Carbon-ion Radiotherapy for Inoperable Solitary Fibrous Tumor of the Skull Base: A Case Report

Abstract

Background/Aim: The curative treatment for solitary fibrous tumors (SFTs) consists of surgery. However, surgery for SFTs in the skull base is difficult due to the anatomy and curative surgery may not be possible. Carbon-ion radiotherapy (C-ion RT) might be useful in the treatment of inoperable SFTs in the skull base because of its biological and physical nature. This study presents the clinical outcomes of C-ion RT for an inoperable SFT of the skull base. Case Report: A 68-year-old female patient experienced hoarseness, deafness on the right side, right facial nerve paralysis, and dysphagia. Magnetic resonance imaging revealed a tumor located in the right cerebello-pontine angle with destruction of the petrous bone, and immunohistochemical studies of the biopsy specimen showed a grade 2 SFT. Firstly, the patient underwent tumor embolization and surgery. However, 5 months after surgery, magnetic resonance imaging revealed regrowth of residual tumor. Subsequently, the patient was referred to our hospital for C-ion RT because curative surgery was unsuitable. The patient received 64 Gy (relative biological effectiveness) of C-ion RT in 16 fractions. Two years after C-ion RT, the tumor showed a partial response. The patient was still alive at the last follow-up without evidence of local recurrence, distant metastasis, or late toxicities. Conclusion: These findings suggest that C-ion RT is a suitable treatment option for inoperable SFTs of the skull base.