The impact of smoking on recurrence and progression of non-muscle invasive bladder cancer: a systematic review and meta-analysis

Abstract

Objectives: Although smoking is a well-recognized causative factor of urothelial bladder cancer and accounts for 50% of cases, less is known about the prognostic significance of smoking on non-muscle invasive bladder cancer (NMIBC) prognosis. This systematic review and meta-analysis aimed to evaluate the effect of smoking on the risk of NMIBC recurrence and progression. Materials and methods: We systematically searched Medline, Web of Science and Scopus databases for original articles published before October 2021 regarding the effect of smoking on NMIBC recurrence and progression. Information about smoking status and the number of events or odds ratio or hazard ratio for event-free survival must have been reported to include the study in the analysis. Quality In Prognosis Studies tool was utilized for the risk of bias assessment. Results: We selected 64 eligible studies, including 28 617 patients with NMIBC with available data on smoking status. In a meta-analysis of 28 studies with 7885 patients, we found that smokers (current/former) were at higher risk for recurrence (OR = 1.68; 95% CI 1.34–2.09; P < 0.0001) compared to never smokers. Subgroup analysis of 2967 patients revealed that current smokers were at a 1.24 higher risk of recurrence (OR = 1.24; 95% CI 1.02–1.50; P = 0.03) compared to former smokers. A meta-analysis of the hazard ratio revealed that smokers are at higher risk of recurrence (HR = 1.31; 95%CI 1.15–1.48; P < 0.0001) and progression (HR = 1.18; 95%CI 1.08–1.29; P < 0.001) compared to never smokers. Detrimental prognostic effect of smoking on progression, but not for recurrence risk was also noted in the subgroup analysis of high-risk patients (HR = 1.30; 95%CI 1.09–1.55; P = 0.004) and BCG-treated ones (HR = 1.15; 95%CI 1.06–1.25; P < 0.001). Conclusion: In conclusion, patients with non-muscle invasive bladder cancer and a history of smoking have a worse prognosis regarding recurrence-free and progression-free survival compared to non-smokers.