Selumetinib for symptomatic, inoperable plexiform neurofibromas in pediatric patients with neurofibromatosis type 1: the first single-center real-world case series in Japan.

Objective: In Japan, selumetinib is used in pediatric patients with neurofibromatosis type 1 (NF1) and symptomatic inoperable plexiform neurofibroma (PN). However, there have been no real-world reports on Japanese patients. In this study, we reported a single-center, short-term experience with selumetinib after its approval in Japan.

Methods: We prospectively collected data from 11 pediatric NF1 patients with symptomatic, inoperable PN who were initiated on selumetinib between November 2022 and May 2023; the selumetinib was administered by the same physician. Various patient factors, tumors, dose and efficacy of selumetinib, and adverse events (AE) were investigated.

Results: Of 11 patients included, 7 were male, with a mean age of 14 years. The sites of symptomatic main PN included the head and neck, pelvis to lower extremities, and paraspinal lesions in five, three, and three patients, respectively. The median maximum diameter of the main PN was 91 mm, and the median follow-up duration was 19 months. All patients with pain or motor dysfunction experienced symptom improvement after treatment, and the tumors tended to shrink in 7 of the 11 patients (64%). Among the six patients with disfigurements, only one experienced improvement. Of 59 AEs observed, 58 (98%) were grades 1 and 2, and 5 patients (46%) underwent temporary selumetinib withdrawal due to AEs. One patient discontinued the drug (9%) because of rash dermatitis.

Conclusions: Despite the relatively short-term results, no serious AEs were observed, and many patients benefited from selumetinib treatment. In some patients, administration was discontinued or interrupted because of the balance between benefits and AEs, and further data are needed to better understand the general safety and efficacy of selumetinib.