Long-Term Outcomes of Atypical Meningioma After Gross Total Resection (GTR) or Subtotal Resection (STR) With or Without Postoperative Radiation Therapy (PORT)

Abstract

The role of adjuvant radiation in patients after surgical resection for WHO Grade II atypical meningioma remains controversial. We sought to characterize the long-term outcomes of this population and to define any factors predictive of worse outcomes. We retrospectively analyzed 151 patients who underwent initial resection for WHO Grade II atypical meningioma at our institution from 2000-2012. GTR was defined as Simpson Grade I-III and STR as Simpson Grade IV-V. Risk factors for progression and death were analyzed with multivariate Cox regression. Kaplan-Meier survival curves were compared with the log-rank test. Median follow-up was 71.5 months. GTR was achieved in 101 patients. PORT was delivered to 34% of the entire cohort. Median age was 62 years. Treatment after 2008, smaller tumors, and STR predicted for PORT delivery. Overall, PORT was associated with improved progression free survival (PFS: HR = 0.47; 95% CI = 0.20-0.74, P = 0.010) after adjustment for confounding variables (size, age) in multivariate analysis. The 5-year/10-year PFS rates were 74%/59% in the PORT arm and 51%/41% in the non-PORT arm, respectively. Improvement in local control (LC: HR = 0.56, 95% CI = 0.32-1.06, P = 0.077) with the addition of PORT neared statistical significance but not for overall survival (OS: HR = 0.84, 95% CI = 0.44-1.61, P = 0.60). The 5-year/10-year LC rates were 83%/66% in the PORT arm and 65%/54% in the non-PORT arm, while the 5-year/10-year OS rates were 85%/53% in the PORT arm and 77%/66% in the non-PORT arm, respectively. PORT was also associated with better PFS in the GTR subgroup (HR = 0.35, 95% CI = 0.02-0.67, P = 0.028) and STR subgroup (HR = 0.41, 95% CI = 0.08-0.74, P = 0.028) multivariate analyses. No differences were seen in OS for either subgroup or LC for the GTR subgroup with the addition of PORT. However, improvement in LC for the STR subgroup neared statistical significance (HR = 0.39, 95% CI = 0.13-1.03, P = 0.059). Of the 45 patients that developed progression, 38 underwent salvage therapy (5 with surgery alone, 21 with radiation alone, 11 with surgery and PORT, one with chemotherapy alone). Almost 50% (17/38 patients) of salvaged patients received at least one more series of salvage therapy for re-progression. Five patients experienced transformation to WHO Grade III malignant meningioma. All had undergone initial GTR, developed recurrence, and received subsequent salvage radiation. Only one patient had undergone PORT as part of initial treatment. To our knowledge, we performed the largest review of patients in the literature with WHO Grade II atypical meningioma managed with initial surgery. Our data suggest that it is reasonable to consider PORT regardless of resection status based on the improvement in PFS. Randomized, prospective trials are ongoing to further assess and confirm the impact of PORT.