Helical tomotherapy and pazopanib-based multimodal therapy for metastatic malignant peripheral nerve sheath tumor with reversible hair depigmentation: a brief report and brief literature review

Purpose Metastatic malignant peripheral nerve sheath tumor (MPNST) at paraspinal or perivascular sites is difficult to manage because of anatomical constraints, limited systemic options, and overlapping toxicity. We describe helical tomotherapy combined with pazopanib and temozolomide, during which reversible hair depigmentation occurred. Methods A 36-year-old man with high-grade mediastinal MPNST developed C2–3, L4–5, and right axillary metastases. Helical tomotherapy was delivered to these sites and to a measurable residual mediastinal lesion within the postoperative tumor bed. Pazopanib was initiated at 800 mg/day and temozolomide at 150 mg/m²/day on days 1–5 of each 28-day cycle. Response and toxicity were evaluated using RECIST v1.1 and CTCAE v5.0. Results Partial response was first documented at 6 months and maintained at 12 months, with no new lesions or unequivocal progression of non-target disease during this period. After the 12-month assessment, PET/CT in May 2026 revealed multiple new metastases, confirming disease progression, while local control was maintained in several irradiated lesions. The pazopanib dose was reduced to 600 mg/day because of anorexia and subsequently to 400 mg/day after a grade 4 decrease in white blood cell count (nadir, 0.88 × 10⁹/L). A grade 3 lung infection required hospitalization, intravenous antimicrobials, and oxygen. Both systemic agents were discontinued on March 26, 2025. Hair depigmentation developed during pazopanib exposure and partially reversed after discontinuation. Conclusion Helical tomotherapy was technically feasible within multimodal treatment for anatomically complex metastatic MPNST, although individual treatment contributions cannot be distinguished. Reversible hair depigmentation is best regarded as an exposure-associated, hypothesis-generating observation rather than a validated pharmacodynamic biomarker.