Solitary fibrous tumor/hemangiopericytoma: treatment results based on the 2016 WHO classification

OBJECTIVE Solitary fibrous tumor/hemangiopericytoma (SFT/HPC) is a new combined entity for which a soft-tissue-type grading system, ranging from grades I to III, has been introduced in the 2016 WHO classification of tumors of the CNS. The results of the treatment of this new disease entity require evaluation. METHODS The authors retrospectively reevaluated the pathological findings and medical records of patients with SFT/HPC. This study included 60 patients (27 men and 33 women, median age 42.5 years, range 13-69 years) treated at Severance Hospital between February 1981 and February 2016. Four, 40, and 16 patients were categorized as having SFT/HPC grades I, II, and III, respectively. Among these patients, SFTs diagnosed in 7 patients were regraded as grades I (n = 4), II (n = 2), and III (n = 1). RESULTS The median overall survival (OS) was 73.2 months (range 1.4-275.7 months), and the progression-free survival (PFS) after the first operation was 53.8 months (range 1.4-217.7 months). Six patients (10%) showed extracranial metastasis during a median period of 103.7 months (range 31.9-182.3 months). Nineteen patients (31.7%) presented with tumor recurrences. The patients in the grade III group had shorter PFS and OS, as well as a shorter period to extracranial metastasis, compared with patients in the grade II group. In the grade II group, patients who underwent gross-total resection showed longer PFS than those who underwent subtotal resection; however, there was no difference in OS. Patients who underwent adjuvant radiation therapy (RT) after surgery had longer PFS compared with that of patients who did not undergo adjuvant RT. CONCLUSIONS The SFT/HPC grade I group showed a relatively benign course compared with those of the other groups. The grade III group presented a course with a more aggressive nature than that of the grade II group. In the grade II group, the extent of resection and adjuvant RT was significantly associated with longer PFS. The long-term follow-up and periodic systemic evaluation are mandatory to detect systemic metastasis.