Luis Souhami (McGill University Health Centre)
**Purpose**: The optimal post-surgical management of atypical meningiomas remains controversial. The aim of this study was to review the long-term outcomes of patients with atypical meningioma following surgery and to identify potential prognostic factors for disease progression. **Materials and Methods**: From August 1992 to August 2013, 72 patients with atypical meningioma were treated at our institution. Patients with multiple tumors, neurofibromatosis type 2 or inadequate imaging follow-up were not eligible. We performed pre- and post-operative serial measurements of tumor volume from magnetic resonance imaging. We assessed age, gender, tumor location, bone involvement, extent of resection, tumor growth rates, use of adjuvant post-operative radiation therapy (PORT), and tumor volume at time of radiation therapy (RT) using uni- and multivariate analysis to determine their impact on disease recurrence. Pathology was reviewed in all patients using the WHO 2007 classification. All patients underwent surgical resection at our institution. The extent of surgical resection was established by post-operative imaging and by the surgeon’s assessment at time of surgery based on Simpson’s grading system. RT was delivered either in the adjuvant post-operative setting (PORT) or at time of tumor recurrence or progression. When used, RT was planned with a gross target volume (GTV) including any residual disease and the surgical cavity, based on a post-operative MRI or on MRI findings at time of disease recurrence. Typically, a clinical target volume (CTV) was created by adding a radial 1 cm margin without cropping-off the meningeal barriers and with inclusion of the inner plate of the skull, if applicable. An additional 3-5 mm was usually added for the planning target volume (PTV). A median dose of 54 Gy (range: 52.2-59.4) at 1.8 Gy per fraction was delivered using different techniques. In case of tumor failure, hypo-fractionated schedules or SRS were used, typically 40 Gy in 16 fractions or single fraction SRS of 8 Gy or 12 Gy, respectively. One patient received concomitant Temozolomide and RT after experiencing a third post-surgical failure. **Results**: Gross total resection (GTR) was achieved in 42 patients (58%) and subtotal resection (STR) was achieved in 30 (42%). PORT was delivered to 12 patients (28.6%) in the GTR cohort and in four (13%) in the STR cohort. The 5-year recurrence-free survival rates for GTR patients with or without PORT were 100% and 30.6%, respectively (p<0.01). Whereas disease control rate for STR patients +/- PORT were 75% and 4%, respectively (p=0.0038). Multivariate analysis revealed that the only significant independent prognostic factors for disease progression were lack of PORT and STR with a HR of 6.83 (95%CI 1.94-24) and 6.21 (95%CI 2.69-14.36), respectively. Residual tumor volume greater than 8.76 cm3 at time of RT was associated with a reduced recurrence-free survival (6.7% vs 44.4 %, p=0.0013). In patients not receiving RT, the median relative growth rate was 115.75%/year, the median absolute growth rate was 4.23 cm3/year and tumor doubling time was 9 months. Post-RT these indices were reduced to 74.5%/year, 2.49 cm3/year and 21 months, respectively. We detected tumor failure earlier on follow-up imaging studies by performing volumetric rather than planimetric measurements. We observed a median time lag between the two detection methods of failure of 18 months. At time of tumor failure diagnosis, the median disease volume on volumetric measurement was 4.89 cm3 compared to a median of 12.3 cm3 for planimetric measurement (i.e. the tumor volume will be already at least 50% larger by the time of planimetric detection), p = 0.0003. Treatments were well-tolerated no no grade 3 or higher toxicity being recorded. **Conclusion**: PORT was associated with improved recurrence-free survival in patients with GTR atypical meningioma. Our study provides new information on the importance of using volume measurement to determine tumor failure and also establishes parameters on tumor growth indices that may aid physicians in identifying patients who may benefit from a more aggressive post-operative management either on the adjuvant setting or at time of recurrence.Our results suggest that patients with residual tumor volume larger than 8.76 cm3 have an increased failure rate and should be considered for early RT. Further prospective, randomized studies are definitively needed to unequivocally establish the role of RT in atypical meningiomas..
|Institution||McGill University Health Centre|
Luis Souhami (McGill University Health Centre)
Bassam Abdulkarim (McGill University Health Centre) George Shenouda (McGill University Health Centre) Jose Joao Mnasure (McGill University Health Centre) Kevin Petrecca (McGill University Health Centre) Marie christine Guiot (McGill University Health Centre) Shakir Shakir (McGill University Health Centre) Valerie Panet-Raymond (McGill University Health Centre)