Incidence of Malignant Peripheral Nerve Sheath Tumor (MPNST) Development in Participants With Neurofibromatosis Type 1 (NF1) Receiving and Not Receiving Medical Therapies Directed at Plexiform Neurofibromas (PN)

Background: NF1 is a genetic syndrome. Tumors appear early in life. Many people with NF1 develop PN. These tumors can become an aggressive cancer called MPNST. People with MPNST may benefit from treatment with a MEK inhibitor (MEKi). Researchers want to learn if there is an increased risk of MPNST formation from MEKi treatment in people with NF1. To do this, they will review data that has been collected in NIH NF1 studies. Objective: To describe the characteristics of people who have taken part in NF1 studies at NIH and to compare the risk of MPNST formation in those treated with MEKi or other PN-directed treatment. Eligibility: People with NF1 who were seen at NIH from Jan. 1, 1998, to Jan. 1, 2020. Design: Participants medical records will be reviewed. Participants who opted out of future use of their data will not be included. Demographic data, like sex, race, and date of birth, will be collected. Data about MEKi and non-MEKi treatments will be collected. Clinical data, such as surgery and treatment details, will be collected. The differences between all participants who were seen at NIH for any NF1 related study will be compared. Participants will be put into 4 groups: History of MEKi therapy Treatment with tumor directed therapy other than MEKi Treatment with both MEKi and non-MEKi tumor directed therapies No tumor directed medical therapy Participants with NF1 who were treated for PN with either a MEKi treatment or a non-MEKi treatment will also be compared. The study will last for 3 to 6 months.