Imaging Evaluation of Plexiform Neurofibromas in Neurofibromatosis Type 1: A Survey-Based Assessment

Abstract

Objective: To assess imaging utilization practices across clinical specialists in neurofibromatosis type 1 (NF1) for the evaluation of symptomatic and asymptomatic children and adults with or without plexiform neurofibromas (PN).

Methods: An institutional review board-exempt survey was administered to medical practitioners caring for individuals with NF1 at the Response Evaluation in Neurofibromatosis and Schwannomatosis (REiNS) meeting in September 2019. The survey included questions on respondent demographic data (9 questions), type of imaging obtained for asymptomatic (4 questions) and symptomatic (4 questions) people with and without PN, and utilization of diffusion-weighted imaging (2 questions).

Results: Thirty practitioners participated in the survey. Most were academic neuro-oncologists at high-volume (>10 patients/week) NF1 centers. Of 30 respondents, 26 had access to whole-body MRI (WB-MRI). The most common approach to an asymptomatic person without PN was no imaging (adults: 57% [17/30]; children: 50% [15/30]), followed by a screening WB-MRI (adults: 20% [6/30]; children: 26.7% [8/30]). The most common approach to a person with symptoms or known PN was regional MRI (adults: 90% [27/30]; children: 93% [28/30]), followed by WB-MRI (adults: 20% [6/30]; children: 36.7% [11/30]). WB-MRI was most often obtained to evaluate a symptomatic child with PN (37% [11/30]).

Conclusions: More than 90% of practitioners indicated they would obtain a regional MRI in a symptomatic patient without known or visible PN. Otherwise, there was little consensus on imaging practices. Given the high prevalence of PN and risk of malignant conversion in this patient population, there is a need to define imaging-based guidelines for optimal clinical care and the design of future clinical trials.

Figure 1. Demographic Data of Survey Respondents

Most respondents were academic neuro-oncologists practicing in the United States in high-volume clinics treating >10 patients with neurofibromatosis type 1 (NF1) per week. NF2 = neurofibromatosis type 2; SWN = schwannomatosis.

Figure 2. Imaging Utilization in Asymptomatic People With Neurofibromatosis Type 1 (NF1) With or Without Known Plexiform Neurofibroma (PN)

In an asymptomatic patient without a visible or known PN, 50%–57% of respondents indicated they do not routinely obtain imaging; 60% of respondents indicated they obtain a regional MRI. n.s. = not significant; STIR = short tau inversion recovery; WB-MRI = whole-body MRI.

Figure 3. Imaging Utilization in Symptomatic People With Neurofibromatosis Type 1 (NF1) With or Without Known Plexiform Neurofibroma (PN)

In a symptomatic pediatric or adult patient without a visible or known PN, ≥90% of respondents indicated preferential use of a regional MRI. n.s. = not significant; STIR = short tau inversion recovery; WB-MRI = whole-body MRI.

Figure 4. Utilization of Quantitative Imaging Markers

Although most survey respondents (26/30 [86%]) reported the use of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) in their imaging practice, 50% of the survey respondents (15/30) reported SUV values from whole-body ¹⁸F-FDG PET-CT imaging to be most valuable for selecting patients for a biopsy.