarrhea can be fatal.^1,3


Radiation therapy-associated diarrhea is the most common acute toxicity among patients undergoing whole-body, pelvic, and abdominal radiotherapy, and is particularly frequent among patients receiving abdominal or pelvic radiotherapy for colorectal, anal, cervical, uterine, prostate, bladder, or testicular cancers.^1,3 Both chemotherapy and radiation therapy can cause diarrhea; when treatments kill nontarget, healthy cells in the mucosal lining of the intestines, absorption of GI fluids is disrupted, contributing to diarrhea.^1,3 Damaged intestinal mucosa also release prostaglandins and disrupt absorption of bile salts, hastening intestinal peristalsis and the movement of fluids and fecal matter through the intestines.^1,3 Radiotherapy-associated diarrhea tends to be more severe than diarrhea associated with other treatments.¹


Chronic or delayed diarrhea associated with radiation enteritis can appear months or even years after radiotherapy and is typically associated with total radiation doses greater than 45 Gy.³ It is less common than acute radiotherapy-associated diarrhea.³ Triggered by delayed intestinal ischemia, fibrosis, and ulceration, chronic radiotherapy-associated diarrhea frequently occurs with nausea, weight loss, and abdominal pain.³ 


Numerous treatments other than radiotherapy can cause treatment-associated diarrhea and interventions vary depending in part on the causative treatment modality or agent.² Careful assessment of the patient’s treatment regimen is therefore necessary before attributing the diarrhea to radiotherapy.³ For example, chemotherapeutic agents such as docetaxel (Docefrez, Taxotere, generics), 5-fluorouracil (5-FU) and its precursor capecitabine (Xeloda), and irinotecan (Camptosar, generics), are each associated with diarrhea.^2,3 Targeted agents like bortezomib (Velcade), erlotinib (Tarceva), sorafenib (Nexavar), sunitinib (Sutent), and imatinib (Gleevec) also include diarrhea among their treatment-associated toxicities.³ Enteral tube feeding, laxatives, and magnesium antacids are common causes of diarrhea, as well.³


Bacterial enteritis involving Salmonella, Escherichia coli, and Campylobacter can cause diarrhea among cancer patients. Another increasingly common and very serious cause of diarrhea, is intestinal infection with Clostridium difficile, a bacteria that excretes diarrhea-causing toxins.^3,4C difficile-associated diarrhea (CDAD) is frequently a hospital-acquired condition, associated with nasogastric intubation, GI surgery, cytostatic chemotherapies, antibiotic therapy, proton pump inhibitors, and inadequate hand hygiene.^3,4 Patients undergoing treatment for head and neck carcinomas appear to be at particular risk for C difficile infections and CDAD.⁴ Morbidity and mortality are high among patients with CDAD, and one recent retrospective study estimated approximately 40% of cases result in interruption of radiotherapy treatments.⁴ In addition to intensive patient screening for C difficile infection, avoiding tube feeding when possible and restricting the administration of antibiotics (particularly the fluoroquinolone moxifloxacin) and proton pump inhibitors appear to be associated with reduced CDAD risks.⁴ 


From the February 01, 2013 Issue of Oncology Nurse Advisor