Diarrhea in Prostate Cancer Patients

The European Society for Medical Oncology notes that older hormonal agents are associated with low and variable incidence of diarrhea, often without clinical relevance 1
Newer hormonal agents used in prostate cancer often cause mild intensity diarrhea, with underlying mechanisms including bile salt malabsorption and pancreatic insufficiency 2
Approximately 60% of patients experience temporary mild diarrhea during pelvic radiation treatment, with pathophysiology including direct radiation damage to intestinal tissue, release of free radicals, and damage to stem cells within intestinal crypts 3
Risk factors for radiation therapy-induced diarrhea include patient-related factors such as low BMI, comorbidities, and smoking history, as well as treatment-related factors like volume of small bowel in radiation field and radiation dose 3
Targeted agents used in advanced prostate cancer can cause diarrhea, with tyrosine kinase inhibitors having a significantly higher risk of causing both all-grade and high-grade diarrhea compared to conventional regimens 4
mTOR inhibitors cause diarrhea through microflora disequilibrium and malabsorption, while CDK4/6 and PARP inhibitors can also cause diarrhea, though underlying mechanisms are not well understood 5, 6
Immune checkpoint inhibitors can cause immune-mediated adverse events including diarrhea, particularly with anti-CTLA-4 therapy, and may present with or without colitis 7

Infectious Causes

C. difficile infection is an important consideration in cancer patients with diarrhea, occurring in 7-50% of cases following antibiotic administration, with risk factors including recent antibiotic use, hospitalization, and immunosuppression from cancer treatment 8
Other infectious causes to consider include bacterial pathogens, viral causes, and parasitic infections 8

The American Society of Clinical Oncology recommends evaluating diarrhea severity, duration, and associated symptoms, as well as assessing for warning signs like fever, neutropenia, dehydration, and severe cramping 8
Laboratory testing should include C. difficile testing, complete blood count, electrolytes, creatinine, and BUN, as well as blood cultures if fever is present 8
Extended workup for persistent symptoms should include testing for other enteric pathogens 8

The National Comprehensive Cancer Network advises always ruling out infectious causes before attributing diarrhea to treatment toxicity, and notes that neutropenic patients may not develop typical pseudomembranes on endoscopy 8
Multiple etiologies may coexist in prostate cancer patients, and accurate assessment of all possible causes is essential for appropriate management 2