Impact of body mass index on the oncological outcomes of patients with upper and lower urinary tract cancers treated with radical surgery: A multi-institutional retrospective study.

AIM: To evaluate the impact of body mass index (BMI) on the oncological outcomes of urothelial carcinoma (UC) patients.

PATIENTS AND METHODS: We retrospectively analyzed data from 818 patients with upper tract urothelial cancer (UTUC) and bladder cancer (BC) who were treated with radical nephroureterectomy (RNU) or radical cystectomy (RC) between 1990 and 2015 at six different institutions in Japan. Patients with distant metastasis at diagnosis and those who received neoadjuvant therapies were excluded, leaving 727 eligible patients (UTUC: n = 441; BC: n = 286). Patients were classified into four groups according to World Health Organization BMI criteria: underweight (BMI <18.5  kg/m2 ), normal weight (BMI 18.5-25 kg/m2 ), overweight (BMI 25.1-30 kg/m2 ), and obese (BMI >30 kg/m2 ).

RESULTS: Overweight UTUC and BC patients achieved significantly better cancer-specific survival (CSS) than the other three groups. However, obese UTUC and BC patients had significantly worse CSS than the other three groups (UTUC: P = 0.031; BC: P = 0.0019). Multivariate analysis of BC patients demonstrated that obesity was an independent predictor of unfavorable CSS (hazard ratio [HR] = 7.47; P = 0.002) and that being underweight was an independent predictor of favorable CSS (HR = 0.37; P = 0.029). However, BMI was not a prognostic factor for CSS in UTUC patients according to multivariate analysis.

CONCLUSIONS: Obesity was an independent predictor of BC patients requiring RC. Conversely, being underweight was associated with a favorable prognosis for BC patients. However, BMI was not an independent prognostic factor in patients with upper urinary tract cancer.