The purpose of this study is to compare the efficacy and safety of multisession radiosurgery to those of single dose radiosurgery for metastatic brain tumors.

Between February 2008 and February 2012, 90 patients with 196 metastatic brain tumors were treated with cyberknife radiosurgery, and we reviewed these patients retrospectively. Among them, 57 patients underwent single dose radiosurgery, and 33 patients multisession radiosurgery. Tumors involving the eloquent area and large tumors (>5 cc) were treated with multisession radiosurgery. The median tumor volume and the median treatment dose of single dose radiosurgery were 2.05±0.72 cc and 19.76±1.54 Gy respectively, and in the case of multisession radiosurgery, 5.30±1.70 cc and 29.6±1.70 Gy respectively. The frequency of multisession dose was 3 to 5 times, on average 3.55 times, and 8.91 Gy were given per 1 session on average.

The overall survival (OS) of multisession radiosurgery was 16.0 months, whereas that of single dose radiosurgery was 11.5 months. The radiologic tumor response rates were 90% in single dose radiosurgery and 95.4% in multisession radiosurgery, respectively. Over 6-month and 1-year periods, the OS rates of single dose radiosurgery were 71.4% and 44.9%, whereas those of multisession radiosurgery were 69.1% and 58.3%, respectively ( p =0.83). Toxicities were seen in 18.1% in the single dose radiosurgery group versus 4% in the multisession radiosurgery group. The difference was significant ( p <0.05).

In this study, the multisession radiosurgery group, despite the location and size constraints, did not differ from the single dose radiosurgery group when comparing the survival and recurrence rates, but complications and toxicity were lower. Thus, multisession radiosurgery is thought to be beneficial for treatment of large tumors and tumors located in the eloquent area.