Comparison of stereotactic radiosurgery (SRS) alone and whole brain radiotherapy (WBRT) plus a stereotactic boost (WBRT + SRS) for one to three brain metastases

Background: The best available treatment of patients with one to three brain metastases is still unclear. This study compared the results of stereotactic radiosurgery (SRS) alone and whole brain radiotherapy (WBRT) plus SRS (WBRT + SRS). Patients and Methods: Survival (OS), intracerebral control (IC), and local control of treated metastases (LC) were retrospectively analyzed in 144 patients receiving SRS alone (n = 93) or WBRT + SRS (n = 51). Eight additional potential prognostic factors were evaluated: age, gender, Eastern Cooperative Oncology Group performance score (ECOG-PS), tumor type, number of brain metastases, extracerebral metastases, recursive partitioning analysis (RPA) class, and interval from tumor diagnosis to irradiation. Subgroup analyses were performed for RPA class I and II patients. Results: 1-year-OS was 53% after SRS and 56% after WBRT + SRS (p = 0.24). 1-year-IC rates were 51% and 66% (p = 0.015), respectively. 1-year-LC rates were 66% and 87% (p = 0.003), respectively. On multivariate analyses, OS was associated with age (p = 0.004), ECOG-PS (p = 0.005), extracerebral metastases (p < 0.001), RPA class (p < 0.001), and interval from tumor diagnosis to irradiation (p < 0.001). IC was associated with interval from tumor diagnosis to irradiation (p = 0.004) and almost with treatment (p = 0.09), and LC with treatment (p = 0.026) and almost with interval (p = 0.08). The results of the subgroup analyses were similar to those of the entire cohort. The increase in IC was stronger in RPA class I patients. Conclusion: WBRT + SRS resulted in better IC and LC but not better OS than SRS alone. Because also IC and LC are important end-points, additional WBRT appears justified in patients with one to three brain metastases, in particular in RPA class I patients.