Elsevier

World Neurosurgery

Volume 104, August 2017, Pages 589-593
World Neurosurgery

Original Article
Repeat Stereotactic Radiosurgery for Locally Recurrent Brain Metastases

https://doi.org/10.1016/j.wneu.2017.04.103Get rights and content

Purpose/Objectives

The outcomes of repeat stereotactic radiosurgery (SRS) after failure of previous SRS are not well established. We report our overall experience using SRS for the retreatment of locally recurrent brain metastases.

Methods

Patients with brain metastases diagnosed between 2003 and 2015 who underwent repeat SRS for local tumor progression following prior SRS were identified. Rates of local control, radiation necrosis, and overall survival were analyzed. Factors affecting local failure and radiation necrosis were assessed by chi-square test.

Results

Twenty-four lesions in 22 patients underwent repeat SRS in a single fraction. Median age was 59 years. The median SRS-1 dose was 18 Gy, and the median SRS-2 dose was 15.5 Gy. The median SRS-1 target volume was 2.25 cm3, and the median SRS-2 target volume was 3.30 cm3. The median follow-up from SRS-2 was 8.8 months. The actuarial local controls for SRS-2 were 94.1% and 61.1% at 6 and 12 months, respectively. The incidences of actuarial radiation necrosis were 9.2% and 9.2% at 6 and 12 months, respectively. Volume of tumor >4 cm3 correlated with increased risk of local failure (P = 0.006) with no local failures recorded with volumes ≤4 cm3. SRS-2 dose, cumulative SRS dose, receipt of whole brain radiotherapy, and use of SRS-2 as boost after surgery did not correlate with local failure or radiation necrosis. Median overall survival after SRS-2 was 8.78 months.

Conclusion

Repeat SRS is feasible for select patients, particularly for those with tumor volume ≤4 cm3. Further evaluation is needed to establish the most appropriate treatment doses and volumes for this approach.

Introduction

Stereotactic radiosurgery (SRS) is an established method of delivering high doses of focused radiation for the treatment of brain metastases. For patients with limited brain metastases, SRS results in favorable tumor control rates of 80%–90% at 6–12 months while sparing normal brain tissue.1, 2, 3, 4, 5, 6, 7, 8, 9 However, for those with local failure following SRS, treatment options are limited. Although repeat SRS to the same lesion has potential to offer durable local tumor control, it is unclear whether normal brain tissue can tolerate reirradiation without an excess risk of radiation necrosis. We, therefore, analyzed our experience using repeat SRS to the same lesion to better understand outcomes.

Section snippets

Inclusion Criteria

In compliance with the institutional review board approval (IRB #224940), we retrospectively reviewed the records of 601 patients treated with Gamma Knife at our institution from 2003–2015. All patients who underwent repeat SRS (SRS-2) to the same brain metastases for local failure following initial SRS (SRS-1) were included for analysis. Local recurrence following SRS-1 was defined as an enlarging area of enhancement at the treated location on contrast-enhanced magnetic resonance imaging (MRI)

Patient Characteristics

A total of 24 brain metastases in 22 patients underwent repeat SRS treatment to the same lesion and were included in this analysis. The median follow-up was 8.8 months. The median age at SRS-2 was 59 (range 43–80). Non–small cell lung cancer (41%) was the most common tumor subtype (Table 1). Median treatment target sizes at SRS-1 and SRS-2 were 2.25 cm3 and 3.30 cm3, respectively (Table 2). Five out of 24 brain metastases (20.8%) were treated to the tumor bed after surgical resection following

Discussion

SRS is an effective up-front treatment option for patients with limited brain metastases. Local control rates of 80%–90% are expected at 6–12 months.1, 2, 3, 4, 5, 6, 7, 8, 9 However, for patients who develop local failure following SRS, salvage treatment possesses a significant challenge. Surgery and/or WBRT are the primary salvage treatment approaches. However, surgery alone results in a high rate of local failure and not all lesions are amenable to safe resection.4, 11 WBRT as a sole

Conclusions

Although local failure and radiation necrosis rates were elevated in this high-risk cohort, repeat SRS is feasible for highly select patients. Target volume was a significant predictor of local failure in the setting of repeat SRS. A better understanding of the most appropriate treatment doses and treatment volumes is needed.

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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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