Abstract
Adjuvant whole-brain radiation therapy (WBRT) after resection of single brain metastases remains controversial. Despite a phase III trial to the contrary, clinicians often withhold WBRT after resection of single brain metastases based on the argument that available evidence does not inform regarding treatment of all patients, such as those with radioresistant tumors. However, there is limited information about whether subpopulations benefit equally from WBRT after resection. Therefore, we undertook a retrospective study to determine the clinical, radiographic, and histologic features that influenced the effectiveness of adjuvant WBRT. We reviewed 358 patients with newly diagnosed, single brain metastases, who underwent resection, of which 142 (40%) received adjuvant WBRT and 216 (60%) did not. Median follow-up was 60.1 months. There were multiple tumor histologies, including 197 (55%) "radiosensitive" and 161 (45%) "radioresistant" tumors. Compared with observation, WBRT significantly reduced recurrence both locally (HR = 0.58; 95% CI 0.35–0.98, P = .04) and at distant brain sites (HR = 0.43, 95% CI 0.30–0.61, P < .001). Multivariate analyses demonstrated that withholding WBRT was an independent predictor of local and distant recurrence. For local recurrence, tumors with a maximum diameter of ≥3 cm that did not receive adjuvant WBRT had an increased risk of recurring locally (HR = 3.14, 95% CI 1.02–9.69, P = .05). For distant recurrence, patients whose primary disease was progressing and who did not receive WBRT had an increased risk of distant recurrence (HR = 2.16, 95% CI 1.01–4.66, P = .05). There was no effect of WBRT based on tumor type. Adjuvant WBRT significantly reduces local and distant recurrences in subsets of patients, particularly those with metastases >3 cm or with active systemic disease.