Clinical Investigation
Stereotactic Irradiation of the Postoperative Resection Cavity for Brain Metastasis: A Frameless Linear Accelerator-Based Case Series and Review of the Technique

This abstract was presented as an oral presentation at the 9th Congress of the European Association of Neurooncology, Maastricht, Netherlands, September 16–19, 2010.
https://doi.org/10.1016/j.ijrobp.2010.10.043Get rights and content

Purpose

Whole-brain radiation therapy (WBRT) is the standard of care after resection of a brain metastasis. However, concern regarding possible neurocognitive effects and the lack of survival benefit with this approach has led to the use of stereotactic radiosurgery (SRS) to the resection cavity in place of WBRT. We report our initial experience using an image-guided linear accelerator-based frameless stereotactic system and review the technical issues in applying this technique.

Methods and Materials

We retrospectively reviewed the setup accuracy, treatment outcome, and patterns of failure of the first 18 consecutive cases treated at Brigham and Women’s Hospital. The target volume was the resection cavity without a margin excluding the surgical track.

Results

The median number of brain metastases per patient was 1 (range, 1–3). The median planning target volume was 3.49 mL. The median prescribed dose was 18 Gy (range, 15–18 Gy) with normalization ranging from 68% to 85%. In all cases, 99% of the planning target volume was covered by the prescribed dose. The median conformity index was 1.6 (range, 1.41–1.92). The SRS was delivered with submillimeter accuracy. At a median follow-up of 12.7 months, local control was achieved in 16/18 cavities treated. True local recurrence occurred in 2 patients. No marginal failures occurred. Distant recurrence occurred in 6/17 patients. Median time to any failure was 7.4 months. No Grade 3 or higher toxicity was recorded. A long interval between initial cancer diagnosis and the development of brain metastasis was the only factor that trended toward a significant association with the absence of recurrence (local or distant) (log-rank p = 0.097).

Conclusions

Frameless stereotactic irradiation of the resection cavity after surgery for a brain metastasis is a safe and accurate technique that offers durable local control and defers the use of WBRT in select patients. This technique should be tested in larger prospective studies.

Introduction

Whole-brain radiation therapy (WBRT) is considered the evidence-based standard of care after surgical resection of a single brain metastasis. This is based on a randomized trial by Patchell et al. that demonstrated that the addition of WBRT reduces the risk of both local and distant relapse within the brain (1). Importantly, this study also demonstrated that the addition of WBRT significantly reduced the risk of neurologic death. However, the addition of WBRT did not appear to offer an overall survival advantage, although the study was not powered to address this question. Despite the proven benefits of WBRT, patients are increasingly rejecting it because to a concern regarding potential detrimental effects of WBRT on neurocognitive function. For this reason, an alternative treatment strategy employing focal radiotherapy techniques, such as stereotactic radiosurgery, hypofractionated stereotactic radiotherapy, or fractionated conventional radiotherapy, is attractive. Stereotactic radiosurgery (SRS) alone to the resection cavity is being used in many centers 2, 3, 4, 5, 6, 7, 8, 9. This approach may be a viable alternative to WBRT, offering excellent local control without compromising survival in this population.

To date, seven previous single-institution retrospective series of SRS to the postoperative resection cavity have been published (Table 1) 2, 3, 4, 5, 6, 7, 8, 9. Here we report our initial experience with frameless linear accelerator-based SRS to the postoperative resection cavity and review the technical issues pertaining to this technique. This is the first report of frameless linac-based delivery of this technique using a non-CyberKnife® (Accuray, Sunnyvale, CA) delivery platform.

Section snippets

Patients

This retrospective study was approved by the Dana-Farber/Harvard Cancer Center Institutional Review Board. We began the delivery of SRS to resection cavities after the introduction of a frameless system in 2009. All cases of SRS performed at Brigham and Women’s Hospital between January 1, 2009, and June 1, 2010, were reviewed to identify patients who received SRS to a postoperative cavity after resection of a brain metastasis. WBRT is typically offered as the standard of care in these cases.

Patient characteristics

During the study period, 167 stereotactic procedures were delivered to 102 patients. Eighteen consecutive cases of stereotactic irradiation of the resection cavity of brain metastases were identified in 17 patients. Patient characteristics are listed in Table 2. Gross total resection was achieved in 17/18 cases. The median age was 61.8 years (range, 38–81). All patients were capable of self-care, with Karnofsky performance scores of 70% or higher. The majority (76%) were RPA Class 2 patients.

Discussion

Surgical resection of a single brain metastasis has been shown to be associated with an overall survival advantage in randomized studies in patients with favorable performance status 11, 12. Surgical resection is also warranted in certain cases for the alleviation of mass effect or to provide histologic confirmation. Because of a reduction in both local and distant recurrences, WBRT is considered the evidence-based standard of care after surgical resection (1). However, WBRT can have an impact

Conclusion

Image-guided frameless stereotactic irradiation of the postoperative cavity after surgical resection of a brain metastasis appears to offer local control rates similar to those seen with whole-brain radiotherapy. This technique may defer the use of WBRT in select patients. A multicenter prospective study should be a priority to further define the optimal use of SRS in this setting.

Acknowledgments

The authors would like to thank Dr David Sher MD MPH, Edward Mannarino, Nancy Pinnell, and Barbara Silver of the Department of Radiation Oncology, Dana-Farber/Brigham and Women’s Cancer Center for their help in the preparation of this manuscript.

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A travel grant was awarded by the European Association of Neurooncology.

Conflicts of interest: none.

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