Non-linear association between body mass index and port-related thrombosis in breast cancer patients: a retrospective cohort study

The association between body mass index (BMI) and the risk of catheter-related thrombosis in breast cancer patients remains unclear, particularly regarding potential non-linear relationships and clinically relevant thresholds. This study aimed to investigate the impact of BMI on the risk of port-related thrombosis and to characterize its dose–response pattern. This retrospective cohort study included 1,247 breast cancer patients who underwent totally implantable venous access port (TIVAP) implantation at a single center between January 2019 and September 2025. Restricted cubic spline (RCS) analysis was performed to explore the non-linear association between BMI and thrombosis risk and to identify a potential threshold. Based on the RCS results, patients were categorized into two groups (BMI ≤ 23 vs. > 23 kg/m²). Logistic regression analyses were conducted to identify independent risk factors, and Kaplan–Meier analysis was used to evaluate thrombosis-free survival. RCS analysis revealed a non-linear association between BMI and the risk of port-related thrombosis, with a threshold at approximately 23 kg/m², beyond which the risk increased progressively. The incidence of thrombosis was significantly higher in patients with BMI > 23 kg/m² compared with those with BMI ≤ 23 kg/m² (9.30% vs. 5.58%, P = 0.013). In multivariate logistic regression analysis, BMI > 23 kg/m² remained an independent risk factor for thrombosis (OR = 1.58, 95% CI: 1.02–2.47, P = 0.042), while hypertension was also associated with increased risk (OR = 2.53, 95% CI: 1.37–4.66, P = 0.003), and HER2-positive status was associated with a lower risk of thrombosis (OR = 0.58, 95% CI: 0.36–0.93, P = 0.024). Kaplan–Meier analysis showed that patients with higher BMI had significantly lower thrombosis-free survival, with early curve separation and a progressively widening difference over time. Elevated BMI is significantly associated with an increased risk of port-related thrombosis in breast cancer patients, with a non-linear dose–response relationship and a threshold effect at approximately 23 kg/m². These findings suggest that BMI may serve as a clinically useful marker for risk stratification and highlight the importance of tailored thromboprophylaxis strategies in high-risk patients.