Study design, materials and methods
We conducted an IRB-approved retrospective review of patients who underwent at least one BTX injection between December 2007 to October 2019 and had at least 5 years of follow up. Patients were instructed to continue therapy only if they perceived significant benefit. We excluded patients with history genitourinary malignancy, genitourinary fistula/malformation or previous bladder augmentation. We examined pre-injection demographic, co-morbidities, medications, ambulatory status, bladder management, and urodynamic parameters. Multivariate logistic regression was used to identify independent predictors of long-term continuation of BTX and a Kaplan Meier survival analysis was conducted to determine attrition rates.
186 patients met our criteria, with 72 (38.7%) continuing therapy for at least 5 years. The mean follow-up was 6.6 ±1.9 years. Patients who continued therapy received an average of 8.3 ±4.1 injections during the 5 years of treatment. The average age of our cohort was 54.7±17.1 years, with 133 (71.5%) being female. At the time of first injection, 73 (39%) were on an OAB medication. At baseline, 87 (47%) were voiding, with 85 (46%) requiring clean intermittent catheterization or 14 (7%) using an indwelling catheter. There were 51 patients (27%) with idiopathic overactivity (iOAB). On univariate analysis, age (OR 1.022, 95% CI 1.002-1.042; p= 0.03), female gender (OR 2.930, 95% CI 1.418-6.053, p<0.01) and diagnosis of nOAB (OR 3.062, 95% CI 1.427-6.574, p<0.01) were predictive of continuing therapy. On multivariate analysis, female gender (OR 3.321, 95% CI 1.179 to 9.352, p=0.02) and diagnosis of nOAB (OR4.934; 95%CI 1.324 to 18.382, p=0.02) were predictors of continuing BTX. There were no urodynamic or baseline questionnaire factors predictive of continuing therapy. A Kaplan Meier survival analysis is shown (Figure 1) noting significantly varying attrition rates between subgroups.
Interpretation of results
This study shows that females and patients diagnosed with neurogenic overactive bladder had an increased likelihood of continuing therapy with BTX for at least 5 years. Within the nOAB population, both genders behaved similarly with attrition rates of 57.1% in males and 55.9% in females. The most notable demonstration of the gender differences appears in the iOAB where females had an attrition rate of 70% compared to the over 90.9% attrition rate in men. Remarkably, only one male patient with iOAB continued for five years with the remainder of patients discontinuing therapy before the one-year mark. Interestingly, there was no correlation between continuation of BTX therapy with urodynamic findings or bladder management strategy.