Intraoperative radiotherapy to treat newly diagnosed solitary brain metastasis: initial experience and long-term outcomes

The authors assessed the feasibility of intraoperative radiotherapy (IORT) using a portable radiation source to treat newly diagnosed, surgically resected, solitary brain metastasis (BrM). In a nonrandomized prospective study, 23 patients with histologically confirmed BrM were treated with an Intrabeam device that delivered 14 Gy to a 2-mm depth to the resection cavity during surgery. In a 5-year minimum follow-up period, progression-free survival from the time of surgery with simultaneous IORT averaged (± SD) 22 ± 33 months (range 1-96 months), with survival from the time of BrM treatment with surgery+IORT of 30 ± 32 months (range 1-96 months) and overall survival from the time of first cancer diagnosis of 71 ± 64 months (range 4-197 months). For the Graded Prognostic Assessment (GPA), patients with a score of 1.5-2.0 (n = 12) had an average posttreatment survival of 21 ± 26 months (range 1-96 months), those with a score of 2.5-3.0 (n = 7) had an average posttreatment survival of 52 ± 40 months (range 5-94 months), and those with a score of 3.5-4.0 (n = 4) had an average posttreatment survival of 17 ± 12 months (range 4-28 months). A BrM at the treatment site recurred in 7 patients 9 ± 6 months posttreatment, and 5 patients had new but distant BrM 17 ± 3 months after surgery+IORT. Six patients later received whole-brain radiation therapy, 7 patients received radiosurgery, and 2 patients received both treatments. The median Karnofsky Performance Scale scores before and 1 and 3 months after surgery were 80, 90, and 90, respectively; at the time of this writing, 3 patients remain alive with a CNS progression-free survival of > 90 months without additional BrM treatment. The results of this study demonstrate the feasibility of resection combined with IORT at a dose of 14 Gy to a 2-mm peripheral margin to treat a solitary BrM. Local control, distant control, and long-term survival were comparable to those of other commonly used modalities. Surgery combined with IORT seems to be a potential adjunct to patient treatment for CNS involvement by systemic cancer.