Antibiotics and steroids, the double enemies of anticancer immunotherapy: a review of the literature

The advent of immunotherapy in onco-haematology has represented a kind of revolution that has been able to modify the prognosis of numerous tumours that until recently would have been rapidly lethal. While much is known about the mechanism of action of these drugs, relatively little is known about the factors that represent potential predictors of response and toxicity. Among these factors, the simultaneous administration of antibiotics and/or steroids seems to have a negative impact. Furthermore, several retrospective studies have highlighted the strong link between cancer and gut microbiota, regardless of the tumour site, and how microbiota, playing a key role in the prevention of systemic inflammation at various levels and in the intestinal homeostasis, can be negatively influenced by the dysbiosis caused by antibiotic therapy administered during or in the weeks immediately preceding the start of immunotherapy. Moreover, we assume that the concurrent administration of steroids, which is often necessary in cancer patients, likely results in a deleterious effect on the therapeutic outcomes of immunotherapy. In this review, we will try to clarify the evidence on the possible detrimental effects of antibiotics and steroids, which are currently considered the double enemies of anticancer immunotherapy.

Effects of Antibiotic Use on Outcomes in Cancer Patients Treated Using Immune Checkpoint Inhibitors: A Systematic Review and Meta-Analysis

Antibiotic (ATB) use seems to negatively affect the outcomes of immune checkpoint inhibitors (ICIs). The aim of this review is to clarify whether ATB use influences the efficacy of ICI treatment in cancer patients. Databases of MEDLINE, Embase, and Cochrane Library were searched for reports published in English between January 2007 and December 2019. We included studies that compared the outcomes of ATB use and no-ATB use in cancer patients using ICIs. Two reviewers independently selected eligible studies and extracted the data. Meta-analysis was performed with pooling of unadjusted hazard ratios (HRs) for overall survival (OS) and progression-free survival (PFS), and with pooling of odds ratios (ORs) for objective response rate (ORR). Thirty-eight studies involving 8409 patients were finally included for qualitative or quantitative analyses. Cancer types included renal cell carcinoma, non-small cell lung cancer, urothelial carcinoma, melanoma, gastrointestinal cancer, and others. Meta-analyses revealed that ATB use was associated with poor OS [HR: 1.80, 95% confidence interval (CI): 1.44-2.26, P<0.001], PFS (HR: 1.55, 95% CI: 1.26-1.91, P<0.001) and ORR (OR: 0.63, 95% CI: 0.42-0.95, P=0.03). Subgroup analysis found that these relationships were not influenced by cancer type or ICI regimens, but were dependent on the timing of ATB use. Narrative results of multivariable analyses further confirmed the negative effects of ATB use on OS and PFS. In cancer patients using ICIs, pre-ATB use close to the start of ICI treatment (within 60 d) was detrimental to outcomes in terms of OS, PFS, and ORR.

NSCLC Immunotherapy Efficacy and Antibiotic Use: A Systematic Review and Meta-Analysis

Immune checkpoint inhibitors (ICIs) have dramatically improved patient outcomes in a variety of tumor types, but with variable efficacy. Recent research has suggested that antibiotic-induced disruption of the microbiota may impact ICI efficacy. We performed a systematic review and meta-analysis of studies that assessed the impact of antibiotic use on the survival of patients diagnosed with NSCLC and treated with ICI. We systematically searched Medline, the Cochrane Library, and major oncology conferences proceedings. Eligible studies mentioned hazard ratio or Kaplan-Meier curves for progression-free survival (PFS) or overall survival (OS) based on antibiotic exposure before or during ICI treatment. We identified 23 eligible studies. The impact of antibiotics was then evaluated in 2208 patients for PFS and 5560 for OS. For both PFS and OS meta-analyses, the between-study heterogeneity was high (Higgins and Thompson I² of 69% and 80%, respectively). The pooled hazard ratio was 1.47 (95% confidence interval [CI]: 1.13-1.90) for PFS and 1.69 (95% CI: 1.25-2.29) for OS revealing a significantly reduced survival in patients with NSCLC exposed to antibiotics. The median OS was reduced on average by 6.7 months (95% CI: 5.1-8.4) in the patients exposed to antibiotics. The effect seems to depend on the time window of exposure with stronger effects reported when the patients took antibiotics [-60 days; +60 days] around ICI initiation. In patients with NSCLC, the findings of the meta-analysis indicate that antibiotic use before or during treatment with ICI leads to a median OS decreased by more than 6 months. Specifically, exposure shortly before or after ICI initiation seems to be particularly detrimental, whereas antibiotic use later during disease course does not seem to alter survival. Because PFS and OS were difficult to compare between studies owing to heterogeneity and the multiple confounding factors identified, further studies are needed to strengthen the understanding of this phenomenon.

Antibiotic use and the efficacy of immune checkpoint inhibitors in cancer patients: a pooled analysis of 2740 cancer patients

The gut microbiota plays a critical role in the anti-tumor immune response. There is increasing data showing that antibiotics (ATBs) change the composition of the gut microbiota and affect the efficacy of immune checkpoint inhibitors (ICIs). However, this is the first meta-analysis to evaluate the association between ATB use and ICI efficacy in cancer patients to provide a better understanding of the strength of this association. We performed a literature search for relevant studies that evaluated the relationship between ATB use and ICI efficacy using the PubMed, Embase, and conference databases. The primary outcomes consisted of overall survival (OS) and progression-free survival (PFS) measured by hazard ratios (HR) and corresponding 95% confidence intervals (CI). Subgroup and sensitivity analyses were also performed. A total of 19 eligible studies comprising 2,740 cancer patients treated with ICIs were included in the analysis. Our results indicated that ATB use was negatively associated with OS in cancer patients (HR = 2.37; 95% CI = 2.05-2.75; P < .001), without heterogeneity (I2 = 0.0%; P = .851). Moreover, ATB use significantly reduced PFS in patients treated with ICIs (HR = 1.84; 95% CI = 1.49-2.26; P < .001; I2 = 56.2%). Similar results were obtained in the subgroup analyses stratified by the time of ATB use and cancer type. Sensitivity analyses confirmed the stability of our results. Therefore, the findings of our meta-analysis indicated that ATB use is negatively associated with OS and PFS in cancer patients treated with ICI immunotherapy.