The prognostic role of tumor volume in the outcome of patients with single brain metastasis after stereotactic radiosurgery

Abstract Background Patients with single brain metastasis (SBM) have better outcomes after stereotactic radiosurgery (SRS). We analyzed our SRS database to evaluate possible prognostic factors in patients with SBM. Methods 584 patients with SBM that were treated with SRS at our institution (2000-2012). Study endpoints were overall survival (OS), and distant and local intracranial progression free survival (DPFS and LPFS, respectively). Multivariable analysis was performed to develop prognostic models. Results Median OS was 10.8 months. 196 patients (36.7%) had distant progression and 102 patients (19.2%) had local progression. New SBM prognostic index (SPI) were devised for OS, DPFS, and LPFS. Graded Prognostic Assessment (GPA), neurological symptoms (P=0.01) and tumor volume (P =0.02) were independently associated with OS. The SPI for OS was defined: “unfavorable” (OS 7.3 months), “intermediate” (OS 10.6 months), and “favorable” (OS 19.8 months). For DPFS, age (P=.0029), tumor volume (P=0.0002), and prior WBRT (P= 0.027) were prognostic, and were used to define SPI for DPFS: “favorable” (6-month CIF = 10.9%), “intermediate” (6-month CIF = 16.7%) and “unfavorable” (6 month CIF 26.0%) (P