LEONORA Protocol: synbiotics after colorectal cancer surgery to reduce gastrointestinal symptom burden — RCT protocol
This paper reports only a trial protocol; no efficacy data have been generated — effect direction remains insufficient.
| Population | Adults undergoing surgical resection for colorectal cancer, recruited at 10 German clinics (planned n = 206) |
|---|---|
| Intervention | Daily oral synbiotic for 12 weeks: 50 billion CFU of 12 bacterial strains (weeks 1–12) plus stepwise inulin 3–10 g/day (weeks 5–12) |
| Comparator | Double placebo: placebo capsules plus maltodextrin (organoleptic substitute for inulin) |
| Outcome | Gastrointestinal quality of life (day 90); Post-operative infection rates; Cancer recurrence; Cancer survival; Blood-based inflammatory biomarkers; Fecal microbiome composition; Fecal and serum metabolome |
Summary of findings
| Outcome | Effect | 95% CI | Certainty | Clinical relevance | Notes |
|---|---|---|---|---|---|
| Gastrointestinal quality of life (day 90) | not reported (protocol only) | — | Very low | — | |
| Post-operative infection rates | not reported (protocol only) | — | Very low | — | |
| Cancer recurrence | not reported (protocol only) | — | Very low | — | |
| Cancer survival | not reported (protocol only) | — | Very low | — | |
| Blood-based inflammatory biomarkers | not reported (protocol only) | — | Very low | — | |
| Fecal microbiome composition | not reported (protocol only) | — | Very low | — | |
| Fecal and serum metabolome | not reported (protocol only) | — | Very low | — |
Context
Colorectal cancer surgery, antibiotics, and chemotherapy profoundly disrupt the gut microbiome, causing chronic diarrhea and impaired quality of life in a substantial proportion of patients. Prior RCTs linked synbiotics to reduced post-operative infections and diarrhea, but gastrointestinal quality-of-life data remain sparse. LEONORA was designed to address this gap in a German surgical population.
What the study showed
The published article is exclusively a study protocol. No participants have been randomized, no clinical data have been collected, and no results are reported. No effect estimates, 95% CIs, or p-values arise from this document. Any efficacy claims derive from prior studies cited in the introduction, not from LEONORA data.
How it was done
Parallel-group, double-blind, placebo-controlled, multicenter RCT (10 centers, Germany). Planned sample: 206 participants (103 per arm). Intervention duration: 12 weeks. Primary endpoint assessed at 90 days post-surgery. Protocol registered and published in BMC Cancer (2026).
Effect magnitude
No effect size estimates are available. The sample size calculation was based on a hypothesized effect to be verified upon trial completion.
Risk of bias
This is a protocol publication: zero outcome data available. Bias risk not assessable (RoB 2 not applicable to protocols). Recruitment restricted to German centers limits generalizability. Adherence to a 12-week post-surgical intervention in oncology patients is a relevant operational challenge not addressed.
What this study does NOT prove
This study does NOT prove efficacy, safety, or any direction of effect of synbiotics on gastrointestinal quality of life after colorectal surgery. It is not generalizable beyond the German CRC surgical profile until results are published.
In clinical practice
No change in clinical practice is supported by this document. Clinicians should await trial results before considering synbiotics as standard post-colorectal-surgery care. The protocol may guide analogous study designs in other countries.
Limitations
This is a protocol publication: zero outcome data available. Bias risk not assessable (RoB 2 not applicable to protocols). Recruitment restricted to German centers limits generalizability. Adherence to a 12-week post-surgical intervention in oncology patients is a relevant operational challenge not addressed.
What is still missing
Primary and secondary results from LEONORA itself — expected after follow-up of all 206 patients is complete. Microbiome and metabolome data have not yet been generated.
Technical appendix
Version history
- 1.0 · 2026-06-29 — Auto-generated under Evidence Standard v1.0