Introduction: The role of radiotherapy in WHO grade II atypical meningioma is controversial as an adjuvant for both gross-total and subtotal resections. Current analyses suggest observation after gross-total resection but adjuvant radiotherapy following subtotal resection, although not all publications have shown a benefit to adjuvant radiotherapy after subtotal resection. Few studies have examined factors associated with treatment failure and disease progression after adjuvant radiotherapy following subtotal resection.
Methods: We retrospectively reviewed the adult patients treated at our institution for cranial atypical meningioma via subtotal resection and either adjuvant stereotactic radiosurgery (SRS) or external-beam radiation (XRT), with complete medical records including pre- and post-operative volumetric imaging.
Results: Forty-six patients (22 female) met inclusion criteria out of all atypical meningioma patients treated between 1992 and 2011. Twenty-five underwent adjuvant SRS and 21 adjuvant XRT. Median post-operative follow-up was 62 months, during which 18 patients had recurrent/progressive disease at a median of 28 months postoperatively. Patient age, gender, pre-operative tumor volume, MIB-1 indexing, and extent of resection were not associated with treatment failure. Post-operative residual tumor volume was strongly associated with disease progression (average volume 8.1 cm3 vs. 1.6 cm3, p < 0.002). Ninety-two percent of patients harboring residual tumor volume > 5 cm3 suffered progression.
Conclusions: A strong association exists between residual tumor volume and disease progression. This may explain the literature heterogeneity regarding the efficacy of adjuvant radiotherapy in subtotally-resected atypical meningioma. Residual tumor volume should be a reported variable in future studies of adjuvant radiotherapy.
Patient Care: Via improved knowledge of the role of radiation therapy in atypical meningioma, especially in patients with large tumors
Learning Objectives: By the conclusion of this session, participants should:
1) Describe the importance of residual tumor volume in adjuvant treatment of atypical meningioma
2) Discuss, in small groups the factors associated with tumor progression after adjuvant therapy in atypical meningioma
3) Identify an effective treatment for the patient with subtotally resected atypical meningioma