Combined primary tumor and extracranial metastasis status as constituent factor of prognostic indices for predicting the overall survival in patients with brain metastases

We retrospectively analyzed the prognostic factors on overall survival (OS) in patients with brain metastasis (BM) and evaluated the role of combined primary tumor and extracranial metastasis (ECM) status as a constituent factor for prognostic index. This study involved 897 patients with BMs who underwent radiotherapy between April 2003 and December 2009. Among the clinical parameters, multivariate analysis showed that age, Karnofsky performance status (KPS), combined primary tumor and ECM status, number of BMs, and treatment group were significant prognostic factors for OS (P < 0.05). To compare the discriminatory ability of 5 prognostic indices, i.e., recursive partitioning analysis (RPA), basic score for BMs (BSBM), score index for radiosurgery (SIR), graded prognostic assessment (GPA), and modified GPA including the combined primary tumor and ECM status (mGPA), the Akaike information criteria (AIC) were calculated. The mGPA showed the lowest AIC value, followed by RPA, GPA, SIR, and BSBM, in that order. It is implicated that modified score of pre-existing factors (i.e., age and KPS) and addition of the combined primary tumor and ECM status to the prognostic index can improve its discriminatory ability and the combined primary tumor and ECM status may be useful as one of constituent factors for prognostic index.