Safe Resection Research Articles

Association of 5-aminolevulinic acid fluorescence guided resection with photodynamic therapy in recurrent glioblastoma: a matched cohort study.

Glioblastoma is a malignant and aggressive brain tumour that, although there have been improvements in the first line treatment, there is still no consensus regarding the best standard of care (SOC) upon its inevitable recurrence. There are novel adjuvant therapies that aim to improve local disease control. Nowadays, the association of intraoperative photodynamic therapy (PDT) immediately after a 5-aminolevulinic acid (5-ALA) fluorescence-guided resection (FGR) in malignant gliomas surgery has emerged as a potential and feasible strategy to increase the extent of safe resection and destroy residual tumour in the surgical cavity borders, respectively. To assess the survival rates and safety of the association of intraoperative PDT with 5-ALA FGR, in comparison with a 5-ALA FGR alone, in patients with recurrent glioblastoma. This article describes a matched-pair cohort study with two groups of patients submitted to 5-ALA FGR for recurrent glioblastoma. Group 1 was a prospective series of 11 consecutive cases submitted to 5-ALA FGR plus intraoperative PDT; group 2 was a historical series of 11 consecutive cases submitted to 5-ALA FGR alone. Age, sex, Karnofsky performance scale (KPS), 5-ALA post-resection status, T1-contrast-enhanced extent of resection (EOR), previous and post pathology, IDH (Isocitrate dehydrogenase), Ki67, previous and post treatment, brain magnetic resonance imaging (MRI) controls and surgical complications were documented. The Mantel-Cox test showed a significant difference between the survival rates (p = 0.008) of both groups. 4 postoperative complications occurred (36.6%) in each group. As of the last follow-up (January 2024), 7/11 patients in group 1, and 0/11 patients in group 2 were still alive. 6- and 12-months post-treatment, a survival proportion of 71,59% and 57,27% is expected in group 1, versus 45,45% and 9,09% in group 2, respectively. 6months post-treatment, a progression free survival (PFS) of 61,36% and 18,18% is expected in group 1 and group 2, respectively. The association of PDT immediately after 5-ALA FGR for recurrent malignant glioma seems to be associated with better survival without additional or severe morbidity. Despite the need for larger, randomized series, the proposed treatment is a feasible and safe addition to the reoperation.

Extended dosing (12 cycles) vs conventional dosing (6 cycles) of adjuvant temozolomide in adults with newly diagnosed high-grade gliomas: a randomized, single-blind, two-arm, parallel-group controlled trial.

Maximum safe surgical resection followed by adjuvant chemoradiation and temozolomide chemotherapy is the current standard of care in the management of newly diagnosed high grade glioma. However, there are controversies about the optimal number of adjuvant temozolomide cycles. This study aimed to compare the survival benefits of 12 cycles against 6 cycles of adjuvant temozolomide adults with newly diagnosed high grade gliomas. Adult patients with newly diagnosed high grade gliomas, and a Karnofsky performance status>60%, were randomized to receive either 6 cycles or 12 cycles of adjuvant temozolomide. Patients were followed-up for assessment of overall survival (OS) and progression-free survival (PFS) by brain MRI every 3 months within the first year after treatment and then every six months. A total of 100 patients (6 cycles, 50; 12 cycles, 50) were entered. The rate of treatment completion in 6 cycles and 12 cycles groups were 91.3% and 55.1%, respectively. With a median follow-up of 26 months, the 12-, 24-, 36-, and 48-month OS rates in 6 cycles and 12 cycles groups were 81.3% vs 78.8%, 58.3% vs 49.8%, 47.6% vs 34.1%, and 47.6% vs 31.5%, respectively (p-value=.19). Median OS of 6 cycles and 12 cycles groups were 35 months (95% confidence interval (CI), 11.0 to 58.9) and 23 months (95%CI, 16.9 to 29.0). The 12-, 24-, 36-, and 48- month PFS rates in 6 cycles and 12 cycles groups were 70.8% vs 56.9%, 39.5% and 32.7%, 27.1% vs 28.8%, and 21.1% vs 28.8%, respectively (p=.88). The Median PFS of 6 cycles and 12 cycles groups was 18 months (95% CI, 14.8 to 21.1) and 16 (95% CI, 11.0 to 20.9) months. Patients with newly diagnosed high grade gliomas treated with adjuvant temozolomide after maximum safe surgical resection and adjuvant chemoradiation do not benefit from extended adjuvant temozolomide beyond 6 cycles. Prospectively registered with the Iranian Registry of Clinical Trials: IRCT20160706028815N3. Date registered: 18/03/14.

Long-Term Outcomes of Surgery and Radiation Treatment for Adult Patients with Craniopharyngioma

Treatment of craniopharyngioma typically entails gross total resection (GTR) or subtotal resection with adjuvant radiation (STR-RT). We analyzed outcomes in adults with craniopharyngioma undergoing GTR versus STR-RT. This retrospective study enrolled 115 patients with craniopharyngioma in 5 institutions. Patients with STR received postoperative RT with stereotactic radiosurgery or fractionated radiation therapy per institutional preference and ability to spare optic structures. Median age was 44 years (range, 19-79 years). GTR was performed in 34 patients and STR-RT was performed in 81 patients with median follow-up of 78.9 months (range, 1-268 months). For GTR, local control was 90.5% at 2 years, 87.2% at 3 years, and 71.9% at 5 years. For STR-RT, local control was 93.6% at 2 years, 90.3% at 3 years, and 88.4% at 5 years. At 5 years following resection, there was no difference in local control (P= 0.08). Differences in rates of visual deterioration or panhypopituitarism were not observed between GTR and STR-RT groups. There was no difference in local control in adamantinomatous and papillary craniopharyngioma regardless of treatment. Additionally, worse local control was found in patients receiving STR-RT who were underdosed with fractionated radiation therapy (P= 0.03) or stereotactic radiosurgery (P= 0.04). Good long-term control was achieved in adults with craniopharyngioma who underwent STR-RT or GTR with no significant difference in local control. First-line treatment for craniopharyngioma should continue to be maximal safe resection followed by RT as needed to balance optimal local control with long-term morbidity.

Supramarginal resection of skull base chordomas: proof of concept and preliminary outcomes.

The mainstay of treatment for skull base chordoma (SBC) is maximal safe resection followed by radiotherapy. However, even after gross-total resection (GTR), the recurrence rate is high due to microscopic disease in the resection margins. Therefore, supramarginal resection (SMR) could be beneficial, as has been shown for sacral chordoma. The paradigm of postoperative radiation therapy for every patient has also begun to change, as molecular profiling has shown variability in the risk of recurrence. The aim of this study was to present the concept of SMR applied to SBC, along with an individualized decision for postoperative radiation therapy. This is a retrospective analysis of all SBCs operated on by the senior author between 2018 and 2023. SMR was defined as negative histological margins of bone and/or dura mater, along with evidence of bone resection beyond the tumor margins in the craniocaudal and lateral planes on postoperative imaging. Tumors were classified into 3 molecular recurrence risk groups (group A, low risk; group B, intermediate risk; and group C, high risk). Postoperative radiation therapy was indicated in group C tumors, in group B chordomas without SMR, or in cases of patient preference. Twenty-two cases of SBC fulfilled the inclusion criteria. SMR was achieved in 12 (55%) cases, with a mean (range) amount of bone resection beyond the tumor margins of 10 (2-20) mm (+40%) in the craniocaudal axis and 6 (1-15) mm (+31%) in the lateral plane. GTR and near-total resection were each achieved in 5 (23%) cases. Three (19%) tumors were classified as group A, 12 (75%) as group B, and 1 (6%) as group C. Although nonsignificant due to the small sample size, the trends showed that patients in the SMR group had smaller tumor volumes (13.9 vs 19.6 cm3, p = 0.35), fewer previous treatments (33% vs 60% of patients, p = 0.39), and less use of postoperative radiotherapy (25% vs 60%, p = 0.19) compared to patients in the non-SMR group. There were no significant differences in postoperative CSF leak (0% vs 10%, p = 0.45), persistent cranial nerve palsy (8% vs 20%, p = 0.57), and tumor recurrence (8% vs 10%, p = 0.99; mean follow-up 15 months) rates between the SMR and non-SMR groups. In select cases, SMR of SBC appears to be feasible and safe. Larger cohorts and longer follow-up evaluations are necessary to explore the benefit of SMR and individualized postoperative radiation therapy on progression-free survival.

Long-term outcome of primary clival chordomas: a single-center retrospective study with an emphasis on the timing of recurrences based on the primary treatment.

This study aimed to provide data on extended outcomes in primary clival chordomas, focusing on progression-free survival (PFS) and overall survival (OS). A retrospective single-center analysis was conducted on patients with clival chordoma treated between 1987 and 2022 using surgery, stereotactic radiosurgery, or proton radiation therapy (PRT). The study included 100 patients (median age 44 years, 51% male). Surgery was performed using the endoscopic endonasal approach in 71 patients (71%). Gross-total resection (GTR) or near-total resection (NTR) was attained in 39 patients (39%). Postoperatively, new cranial nerve deficits occurred in 7%, CSF leak in 4%, and meningitis in none of the patients. Radiation therapy was performed in 79 patients (79%), with PRT in 50 patients (50%) as the primary treatment. During the median follow-up period of 73 (interquartile range [IQR] 38-132) months, 41 recurrences (41%) and 31 deaths (31%) were confirmed. Patients with GTR/NTR had a median PFS of 41 (IQR 24-70) months. Patients with subtotal resection or biopsy had a median PFS of 38 (IQR 16-97) months. The median PFS of patients who received radiation therapy was 43 (IQR 26-86) months, while that of patients who did not receive radiation therapy was 18 (IQR 5-62) months. The Kaplan-Meier method showed that patients with GTR/NTR (p = 0.007) and those who received radiation therapy (p < 0.001) had longer PFS than their counterparts. The PFS rates following primary treatment at 5, 10, 15, and 20 years were 51%, 25%, 17%, and 7%, respectively. The OS rates at the same intervals were 84%, 60%, 42%, and 34%, respectively. Multivariate Cox regression analysis showed that age < 44 years (p = 0.02), greater extent of resection (EOR; p = 0.03), and radiation therapy (p < 0.001) were associated with lower recurrence rates. Another multivariate analysis showed that age < 44 years (p = 0.01), greater EOR (p = 0.04), and freedom from recurrence (p = 0.02) were associated with lower mortality rates. Regarding pathology data, brachyury was positive in 98%, pan-cytokeratin in 93%, epithelial membrane antigen in 85%, and S100 in 74%. No immunohistochemical markers were associated with recurrence. In this study, younger age, maximal safe resection, and radiation therapy were important factors for longer PFS in patients with primary clival chordomas. Preventing recurrences played a crucial role in achieving longer OS.

Automated online safety margin (GLIOVIS) for glioma surgery model.

Glioblastoma is the most common type of primary brain malignancy and has a poor prognosis. The standard treatment strategy is based on maximal safe surgical resection followed by radiotherapy and chemotherapy. Surgical resection can be optimized by using 5-delta-aminolevulinic acid (5-ALA)-induced fluorescence, which is the current mainstay. Although 5-ALA-induced fluorescence has gained general acceptance, it is also limited by inter-observer variability and non-standardized fluorescence parameters. We present a new software for processing images analysis to better recognize the tumor infiltration margins using an intraoperative immediate safety map of 5-ALA-induced fluorescence. We tested this in a brain model using a commercial surgical exoscope. A dedicated software GLIOVIS (ACQuF-II, Advanced Colorimetry-based Quantification of Fluorescence) was designed for processing analysis of images taken on the Intraoperative Orbital Camera Olympus Orbeye (IOC) to determine the relative quantification of Protoporphyrin IX (5-ALA metabolite) fluorescence. The software allows to superpose the new fluorescence intensity map and the safety margins over the original images. The software was tested on gel-based brain models. Two surrogate models were developed: PpIX agarose gel-integrated in gelatin-based brain model at different scales (1:25 and 1:1). The images taken with the IOC were then processed using GLIOVIS. The intensity map and safety margins could be obtained for all available models. GLIOVIS for 5-ALA-guided surgery image processing was validated on various gelatin-based brain models. Different levels of fluorescence could be qualitatively digitalized using this technique. These results need to be further confirmed and corroborated in vivo and validated clinically in order to define a new standard of care for glioblastoma resection.

Preoperative Angiographic Protocol for the Surgical Management of Spinal Dural Arteriovenous Fistulas: A Technical Nuance for Safe Minimally Invasive Surgery

BackgroundInterruption of the fistoulus point is the goal of the treatment of spinal dural arteriovenous fistula (dAVFs). Microsurgery still represents a highly efficient treatment in terms of complete occlusion with the lowest risk of recurrence rate. It is reported that the hardest step consists in finding the fistulous site itself, potentially extending surgical access and time, and increasing potential post-operative surgical-related complications. The accurate preoperative detection of the shunt and spinal level together is crucial for guiding optimal, fast and safe microsurgical treatment. MethodsIn the present paper, the authors describe a preoperative angiographic protocol for achieving a safe and simple resection of spinal dAVFs based on a six-year Institutional experience of forty-two patients who underwent minimally invasive. Two illustrative cases are also included in order to support the technical descriptions. ResultsThe suspected artery associated to the vascular malformation of interest is studied in our angiographic protocol through non-subtracted selective acquisitions in the lateral projection. The resulting frames are reconstructed with 3D Rotational Angiography. The implementation of the preoperative angiographic protocol allowed 100% of intraoperative identification of the fistoulus point in all cases with the use of minimally invasive approach. ConclusionsNowadays, neurosurgeons advocate for minimally invasive procedures and low morbidity risk procedures for the treatment of spinal dAVFs.Our preoperative approach for accurate angigoraphic localization of the fistoulus point through non-subtracted and 3D reconstructed angiography allowed to achieve safe and definitive occlusion of the shunt.

Aneurysmal artery supplying pulmonary sequestration: successful combined approach.

A 62-year-old man was diagnosed with an asymptomatic intralobar pulmonary sequestration supplied by a short-neck proximal 57×25 mm aneurysmal artery originating from the mid-descending aorta. The patient underwent thoracic endovascular aneurysm repair; an aortic endograft was released to entirely restore the aberrant vessel. Then, pulmonary resection was performed. A triportal video-assisted left lower lobectomy was carried out. The thoracic endovascular aneurysm repair minimized the risk of bleeding and allowed a safe pulmonary resection with a minimally invasive approach.

Minimally invasive resection of intracranial lesions using tubular retractors: A single surgeon series

ObjectiveTubular retractors are increasingly used due to their low complication rates, providing easier access to lesions while minimizing trauma from brain retraction. Our study presents the most extensive series of cases performed by a single surgeon aiming to assess the effectiveness and safety of a transcortical-transtubular approach for removing intracranial lesions. MethodsWe performed a retrospective review of patients who underwent resection of an intracranial lesion with the use of tubular retractors. Electronic medical records were reviewed for patient demographics, preoperative clinical deficits, diagnosis, preoperative and postoperative magnetic resonance imaging (MRI) scans, lesion characteristics including location, volume, extent of resection (EOR), postoperative complications, and postoperative deficits. Results112 transtubular resections for intracranial lesions were performed. Patients presented with a diverse number of pathologies including metastasis (31.3 %), GBM (21.4 %), and colloid cysts (19.6 %) The mean pre-op lesion volume was 14.45 cm3. A gross total resection was achieved in 81 (71.7 %) cases. Seventeen (15.2 %) patients experienced early complications which included confusion, short-term memory difficulties, seizures, meningitis and motor and visual deficits. Four (3.6 %) patients had permanent complications, including one with aphasia and difficulty finding words, another with memory loss, a third with left-sided weakness, and one patient who developed new-onset long-term seizures. Mean post-operative hospitalization length was 3.8 days. ConclusionTubular retractors provide a minimally invasive approach for the extraction of intracranial lesions. They serve as an efficient tool in neurosurgery, facilitating the safe resection of deep-seated lesions with minimal complications.

En Bloc Inferior Vena Cava (IVC) Resection Without Reconstruction With Right Hepatectomy and Right Nephrectomy for a Large IVC Leiomyosarcoma.

Radical resection remains the only potential cure in the management of inferior vena cava (IVC) leiomyosarcomas with multivisceral resections often needed (Borghi et al. in J Cardiovasc Surg (Torino) 63:649-663, 2022). This video describes the technical nuances of surgical resection of a large retrohepatic IVC leiomyosarcoma. Computed tomography of a 60-year-old woman revealed a 12 × 12 × 9.5 cm mass in the right suprarenal region infiltrating the IVC with intraluminal extension up to the hepatic venous confluence. The mass involved the right hepatic vein with infiltration of segment 7 of the liver and splaying of the right portal vein. Robust lumbar venous drainage from the infratumoral IVC was seen. En bloc IVC resection without reconstruction along with a right hepatectomy and right nephrectomy was performed via a right thoracoabdominal approach. After a Catell-Braasch maneuver, the surgery can be broadly divided into four major steps: (1) Right retroperitoneal mobilization of the tumor and right kidney with infratumoral IVC control, (2) mobilization of the right liver with suprahepatic IVC control, (3) division of the right portal structures with right hepatectomy, and (4) en bloc resection of the IVC tumor. Reconstruction of the IVC was not performed owing to the presence of venous collaterals (Langenbecks et al. in Arch Surg 407:1209-1216, 2022). Final histopathology showed a high-grade leiomyosarcoma with histologic organ invasion in the liver and right kidney with resected margins free of the tumor (R0). Meticulous preoperative planning and expertise in liver resection and retroperitoneal surgeries facilitates such radical yet safe multivisceral resection for a large retrohepatic IVC leiomyosarcoma without the need for a cardiopulmonary bypass.

Microsurgical resection of a large petroclival meningioma through an extended retrosigmoid approach: how I do it.

Petroclival meningiomas are challenging tumors. Several skull base approaches have been proposed in the last decades, with variable rates of postoperative morbidity and extent of resection. We herein reported the step-by-step microsurgical resection of a large petroclival meningioma through an extended retrosigmoid approach. Detailed surgical technique has been accompanied by a 2D operative video. The extended retrosigmoid approach allowed for a safe gross total resection of the tumor, as confirmed by the postoperative MRI. The patient did not experience any new postoperative deficit, despite a transient diplopia, and was discharged on postoperative day 7.

Microsurgical removal of supratentorial and cerebellar cavernous malformations: what has changed? A single institution experience.

BackgroundFeatures associated with a safe surgical resection of cerebral cavernous malformations (CMs) are still not clear and what is needed to achieve this target has not been defined yet. MethodsClinical presentation, radiological features and anatomical locations were assessed for patients operated on from January 2008 to January 2018 for supratentorial and cerebellar cavernomas. Supratentorial CMs were divided into 3 subgroups (non-critical vs. superficial critical vs. deep critical). The clinical outcome was assessed through modified Rankin Scale (mRS) and was divided into favorable (mRS 0–1) and unfavorable (mRS ≥ 2). Post-operative epilepsy was classified according to the Maraire Scale. ResultsA total of 144 were considered eligible for the current study. At 6 months follow-up the clinical outcome was excellent for patients with cerebellar or lobar CMs in non-critical areas (mRS ≤ 1: 91.1 %) and for patients with superficial CMs in critical areas (mRS ≤ 1: 92.3 %). Patients with deep-seated suprantentorial CMs showed a favorable outcome in 76.9 %. As for epilepsy 58.5 % of patients presenting with a history of epilepsy were free from seizures and without therapy (Maraire grade I) at last follow-up (mean 3.9 years) and an additional 41.5 % had complete control of seizures with therapy (Maraire grade II). ConclusionsSurgery is safe in the management of CMs in non-critical but also in critical supratentorial locations, with a caveat for deep structures such as the insula, the basal ganglia and the thalamus/hypothalamus.

Tumor regression and safe distance of distal margin after neoadjuvant therapy for rectal cancer.

Neoadjuvant therapy has been widely employed in the treatment of rectal cancer, demonstrating its utility in reducing tumor volume, downstaging tumors, and improving patient prognosis. It has become the standard preoperative treatment modality for locally advanced rectal cancer. However, the efficacy of neoadjuvant therapy varies significantly among patients, with notable differences in tumor regression outcomes. In some cases, patients exhibit substantial tumor regression, even achieving pathological complete response. The assessment of tumor regression outcomes holds crucial significance for determining surgical approaches and establishing safe margins. Nonetheless, current research on tumor regression patterns remains limited, and there is considerable controversy surrounding the determination of a safe margin after neoadjuvant therapy. In light of these factors, this study aims to summarize the primary patterns of tumor regression observed following neoadjuvant therapy for rectal cancer, categorizing them into three types: tumor shrinkage, tumor fragmentation, and mucinous lake formation. Furthermore, a comparison will be made between gross and microscopic tumor regression, highlighting the asynchronous nature of regression in the two contexts. Additionally, this study will analyze the safety of non-surgical treatment in patients who achieve complete clinical response, elucidating the necessity of surgical intervention. Lastly, the study will investigate the optimal range for safe surgical resection margins and explore the concept of a safe margin distance post-neoadjuvant therapy.

291 Supra-maximal Extent of Resection is Associated With Improved Progression-Free Survival in Patients With IDH Wild-Type Glioblastoma Once Negative TERT Promoter Molecular Margins are Achieved

INTRODUCTION: The standard of care for isocitrate dehydrogenase (IDH) wild-type GBM involves safe maximal resection with subsequent chemoradiation. TERT promoter (TERTp) mutations are clonal in &gt;85% of IDH wild-type GBMs, detectable in all tumor cells. Advances in surgical management have focused on optimizing maximal resection given the positive correlation between extent of resection (EOR) and post-operative outcomes. METHODS: TERTp mutation detection in margin specimens was performed via a novel 30min qPCR-based method. A machine learning algorithm incorporating preoperative anatomic and intraoperative characteristics was developed using 148 patients to predict EOR. This model was prospectively applied to 44 patients to assess the correlation between a TERTp mutation negative margin and survival in cases when GTR was predicted. RESULTS: Retrospective analysis of 148 patients who underwent resection of GBM revealed significant improvement in 36-month survival with residual volume (RV) &lt;4.9 cc). The primary predictive characteristics for achieving this RV were tumor volume, ventricular contact, multifocality, and Sawaya grade. Prospective analysis of 44 patients showed that, in cases where GTR was predicted and achieved, 26% obtained a TERTp negative margin. Although small, this group's PFS was significantly prolonged (0% vs 75% event-free at 30 months, p = 0.02), and a numerically superior prolonged OS was observed, while survival in GTR with positive molecular margin was indistinguishable from STR. CONCLUSIONS: These findings provide novel evidence supporting the utility of supramaximal resection targeting a “molecular margin” to maximize postoperative survival for a subset of patients with “localized” GBM. Further study is warranted to assess intraoperative, quantitative testing of TERTp mutation in GBM specimens to guide marginal resection in these patients.

Transorbital neuroendoscopic surgery for treatment of sphenoid wing meningiomas extending to the cavernous sinus: clinical implications and a technical illustration.

The aim of this study was to evaluate the efficacy and safety of transorbital neuroendoscopic surgery (TONES) in the management of sphenoid wing meningiomas (SWMs) with cavernous sinus and orbital invasion. The authors conducted a retrospective review of 32 patients with SWMs treated at Gazi University using TONES from October 2019 to May 2023. The study includes clinical applications to elucidate the endoscopic transorbital approach. Surgical techniques focused on safe subtotal resection, aiming to minimize residual tumor volume for subsequent radiosurgery. Data were collected on patient demographics, tumor characteristics, surgical procedures, complications, and postoperative outcomes, including radiological imaging and ophthalmological evaluations. Surgical dissections delineated a three-phase endoscopic transorbital approach: extraorbital, intraorbital, and intracranial. In the clinical application, gross-total resection was not achieved in any patient because of planned postoperative Gamma Knife radiosurgery. The mean follow-up period was 16.3 months. Of 30 patients with preoperative proptosis, 25 experienced postoperative improvement. No new-onset extraocular muscle paresis or visual loss occurred postoperatively. The average hospital stay was 1.15 days, with minimal complications and no significant morbidity or mortality. Total resection of SWMs invading the cavernous sinus and orbit is associated with substantial risks, particularly cranial nerve deficits. TONES offers a minimally invasive alternative, reducing morbidity compared with transcranial approaches, and represents a significant advancement in the surgical management of SWMs, especially those extending into the cavernous sinus and orbit. The approach provides a safe, effective, and patient-centric approach, prioritizing subtotal resection to minimize neurological deficits while preparing patients for adjunctive radiosurgery. This study positions TONES as a transformative surgical technique, aligning therapeutic efficacy with neurovascular preservation and postoperative recovery.

Transoral robotic surgery for oropharyngeal cancer: a systematic review on the role of margin status.

Nowadays, robotic surgery finds application in the field of head and neck in the treatment of oropharyngeal tumors. The aim of this work is to examine the efficacy of transoral robotic surgery (TORS) in performing safe oncological resections of oropharyngeal squamous cell carcinoma (OPSCC), with particular attention to the status of margins. Literature search of English-language studies focused on TORS through PubMed, the Cochrane Library and EMBASE databases. A total of 431 papers returned to search, but only 24 met the inclusion criteria. The review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) Guidelines. Within the selected studies, the overall rate of OPSCC positive margins following TORS is minimal, especially when patient selection is adequate and when TORS is used by high volume centers. TORS is a very precise and viable therapeutic tool that provides good results in terms of surgical radicality with low positive margin rates and good results in terms of overall survival and disease-free survival; however, there is still a great heterogeneity in margins definition within the available literature. Consequently, even if this surgical approach is very promising, it is still challenging to draw firm conclusions nowadays.

200 DWI and ADC Changes in Patients With Glioblastoma IDH-Wild Type Following Surgical Tumor Resection

INTRODUCTION: Current standard of care for glioblastoma (GBM) entails maximal tumor resection to achieve better outcomes while preserving neurological function. Early postoperative DWI has elucidated that peritumoral ischemia is common following glioma resection, but radiographic characteristics, risk factors, and outcomes have not been well described. METHODS: This retrospective cohort included 324 patients (18-86 years) who underwent surgical resection for glioblastoma IDH-wildtype between 2005 and 2022. All patients had structural MRI and DWI acquired preoperatively and within 72 hrs after resection. Areas of restricted diffusion on postoperative DWI were classified as rim, sector, mixed, or remote. RESULTS: Areas of restricted diffusion on postoperative DWI were found in 173 (53%) patients. 55 (32%) were rim-shaped, 103 (59%) sector-shaped, 10 (6%) mixed, and 5 (3%) remote. Preoperative tumor volume was positively correlated with areas of ischemia (p = 0.048), but peritumoral DWI was not correlated with decreased overall survival (OS) or Karnofsky Performance Score (KPS). In the full cohort analysis, gross total resection (GTR) correlated with improved OS compared to subtotal total resection (STR) (p = 0.016); however, subgroup analysis revealed that this survival benefit was exclusively found in patients without peritumoral infarction on DWI (21 months vs. 13 months, p = 0.043). CONCLUSIONS: Larger tumor volume was a risk factor for larger peritumoral infarction. The survival benefit of GTR was only seen in patients who did not experience postoperative peritumoral infarction, underscoring the importance of maximal safe tumor resection. Future study on specific causes of postoperative peritumoral infarctions may improve surgical management and outcomes in glioblastoma patients.

205 Microglia-Mediated Survival Outcomes in Preoperative Radiation for Glioblastoma: Insights From a Preclinical Model

INTRODUCTION: Glioblastoma (GBM) is the most common and devastating primary brain tumor in adults. The current standard of care includes maximal safe resection followed by concurrent radiation and temozolomide-based chemotherapy. However, preoperative radiotherapy is used in different cancer types and commonly used for brain metastasis to shrink tumors, but it has never been used in for primary GBM. METHODS: Thirty-nine immunocompromised adult athymic nude female rats were orthotopically engrafted with a GBM1A patient-derived glioma cell line and randomized to either receive radiotherapy prior to tumor resection (RTRE) or postoperative radiotherapy (RERT). The rats received 30 Gy hypofractionated stereotactic radiation in 5 fractions of 6 Gy. Kaplan-Meier curve was used to plot the survival. Hematoxylin-eosin staining, microglia/macrophages using IBA-1 and TMEM119 markers were used in resected and recurrent tumor tissues. Moreover, nuclei area was measured on all tumor samples. Student’s T-test and analysis of variance (ANOVA) were used for statistical analysis. RESULTS: Kaplan-Meier analysis showed a significant survival benefit in the RTRE group, with median survival of 18.28 weeks compared to 14.85 weeks for RERT (p &lt; 0.001), which correlated with the time of recurrence. Simultaneously, an increase in the nuclei area was found in the resected tumor tissues from the RTRE group (p &lt; 0.001) and RERT recurrent tumor tissues (p &lt; 0.001). Interestingly, we found lower microglia/macrophage recruitment in RTRE in the recurrent tumors (p &lt; 0.01) and throughout the tumor areas compared to the RERT group. CONCLUSIONS: Our study represents the first preclinical study demonstrating the feasibility and longer overall survival using RTRE instead of RERT in vivo. Moreover, RTRE shows an important effect in the macrophages/microglia recruitment and in the immune profile. This suggests strong superiority for new clinical radiation strategies.

292 Intraoperative Confocal Laser Endomicroscopy During 5-ALA Guided Glioma Surgery: Significant Considerations for Resection at the Tumor Margins

INTRODUCTION: Fluorescence-guided surgery using 5-aminolevulinic acid (5-ALA) has proven effective in aiding the detection of glioma marginal zones and enhancing maximal safe resection. FDA-cleared confocal laser endomicroscopy is another imaging modality for intraoperative brain tissue discrimination on cellular level that could improve visualization at the glioma margin. METHODS: 5-ALA wide-field imaging and CLE were used in 9 patients with gliomas (6 enhancing, 3 non-enhancing). CLE imaging was enhanced by the use of a telesurgical pathology software platform to enable real-time conversation between neurosurgeons and pathologists located remotely. CLE was used for imaging tumor regions subjectively regarded as tumor margins under normal visualization with the operative microscope. After CLE imaging, 5-ALA wide-field imaging was performed in the same regions. A tissue was harvested at imaging locations, and interpretations of CLE and 5-ALA wide-field imaging were compared to permanent histological sections. RESULTS: Overall, 20 deep and superficial margin regions of interest (ROI) were imaged with CLE and 5-ALA imaging. Most of the ROIs interpreted by the neuropathologist as infiltrative glioma based on CLE imaging lacked 5-ALA-induced fluorescence. Permanent histological sections from the corresponding regions were concordant with the interpretation of CLE images in 15 of 20 (75%) ROIs and with the interpretation of 5-ALA imaging in 11 of 20 (55%) ROIs. Sensitivity/specificity of CLE and 5-ALA for interpretation of tumor margins were 79%/67%, and 50%/67%, respectively. Positive/negative predictive values for CLE and 5-ALA were 85%/57%, and 78%/37%, respectively. CONCLUSIONS: Conventional intraoperative understanding of tumor margins based on wide-field fluorescence could underestimate the invasiveness of gliomas. The ongoing study demonstrates that CLE shows higher accuracy in detecting regions with infiltrating tumor than intraoperative 5-ALA imaging.

384 BOLD Asynchrony Reveals Tumor Burden in IDH-Wildtype Gliomas

INTRODUCTION: IDH-wildtype gliomas are aggressive, highly invasive, and invariably fatal. Maximal safe resection of tumors is the primary goal in glioma surgery, as it has been associated with improved survival and better outcomes. However, there is no clinically accepted method for identifying the extent of tumor burden in these neoplasms. This uncertainty poses a challenge for clinicians who must balance tumor removal with the sparing of healthy brain. METHODS: Forty stereotactically-localized biopsies were obtained during open surgical resection from twenty treatment-naÏve patients with IDH-wildtype gliomas who received standard-of-care preoperative imaging as well as echo-planar resting-state BOLD fMRI. Signal intensity for BOLD asynchrony and standard-of-care imaging was compared to cell counts of total cellularity (H&amp;E), tumor density (Sox2), cellular proliferation (Ki67), and neuronal density (NeuN), for each corresponding sample. RESULTS: BOLD asynchrony was directly related to tumor density as well as cellular proliferation and inversely related to neuronal density. Peritumoral regions that appeared normal on standard-of-care imaging but with elevated BOLD asynchrony showed elevated tumor burden on histology. CONCLUSIONS: BOLD asynchrony is a novel imaging technique that can elucidate tumor burden that is not observable on standard-of-care imaging. Including BOLD asynchrony in preoperative planning can provide more accurate margins for tumor resection, which may improve patient outcomes and overall survival.