(161) Xiaflex Nonresponders Show Alteration in Penile Measurements: Post-Market Analysis of Predictors for Treatment Success
Authors: Caputo S , Blair G , Hampel G , Greenberg J , Herzog B , Nguyen T , Almajed W , Sikka S , Hellstrom W 
Published: May 2023

Abstract

Introduction
The IMPRESS trial revealed that intralesional collagenase clostridium histolyticum, Xiaflex, is safe and efficacious for treating the physical and subjective effects of Peyronie’s Disease (PD). However, little is known about the other manifestations of PD, namely penile shortening and efficacy for patients of diverse racial backgrounds or with severe penile curvatures.

Objective
To evaluate predictors associated with response to treatment and alterations in penile morphological measurements.

Methods
Consecutive patients treated with Xiaflex for dorsal, lateral, and ventral penile curvatures ≥ 25°, in the absence of hourglass deformity, were included in this study. Before treatment and eight weeks after the last injection cycle, during penile duplex Doppler ultrasound evaluation, penile curvature was measured with a goniometer after induced artificial erection via injection of prostaglandin E1 (PGE1). IIEF score, PGE1 dose, circumference, and erectile as well as stretched penile length were also assessed at these times. Based on the results of the IMPRESS trial, patients were considered Xiaflex responders if the decrease in their penile curvature were ≥ 15° (n =134) and Xiaflex nonresponders if the decrease in their penile curvature were &lt; 15° (n =89). Initial measurements were in increments of 5°. Intention to treat analysis was performed.

Results
Two hundred and twenty-three patients with penile curvature ≥ 25° who received XIAFLEX were included in this study. One hundred and thirty-four patients (60.1%) responded to Xiaflex, while 89 (39.9%) patients did not respond. African American men were 3 times more likely to respond to treatment than their non-African American counterparts (Odds Ratio (OR) =3.35 (95% CI, 1.15-10.70), p =0.031). On the other hand, men with an initial penile curvature of greater than 60° were less likely to respond to Xiaflex (OR = 0.34; 95% CI, 0.16-0.69; p=0.003). However, patients with lateral and ventral curvatures responded at comparable rates to those with dorsal curvatures. Subsequently, changes in penile morphologic measurements post Xiaflex were analyzed. Average stretched penile length, erectile length, and erectile circumference prior to treatment for responders were 13.93 cm, 13.39 cm, and 11.81 cm, respectively; for nonresponders, it was 14.27 cm, 13.72 cm, 11.64 cm, respectively. Nonresponders were shown to experience a significant decrease in penile erect length (-0.55 cm) and circumference (-0.58 cm) (p=0.002 and p=0.002, respectively), whereas responders showed no significant alterations in penile morphologic measurements.

Conclusions
Our analysis revealed that men with penile curvatures ≥ 60° are less likely to respond to Xiaflex injections and thus may be considered for surgical intervention upon initial presentation. Furthermore, men who do not respond may even be at a higher risk for shortening of penile erect length and circumference. The actual clinical significance of a decrease in average erect length of 0.55 cm and circumference of 0.58 cm is difficult to determine and should be considered per patient preferences. Further investigations into predictors for response to Xiaflex and the pathophysiology behind penile shortening in Xiaflex nonresponders are warranted.

Disclosure
No