Residual Tumor Volume and Tumor Progression after Subtotal Resection and Observation of WHO Grade I Skull Base Meningiomas.

This study investigated the impact of residual tumor volume (RTV) on tumor progression after subtotal resection and observation of WHO grade I skull base meningiomas.  This study is a retrospective volumetric analysis.  This study was conducted at a single institution.  Patients who underwent subtotal resection of a WHO grade I skull base meningioma and postsurgical observation (July 1, 2007-July 1, 2017).  The main outcome was radiographic tumor progression.  Sixty patients with residual skull base meningiomas were analyzed. The median (interquartile range) RTV was 1.3 (5.3) cm . Tumor progression occurred in 23 patients (38.3%) at a mean duration of 28.6 months postsurgery. The 1-, 3-, and 5-year actuarial progression-free survival (PFS) rates were 98.3, 58.6, and 48.7%, respectively. The Cox multivariate analysis identified increasing RTV (  = 0.01) and history of more than 1 previous surgery (  = 0.03) as independent predictors of tumor progression. In a Kaplan-Meier analysis for PFS, the RTV threshold of 3 cm maximized log-rank testing significance between groups of patients dichotomized at 0.5 cm thresholds (  < 0.01). The 3-year actuarial PFS rates for meningiomas with RTV ≤3 cm and >3 cm were 76.2 and 32.1%, respectively. When RTV >3 cm was entered as a covariate in the Cox model, it was the only factor independently associated with tumor progression (  < 0.01).  RTV was associated with tumor progression after subtotal resection of WHO grade I skull base meningioma in this cohort. An RTV threshold of 3 cm was identified that minimized progression of the residual tumor when gross total resection was not safe or feasible.