Gut microbiota and metabolite disruption during breast cancer chemotherapy is associated with peripheral neuropathy sensory symptoms and pain.

Chemotherapy-induced peripheral neuropathy (CIPN) is a common and serious adverse effect of chemotherapeutic agents such as taxanes, platinum compounds, and vinca alkaloids. Efforts to prevent and treat CIPN are impeded by an incomplete understanding of its pathogenesis. Recently, the gut microbiota has been causally linked to CIPN in rodent models. However, human studies exploring this connection are limited. Here, in a cohort of 70 patients with early-stage breast cancer, relationships between disruptions in the gut microbiota during chemotherapy and both participant CIPN symptoms and general pain symptoms were investigated. Study participants provided fecal samples (for 16S rRNA sequencing and targeted metabolomics), blood samples, and sensory symptom information during the three days prior to their first and their final chemotherapy (including a taxane drug) infusions. Sensory neuropathy symptoms increased during treatment, as did circulating levels of neurofilament light chain (NFL), a putative biomarker of CIPN. Decreases in microbiota alpha diversity during chemotherapy were associated with worse neuropathy symptoms during treatment, along with worsening of general pain, after controlling for pre-treatment baseline symptoms. Larger shifts in beta diversity from baseline to last infusion also coincided with more severe neuropathy symptoms. Bacterial producers of short-chain fatty acids were decreased in participants with neuropathy symptoms at the final chemotherapy infusion. Furthermore, decreases in fecal levels of short-chain fatty acids during treatment were related to worse neuropathy symptoms, suggesting a potential mechanism by which gut microbiota alterations could influence CIPN. Collectively, these findings corroborate preclinical work linking the gut microbiota to CIPN and provide evidence of potential microbiota involvement in general pain symptoms as well. Larger confirmatory studies in the future could support microbiota-targeted interventions for CIPN, such as fecal microbiota transplants or dietary interventions.