Participants and Eligibility
We have analyzed all patients with LLG treated with Io-MRI surgery at the Sant’Andrea Hospital, University of Rome, since 2008 to 2018. A retrospective analysis was performed on 66 patients with histological diagnosis of LLG and we divided them into two groups: 37 cases of Diffuse astrocytoma IDH-mutant and 29 cases of Oligodendroglioma, IDH-mutant and 1p/19q-codeleted.
Inclusion criteria of this paper are:
1) histological diagnosis of WHO grade II of glioma histopathology, Diffuse astrocytoma IDH-mutant and Oligodendroglioma IDH-mutant and 1p/19q-codeleted,
2) evidence of surgical intervention with extent of resection (EOR) subtotal resection or gross total resection,
3) confirmed 1p/19q status of either absent or present and
4) patients ≥18 years old
No patient received a chemo-radiotherapy treatment before the surgical treatment. All patients and tumor characteristics were separated into two groups based on 1p/19q codeletion status being absent or present. The present retrospective analysis of patients suffering from LGG was performed on lesions whose diagnoses were obtained on the ground of the WHO 2016 classification. Immunochemical and genetic evaluations were carried out according to the current guidelines.
Radiological Protocol
Preoperative study included an objective neurological examination with evaluation of KPS score and a radiological study performed with MRI 1.5T after the administration of gadolinium and fluid-attenuated inversion recovery (FLAIR) with the integration of DWI, PWI sequences, and spectroscopy. In the case of patients with a lesion in an eloquent area, a functional MRI was performed. All patients carried out one or more Io-MRI with gadolinium and FLAIR after removing the tumor to verify that they had reached the target. Pre- and postoperative tumor volumes were assessed in a semiautomatic fashion using the Smart Brush tool in Brainlab Elements (version 2.1.0.15) and the T2w-FLAIR sequence (volumetric MPR whenever possible) was used for pre- and postoperative volumetric assessment. The EOR was determined by comparing early contrast-enhanced MRI images (with T2w-FLAIR sequence ) acquired within 24 h after surgical treatment with the preoperative ones and calculated with the ABC/2 method.The Residual Volume (RV) was thereafter recorder either, in cm3.
Surgical Protocol
The surgical procedures of the 93.8 % of patients with LLG in the eloquent area were conducted under cortical and subcortical white matter intraoperative electrical stimulation (IES). A neuronavigation system (BrainLab, Vector Vision) was used in all cases a DTI Fibertracking[6] was carried out the disclose the anatomical relationship between the lesions and the tract cortico-spinal (CST) and arcuate fasciculus (AF).
Patients harboring lesions involving eloquent cortical and subcortical structures, underwent Awake Surgery procedures (AS) with the aid of Intraoperative Neuromonitoring (IoN), cortical and subcortical mapping through Direct Stimulation. Specifically, the patients underwent an “asleep-awake-asleep” approach employing a combination of propofol-remifentanyl and local analgesia, performed by a bilateral scalp block, at the supraorbital nerve, retro-auricular nerve, great occipital nerve and at the pinsite of the Mayfield head frame using a combination of lidocaine and ropivacaine.
Awake surgery was performed in a total of 32 patients (48.4%) suffering from lesions involving eloquent areas. Eleven patients presenting lesions located in the somatosensory area and in the dominant temporal lobe, premotor lobe and insula. Similarly, 5 patients affected by lesions involving non-dominant supplementary and primary motor areas and non dominant insular lobes were treated in AS, in which cortical and subcortical IES enabled the detection of corticospinal pathways. All patients remaining awake from the beginning of the procedure with light sedation during skull opening, Io-MRI and closing. Throughout the procedure to monitor the occurrence of intraoperative seizures, Electrocorticography and Electroencephalography in free run mode were routinely added to the standard monitoring setup. The cortical brain mapping needed a maximum of 4 mA of current intensity and subcortical brain mapping of 6 or 8 mA of simulation. The language function was tested with standard stimuli such as counting, picture naming and reading tasks.
Clinical and Oncologic Follow Up Program
Overall Survival was recorded in months; it was measured from date of diagnosis to date of death or date of last contact if alive. Clinical and demographic information was obtained by the digital database of our Institution, whereas OS data, were obtained by telephone-interview. A special focus was on the KPS results: such parameter was considered, as previously observed as associated to Survival. In particular it was recorded in three different moments: 1. Before surgery, 2. At 30 day after surgery and 3. At the end of the adjuvant treatment (the moment of the last outpatient evaluation). A close range dedicated neuro-imaging follow-up program was routinely performed in our Institution. This program included:
- A standard early (maximum 24 hours after surgery) postoperative volumetric brain MRI.
- At approximately one month from surgery (25-35 days) a volumetric brain MRI scan was repeated for a first step follow-up control and to provide information for the radiation treatment planning.
- Depending on the histological diagnoses, a volumetric brain MRI scan was performed every three or six months.
Generally, in case of malignant transformation, the follow-up as well as the adjuvant and surgical indication for further treatments followed the principles of high grade glioma (HGG) management. Malignant transformation is a MRI derived diagnosed including a combination of Perfusion parameters, Spectroscopic parameters change plus the Gadolinium enhancement.
Statistical Methods
Univariate analyses were performed within the single subgroups for sex, age, EOR, radiotherapy dose and fraction, IDH1 mutations status, EGFR, TP53, and Ki-67 expression index, the different subgroups were compared concening Overall Survival (OS) and Progression Free Survival (PFS) were conducted with Kaplan-Meier survival curves with log-rank tests. Nominal and dichotomous variables were compared Ⲭ2, or t-student tests whenever appropriate. Univariate Cox regression analyses and multivariate ANOVA analyses were then carried out with bootstrap regression, conducting different regression analyses on the data. The independent variables used were sex, age, preoperative KPS, EOR (GTR, STR), radiotherapy dose, radiotherapy fraction, EGFR over-expression and TP53 mutation. The dependent and endpoint variables were OS, PFS, and postoperative KPS. The so-called “enter” method was used in all regressions. It corresponds to a simultaneous regression model in which all the independent variables are simultaneously introduced into the regression equation. The analyses were carried out by means of the IBM® SPSS 25 statistics software.
Power of the study
A potential source of bias is expected from exiguity of the sample, which nevertheless, in regards to the endpoints selected, presents an excellent post-hoc statistical estimated power (1-β = 0.904 for α 0.05 and effect size “f” = 0.74), thus providing reliable conclusions.
The informed consent was approved by the Institutional Review Board of our Institution. Before surgical procedure, all the patients gave informed written explicit consent after appropriate information. Data reported in the study have been completely anonymized. No treatment randomization has been performed. This study is perfectly consistent with Helsinki declaration of Human Rights.