Elsevier

World Neurosurgery

Volume 99, March 2017, Pages 111-117
World Neurosurgery

Original Article
More than Just the Number of Brain Metastases: Evaluating the Impact of Brain Metastasis Location and Relative Volume on Overall Survival After Stereotactic Radiosurgery

https://doi.org/10.1016/j.wneu.2016.11.119Get rights and content

Objective

Most evidence describing outcomes of patients with brain metastases is based on number of brain metastases, rather than location or volume. We evaluated the impact of tumor location and relative volume on overall survival (OS) among a large cohort of patients treated with stereotactic radiosurgery.

Methods

Clinical, radiographic, and dosimetric data were collected on patients treated with first (if multiple) stereotactic radiosurgery for brain metastases. Multivariate analyses were performed to investigate the impact of brain metastasis relative location and volume on OS after stereotactic radiosurgery.

Results

Analysis included 300 patients with 817 tumors (116 patients with single brain metastasis). The most common tumor locations were supratentorial (75% of tumors), cerebellar (19%), and brainstem (5%). Median tumor volume was 0.4 mL (range, 0.003–65.0 mL). Tumor-specific factors associated with inferior OS included brainstem location versus both supratentorial and cerebellum locations for particular assumed values of cube root tumor volume (P < 0.001 for each) and increasing total supratentorial tumor volume (P = 0.004). Patients with supratentorial tumors and cerebellar tumors demonstrated similar OS, and cube root total tumor volume within the cerebellum and brainstem did not predict for OS.

Conclusions

The presence of brainstem metastases and cumulative supratentorial tumor volume are adverse features that result in inferior survival. These results can be used to inform patient prognosis and future clinical trial design.

Introduction

As improvements in therapies available for systemic malignancies have allowed patients to live longer after diagnosis of primary cancer, the incidence of brain metastases has increased.1 Classically, therapeutic options for brain metastases include conventionally fractionated whole-brain radiotherapy (WBRT) and chemotherapy. WBRT was considered the standard treatment for brain metastases, concordant with the idea that the entire brain may be seeded with micrometastases, as most malignancies spread to the brain hematogenously. In the 1990s, evidence from randomized trials emerged supporting local treatment of select patients with brain metastases through open neurosurgical resection.2, 3 This evidence base has since been expanded to support locally ablative radiotherapy techniques, such as stereotactic radiosurgery (SRS).4, 5

To date, the evidence supporting SRS alone in patients with brain metastases has been based on trials with inclusion criteria based mainly on the number of brain metastases involved.5, 6, 7, 8 Although the number of brain metastases has been shown to be an important prognostic factor, it is not the only one.9, 10 Specifically, individual tumor location and volume are features of brain metastases that would rationally impact patient survival, but these have been infrequently investigated to date. The purpose of this study was to evaluate how tumor location and cumulative regional volume may impact overall survival (OS) after SRS.

Section snippets

Patient Population

Before initiation, this study received approval from our center's institutional review board. Data were collected through an institutional review board–approved, retrospective chart review of patients with brain metastases treated with SRS at a single institution between 1995 and 2014. Patients with brainstem tumors were selected through a previously identified cohort of patients.11 The remaining patients were selected through an ordering of the medical record numbers of the patients treated

Patient Cohort and Survival

The analysis included 300 patients with 817 tumors. Of patients, 116 (39%) were treated with SRS for a single brain metastasis. Table 1 lists the clinical, radiographic, and dosimetric characteristics of the patients included in our series. The most common tumor location was supratentorial (75% of tumors), followed by cerebellar (19%), brainstem (5%), and “other” (1%). Median volume of all tumors was 0.4 mL (range, 0.003–65.0 mL). Table 2 lists the median tumor volumes and ranges within each

Discussion

Previous studies have reported that prognostic factors for survival include patient Karnofsky performance scale score, age, extent of extracranial disease, number of brain metastases, overall intracranial tumor volume, and tumor histology.9, 10, 14, 15 Our results confirm these findings in an independent cohort of patients, but moreover, our results confirm that individual brain tumor location and tumor volume are each independent prognostic factors for survival of patients with brain

Conclusions

Informing prognosis in patients with brain metastases is difficult secondary to the inherent heterogeneity in patients with brain metastases. Our results confirm that patients with brainstem metastases and patients with a large total supratentorial tumor volumetric burden demonstrate inferior survival compared with their counterparts. These results can be used to inform patient prognosis and clinical trial design in the future.

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    • Cited by (0)

    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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