title: Low-grade glioma surgery in eloquent areas: volumetric analysis of extent of resection and its impact on overall survival. A single-institution experience in 190 patients: clinical article.
abstract: OBJECTIVE
  A growing number of published studies have recently demonstrated the role of resection in overall survival (OS) for patients with gliomas. In this retrospective study, the authors objectively investigated the role of the extent of resection (EOR) in OS in patients with low-grade gliomas (LGGs).
  
  
  METHODS
  Between 1998 and 2011, 190 patients underwent surgery for LGGs. All surgical procedures were conducted under corticosubcortical stimulation. The EOR was established by analyzing the pre- and postoperative volumes of the gliomas on T2-weighted MRI studies. The difference between the preoperative tumor volumes was also investigated by measuring the volumetric difference between the T2- and T1-weighted MRI images (ΔVT2T1) to evaluate how the diffusive tumor-growing pattern affected the EOR achieved.
  
  
  RESULTS
  The median preoperative tumor volume was 55 cm(3), and in almost half of the patients the EOR was greater than 90%. In this study, patients with an EOR of 90% or greater had an estimated 5-year OS rate of 93%, those with EOR between 70% and 89% had a 5-year OS rate of 84%, and those with EOR less than 70% had a 5-year OS rate of 41% (p < 0.001). New postoperative deficits were noted in 43.7% of cases, while permanent deficits occurred in 3.16% of cases. There were 41 deaths (21.6%), and the median follow-up was 4.7 years. A further volumetric analysis was also conducted to compare 2 different intraoperative protocols (Series 1 [intraoperative electrical stimulation alone] vs Series 2 [intraoperative stimulation plus overlap of functional MRI/fiber tracking diffusion tensor imaging data on a neuronavigation system]). Patients in Series 1 had a median EOR of 77%, while those in Series 2 had a median EOR of 90% (p = 0.0001). Multivariate analysis showed that OS is influenced not only by EOR (p = 0.001) but also by age (p = 0.003), histological subtype (p = 0.005), and the ΔVT2T1 value (p < 0.0001). Progression-free survival is similarly influenced by histological subtype (fibrillary astrocytoma, p = 0.003), EOR (p < 0.0001), and ΔVT2T1 value (p < 0.0001), as is malignant progression-free survival (p = 0.003, p < 0.0001, and p < 0.0001, respectively). Finally, the study shows that the higher the ΔVT2T1 value, the less extensive the currently possible resection, highlighting an apparent correlation between the ΔVT2T1 value itself and EOR (p < 0.0001).
  
  
  CONCLUSIONS
  The EOR and the ΔVT2T1 values are the strongest independent predictors in improving OS as well as in delaying tumor progression and malignant transformation. Furthermore, the ΔVT2T1 value may be useful as a predictive index for EOR. Finally, due to intraoperative corticosubcortical mapping and the overlap of functional data on the neuronavigation system, major resection is possible with an acceptable risk and a significant increase in expected OS.
authors.affiliation: Department of Neurosurgery, Azienda Ospedaliero-Universitaria Santa Maria della Misericordia, Udine, Italy.
authors.forename: Tamara
authors.initials: T
authors.lastname: Ius
authors.forename: Miriam
authors.initials: M
authors.lastname: Isola
authors.forename: Riccardo
authors.initials: R
authors.lastname: Budai
authors.forename: Giada
authors.initials: G
authors.lastname: Pauletto
authors.forename: Barbara
authors.initials: B
authors.lastname: Tomasino
authors.forename: Luciano
authors.initials: L
authors.lastname: Fadiga
authors.forename: Miran
authors.initials: M
authors.lastname: Skrap
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001931:Brain Mapping; D001932:Brain Neoplasms / Q000401:mortality* / Q000473:pathology / Q000601:surgery*; D002471:Cell Transformation, Neoplastic; D056324:Diffusion Tensor Imaging; D018450:Disease Progression; D018572:Disease-Free Survival; D005260:Female; D005910:Glioma / Q000401:mortality* / Q000473:pathology / Q000601:surgery*; D006801:Humans; D053208:Kaplan-Meier Estimate; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D009361:Neoplasm Invasiveness; D038361:Neuronavigation; D019635:Neurosurgical Procedures / Q000009:adverse effects / Q000379:methods*; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D016896:Treatment Outcome