Body mass index and survival among patients with advanced biliary tract cancer: a single-institutional study with nationwide data-based validation.

Background: Excess body weight may modulate the progression of various cancer types. The prognostic relevance of body mass index (BMI) has not been fully examined in patients with biliary tract cancer.

Methods: Using a single-institutional cohort of 360 patients receiving gemcitabine-based chemotherapy for advanced biliary tract cancer, we examined the association of BMI with overall survival (OS). Using the Cox regression model with adjustment for potential confounders, we calculated hazard ratios (HRs) and 95% confidence intervals (CIs) for OS according to BMI. The findings were validated using a Japanese nationwide inpatient database including 8324 patients treated at 201 hospitals.

Results: In the clinical cohort, BMI was not associated with OS (P_trend = 0.34). Compared to patients with BMI = 18.5-24.9 kg/m², patients with BMI < 18.5 kg/m² and ≥ 25.0 kg/m² had adjusted HRs for OS of 1.06 (95% CI, 0.78-1.45) and 1.01 (95% CI, 0.74-1.39), respectively. There was no evidence on a non-linear relationship between BMI and OS (P_nonlinearity = 0.63). In the nationwide cohort, the null findings were validated (P_trend = 0.18) with adjusted HRs of 1.07 (95% CI, 0.98-1.18) for BMI < 18.5 kg/m² and 1.05 (95% CI, 0.96-1.14) for BMI ≥ 25.0 kg/m² (vs. BMI = 18.5-24.9 kg/m²). In the clinical cohort, BMI was not associated with progression-free survival (P_trend = 0.81).

Conclusions: BMI was not associated with survival outcomes of patients with advanced biliary tract cancer. Further research is warranted incorporating more detailed body composition metrics to explore the prognostic role of adiposity in biliary tract cancer.