Body mass and smoking are modifiable risk factors for recurrent bladder cancer

Abstract

Background: In the Western world, bladder cancer is the fourth most common cancer in men and the eighth most common in women. Recurrences frequently occur, and continued surveillance is necessary to identify and treat recurrent tumors. Efforts to identify risk factors that are potentially modifiable to reduce the rate of recurrence are needed.

Methods: Cigarette smoking behavior and body mass index were investigated at diagnosis for associations with bladder cancer recurrence in a population-based study of 726 patients with bladder cancer in New Hampshire, United States. Patients diagnosed with non-muscle invasive urothelial cell carcinoma were followed to ascertain long-term prognosis. Analysis of time to recurrence was performed using multivariate Cox regression models.

Results: Smokers experienced shorter time to recurrence (continuing smoker hazard ratio [HR] = 1.51, 95% confidence interval [CI] = 1.08-2.13). Although being overweight (body mass index > 24.9 kg/m(2) ) at diagnosis was not a strong independent factor (HR = 1.33, 95% CI = 0.94-1.89), among continuing smokers, being overweight more than doubled the risk of recurrence compared to smokers of normal weight (HR = 2.67, 95% CI = 1.14-6.28).

Conclusions: These observational results suggest that adiposity is a risk factor for bladder cancer recurrence, particularly among tobacco users. Future intervention studies are warranted to evaluate whether both smoking cessation and weight reduction strategies reduce bladder tumor recurrences.

Keywords: bladder cancer; body mass index; obesity; recurrence; smoking; urothelial cell carcinoma.

Figure 1

Bladder cancer recurrence by cigarette smoking status after diagnosis. The Kaplan-Meier plot indicates shorter time to recurrence among patients who reported being either former or continued smokers when compared to never smokers (Log-rank p=0.0096). Inset graphic shows relative group size of never (green; 17.2%), former (orange; 52.9%), and current (red; 29.9%) smokers.

Figure 2

Bladder cancer recurrence by BMI at diagnosis. The Kaplan-Meier plot indicates shorter time to recurrence for individuals who were overweight (BMI >24.9) at diagnosis compared with normal weight individuals (Log-rank p=0.026). Inset graphic shows relative group size of normal (blue; 26.6%) and overweight (red; 73.4%) individuals.

Figure 3

Bladder cancer recurrence by BMI at diagnosis among continued cigarette smokers. The Kaplan-Meier plot indicates shorter time to recurrence for overweight (BMI >24.9) continuing smokers compared with all normal weight and non-smoking overweight patients (log-rank p=0.0046). Inset graphic shows relative group size of overweight smokers (red; 18.9%) and all normal weight and non-smoking overweight patients combined (green; 81.1%).