Predictors of Poor Response and Adverse Events Following Botulinum Toxin A for Refractory Idiopathic Overactive Bladder: A Systematic Review

Botulinum toxin A (BTX-A) injections are effective in managing refractory overactive bladder (OAB). However, some patients exhibit a poor response and/or experience adverse events (AEs) such as voiding dysfunction necessitating clean intermittent self-catheterisation (CISC) and urinary tract infections (UTIs). To systematically evaluate whether poor response/AEs to BTX-A for idiopathic OAB are predictable. MEDLINE, EMBASE, and Google Scholar database were searched in March 2020. Studies reporting predictive factors for poor response or AEs were included. Two reviewers independently screened articles, searched references, and extracted data. Risk of bias (Quality in Prognosis Studies [QUIPS]) and quality of evidence (Grading of Recommendations Assessment, Development and Evaluation [GRADE]) tools were utilised. Of 1579 articles, 17 met the inclusion criteria. These were cohort studies with predominantly level 3 evidence. Factors including male gender, frailty, comorbidity, increasing age, smoking, baseline leakage episodes, and various urodynamic parameters (bladder outlet obstruction index [BOOI], high pretreatment maximum detrusor pressure, and poor bladder compliance) were proposed as predictors of nonresponse. In predicting CISC use, male gender, comorbidity, increasing age, number of vaginal deliveries, hysterectomy, and urodynamic parameters (bladder capacity, postvoid residual volume, projected isovolumetric pressure value, bladder contractility index, and BOOI) were implicated. Female gender, males with their prostates in situ, and CISC were suggested to increase UTIs after BTX-A. This review has identified factors that may predict poor response/AEs following bladder BTX-A and help in counselling of patients. Overall, the quality of individual studies included was poor, limiting the certainty of evidence reported. Larger-scale, better-designed trials with uniform definitions of poor response are required to confirm these preliminary findings. This review assessed whether we could predict poor response or side effects to bladder botulinum toxin A injections in managing overactive bladder. Many different factors based on the patient, medical conditions, previous surgery, and pretreatment investigations were identified. However, the quality of included studies was generally poor, limiting their conclusions.