Continuing Collagenase Clostridium Histolyticum Injections Among Initial Nonresponders Results in Significant Curvature Improvements in the Majority of Peyronie's Disease Men

Background: It is currently unclear if men with Peyronie's Disease (PD) who achieve minimal benefits with the first 2 series of Collagenase Clostridium Histolyticum (CCH) injections should continue with additional injections. Aim: To analyze curvature improvements from the final two series of CCH injections based on amount of improvement during the first 2 series. Methods: A prospective registry was analyzed of all men undergoing CCH injections for PD at a single institution. Men were included if they had completed a full 4 series (8 injections) of CCH and had baseline, interval (after 2 series), and/or final (after 4 series) curvature assessments available. Men were stratified into cohorts using baseline-to-interval assessments of <= 10 degrees (or <= 20%) and >10 degrees (or >20%), and improvements were compared using interval-to-final assessments. Outcomes: The primary outcome was interval-to-final curvature improvements stratified by <= 10 degrees/>10 degrees or <= 20%/>20% improvements achieved during the baseline-to-interval period. Secondary outcomes included analyses of demographic and pathophysiologic variables to determine associations with significant improvements during the final 2 CCH series. Results: A total of 296 PD men were identified as receiving at least one CCH injection, of whom 175 had baseline-to-interval, 84 interval-to-final, and 115 with baseline-to-final measurements. Mean age was 56.6, PD duration 28.6 months, baseline curvature 63.4 degrees, hourglass deformity 36.2%, and calcification 20%. Mean overall curve improvement was -21.5 degrees (33.1%). Among men who experienced <= 20% improvements after 2 series, the mean subsequent curvature change was -24.6% during the final two series (vs +4.3% of those with >20% initial improvement, P<.001), and they were 2.7x more likely to experience >20% subsequent curve improvements. Thirty-one percent of those who achieved >10 degrees during the first 2 series experienced benefits during the final 2 series compared to 70% of men who had <= 10 degrees improvement initially. No demographic or pathophysiological variables predicted likelihood for improvements during the final 2 series of injections. Clinical Implications: Men who fail to achieve significant benefits with 2 series of CCH injections may benefit from completing the final 2 series. Strengths and Limitations: Strengths including a relatively large, prospective series. Limitations include a single center, nonrandomization, nonblinded assessments, and restriction to men who completed eight injections. Conclusions: In the current series, approximately 2/3 of men who fail to achieve >10 degrees or 20% curve improvements with an initial 2 series of CCH injections achieved >10 degrees or 20% improvements with the subsequent 2 series. Copyright (C) 2021, International Society of Sexual Medicine. Published by Elsevier Inc. All rights reserved.