To explore changes in serum diamine oxidase (DAO) levels and their clinical significance in patients with gastrointestinal toxicity induced by fluorouracil antineoplastic drugs.

Patients with gastrointestinal tumors receiving fluorouracil-based antineoplastic therapy were divided into treatment group and control group according to whether gastrointestinal toxicity occurred during chemotherapy. The treatment group was further subdivided into ≤grade Ⅱ group and grade Ⅲ group based on the severity of gastrointestinal toxicity. General clinical data were collected, and serum DAO levels before chemotherapy and 7 days after chemotherapy were compared between treatment and control groups, as well as among patients with different grades of gastrointestinal toxicity. Logistic regression model was used to analyze the relationship between DAO levels and gastrointestinal toxicity, and receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive value of serum DAO levels 7 days after chemotherapy for the occurrence of gastrointestinal toxicity.

A total of 50 patients were ultimately included as study subjects, with 26 in treatment group and 24 in control group. The serum DAO levels 7 days after chemotherapy were (14.71±3.44) and (10.89±3.67) U·L^-1 in treatment and control groups, respectively. The serum DAO level in treatment group was significantly higher than that in control group 7 days after chemotherapy (P<0.05). The serum DAO levels 7 days after chemotherapy in ≤grade Ⅱ subgroup and grade Ⅲ subgroup were (13.38±3.06) and (16.37±3.25) U·L^-1, respectively. The serum DAO level in the ≤grade Ⅱ subgroup was significantly lower than that in the grade Ⅲ subgroup (P<0.05). Multivariate logistic regression analysis indicated that the serum DAO level 7 days after chemotherapy was an influencing factor for the occurrence of gastrointestinal toxicity in patients (P<0.001). ROC curve analysis showed that the optimal threshold for serum DAO in predicting gastrointestinal toxicity after chemotherapy was 11.92 U·L^-1, with an area under the curve (AUC) of 0.79 (P<0.05). The sensitivity and specificity were 77.78% and 86.96%, respectively.

Chemotherapy with fluorouracil-based antineoplastic drugs can lead to elevated serum DAO levels in patients with gastrointestinal tumors. The serum DAO level is associated with the severity of gastrointestinal toxicity and the grade of adverse drug reactions, and may serve as a predictive indicator for the occurrence of gastrointestinal toxicity following chemotherapy.