Cumulative Intracranial Tumor Volume and Number of Brain Metastasis as Predictors of Developing New Lesions After Stereotactic Radiosurgery for Brain Metastasis

Objectives To identify risk factors associated with early distant radiographic progression in patients undergoing stereotactic radiosurgery (SRS) for brain metastases (BM). Methods Following Institutional Review Board approval, data of 1427 patients (4283 BM lesions) who were treated by SRS at the Cleveland Clinic for 2000–2012 were collected. Local tumor progression (LTP), distant tumor progression (DTP), and radiographic radiation necrosis (RN) were the primary endpoints. Patient, imaging, radiosurgery, and tumor variables and follow-up data were collected. Results The median number of targets was 2 (range, 1–17); 45% of the patients had a single lesion. DTP was observed in 10% at 3 months and 19% at 6 months. Patients with 5–10 target lesions for SRS were more likely to develop new lesions at both 3 and 6 months compared to those with 2–4 lesions (odds ratio [OR], 0.83, 95% confidence interval [CI], 0.40–0.85 and OR, 0.85, 95% CI, 0.45–0.86 respectively; P < 0.05). Younger age (<65 years; P < 0.001), higher number of lesions (>1; P < 0.001), cumulative intracranial tumor volume (CITV) <2.75 cc (P = 0.023), type of SRS (upfront and salvage vs. boost; P < 0.001), and tumor pathology (radiosensitive; P < 0.001), were independent predictors of early distant tumor progression following SRS. Conclusions The number of target lesions and low CITV are both independent predictors of early DTP following SRS for BM. Radiosensitive tumor histology, younger age (<65 years), and SRS without previous whole-brain radiation therapy (upfront or salvage) were also predictors of early DTP.