Effect of Antibiotic Use on Outcomes with Systemic Therapies in Metastatic Renal Cell Carcinoma.

BACKGROUND: Antibiotic use alters commensal gut microbiota, which is a key regulator of immune homeostasis. OBJECTIVE: To investigate the impact of antibiotic use on clinical outcomes in metastatic renal cell carcinoma (mRCC) patients treated with systemic agents. DESIGN, SETTING, AND PARTICIPANTS: We analyzed two cohorts: an institutional cohort (n=146) receiving programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1)-based immune checkpoint inhibitors (ICIs) and a trial-database cohort (n=4144) receiving interferon-α (n=510), mammalian target of rapamycin (mTOR) inhibitors (n=660), and vascular endothelial growth factor targeted therapies (VEGF-TT; n=2974) on phase II/III clinical trials. OUTCOMES MEASUREMENTS AND STATISTICAL ANALYSIS: The association of antibiotic use (defined as use from 8 wk before to 4 wk after the initiation of anticancer therapy) with progression-free survival (PFS) and overall survival (OS) was evaluated using Cox regression, adjusted for known prognostic factors including International Metastatic RCC Database Consortium risk factors. RESULTS AND LIMITATIONS: Most patients were male, had clear cell histology, and were at an intermediate risk. Overall, in the institutional cohort, objective response rate (ORR) was 30%, PFS was 7.2 mo, and 1-yr OS was 77%. Antibiotic users (n=31, 21%) had a lower ORR (12.9% vs 34.8%, p=0.026) and shorter PFS (adjusted hazard ratio [HR]=1.96, 95% confidence interval [CI] 1.20-3.20, p=0.007) than antibiotic nonusers. In the trial-database cohort, antibiotic use (n=709, 17%) adversely impacted OS in patients treated with interferon (HR=1.62, 95% CI 1.13-2.31, p=0.008) or with VEGF-TT and prior cytokines (HR=1.65, 95% CI 1.04-2.62, p=0.033), but not patients treated with mTOR inhibitors or VEGF-TT without prior cytokines. Limitations include retrospective design, and limited details regarding concomitant medications and antibiotic indication/duration. CONCLUSIONS: Antibiotic use appears to reduce the efficacy of immunotherapy-based regimens in mRCC. The modulation of gut microbiota may play an important role in optimizing outcomes of patients treated with ICIs. PATIENT SUMMARY: We evaluated metastatic renal cell carcinoma patients and found that those who were treated with immunotherapy had worse outcomes if they also received antibiotics at the start of treatment. This study highlights the importance of judicious antibiotic use.