Interstitial cystitis / bladder pain syndrome (IC/BPS) is a debilitative disease of not well determined etiology. In clinical trial for human IC/BPS, the functional bladder capacity (FBC), cystometric bladder capacity (CBC), bladder pain visual analog scale (VAS) were increased after increased after BoNT-A injection. However, not all IC/BPS patients can benefit from BoNT-A treatment, the success rate was reported around 60% or less in the large cohort clinical trial. This study retrospectively analyzed our previous enrolled IC/BPS patients who were treated with intravesical BoNT-A injection, and search for the predictive factors for a successful treatment outcome.

A total of 433 patients with bladder-centric IC/BPS were analyzed. All patients received comprehensive urological examination, videourodynamic study, and cystoscopic hydrodistention, and the cystoscopic maximal bladder capacity (MBC) and glomerulation grade were documented. Patients received consecutive intravesical BoNT-A 100U injections every 6 months. The patients’ clinical responses were assessed at baseline and at 3 months after BoNT-A injection; and the overall satisfaction to the BoNT-A treatment was requested to report by the Global Response Assessment (GRA). The clinical demographics, IC/BPS subtypes, cystoscopic parameters, and VUDS parameters were compared between successful and failed subgroups. Predictive factors for treatment success were analyzed using logistic regression.

In total, 203 (48.0%) patients had a GRA =3 (n=33, 7.6%) or GRA=2 (n=175, 40.4%) treatment outcome. The other 235 (52.0%) patients failed the treatment, including 136 (31.4%) with a GRA=1 and 89 (20.6%) with a GRA=0. Dysuria was complained in 130 (30.0%) patients and UTI was reported in 32 (7.4%) patients. The adverse event dysuria did not affect treatment outcome, however, 68.5% (22/32) of patients with UTI after BoNT-A injection reported a failed treatment outcome and only 30.3% had a successful outcome. When we compared patients with successful (GRA=2 and 3) and failed (GRA=1 and 0) treatment outcome, patients with a successful treatment outcome had significantly greater MBC (820 ± 162 ml vs 625±196ml, p<0.001), lower grade of glomerulation (1.23 ± 0.9 vs 1.68 ± 0.9, p <0.001), and larger bladder capacity in voided volume (247 ± 126 ml vs 201 ± 100 ml, p <0.001) or cystometry (283 ± 122 ml vs 231 ± 106 ml, p <0.001). The other VUDS findings did not affect the BoNT-A treatment outcome. Among 23 patients with Hunner’s IC/BPS, 19 (82.6%) failed the treatment (Table 1). Table 2 show the logistic regression results. In univariate analysis, the MBC, glomerulation grade, HIC, and bladder capacity parameters were significantly different between successful and failed treatment groups. Multivariate analysis showed a higher MBC and lower glomerulation grade predict a successful treatment outcome after intravesical BoNT-A injection for IC/BPS.

The results of this study reveal that IC/BPS patients with a larger MBC and low grade of glomerulation will benefit from intravesical BoNT-A injection compared with those without these factors. Among 23 patients with Hunner’s IC/BPS, only 17.4% of patients had a successful outcome after BoNT-A injection. Based on the results of this study, the patients with greater urothelial dysfunction as shown by higher glomerulation grade and smaller MBC might have a risk to fail BoNT-A treatment.

Intravesical BoNT-A injection is successful in 48.0% of patients with IC/BPS. Only 17.4% of patients with Hunner’s IC/BPS can benefit from this treatment. Patients with a successful treatment outcome had a higher MBC and lower grade of glomerulation, suggesting BoNT-A injection is effective on IC/BPS with a lower degree of bladder inflammation. Patients with failed treatment outcome might need more BoNT-A injections.