Mechanical dilation and direct visualization internal urethrotomy (DVIU) are the most widely utilized treatments for urethral stricture disease, but recurrence rates are high after re-treatment. The Optilume® Urethral Drug Coated Balloon (DCB) is a urethral dilation balloon with a proprietary paclitaxel coating that combines mechanical dilation of the stricture for immediate symptomatic relief with local drug delivery to maintain urethral patency. The ROBUST I study investigates the safety and efficacy of the Optilume DCB for the treatment of recurrent anterior urethral strictures.

ROBUST I was a prospective, single-arm, open-label study conducted under a common protocol in Latin America. Eligible participants were adult men with a single anterior urethral stricture <12F and ≤2cm in length with 1-3 prior endoscopic treatments, International Prostate Symptom Score (IPSS) ≥13, and maximum flow rate (Qmax) <10 mL/sec.  After treatment with the Optilume DCB, subjects were followed at 5 days (Foley removal), 14 days, 30 days, 3 months, 6 months, and annually through 3 years. The primary safety endpoint was the rate of treatment-related serious urinary adverse events. The efficacy endpoint was the proportion of subjects with ≥ 50% improvement in IPSS at 3 years. Subjects receiving secondary treatment were treated as failures for this endpoint. Secondary outcomes included quality of life (QOL), freedom from repeat intervention, erectile function, Qmax, and post-void residual (PVR) urine volume.

A total of 53 subjects were enrolled and treated with the Optilume DCB at 4 centers. Subjects had bulbar strictures, with an average stricture length of 0.9 cm, and 1.7 prior dilations; 43% of men had undergone ≥2 previous dilations. Of the 53 treated subjects, 43 were evaluable at the 3-year follow-up for the efficacy endpoint. There were no serious adverse events related to treatment at 3 years. Success at 3 years was achieved in 67% (29/43) which is consistent with 2-year results (68%, 32/47).  Subjects treated with the 30F diameter Optilume DCB had significantly higher responder rate at 3 years compared to subjects treated with the 24F diameter (83% vs 50%).  IPSS improved from a mean of 25.2 at baseline to 5.5 at 3 years (unpaired t-test, p<0.001). Freedom from repeat intervention of the study stricture at 1, 2, and 3 years was 83% (40/48), 81% (38/47), and 77% (33/43), respectively. From baseline to 3 years, IPSS QOL improved from 4.9 to 0.7, Qmax improved from 5.0 mL/sec to 15.1 mL/sec, and PVR urine volume improved from 141.4 mL to 50.2 mL (unpaired t-test, p<0.001 for all). The International Index of Erectile Function (IIEF) overall satisfaction score improved from 6.5 at baseline to 8.2 at 3 years.

Significant improvements from baseline in symptom severity, quality of life, and voiding function were observed at 3 years after treatment with the Optilume DCB. Functional success at 3 years was consistent with 2-year results. There was no negative impact of the treatment on erectile function. Follow-up is planned through 5 years to further define the durability of the treatment.

Subjects with recurrent bulbar strictures treated with the Optilume paclitaxel-coated balloon exhibited significant improvement in symptomatic and functional outcomes through 3 years post-treatment. Long-term follow-up will continue through 5 years in the ROBUST I study and a randomized trial is ongoing.