Using Durometers to Quantify Stiffness as an Outcome Measure for Cutaneous Neurofibroma in Neurofibromatosis Type 1

Area of Science:

• Biomedical Engineering
• Dermatology
• Oncology

Background:

• Neurofibromatosis type 1 (NF1) patients develop numerous cutaneous neurofibromas (cNFs).
• Currently, no effective drug therapies exist for cNFs; physical removal is the primary treatment.
• Quantitative methods are needed to assess treatment efficacy in clinical trials, particularly changes in tumor stiffness.

Purpose of the Study:

• To evaluate the reproducibility of two instruments, the Rex Gauge durometer (REX) and Delfin SkinFibroMeter (DELFIN), in measuring cNF stiffness.
• To establish reliable quantitative techniques for assessing cNF changes in response to potential therapies.

Main Methods:

• Ninety-seven cNFs from NF1 patients were measured using both REX and DELFIN devices.
• Measurements were taken at two separate visits, approximately two weeks apart, to assess within-tumor and within-visit agreement.
• Intraclass correlation coefficients (ICCs) were calculated to determine measurement reliability, accounting for repeated measures and patient clustering.

Main Results:

• The REX demonstrated excellent within-visit agreement (ICC = 0.937) and moderate within-tumor agreement (ICC = 0.740).
• The DELFIN showed moderate within-visit agreement (ICC = 0.732) and moderate within-tumor agreement (ICC = 0.607).
• Both instruments were found to be user-friendly and provided consistent quantification of cNF stiffness.

Conclusions:

• Both the REX Gauge and Delfin SkinFibroMeter are reliable tools for quantifying cutaneous neurofibroma stiffness.
• These instruments can support clinical trials by providing objective measures of treatment response in neurofibromatosis type 1.
• Further research can utilize these validated tools to assess the efficacy of emerging therapies for cNFs.