Recurrence after postoperative intravesical instillation therapy in Hunner type interstitial cystitis

We performed a prospective, single-arm study comparing outcomes between transurethral ablation plus postoperative instillation of hyaluronic acid and chondroitin sulfate (HACS group) and transurethral ablation only in patients with Hunner type interstitial cystitis (historical control group). A total of 78 patients were enrolled, and 51 were included in the per-protocol analysis set. The 2-year recurrence rate was 47.1% (95% CI, 32.9–61.5) in the HACS group, which was significantly lower than that in the control group (86.2%; 95% CI, 74.6–93.9, P < 0.001). After instillation therapy, the hazard ratio for recurrence was 0.38 (95% CI, 0.23–0.65, P < 0.001). The HACS group had an increased recurrence-free survival with the median interval not being reached, while it was 11.4 months in the control group (95% CI, 8.8–13.8, P < 0.001). Regardless of the instillation treatment, there were significant improvements in all symptom questionnaire scores and pain compared to the baseline. However, in the instillation group, improvement was stable even after 12 months. In patients with Hunner type interstitial cystitis, intravesical instillation of hyaluronic acid and chondroitin sulfate after transurethral ablation significantly reduced the recurrence rate and maintained symptom improvement for more than 1 year.


Voiding diary parameters
Both groups showed the lowest daytime frequency, nocturia, and urgency episodes 1 month after surgery.The differences in voiding diary parameters between the control and HACS groups were not significant at any time.However, from 12 to 24 months, the degree of improvement in the daytime frequency, number of nocturia episodes, and urgency episodes in the HACS group were greater than those in the control group, and more patients showed a tendency to maintain well (Table 5).

Discussion
In this prospective study involving patients with Hunner type IC, the recurrence rate was significantly lower among patients who received intravesical HACS instillation treatment after transurethral ablation of the Hunner lesion than among those who underwent ablation alone.The patients' subjective symptoms showed significant improvement only with surgical treatment; however, the maintenance period of the improved condition tended to increase in the HACS group.
Although the exact etiology of IC remains unclear, Hunner lesions are characterized by severe inflammation and urothelial denudation.Recently, accumulating evidence has shown that IC/BPS without Hunner lesions and Hunner type IC are distinct pathological entities.Patients with Hunner type IC responded remarkably well to targeted endoscopic ablation of Hunner lesions.The improvement in symptoms was dramatic and persisted for approximately 12 months until the recurrence of the Hunner lesions.Interestingly, the bladder mucosa, which appears normal without Hunner lesions in patients with Hunner type IC, shows severe histological inflammation.Notably, these histological changes can be observed in the entire bladder and are not confined to the Hunner lesions 7 .Even when the recurrence pattern was prospectively observed after endoscopic ablation, most recurrences of Hunner lesions occurred in the vicinity of the ablation site, but the rate of recurrence at new sites reaches about 50% 17 .For severe pain caused by Hunner lesions, symptom relief may be maintained for a while by ablation of the Hunner lesions.However, it is still not possible to prevent the recurrence of the Hunner lesions and the progression of inflammation.Prevention of newly developed Hunner lesions will ultimately be the best way to treat IC/BPS as a severe inflammatory disease.
In this respect, GAG replacement is certainly a good treatment option for the entire bladder.IC/BPS may be related to a primary defect in the GAG layer of the urothelium and reduced expression of tight junctions [18][19][20] .In addition, a "cascade" of inflammatory events, which fail to be restored, may lead to chronic extracellular matrix degradation and neuroinflammation.In this regard, the restoration of the urothelium with exogenous GAG installation can help reinstate epithelial integrity in patients with IC/BPS [21][22][23] .However, it may not be very effective in cases of IC that already have Hunner lesions.In this study, we believe that GAG replacement, such  Commercially available GAG-replenishing substances include heparin, HA, CS and pentosan polysulfate.CS is a glycoprotein and a component of the GAG layer of bladder mucosa.CS has been reported to play a key role in inflammation and might stimulate proteoglycan synthesis, thus reconstituting the urothelium 24 .HA is the only non-sulfated GAG that directly interacts with the cell surface 25 .This interaction may reduce urothelium permeability and stimulate sulfated GAG synthesis 26 .These agents have been used in patients who respond poorly to conventional therapies.GAG replacement has been used for a long time to treat patients with IC/BPS, but the level of evidence is low.
HA is used at a concentration of 0.8% for intravesical instillation treatment for IC/BPS.In a study in which intravesical HA was administered for 4 weeks and monthly instillation for 6 months in patients with refractory IC, the response rate at 12 weeks was 71% and was maintained well until 20 weeks 27 .In 2010 and 2012, Nickel et al. 28,29 conducted two consecutive studies on 98 women who were administered 2% CS for 8 weeks and found no significant difference in pain and voiding symptoms at 4 weeks compared to the placebo group.Cervigni et al. 29 randomized 110 women to receive either HACS or DMSO and evaluated the VAS for pain after 6 months.HACS group was as effective as DMSO and showed a more favorable outcome in terms of safety.Porru et al. 30 fount that an improvement rate of 54% at 6 months after HACS instillation in 20 patients.In patients with refractory IC/BPS patients, the HACS maintained improvement in symptoms for up to 3 years, so the HACS might be more effective than the monotherapy 31 .Installing HA and CS together may offer more effective and long-lasting therapeutic advantages than either one alone.
Most studies related to HA and CS for patients with IC/BPS were conducted on women, and the studies were conducted regardless of the presence of Hunner lesions; therefore, it was not possible to distinguish between Hunner type IC or IC/BPS without Hunner lesions.In addition, the number of patients was relatively small, and the follow-up period was very short.The primary outcome of previous studies was mostly the subjective symptoms of the patient, such as pain and urinary symptoms, and there were no studies confirming the recurrence of Hunner lesions after intravesical instillation treatment.It is significant to note that we prospectively observed 78 patients with Hunner type IC in men as well as women who complained of chronic bladder pain for 2 years.In addition, periodic cystoscopy was performed to confirm the recurrence of the Hunner lesion, and subjective symptom worsening was specifically evaluated through disease-specific questionnaires.
However, this study had several limitations.First, since the incidence of Hunner type IC patients was not high, it was difficult to conduct a randomized controlled trial.To compensate for this limitation, propensity score matching was performed between the two groups.Despite these findings, caution is required when interpreting the results.Further randomized clinical trials are needed to validate these findings.Second, we defined only those patients who received 10 HACS instillations as the analysis set.This study aimed to confirm the effect of instillation treatment by maintaining the same instillation time.Some patients refused instillation treatment and were not included in the analysis set because they were not able to receive 10 intravesical instillations.One patient failed to receive the full number of HACS instillations due to recurrence, and this patient was included in the analysis.Third, if intravesical treatment, such as HACS is effective for Hunner type IC, a clear protocol on how long it should be maintained and whether it is better to use it continuously needs to be clarified in further studies.
In conclusion, among the treatment methods known to date, intravesical HACS instillation after transurethral ablation of the Hunner lesions is an effective treatment for Hunner type IC through structural and functional regeneration of the bladder as well as improvement of subjective symptoms.

Study design and patients
This was a single-center, prospective, single-arm study in which the treatment group was compared with a historical control group.The eligible participants were patients aged > 20 years with IC/BPS who had bladder pain with a pain for VAS of 4 or higher lasting for more than 6 months and Hunner lesions confirmed through cystoscopy, who were scheduled to undergo transurethral ablation.One month after surgery, the patients underwent intravesical HACS instillation and were followed up for 2 years (HACS group).Informed consent was obtained from all patients enrolled in this study.This clinical trial was conducted in accordance with the principles of the Vol:.(1234567890) The historical control group consisted of patients who were registered in our institute's IC/BPS registry and were followed up for one year after undergoing transurethral ablation of the Hunner lesions in the previous study 15 .Since this historical control group has been further followed up, we considered the extended historical control group by applying the same inclusion and exclusion criteria and assessments as used for the HACS group (see "Supplementary" for details).Patients with a history of HACS instillation were excluded from the extended historical control group.

Assessments
A 3-day voiding diary and self-reported questionnaires, including ICSI and ICPI, PUF symptom scale, and VAS for pain were used to evaluate the severity of symptoms at baseline and 1 month after surgery and 7, 10, 13, 19 and 25 months after surgery (i.e., 1, 4, 7, 13 and 19 months respectively, after intravesical instillation treatment).Table 5. Changes in voiding diary parameters after treatment between the groups at each study visit (Per-Protocol Set).HACS hyaluronic acid and chondroitin sulfate; NA not applicable (analysis was not performed because the number of control groups was less than five).*Compared to baseline, † between the two groups.To assess recurrence, all patients underwent cystoscopy 3 months after surgery and 1 and 19 months after intravesical instillation treatment (7 and 25 months after surgery).If the patient's symptoms aggravated, an additional cystoscopic examination was performed to confirm recurrence.All patients who visited the hospital at least once after the surgery were included in the analysis.Descriptive safety data were collected at every visit.

End-points
The primary outcome was the recurrence of which the 2-year rate was compared between the HACS group and the historical control group.Recurrence was defined as a case in which pain returned to the baseline level and the Hunner lesion was identified on cystoscopy.Recurrence included recurrence at a previous ablation site and new lesions elsewhere in the bladder.The secondary outcomes included time-to-recurrence, changes in voiding symptoms from baseline using the 3-day voiding diary parameters, and changes in quality of life and symptom severity from baseline assessed using ICSI, ICPI, PUF, and VAS for pain.They were analyzed in the HACS and the extended historical control group.

Comparison of the 2-year recurrence rate between the HACS group versus the historical control group
After transurethral ablation, the recurrence rate for 2 years was 75% according to the previous study 15 .The primary hypothesis for efficacy evaluation was that the 2-year recurrence rate after intravesical instillation of HACS would be less than that of the historical control group (i.e., 75%).The 2-year recurrence rate for the HACS group was estimated with 95% confidence interval (CI) using the Clopper-Pearson exact method and compared with the historical control group by a one-sample one-sided binomial test.For sample size calculation, we assumed that a clinically important reduction in the recurrence rate for HACS group would be at least 15%.Then, 62 participants in the HACS group were required to prove the primary hypothesis with a significance level of 5% and an expected power of 80%.Without considering the dropout rate, we enrolled patients who had received all scheduled HACS treatments until the number of participants reached 62.

Comparison of the recurrent-free survival between the HACS versus the extended historical control group groups
For the additional efficacy evaluation, the recurrent-free survival (RFS) was compared between the HACS and the extended historical control groups.Primary analysis was performed on the per-protocol analysis (PPA) set, along with a supplementary analysis based on the full analysis (FA) set.Definitions of the PPA and FA sets are provided in the "Supplementary Information".Safety was evaluated in the FA set of the HACS group.Baseline characteristics were summarized by mean with standard deviation and frequency with percentage for continuous and categorical variables, respectively.Group comparisons were conducted using t-test or Wilcoxon rank sum test for continuous variables; and using chi-square test or Fisher's exact test for categorical variables, according to the satisfaction of the normality assumption.RFS curves for the two groups were estimated using the Kaplan-Meier method and compared using the logrank test.Multivariable Cox proportional hazards (PH) regression model was used for comparison after adjusting for potential confounders that showed statistical significance with p-value < 0.2 in the descriptive analysis or clinical significance among baseline characteristics.Proportional hazard assumption was checked using Schoenfeld residuals.If the assumption was violated, we used the time-dependent Cox PH regression model.The median follow-up time was estimated by the reverse Kaplan-Meier method.
All analyses were performed using the SAS software (version 9.4; SAS Institute Inc.).Statistical significance was declared with p-value < 0.05 unless specified.

Figure 1 .
Figure 1.Recurrence-free survival curve estimated by the Kaplan-Meier method.

Figure 2 .
Figure 2. Changes in questionnaire and visual analogue scale for pain after treatment at each follow-up.

Table 1 .
Baseline characteristics*.BMI body mass index; HACS hyaluronic acid and chondroitin sulfate; VAS visual analog scale.*Values are expressed as mean ± standard deviation.

Table 2 .
Multivariable logistic regression analysis for recurrence.CI confidence interval; HACS hyaluronic acid and chondroitin sulfate; PUF Pelvic pain and urgency/frequency.

Table 3 .
Cox regression for factors associated with recurrence of hunner type interstitial cystitis.FA full analysis; HACS hyaluronic acid and chondroitin sulfate; HR hazard ratio; PPA per-protocol analysis.*After adjusting for age, sex, number of Hunner lesions, pelvic pain, urgency/frequency symptom score, interaction of time, and symptom score.

Table 4 .
Changes in O'Leary-Sant interstitial cystitis questionnaire scores, pelvic pain and urgency/frequency symptom scale, and visual analog scale score for pain after treatment between the groups at each study visit (Per-Protocol Set).HACS hyaluronic acid and chondroitin sulfate; ICSI O'Leary-Sant Interstitial Cystitis questionnaire symptom index; ICPI O'Leary-Sant Interstitial Cystitis questionnaire problem index; PUF Pelvic pain and urgency/frequency; VAS visual analog scale.*Compared to baseline, † between the two groups.

Control group HACS group P †
Figure 3. Study flow.