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Improved overall survival (OS) due to advances in cancer treatment and improvements in neuroimaging results in an increasing number of patients presenting with brain metastases.

Stereotactic radiosurgery (SRS) is increasingly used instead of whole-brain radiotherapy (WBRT) for patients with limited brain metastases, as WBRT has known side effects, which are of increasing concern due to improvement in prognosis. The benefits of SRS compared to WBRT include reduced toxicity, as it is possible to reduce the radiation dose to the whole brain and an expected increase in local control. However, despite treatment advances, the prognosis for the majority of patients with brain metastases remains poor. This study aimed to evaluate survival after the first treatment with SRS and identify groups of patients with a better prognosis.  

Patients from a single institution with up to four brain metastases, diameter <3 cm, treated from April 2011 to February 2018 were included, regardless of the primary cancer diagnosis.  Single metastases between 3 and 4 cm were allowed. Patients were prospectively registered, and clinical data were gathered retrospectively (tumor histology, performance status (PS), age, and number of metastases). As follow-up procedure, MRI was performed one month after treatment and every 3rd month hereafter. In case of progression or recurrence, the possibility of SRS, WBRT, surgery, systemic treatment, or best supportive care was evaluated. No patients were lost to follow up. The dose to the edge of the gross tumor volume (GTV) was 20 Gy/ 1 F or, in case of larger metastases or proximity to organs at risk, 27 Gy/ 3F.  All patients were planned with CT- and MR scans. Radiologists and oncologists in collaboration defined GTV. The treatment was performed with three arcs on a linac, one coplanar and two non-coplanar. Orfit® 5-points immobilization system was used. PTV margin was 2-3 mm.

In total, 285 patients were treated with SRS. Baseline characteristics in table 1. The median survival was eight months. OS after 1 and 2 years was 29% and 13% respectively. Median survival for breast cancer patients was 19.4 months, 9.8 months for malignant melanoma, and 7.6 months for lung cancer patients. Patients with a PS 0-1 and breast cancer diagnosis had significantly better survival. Patients with PS ≥2 had a median survival of only four months (table 2).

In a cox regression analysis PS, female sex and breast cancer diagnosis had a statistically significant positive impact on survival, whereas number of brain metastases (1 vs ≥2) and age ≤70 did not.

Compared to WBRT(historical data), SRS performed with VMAT appear to improve survival. The majority of the patients with brain metastases still have a poor prognosis, but selected patients gained improved survival. Patients with PS ≥2 have doubtful gain of SRS in terms of survival, but SRS may be effective as treatment of symptoms. 

Table 1 Baseline Characteristics 

Table 2 Median survival and Hazard Ratios