Peyronie's Disease Intervention Studies: An Exploration of Modern-Era Challenges in Study Design and Evaluating Treatment Outcomes
Authors: Ziegelmann Matthew J. , Trost Landon W. , Russo Giorgio I. , Levine Laurence A. 
Published: January 2020

Introduction

Peyronie's disease (PD) is characterized by pain, deformity, sexual dysfunction, and psychological bother. Several treatments are available with varying levels of efficacy, and significant limitations exist with the currently available literature.

Aim

To explore modern-era methodological challenges inherent to PD research as they pertain to intervention studies.

Methods

We performed a critical review of the PD intervention literature to identify common methodological challenges with emphasis on aspects of patient assessment and treatment outcomes, study design, and statistical analysis. The key objective was to provide an impetus on which to build future research protocols, rather than focus on weaknesses with any individual studies.

Main Outcome Measure

Expert opinion was used to summarize limitations with commonly reported objective outcomes such as penile curvature, girth, and length along with imaging modalities and objective questionnaires. Appropriate study design and statistical analysis were also reviewed to discuss common pitfalls in the PD literature.

Results

There are multiple shortcomings inherent to studying objective PD outcomes such as penile curvature, girth, and length. These include lack of standardized protocols for preintervention and postintervention assessment, interobserver and intraobserver variability, and lack of consistent definitions for what defines an objective outcome as clinically “meaningful” for patients. Similarly, imaging studies including penile ultrasound are subject to marked variation, thereby limiting their utility to measure predefined primary or secondary study outcomes including cavernosal artery hemodynamics and penile plaque size. Objective and validated questionnaires such as the Peyronie's Disease Questionnaire and International Index of Erectile Function require that patients have recently engaged in sexual activity, which is challenging for many patients as a result of penile deformity with PD. Finally, careful study design and statistical analysis (including appropriate study power) are imperative to ensure reliable results. Current shortcomings in the majority of studies contribute to the low level of evidence available for most PD interventions.

Clinical Implications

Future PD intervention studies should focus on optimizing study design and statistical analysis. Furthermore, authors must incorporate standardized protocols for assessing preintervention and postintervention outcomes.

Strength & Limitations

The current analysis and recommendations for future study are based on the expertise and opinion of the manuscript authors.

Conclusion

Multiple areas of weakness in study design, statistical analysis, and patient outcomes assessment limit the reliability of data derived from PD intervention studies in the modern era. The global themes identified herein should serve as a basis upon which to build future research protocols.