BACKGROUND: Two intracranial tumor volume variables have been shown to prognosticate survival of stereotactic-radiosurgery-treated brain metastasis patients: the largest intracranial tumor volume (LITV) and the cumulative intracranial tumor volume (CITV). OBJECTIVE: To determine whether the prognostic value of the Scored Index for Radiosurgery (SIR) model can be improved by replacing one of its components-LITV-with CITV. METHODS:We compared LITV and CITV in terms of their survival prognostication using a series of multivariablemodels that included known components of the SIR: age, Karnofsky Performance Score, status of extracranial disease, and the number of brain metastases. Models were compared using established statistical measures, including the net reclassification improvement (NRI > 0) and integrated discrimination improvement (IDI). The analysis was performed in 2 independent cohorts, each consisting of ∼3000 patients. RESULTS: In both cohorts, CITV was shown to be independently predictive of patient survival. Replacement of LITV with CITV in the SIR model improved the model's ability to predict 1-yr survival. In the first cohort, the CITVmodel showed an NRI>0 improvement of 0.2574 (95% confidence interval [CI] 0.1890-0.3257) and IDI of 0.0088 (95% CI 0.0057-0.0119) relative to the LITVmodel. In the second cohort, the CITV model showed a NRI>0 of 0.2604 (95% CI 0.1796-0.3411) and IDI of 0.0051 (95% CI 0.0029-0.0073) relative to the LITV model. CONCLUSION: After accounting for covariates within the SIR model, CITV offers superior prognostic value relative to LITV for stereotactic radiosurgery-treated brain metastasis patients.
Bibliographical noteFunding Information:
The project described was partially supported by the National Institutes of Health (NIH), Grant 1TL1TR001443. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH. There are no other financial disclosures relevant to this manuscript. The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
Copyright © 2017 by the Congress of Neurological Surgeons.
- Brain metastases
- Cumulative intracranial tumor volume
- Net reclassification improvement
- Prognostic model