How can the gut-brain axis be supported in oncology patients undergoing cancer treatment?

Supporting the Gut-Brain Axis in Oncology Patients

Oncology patients undergoing cancer treatment should receive comprehensive gastrointestinal symptom management through validated assessment tools, targeted nutritional interventions including probiotic supplementation, and multidisciplinary supportive care to optimize both treatment tolerance and quality of life. 1, 2

Systematic Assessment and Monitoring

Use validated symptom questionnaires or patient-reported outcome measures (PROMs) routinely at every clinic visit to ensure accurate comprehensive assessment of gastrointestinal symptoms. 1, 2 Clinical symptoms alone are unreliable for diagnosing underlying physiological changes; comprehensive investigation is required if empirical therapy does not lead rapidly to significant benefits. 1

• Most patients developing GI symptoms after cancer treatment have more than one cause for their symptoms—all must be diagnosed and optimally treated to achieve resolution. 1
• Common treatable physiological changes include bile acid diarrhea, carbohydrate intolerance, pancreatic exocrine insufficiency, and small intestinal bacterial overgrowth. 2

Nutritional Support Strategy

Energy and Protein Requirements

• Target 25-30 kcal/kg/day for ambulatory patients and 20-25 kcal/kg/day for bedridden patients using actual body weight. 3
• Provide minimum 1.0 g protein/kg/day, with optimal range of 1.2-1.5 g protein/kg/day to maintain fat-free mass and reduce malnutrition risk. 3

Dietary Composition

• Emphasize a diet high in vegetables, fruits, and whole grains with low saturated fat. 4
• Focus on micronutrient-rich and phytochemical-rich foods, particularly cruciferous vegetables and tomato products. 4
• Ensure adequate vitamin D intake (at least 600 IU daily) and moderate calcium (not exceeding 1200 mg daily). 4

Nutritional Counseling

Individualized nutritional counseling by a trained professional is superior to simply providing supplements or standard care. 4 Counseling should focus on meeting energy and protein requirements, minimizing weight loss, and maintaining quality of life. 4

Microbiome-Targeted Interventions

Probiotic Supplementation

Probiotic supplementation demonstrates the strongest evidence for reducing GI symptoms during cancer therapy. 5 Meta-analysis shows probiotics significantly reduce:

• Abdominal pain incidence 5
• Vomiting incidence 5
• Diarrhea incidence 5

The gut microbiota plays crucial roles in regulating immune checkpoint inhibitor therapy efficacy through multiple mechanisms: metabolites directly affect immune homeostasis, certain microbes reverse T-cell function inhibition, and gut-brain axis communication regulates immune cell function in the brain. 6

Fecal Microbiota Transplantation

Emerging evidence suggests fecal microbiota transplantation (FMT) may enhance immune checkpoint inhibitor therapy response in some patients by optimizing gut microbiota structure and improving immune status. 6 This represents a frontier approach for patients with refractory symptoms or poor treatment response. 7

Enteral Nutrition Support

Indications for Tube Feeding

Initiate tube feeding when oral intake is inadequate (<60% of estimated energy expenditure) for more than 10 days, or when undernutrition already exists. 3

For radiation-induced severe mucositis or obstructive tumors of the head-neck or thorax, enteral feeding using nasogastric or percutaneous tubes is recommended. 1

Route Selection

• Short-term feeding (<30 days): Use nasogastric tubes 1, 3
• Longer-term feeding (>4 weeks): Consider percutaneous gastrostomy (PEG or RIG) 1, 3
• Recent evidence shows nasogastric tubes may have lower complication rates than PEG in head and neck cancer patients 3

Prophylactic Tube Feeding

In high-risk situations (hypopharyngeal primary site, T4 tumors, female sex, or combined radiochemotherapy), prophylactic tube feeding may maintain nutritional status and prevent treatment interruptions. 1

Parenteral Nutrition

Routine use of parenteral nutrition during chemotherapy, radiotherapy, or combined therapy is not recommended. 1 However, if patients are malnourished or facing starvation longer than one week and enteral support is not feasible, parenteral nutrition is indicated. 1

Specific Indications for Long-term PN

In aphagic incurable cancer patients with intestinal failure, offer long-term PN if: 1

1. Enteral nutrition is insufficient
2. Expected survival due to tumor progression exceeds 2-3 months
3. PN can stabilize or improve performance status and quality of life
4. The patient desires this mode of support

Mind-Body and Complementary Approaches

Mind-body modalities focusing on brain-mind-body interactions serve as effective adjunct therapies for managing symptoms like pain, dyspnea, and fatigue. 2 Massage therapy techniques reduce anxiety, depression, and pain, while acupuncture demonstrates efficacy in treating cancer-related nausea/vomiting and pain. 2

Critical Pitfalls to Avoid

• Do not use restrictive diets (ketogenic, fasting) in patients with or at risk of malnutrition—they lack clinical evidence and may cause insufficient energy intake and weight loss. 3
• Avoid diets that restrict energy intake, as they increase micronutrient deficiency risk. 3
• Do not rely on symptom clusters alone to distinguish underlying causes—investigations are required. 1
• Avoid excessive calcium supplementation (>1200 mg/day). 4

Multidisciplinary Team Approach

Cancer care should be delivered by specialized teams with access to rehabilitation specialists, psychologists, physiotherapists, and registered dietitians. 2 A specialized nurse or healthcare practitioner should serve as patient navigator throughout the cancer journey. 2 This integrated approach addresses the physical, emotional, and financial costs of cancer therapy that can be considerable for individuals, families, and society. 1