Significance of the number of brain metastases for identifying patients who don't need whole brain radiotherapy: implication as oligometastases of the brain.

Background and Purpose: To investigate the significance of the number of brain metastases in the treatment with stereotactic radiotherapy (SRT) with or without whole brain radiotherapy (WBRT).
Material and Methods: Between February 2003 and October 2010, 218 consecutive patients with brain metastases who underwent SRT alone or WBRT plus SRT were investigated. The prognostic factors affecting overall survival and brain progression-free survival were analyzed by multivariate and univariate analysis. By logistic regression analysis, factors associated with the number recurrences of brain metastasis after SRT were also investigated.
Results: The median overall and brain progression-free survivals were 7.2 months and 4.3 months, respectively. Significant prognostic factors for overall survival in multivariate analyses were performance status (hazard ratio [HR] = 1.71, 95% confidence interval [CI] 1.13-2.57, p = 0.01) and the number of brain metastases (HR = 1.75, 95% CI 1.08-2.83, p = 0.02). Cut-off line of the number of brain metastases was between 3 and 4, and 3 or fewer brain metastases were significantly better than 4 or more in prognosis by univariate and multivariate analysis (p < 0.01, p = 0.02).
Conclusions: The patients with 3 or fewer brain metastases were associated with brain progression free survival and 3 or fewer brain relapse. Repeated SRT without WBRT may be effective for patients with 3 or fewer brain metastases.