Abstract
BACKGROUND: Half of patients with Neurofibromatosis type 1 (NF1) develop plexiform neurofibromas (PNs). PNs may grow during childhood causing significant complications, including pain, functional impairment, and disfigurement. Treatment options are limited, given their tendency to regrow following surgery and their propensity to transform into malignant tumors following radiation. Selumetinib is an oral selective inhibitor of RAS-mitogen activated protein kinase (MAPK) 1 and 2, which has shown efficacy for tumor shrinkage/ stabilisation and symptom improvement. METHODS: Single-institution retrospective review of patients with NF1 treated with selumetinib for symptomatic PNs between 2020 and 2023. Clinical data were abstracted from medical records. Treatment consisted of selumetinib 25 mg/m2 BID. Patient follow-up included monthly complete physical examination, evaluation of treatment adherence, blood analysis, echocardiogram, ophthalmologic assessment every 3 months, and MRI every 6 months. Response evaluation criteria in solid tumors (RECIST) was used for assessment. RESULTS: Ten patients were treated with selumetinib during the period indicated. Mean age 13.9 years (range 7-21). Predominant target locations were head and neck (60%), and abdomen-pelvis (30%). The most important comorbidities were disfigurement (50%) and pain (50%). The mean follow-up time was 519 days (range 45–1460). None of the patients presented grade 3-4 toxicities; all of them had associated grade 1-2 skin toxicity. None presented cardiac or ophthalmologic alterations. All the patients with pain had sustained clinical improvement in the first 35–60 days of treatment. At one year of treatment 6/8 patients showed stable disease and 2/8 partial response on MRI. In one patient, treatment was discontinued after 270 days (lack of clear benefit).Another patient has not reached one year of therapy yet. CONCLUSIONS: In this study we expose that selumetinib for symptomatic, inoperable plexiform neurofibromas in NF1 was associated with clinical and radiological response. Our study also confirms the safety and good tolerance of this drug.