Clinical Review

Role of Radiosurgery in the Treatment of Brain Metastasis

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Another comparative study of SR and SRS for solitary brain metastasis revealed no statistically significant difference in survival between the 
2 therapeutic modalities (SR or SRS); the 1-year survival rate was 62% (SR) and 56% (SRS).4 A significant prognostic factor for survival was a good performance status of the patients. There was, however, a significant difference in local tumor control: None of the patients in the SRS group experienced local recurrence in contrast to 19 (58%) patients in the SR group.

Whereas selection criteria and treatment choice depend to a large extent on tumor location, tumor size, and availability of SRS, most studies demonstrated that both surgery and SRS result in comparable OS rates for patients with a single brain metastasis.

Multiple Brain Metastases

Jawahar and colleagues studied the role of SRS for multiple brain metastases.8 In their retrospective review of 50 patients with ≥ 3 brain metastases, they found an overall response rate (RR) of 82% and a median survival of 12 months after SRS. As a result of similar studies and their own data, Hasegawa and colleagues recommended radiosurgery alone as initial therapy for patients with a limited number of brain metastases.9

SRS vs SRS Plus WBRT

Studies on the role of SRS plus WBRT are somewhat conflicting. A Radiation Therapy Oncology Group study revealed statistically significant improvement in median survival when SRS boost therapy was added to WBRT in patients with a single brain metastasis compared with SRS alone.5 According to another study, the addition of SRS to WBRT provided better intracranial and local control of metastatic tumors.10

A randomized controlled study by Aoyama and colleagues reported no survival improvement using SRS and WBRT in patients with 1 to 4 brain metastases compared with SRS alone.11 In addition, a retrospective review found no difference in median survival outcomes between SRS alone and SRS plus WBRT (Table 4). In the absence of a clear survival benefit with the use of both modalities and in light of the added toxicity of WBRT, most clinicians have ceased offering both modalities upfront and instead reserve WBRT as a salvage option in cases of subsequent intracranial progression of disease.

SRS vs WBRT

In general, both SR (crainotomy) and SRS for the treatment of brain metastases seem to be effective therapeutic modalities. Comparisons of both treatments did not reveal significant differences and showed similar outcomes after treatment of smaller lesions. For example, Rades and colleagues reported that SRS alone is as effective as surgery and WBRT for limited metastatic lesions (< 2) in the brain.16 Either SRS or surgery can be used, depending on performance status and metastatic burden (size, location, number of lesions, etc).

There are some inconsistencies in the final results of various studies, such as survival, local tumor control, mortality rate, and pattern of failures. For large, symptomatic brain metastasis, initial surgical debulking remains the preferred approach as a way of achieving immediate decompression and relief of swelling/symptoms. Additionally, for patients who have > 10 brain lesions and/or a histology that corroborates diffuse subclinical involvement of the brain parenchyma (eg, small-cell lung cancer), WBRT is also typically preferred to upfront SRS. Alternatively, radiosurgery is the preferred method for fewer and smaller lesions as a way of minimizing the toxicity from whole brain irradiation. The optimal treatment of multiple small brain metastases remains controversial with some investigators recommending SRS for > 4 metastases only in the setting of controlled extracranial disease based on the more favorable expected survival of such patients.

Multidisciplinary Approach for Lung and Breast Cancers

Prognostic outcomes of patients with brain metastases can vary by primary cancer type. Therefore, clinicians should consider cancer-specific management and tailor their recommendation for specific types of radiation depending on the 
individual cancer diagnosis. Various investigators have attempted to develop disease-specific prognostic tools to aid clinicians in their decision making. For example, Sperduto and colleagues analyzed significant indexes and diagnosis-specific prognostic factors and published the 
diagnostic-specific graded prognostic assessment factors.17 They were able to identify several significant prognostic factors, specific to different primary cancer types.

Bimodality Therapies

For certain cancers such as lung and breast primary cancers, bimodality therapy using chemotherapy and radiation treatment should be considered based on promising responses reported in the literature.

Recent studies on the efficacy of chemotherapy for brain metastases from small-cell lung cancer (43%-82%) have also been reported.18-20 Postmus and colleagues reported superior RR of 57% with combination chemotherapy and radiation vs a 22% RR for chemotherapy alone.21 They also found favorable long-term survival trends in patients treated with combined radiochemotherapy.

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