Dose Escalation in Patients Receiving Whole-Brain Radiotherapy for Brain Metastases from Colorectal Cancer

Whole-brain radiotherapy (WBRT) alone is the most common treatment for brain metastases from colorectal cancer, as most patients are not candidates for more aggressive therapies such as resection or radiosurgery. The standard WBRT regimen, 30 Gy in ten fractions (10 x 3 Gy), has generally resulted in poor outcomes. This study investigated whether an escalation of the WBRT dose improves these results. Data from 53 patients receiving WBRT alone for brain metastases from colorectal cancer were retrospectively analyzed. 10 x 3 Gy (n = 35) was compared to higher doses (40 Gy/20 fractions or 45 Gy/15 fractions; n = 18) for overall survival (OS) and local control (LC). Additional factors evaluated for prognostic importance included age, gender, performance status, number of metastases, and extracerebral metastases. The OS rates at 6 months were 17% after 10 x 3 Gy and 50% after 20 x 2 Gy/15 x 3 Gy (p = 0.014). On multivariate analysis, improved OS was significantly associated with higher WBRT dose (p = 0.047), Karnofsky Performance Score (KPS) a parts per thousand yen 70 (p = 0.034), less than four brain metastases (p = 0.036), and lack of extracerebral metastases (p = 0.010). The LC rates at 6 months were 17% after 10 x 3 Gy and 50% after higher doses (p = 0.018). On multivariate analysis of LC, higher WBRT dose was significant (p = 0.028). A trend was observed for KPS a parts per thousand yen 70 (p = 0.08) and less than four brain metastases (p = 0.06). These data suggest that patients with brain metastases from colorectal cancer treated with WBRT alone appeared to benefit from escalation of the radiation dose beyond 10 x 3 Gy in terms of improved OS and LC.