Effects of baseline neurological disorders on composite gastrointestinal toxicity risk in cancers of the lip, oral cavity, and pharynx, and in breast cancer through the gut-brain axis: A propensity-matched cohort study.

e18127 Background: Neurological disorders (NDs) such as depression and anxiety may influence the gut-brain axis, potentially exacerbating gastrointestinal adverse events during cancer treatment. However, their impact on adverse events (AEs) in cancers of the lip, oral cavity, and pharynx (CLOP) and breast cancer (BC) remains under explored. We evaluated the association between baseline NDs and the incidence of gastrointestinal AEs within 180 days following diagnosis in patients with CLOP or breast cancer. Methods: This study leveraged retrospective cohort TriNetX federated health research network database. Adults aged 18 years or older diagnosed with CLOP or BC were divided into cohorts with and without baseline NDs. Propensity score matching (1:1) was applied for demographics, race, ethnicity, body mass index, and ECOG performance status. Primary outcomes were the risk of gastrointestinal AEs (diarrhea, mucositis, nausea/vomiting, digestive system diseases (DD), fluid/electrolyte imbalance (FE), dry mouth (DM), GI mucositis (GIM), and a composite measure (CM) of all AEs) assessed via risk ratios (RR), hazard ratios (HR) from Kaplan-Meier survival analysis, and number of instances, excluding patients with prior outcomes. Results: For CLOP (64,558 matched patients per cohort) with NDs had higher risks--for diarrhea, RR was 2.39 (95% CI, 2.23-2.56) and HR 2.28 (95% CI, 2.12-2.45); mucositis, RR 1.44 (95% CI, 1.38-1.50) and HR 1.38 (95% CI, 1.32-1.44); nausea and vomiting, RR 1.74 (95% CI, 1.67-1.81) and HR 1.68 (95% CI, 1.60-1.75); DD, RR 1.24 (95% CI, 1.19-1.27) and HR 1.19 (95% CI, 1.16-1.23); FE, RR 1.52 (95% CI, 1.46-1.58) and HR 1.44 (95% CI, 1.38-1.50); DM, RR 1.56 (95% CI, 1.48-1.66) and HR 1.48 (95% CI, 1.39-1.58); GI mucositis, RR 2.01 (95% CI, 1.75-2.29) and HR 1.89 (95% CI, 1.65-2.17); CM, RR 1.56 (95% CI, 1.52-1.61) and HR 1.54 (95% CI, 1.49-1.59). For BC (315,342 matched patients per cohort), similar patterns emerged: DD, RR 1.78 (95% CI, 1.75-1.81) and HR 1.72 (95% CI, 1.69-1.75); diarrhea, RR 2.48 (95% CI, 2.39-2.57) and HR 2.35 (95% CI, 2.26-2.44); mucositis, RR 2.39 (95% CI, 2.25-2.53) and HR 2.25 (95% CI, 2.12-2.38); nausea and vomiting, RR 1.98 (95% CI, 1.93-2.01) and HR 1.89 (95% CI, 1.84-1.94); FE, RR 2.01 (95% CI, 1.95-2.07) and HR 1.89 (95% CI, 1.84-1.95); GIM, RR 2.31 (95% CI, 2.17-2.48) and HR 2.18 (95% CI, 2.04-2.33); DM, RR 3.38 (95% CI, 2.97-3.88) and HR 3.18 (95% CI, 2.78-3.62); CM, RR 1.98 (95% CI, 1.94-2.02) and HR 1.89 (95% CI, 1.86-1.94). Conclusions: Baseline ND are associated with significantly higher risks of gastrointestinal AEs in the 6 months following CLOP or BC diagnosis, suggesting a role for the gut-brain axis in treatment toxicities. Screening for neurological conditions may inform personalized supportive care strategies.