Intravesical instillation of high molecular weight sodium hyaluronate in radiation-induced cystitis: a prospective pilot study

To assess the efficacy and safety of intravesical instillation of high molecular weight sodium hyaluronate (HMW-HA) for the treatment of radiation-induced cystitis.This prospective cohort study was conducted in seven centers in France. Eligible patients with radiation-induced cystitis were recruited between April 2020 and March 2021. A sterile disposable 50 ml prefilled solution containing 0.16% (80 mg/50 mL) HMW-HA (INSTYLAN) was instilled weekly into the bladder. The treatment consisted of 6 sessions (V1 to V6). Outcomes were assessed 1 week (V7) and 4 weeks (V8) after the last session and were compared with baseline (V0). The primary endpoint was bladder pain, evaluated by a Questionnaire with 5 closed-ended response options. Secondary endpoints included changes from baseline for hematuria, urinary frequency, and the effect of urgencies on Quality of Life (QoL). Adverse events (AEs) were graded according to the CTCAE 3.0 classification.A total of 30 participants were enrolled. The Intent-to-Treat analysis showed a significant reduction in pelvic pain intensity (- 45.81%, p < 0.001), hematuria (- 26.87%, p = 0.008), total 24 h voids (- 23.92%, p < 0.001) and the effect of urgencies on QoL (- 33.92%, p < 0.001) at V7. The improvement for each outcome remained stable during the post-therapeutic period between V7 and V8. Bladder instillation therapy was well-tolerated: two treatment-related AEs (6.6%) were reported corresponding to two grade 1 hematuria.Intravesical instillation of HMW-HA appears to be effective in the treatment of radiation-induced cystitis. Further comparative studies with longer follow-up are needed to confirm our preliminary results.