The role of radiotherapy in intracranial hemangiopericytoma/solitary fibrous tumors : A Turkish Society for Radiation Oncology Central Nervous System Tumors Group Study (TROD 07-008).

Objective: Intracranial hemangiopericytomas (HPC) are rare tumors. Radiotherapy (RT) is frequently performed after surgery, depending on tumor size, location, and the type of resection. Moreover, RT is preferred as an effective treatment for local recurrence and metastasis. With this multicenter study, we aimed to investigate the effectiveness of postoperative RT in intracranial HPC patients using modern RT techniques.

Materials and methods: Patients aged 16 years and older who underwent RT for histologically confirmed intracranial HPC were evaluated retrospectively. Forty-four patients from 17 institutions were included. Demographic characteristics of the patients, pathological findings, and prognostic factors were documented. The Kaplan-Meier method was used for local control (LC), distant metastasis-free survival (DMFS), progression-free survival (PFS), and overall survival (OS). The interval for survival analyses was calculated according to the end date of RT. Univariate and multivariate analysis methods were used for factors associated with survival and recurrence.

Results: Median age was 42 years (16-71) and 70% of the patients were male. The most common initial symptoms were pain (47.7%) and vision problems (15.9%). A supratentorial location was observed in 79.5% of patients. The median maximum tumor dimension was 4.7 (1.6-14) cm. Gross total (GTR) and subtotal resection (STR) were performed in 43.2% and 47.7% of patients, respectively. Adjuvant RT commenced a median of 6 (2-16) weeks after surgery. Postoperative RT was administered using conventionally fractionated intensity-modulated radiotherapy (IMRT) or stereotactic radiosurgery (SRS). A total median dose of 60 (38-66) Gy in a median of 30 (19-33) fractions was used for patients treated with IMRT and a total median dose of 24 (12-25) Gy in a median of 3 (1-5) fractions was used for patients treated with SRS. Local recurrence occurred in 9 patients and locoregional recurrence in 2 patients at a median of 48 months (range 26-143 months) after RT. Reoperation and reirradiation were applied to 5 patients, reirradiation to 4 patients, and reoperation to 2 patients as salvage treatments. Reirradiation was administered at a median dose of 35 (13.5-54) Gy using a median of 5 (1-30) fractions. At a median follow-up of 63 (6-262) months, 5‑year LC was 68.7%, DMFS 87.2%, PFS 60.8%, and OS 95.7%. The presence of residual macroscopic tumor before RT was associated with lower LC (p = 0.01) and shorter PFS (p = 0.04). In the presence of residual tumor before RT, 5‑year LC decreased from 92.9% to 46.7%, while 5‑year PFS decreased from 81.1% to 43.5% compared to patients with GTR. The presence of postoperative tumor was associated with a lower LC rate in Cox regression analyzes (p = 0.02). The hazard ratio was 6.2 (1.2-30). However, the effect of residual disease before RT on OS was not statistically significant.

Conclusion: Adjuvant radiotherapy is performed in the majority of patients with HPC, especially in cases where GTR cannot be performed. In our study, postoperative macroscopic residual tumor was found to be the only factor affecting LC and PFS in patients undergoing adjuvant RT, but its effect on OS was not shown. This may be due to the effectiveness of reoperation and/or reirradiation in the presence of recurrence after RT.