Colorectal cancer metastatic to the brain: analysis of prognostic factors and impact of KRAS mutations on presentation and outcome

ABSTRACT

Background. Treatment concepts for metastatic colorectal cancer continue to evolve. While the presence of RAS mutations impacts systemic therapy, little is known about the influence of such mutations in patients with brain metastases. Patients and methods. Pooled retrospective analysis was conducted of 57 patients with brain metastases from colorectal cancer treated in two different institutions (2005-2013). Results. The only mutations analyzed in a relatively large subgroup were KRAS mutations (14 wild type, 12 mutated). Mutation status was not associated with baseline characteristics such as number or location of metastases, and did not impact prognosis. Three factors were significantly associated with survival in multivariate analysis: Karnofsky Performance Status (KPS), management strategy, and systemic treatment. Median survival was 0.6 months with best supportive care, 3.0 months with initial whole-brain radiotherapy (WBRT), and 12.7 months if initial treatment included surgery or stereotactic radiosurgery (SRS), p = 0.0001. The survival difference between the WBRT and surgery/SRS groups was largest in patients with KPS 80-100. Conclusion. Effective local treatment was a prerequisite for improved survival. The only significant prognostic baseline factor was KPS, which forms the basis of the diagnosis-specific graded prognostic assessment (DS-GPA) score. Thus, our results validate the DS-GPA in this patient population. So far, neither this nor other studies suggest a clinically important impact of KRAS mutations beyond their previously reported association with development of brain metastases. Studies focusing on patients who develop brain metastases early during the course of metastatic disease might be warranted, because the influence of different systemic therapies might be larger in this subgroup (AU)

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