Feasibility and safety of cavity-directed stereotactic radiosurgery for brain metastases at a high-volume medical center

Abstract

ObjectiveOur objective was to report safety and efficacy of stereotactic radiosurgery (SRS) to the surgical bed following resection of brain metastases.MethodsEighty-seven consecutive patients who underwent cavity-directed SRS to the operative bed for the treatment of brain metastases between 2002 and 2010 were evaluated. SRS required a gadolinium-enhanced, high-resolution, T1-weighted magnetic resonance imaging for tumor targeting and delivered a median dose of 18 Gy (14-22 Gy) prescribed to encompass the entire resection cavity. Whole brain irradiation was reserved for salvage. Patients were followed every 3 months with clinical examination and magnetic resonance imaging. Overall survival, local and regional recurrence, and factors affecting these outcomes were evaluated using Kaplan-Meier and log-rank analyses.ResultsThe median imaging follow-up was 7.1 months, with >40% of patients having imaging for ≥1 year. Local control at 1 and 2 years was 82% and 75%, respectively. Cavity recurrence was more common with a tumor diameter >3 cm (P < .020) or resection cavity volume >14 mL (P < .050). One-year local control for tumors <2 cm, 2 cm to 3 cm, and >3 cm were 100%, 86%, and 72%, respectively. Neither subtotal resection nor target margins >2 mm to 3 mm affected local control. The median overall survival was 14.3 months with actuarial 5-year survival of 20%. Actuarial regional central nervous system recurrence was 44% at 1 year. On univariate analysis, only the presence of extracranial disease was associated with survival (P < .001) and central nervous system failure (P < .030).ConclusionsExcellent local control is achievable with cavity-directed SRS in well-selected patients, particularly for lesions with diameter <3 cm and resection cavity volumes <14 mL. Long-term survival is possible for select patients.

A Dose-Response Model of Local Tumor Control Probability After Stereotactic Radiosurgery for Brain Metastases Resection Cavities

“…Our data are consistent with prior studies reporting higher rates of local recurrence in patients with larger preoperative tumors 2 , 4 , 6 , 7 , 8 , 9 or larger postoperative resection cavities. 4 , 9 , 10 , 11 , 12 , 13 , 14 , 15 Specifically, PTV volumes greater than 12 cm 3 to 17 cm 3 and CTV volumes greater than 8 cm 3 to 10 cm 3 have been shown to predict greater risk of local recurrence. 9 , 10 , 11 , 12 , 13 Similarly, we report a 3 times higher risk of local recurrence among cavities with PTV greater than 12 cm 3 .…”

“…Our data are consistent with prior studies reporting higher rates of local recurrence in patients with larger preoperative tumors 2,4,[6][7][8][9] or larger postoperative resection cavities. 4,[9][10][11][12][13][14][15] Specifically, PTV volumes greater than 12 cm 3 to 17 cm 3 and CTV volumes greater than 8 cm 3 to 10 cm 3 have been shown to predict greater risk of local recurrence.…”

“…In the treatment of brain metastases, retrospective studies suggest that resection followed by SRS to the cavity provides excellent local control, often exceeding 80% at 1-year follow-up. 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 However, recent randomized controlled trials report considerably lower rates of 1-year local control, ranging from 61.8% to 72%. 1 , 2 These findings demand a more sophisticated understanding of the factors that influence local treatment failure after resection cavity SRS.…”

“…In the randomized controlled trial conducted by Mahajan et al, 2 patients received a median dose of 16 Gy in 1 fraction (range, [12][13][14][15][16][17][18], compared with higher median doses in several recent retrospective studies that treated with a single fraction. [3][4][5] Potential reasons for poorer control rates in the postoperative setting compared with intact brain metastases include greater tumor hypoxia, disruption of the tumor microenvironment, and microscopic contamination related to surgical intervention. Quantitative modeling may help to predict the effect of higher radiation doses in improving local control.…”

Tumor Cavity Recurrence after Stereotactic Radiosurgery of Surgically Resected Brain Metastases: Implication of Deviations from Contouring Guidelines

“…1). Others have questioned the benefit of routine coverage of the surgical tract [10]. The proposed guidelines recommend coverage of the surgical tract; however, this was not routinely incorporated in the MDACC and NCCTG studies [1, 2].…”