Is it safe to give probiotics (live microorganisms) to patients with cancer?

Probiotics in Cancer Patients: Safety and Efficacy Considerations

Probiotics can be given to cancer patients undergoing radiotherapy with caution, but there is insufficient evidence to recommend them routinely, and safety concerns exist in immunocompromised patients. 1

Key Guideline Recommendations

For Radiation-Induced Diarrhea

The ESPEN (European Society for Parenteral and Enteral Nutrition) guidelines explicitly state there are insufficient consistent clinical data to recommend probiotics to reduce radiation-induced diarrhea, despite some indication of protective effects. 1 This recommendation carries a "strength of recommendation: none" with low-level evidence and strong consensus. 1

However, the Italian Association of Radiotherapy and Clinical Oncology (AIRO) 2024 guidelines present more favorable evidence, noting that probiotics during pelvic radiotherapy significantly reduced acute toxicity in several studies. 1 Specifically:

• Probiotics reduced diarrhea incidence (53.8% vs 82.1%, p<0.05) 1
• Decreased severity of diarrhea and need for loperamide (p<0.01) 1
• Reduced grade 2 abdominal pain significantly (p<0.001) 1

Critical Safety Concerns

The primary concern is safety in immunocompromised patients, not general cancer patients. 1 The ESPEN guidelines emphasize that "the safety of using probiotics has to be reliably addressed before these products can be recommended in immunocompromised patients." 1

Documented serious adverse events include: 1

• Bacterial sepsis linked to lactobacilli-containing probiotics 1
• Gastrointestinal mucormycosis from mold contamination 1
• Increased mortality in severe acute pancreatitis patients 1

Clinical Decision Algorithm

Safe to Use:

• Immunocompetent cancer patients undergoing pelvic radiotherapy who develop radiation-induced diarrhea can receive probiotics (particularly Lactobacillus and Bifidobacterium species) 1
• Patients with intact intestinal mucosa and normal immune function 1

Use with Extreme Caution or Avoid:

• Immunocompromised patients (neutropenic, post-chemotherapy with severe immunosuppression) 1
• Patients with damaged intestinal mucosa 1
• Critically ill or hospitalized patients 1
• Patients undergoing high-dose chemotherapy or stem cell transplantation 1

Contraindicated:

• Severely debilitated patients 1
• Patients with central venous catheters and severe immunosuppression (risk of catheter-related sepsis) 2

Evidence Quality and Heterogeneity

The major limitation preventing a strong recommendation is heterogeneity in study design: 1

• Different bacterial strains used across trials 1
• Varying dosages and treatment durations 1
• Methodological weaknesses in trial quality 1
• Conflicting results even in well-designed studies 1

The 2017 ESPEN guidelines reviewed six randomized controlled trials: three showed no effect on diarrhea, while three reported reduced incidence. 1 However, all four trials examining fecal consistency unanimously showed benefit. 1

Practical Recommendations

If you decide to use probiotics in appropriate patients: 1

• Choose Lactobacillus and Bifidobacterium species specifically 1
• Initiate during radiotherapy and continue for three weeks afterward 1
• Monitor closely for signs of infection (fever, sepsis) 1
• Ensure product quality from reputable manufacturers (contamination risk exists) 1

Common pitfalls to avoid: 1

• Do not assume safety findings from one probiotic strain apply to others 1
• Avoid high-concentration products (450-900 billion bacteria/dose) in vulnerable patients 1
• Do not use in patients with predicted severe complications 1

Bottom Line

While the most recent 2024 radiotherapy guidelines show promising results for probiotics in reducing radiation-induced gastrointestinal toxicity 1, the authoritative ESPEN guidelines (2021) maintain that insufficient evidence exists for routine recommendation 1. The divergence reflects evolving evidence, but safety concerns in immunocompromised patients remain paramount. In clinical practice, probiotics may be considered for immunocompetent cancer patients undergoing radiotherapy who develop diarrhea, but should be avoided in severely immunocompromised or critically ill cancer patients. 1