# Protect the gut flora of patients about to start immunotherapy

Source: https://onco.cc/ideas/idea-bio2-antibiotic-stewardship-io/  
OnCo record `idea-bio2-antibiotic-stewardship-io` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Antibiotics given in the weeks before immunotherapy are linked to much worse results. A simple stewardship rule could preserve benefit at no cost.

## Summary

Multiple cohort studies and meta-analyses report substantially worse survival in patients receiving broad-spectrum antibiotics within roughly 30 days before checkpoint blockade. Causality is uncertain because antibiotic use marks infection and frailty. A stewardship intervention (narrow-spectrum choice, shortest effective duration, deferral of non-urgent prophylaxis, and where necessary delaying checkpoint start) is testable and cheap either way.

## Fields

- Kind: Idea
- Last checked: 2026-09-08
- Hypothesis: A protocolised antibiotic stewardship bundle before checkpoint therapy improves 12-month survival compared with usual prescribing, which would establish that at least part of the observed association is causal and modifiable.
- Rationale: The association is large and consistent across tumour types, and antibiotic prescribing is highly modifiable. If the effect is confounding rather than causation, the trial establishes that cheaply and stops a growing body of over-interpretation.
- Proposed test: A cluster-randomised stewardship trial across oncology units, with antibiotic exposure metrics as process outcomes and survival as the clinical endpoint, plus a microbiome substudy.
- Maturity: early-clinical
- Actor: clinic

## Sources

- Bottleneck evidence (No one can predict who responds to immunotherapy): Haslam & Prasad (JAMA Network Open 2019): https://doi.org/10.1001/jamanetworkopen.2019.2535

## Connected records

- cancers: [Melanoma](https://onco.cc/cancers/melanoma/), [Non-small-cell lung cancer](https://onco.cc/cancers/nsclc/), [Renal cell carcinoma](https://onco.cc/cancers/rcc/)
- technologies: [Immune checkpoint inhibitors](https://onco.cc/technologies/checkpoint-inhibitor/), [Probiotics, antibiotics and stewardship around immunotherapy](https://onco.cc/technologies/probiotics-antibiotic-stewardship-io/)
- people: [Laurence Zitvogel](https://onco.cc/people/laurence-zitvogel/)
- bottlenecks: [Fragmented care and guideline gaps](https://onco.cc/bottlenecks/b-care-fragmentation/), [No incentive to repurpose cheap drugs](https://onco.cc/bottlenecks/b-generic-repurposing/), [No one can predict who responds to immunotherapy](https://onco.cc/bottlenecks/b-immunotherapy-response/)
- key papers: [Estimation of the Percentage of US Patients With Cancer Who Are Eligible for and Respond to Checkpoint Inhibitor Immunotherapy Drugs](https://onco.cc/key-papers/paper-haslam-jama-netw-open/)
- ideas: [Capture diet, fibre and antibiotic exposure in every immunotherapy pivotal trial](https://onco.cc/ideas/idea-nl-diet-covariates-io-trials/)

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