Skull Base Malignancies Research Articles

Rapid Automated Analysis of Skull Base Tumor Specimens Using Intraoperative Optical Imaging and Artificial Intelligence.

Accurate specimen analysis of skull base tumors is essential for providing personalized surgical treatment strategies. Intraoperative specimen interpretation can be challenging because of the wide range of skull base pathologies and lack of intraoperative pathology resources. To develop an independent and parallel intraoperative workflow that can provide rapid and accurate skull base tumor specimen analysis using label-free optical imaging and artificial intelligence. We used a fiber laser-based, label-free, nonconsumptive, high-resolution microscopy method (<60 seconds per 1 × 1 mm2), called stimulated Raman histology (SRH), to image a consecutive, multicenter cohort of patients with skull base tumor. SRH images were then used to train a convolutional neural network model using 3 representation learning strategies: cross-entropy, self-supervised contrastive learning, and supervised contrastive learning. Our trained convolutional neural network models were tested on a held-out, multicenter SRH data set. SRH was able to image the diagnostic features of both benign and malignant skull base tumors. Of the 3 representation learning strategies, supervised contrastive learning most effectively learned the distinctive and diagnostic SRH image features for each of the skull base tumor types. In our multicenter testing set, cross-entropy achieved an overall diagnostic accuracy of 91.5%, self-supervised contrastive learning 83.9%, and supervised contrastive learning 96.6%. Our trained model was able to segment tumor-normal margins and detect regions of microscopic tumor infiltration in meningioma SRH images. SRH with trained artificial intelligence models can provide rapid and accurate intraoperative analysis of skull base tumor specimens to inform surgical decision-making.

The recent concept in the management of anterior Skull base tumor: A review of the literature

Introduction Tumor of the skull base are classified based on their tissue of origin. Tumor originates from epithelium, mesenchyme, and neuroectoderm. Management of tumors depends on location, histologic characteristics, and their behaviors. A sinus endoscopy, Computerized tomography scan, and Magnetic Resonance Imaging should be performed to know the type and extent of the tumor. Treatment includes surgical excision either endoscopic vs open, chemotherapy and immunotherapy. We are highlighting the management option of each tumor according to their type of tissue origin and its location. Methods: A PubMed search was conducted for relevant publications using the terms “anterior skull base malignancies” and “anterior skull base malignancies treatment and “open vs endoscopic anterior skull base malignancies.” The publication language should be English. Results: Articles published after 2000 that cover the most recent paradigm shift in the treatment of anterior skull base tumors were included. There have been 35 articles found, despite 20 of them are being rejected due to the lack of full text, abstract, and non-english. Three of the fifteen articles have been downloaded twice, thus they have been excluded. Conclusion: Skull base tumors are treated based on findings of diagnostic nasal endoscopy and imaging results. CT scans and MRIs are becoming more significant in the diagnosis of diseases. Endoscopic techniques to the skull base were beneficial in treating the malignancy. Chemotherapy can be used as a gold standard first-line treatment with radiation and surgery for significant types of head and neck tumors. immunotherapy-like checkpoint inhibitors targeting PD1 are the second-line treatments of advanced HNSCC. Prospective research and trials will be required in the future.

Predictors of surgical complications in patients with sinonasal malignancy.

Sinonasal and skull base tumors are rare, making it difficult to identify trends in surgical outcome. This study examines complications in a large cohort of patients undergoing surgery for sinonasal malignancy. Following IRB approval, an institutional database was reviewed to identify patients who underwent surgery for sinonasal or skull base malignancies from 1973 to 2016 at our institution. Charlson comorbidity index score and Clavien-Dindo grade were calculated. The main study endpoint was subgroup analysis of Clavien-Dindo Grade 0, Grades 1-2, and Grades 3-5 complications. An ordinal logistic regression model was constructed to assess the association between comorbidities, demographics, tumor characteristics, and surgical complications. In total, 448 patients met inclusion criteria. Perioperative mortality rate at 30 days was 1.6% (n = 7). The rate of severe complications (Clavien-Dindo 3 or higher) was 13.6% (n = 61). Multivariate analysis using an ordinal logistic regression model showed no association between Charlson comorbidity index score and Clavien-Dindo grade of postoperative complication. Advanced T-stage was significantly associated with complications (p = 0.0014; odds ratio: 3.442 [95% confidence interval: 1.615, 7.338]). Surgery for sinonasal and skull base tumors is safe with a low mortality rate. Advanced T-stage is associated with postoperative complications. These findings have implications for preoperative risk stratification. Key Points Surgery for sinonasal malignancy is safe with a 30 mortality of 1.6% and rate of severe complications of 12.8%. There is no association between patient comorbidity and post operative complication. On multivariate analysis, only advanced T stage was associated with increased rate of surgical complication.

Prognosis of Distant Metastatic Sites in Anterior Skull Base Malignancies.

Objective This study aimed to provide information regarding the prognosis of patients presenting with metastatic anterior skull base malignancies based upon histology and site of distant metastasis (DM). Patients and Methods The National Cancer Database was queried for patients with anterior skull base malignant neoplasms with DM. Outcomes Prognosis was compared between site of DM and tumor histologies. A multivariable Cox proportional hazards model was used to identify prognostic factors for overall survival (OS). Results A total of 481 patients were identified. Lung was the most common site of DM (24.9%), followed by bone (22.2%), liver (5.6%), and brain (2.5%). Lung was the most common site for squamous cell carcinoma (SCCa) (28.3%), melanoma (37.7%), and adenoid cystic carcinoma (ACC; 31.4%). The median survival for patients presenting with metastatic disease regardless of tumor histology was 9.0 months (95% confidence interval [CI]: 8.2-10.3), and patients with metastasis to the liver had the best median survival at 15.5 months (95% CI: 10.5-25.6). The median survivals for the most common histologies, SCCa, melanoma, and ACC were 8.2 months (95% CI: 5.5-10.2), 10.5 months (95% CI: 8.7-14.1), and 15.0 months (95% CI: 11.1-61.1), respectively. Multivariable analysis demonstrated worse overall survival (OS) for older patients, higher Charlson-Deyo comorbidity scores, and tumors with higher grade and T stage. Compared with metastasis to bone, lung metastasis had better OS on multivariable analysis (hazard ratio [HR]: 0.70, 95% CI: 0.51-97). Adenoid cystic carcinoma had improved OS compared with SCCa (HR: 0.62, 95% CI: 0.39-99). Conclusion Tumor histology, metastatic sites, and several disease factors affected prognosis in anterior skull base malignancies with DM.

Vascularized Pericranial Flap for Endonasal Anterior Skull Base Reconstruction.

Introduction As the limits of advanced skull base malignancies that can be managed through an endoscopic endonasal approach continue to be expanded, the resultant anterior skull base defects are of increasing size and complexity. In the absence of nasoseptal or turbinate flaps, the vascularized pericranial flap has been employed at our institution with excellent results. Objective The study aimed to review the outcomes of patients who underwent endonasal anterior craniofacial resection with anterior skull base reconstruction using a vascularized pericranial flap. Design Retrospective chart review of patients treated by the University of California - San Francisco minimally invasive skull base service from the years 2011 to 2017. Average duration of follow-up was 16.4 months. Setting This study was conducted at Academic tertiary referral center. Participants A total of nine patients with advanced anterior cranial base malignancies were identified who were treated with a minimally invasive, endoscopic anterior craniofacial resection from the years 2011 to 2017. Due to the nature of the resection in these patients, nasoseptal flaps and inferior/middle turbinate flaps were unavailable or insufficient for anterior skull base defect repair. Each patient underwent reconstruction of the anterior cranial base defect using an anteriorly based pericranial flap harvested by bicoronal incision, and tunneled anteriorly to the nasal cavity through a frontoethmoidal incision.

Endoscopic approaches to skull base malignancies affecting the anterior fossa.

Anterior skull base malignancies are rare and comprise distinct histological entities. Surgery encompasses the traditional craniofacial resections (CFR), and more recently, endoscopic endonasal approaches (EEA) or a hybrid cranioendoscopic (CEA) technique. Although the CFR is still considered the "gold-standard;" there is growing evidence supporting that EEA yield equivalent oncologic outcomes with less morbidity in well-selected cases. Therefore, this article aims to review the current state-of-art in addressing anterior cranial base malignancies using expanded endoscopic endonasal approaches (EEA) with particular references to surgical anatomy and nuances of hybrid cranioendoscopic techniques. Cadaveric dissections and illustrative cases are presented to detail our current surgical technique allied with tailored adjuvant therapies, and treatment strategies are further discussed based on tumor histology.

Endometrial Sarcoma Metastasis to the Pterygopalatine Fossa: A Case Report and Review of the Literature.

Metastatic skull base malignancies infrequently occur but, when present, typically arise from breast malignancies. Pterygopalatine fossa (PPF) metastasis of any malignancy is further seldom reported, and metastasis of gynecologic malignancies to the PPF has not been previously described in the literature. We present a single case of a 42-year-old female with the first likely case of high-grade endometrial sarcoma metastatic to the PPF. The patient presented with facial pain and numbness in the V2 distribution presented for evaluation. History was significant for several months of dysmenorrhea and metrorrhagia. Computed tomography, magnetic resonance imaging, and positron emission tomography imaging revealed a PPF mass with local extension and bony metastases. Endoscopic biopsy was performed, and final pathology was most consistent with metastatic high-grade endometrial stromal sarcoma. This is the first reported case of likely metastatic endometrial sarcoma to the PPF. This case report highlights the possibility of rare distant metastasis of gynecologic malignancy to this area of the skull base.

Craniofacial Resection for Treatment of Skull Base Malignancy

Craniofacial Resection for Treatment of Skull Base Malignancy

Facial nerve management in patients with malignant skull base tumors.

The course of the facial nerve through the cerebellopontine angle, temporal bone, and parotid gland puts the nerve at risk in cases of malignancy. In contrast to Bell's palsy, which presents with acute facial paralysis, malignancies cause gradual or fluctuating weakness. We review malignancies affecting the facial nerve, including those involving the temporal bone, parotid gland, and cerebellopontine angle, in addition to metastatic disease. Intraoperative management of the facial nerve and long term management of facial palsy are reviewed. Intraoperative management of the facial nerve in cases of skull base malignancy may involve extensive exposure, mobilization, or rerouting of the nerve. In cases of nerve sacrifice, primary neurorrhaphy or interposition grafting may be used. Cranial nerve substitution, gracilis free functional muscle transfer, and orthodromic temporalis tendon transfer are management options for long term facial paralysis. Temporal bone, parotid gland, and cerebellopontine angle malignancies pose a tremendous risk to the facial nerve. When possible, the facial nerve is preserved. If the facial nerve is sacrificed, static and dynamic reanimation strategies are used to enhance facial function.

Excellent Local Control and Survivals after Particle Beam Radiation Therapy for Skull Base Malignancies

Complete resection of skull base malignancies (SBM) is challenging, and prognoses of patients with unresected or incompletely resected SBM is suboptimal. Radiotherapy (RT) plays a significant role in the treatment of SBM. Particle beam radiation therapy (PBRT), such as proton and carbon-ion radiotherapy (PRT and CIRT) demonstrates prominent advantages with its physical properties which enable improved dose coverage to the tumor target(s) and avoid overdosing to adjacent organs at risk thereby achieve optimal efficacy and safety. The purpose of this study is to report the clinical outcomes of intensity modulated PBRT for a relatively large group of patients with SBM. All patients with SBM (chordoma excluded due to its indolent behavior) treated at the Shanghai Proton and Heavy Ion Center from 06/2014 to 07/2019 were included in this analysis. The overall survival (OS), progression-free survival (PFS), locoregional relapse-free survival (LRFS), and distant metastasis-free survival (DMFS) rates were calculated using the Kaplan-Meier method. Multivariate analyses (MVA) on survivals were performed using Cox proportional hazards model. Indicators used for MVA included age, sex, pathology, T-category, status of recurrence (post-RT or surgery), R0/1 vs. R2 resection, use of chemotherapy, and PBRT technology (PRT vs. CIRT vs. PRT+CIRT). Acute and late toxicities were assessed with the CTCAE (v. 4.03). Among the 176 consecutive patients with SBM (adenoid cystic carcinoma 53, soft tissue sarcoma 31, chondrosarcoma 29, squamous cell carcinoma 19, melanoma 12, adenocarcinoma 10, esthesioneuroblastoma 8, osteosarcoma 6, and other histologies 8) treated, 134 patients (76.1%) had locally advanced (T3/4) disease, 136 (77.3%) were radiation-naïve and 40 (22.7%) failed prior radiotherapy, and 134 (76.1%) received R2 resection before PBRT. Patients were treated with CIRT (n = 126) alone, PRT (n = 9) alone, or PRT+CIRT boost (n = 49). The median dose was 66 Gy (RBE). Chemotherapy was used in 20.5% of the patients. With median follow-up of 20.0 months, the 1-/2-year OS, LRFS, and DMFS, and PFS rates were 93.9/87.1%, 90.3/82.2%, 89.9/84.9%, and 66.1/46.6%, respectively. On MVA, age of ≥ 40 was associated with significantly worse OS (p = 0.05) and PFS (p = 0.02). Patients presented with failure after prior radiotherapy (p = 0.009) or surgery (p = 0.029) had significantly worse LRFS after PBRT. Additionally, higher T-classification (i.e., T3/T4) (p = 0.017) and recurrence after surgery (p = 0.06) was associated with significantly worse PFS (Table). Severe (≥ grade 3) acute toxicities included mucositis (n = 1), visual impairment (n = 2), and hemorrhage (n = 1). Severe late toxicities included oligosialia (n = 2), decreased vision (n = 2), osteonecrosis (n = 1), and hemorrhage (n = 1). PBRT provides effective disease control and survivals for SBM with favorable toxicity profiles. Further follow-up is needed to understand the long-term efficacy and safety.

Radiation therapy strategies for skull-base malignancies.

The management of skull base malignancies continues to evolve with improvements in surgical technique, advances in radiation delivery and novel systemic agents. In this review, we aim to discuss in detail the management of common skull base pathologies which typically require multimodality therapy, focusing on the radiotherapeutic aspects of care. Technological advances in the administration of radiation therapy have led to a wide variety of different treatment strategies for the treatment of skull base malignances, with outcomes summarized herein. Radiation treatment plays a key and critical role in the management of patients with skull base tumors. Recent advancements continue to improve the risk/benefit ratio for radiotherapy in this setting.

Prevalence and Clinical Significance of Radiographic Sinus Disease on Preoperative Computed Tomography Imaging in the Endoscopic Skull Base Surgery Population.

Endoscopic skull base surgery (ESBS) provides a safe, minimally invasive approach to treat benign and malignant skull base lesions. The significance of concomitant sinonasal pathology on imaging in patients undergoing ESBS and its effect on perioperative management is not well described. We sought to identify the prevalence and clinical significance of incidentally found radiographic sinus disease on preoperative imaging in patients undergoing ESBS and provide a protocol for management of these patients. A retrospective chart review was performed of consecutive patients who underwent ESBS from January 1, 2016 to June 30, 2018. Preoperative computed tomography (CT) scans were reviewed and scored using the Lund-Mackay (LM) staging system. Preoperative nasal endoscopy findings were analyzed. Any preoperative treatment based on these findings and changes in intraoperative management were examined. A total of 156 patients (81 women, 74 men) who underwent ESBS were reviewed. The average LM score was 2 ± 2.7 (range: 0-12). A total of 94 patients (60.3%) had evidence of radiographic sinus disease (LM score > 0) and 23 patients (14.7%) had presence of sphenoid sinus disease. Seven patients (4.5%) were treated preoperatively based on CT and/or nasal endoscopy findings. All patients who received preoperative treatment had evidence of sinus disease on imaging with an average score of 4.7 and were evaluated and treated within 1-2 weeks prior to ESBS. One patient had ESBS postponed until endoscopic sinus surgery was performed for extensive chronic rhinosinusitis (CRS) findings on imaging. A review of preoperative imaging in patients undergoing ESBS can help identify concurrent sinonasal disease, which has the potential to alter preoperative as well as intraoperative management in these patients. We report a diligent but conservative approach for the treatment of concomitant CRS in the ESBS population with decision for preoperative treatment guided by various factors.

The Role of Advanced Endoscopic Resection of Diverse Skull Base Malignancies: Technological Analysis during an 8-Year Single Institutional Experience.

Background Resection of skull base malignancies poses complex pathological and treatment-related morbidities. Recent technological advancements of endoscopic endonasal surgery (EES) offer the ability to reexamine traditional treatment paradigms with endoscopic procedures. The utility of EES was quantitatively examined in a longitudinal series with attention to morbidities and postoperative outcomes. Methods A single-center retrospective review was performed of all malignant sinonasal tumors from 2010 to 2018. Patients with purely EES were selected for analysis. Disease features, resection extent, complications, adjuvant treatment, recurrence, and survivability were assessed. Despite the mixed pathological cohort, analysis was performed to identify technical aspects of resection. Results A total of 68 patients (47.6% males and 52.4% females, average age: 60.3 years) were included. A diversity of histotypes included clival chordoma (22.1%), olfactory neuroblastoma (14.7%), squamous cell carcinoma (11.8%), and adenoid cystic carcinoma (11.8%). Gross total resection (GTR) was achieved in 83.8% of cases. Infection (4.4%) and cerebrospinal fluid leak (1.5%) were the most common postoperative complications. Total 46 patients (67.6%) underwent adjuvant treatment. The average time between surgery and initiation of adjunctive surgery was 55.7 days. Conclusion In our 8-year experience, we found that entirely endoscopic resection of mixed pathology of malignant skull base tumors is oncologically feasible and can be accomplished with high GTR rates. There may be a role for EES to reduce operative morbidity and attenuate time in between surgery and adjuvant treatment, which can be augmented through recent mixed reality platforms. Future studies are required to systematically compare the outcomes with those of open surgical approaches.

Patient-Reported Outcomes in Sinonasal and Skull Base Malignancy: An Assessment of Study Quality and Clinical Relevance.

Sinonasal and skull base malignancies can cause significant adverse effects on functional status and survival. The goal of this study was to systematically review the published literature of patient-reported outcomes pertaining to treatment of sinonasal and skull base malignancy. A systematic literature search of Medline was conducted with PubMed to identify studies that assessed patient-reported outcomes in patients with sinonasal or skull base malignancy. Patient-reported outcomes studies with at least 10 patients published in English from January 2000 to April 2017 were included. Criteria from International Society for Quality of Life guidelines and criteria unique to sinonasal and skull base malignancies were used to calculate a composite score for each article. Studies with the top 33% of scores were categorized as high quality articles. Twenty-two articles met inclusion/exclusion criteria. Three studies (14%) reported a priori hypothesis. Eleven (50%) assessed specific quality of life domains and 10 studies (45%) performed statistical analysis on these domains. Specific symptoms were assessed in up to 32% of studies. Eight studies were characterized as high quality; these studies had higher sample sizes and more often assessed patient-reported outcomes prior to treatment compared to low quality studies. The goal of the current study was to evaluate the quality of the current patient-reported outcomes literature on sinonasal and skull base malignancies. Areas of improvement for future studies include analysis of individual domains and disease-specific symptoms, reporting a priori hypotheses, and collecting preoperative and longitudinal patient-reported outcomes data.

Targeted 595-gene genomic profiling demonstrates low tumor mutational burden in olfactory neuroblastoma.

Olfactory neuroblastoma (ONB) is a rare skull-base malignancy associated with delayed local recurrence. Treatment options in recurrent disease are few and unreliable. We undertook analysis of the ONB exome and immune environment in order to identify potential future immunotherapy treatment options. Retrospective chart review and next-generation targeted 595-gene genomic profiling was performed on a cohort of 14 ONB cases utilizing Tempus proprietary DNA and RNA sequencing technology. Tempus analysis provided a measurement of tumor mutational burden (TMB) and composition of the immune cell infiltrate present in tumor samples. Clinically relevant genomic alterations and associated targeted therapies were identified using cancer.gov and clinicaltrials.gov. TMB was tested by univariate analysis against clinical stage, pathologic grade, recurrence risk, and immune cell infiltration. The mean age for the subjects was 50 years (range, 13 to 76 years) with a male:female ratio of 1:1. TMB for ONB samples ranged from 1.3 to 9.6 mutations/megabase (Mb) with mean of 3.8 mutations/Mb. Univariate analysis showed no association between TMB and tumor stage, pathologic grade, risk of recurrence, or immune cell infiltration. Genomic profile revealed that 6 of 13 tumors had genetic alterations with targeted therapies in clinical trials, whereas 1 tumor demonstrated KRAS Q61R mutation with U.S. Food and Drug Administration (FDA)-approved targeted therapies. TMB is a novel biomarker guiding the classification of neoplasms in the emerging era of immunotherapy. The characterization of ONB as a low-TMB pathology contributes to the overall taxonomy of all cancers and suggests limited utility of immunotherapy treatment.

Surgical outcomes in patients with endoscopic versus transcranial approach for skull base malignancies: a 10-year institutional experience

Object The authors performed an extensive comparison between patients treated with open versus an endoscopic approach for skull base malignancy with emphasis on surgical outcomes. Methods A single-institution retrospective review of 60 patients who underwent surgery for skull base malignancy between 2009 and 2018 was performed. Disease features, surgical resection, post-operative morbidities, adjuvant treatment, recurrence, and survival rates were compared between 30 patients who received purely open surgery and 30 patients who underwent purely endoscopic resection for a skull base malignancy. Results Of the 60 patients with skull base malignancy, 30 underwent open resection and 30 underwent endoscopic resection. The most common hisotype for endoscopic resection was squamous cell carcinoma (26.7%), olfactory neuroblastoma (16.7%), and sarcoma (10.0%), and 43.3%, 13.3%, and 10.0% for the open resection cohort, respectively. There were no statistical differences in gross total resection, surgical-associated cranial neuropathy, or ability to achieve negative margins between the groups (p > 0.1, all comparisons). Patients who underwent endoscopic resection had shorter surgeries (320.3 ± 158.5 minutes vs. 495.3 ± 187.6 minutes (p = 0.0003), less intraoperative blood loss (282.2 ± 333.6 ml vs. 696.7 ± 500.2 ml (p < 0.0001), and shorter length of stay (3.5 ± 3.7 days vs. 8.8 ± 6.0 days (p < 0.0001). Additionally, patients treated endoscopically initiated adjuvant radiation treatment more quickly (48.0 ± 20.3 days vs. 72.0 ± 20.5 days (p = 0.01). Conclusions An endoscopic endonasal approach facilitates a clinically meaningful improvement in surgical outcomes for skull base malignancies.

Surgical management of carcinomas of the infratemporal fossa and skull base: patterns of failure and predictors of long-term outcomes.

Infratemporal fossa (ITF) tumors are unique in histological characteristics and difficult to treat. Predictors of patient outcomes in this context are not known. The objective of this study was to identify independent predictors of outcome and to characterize patterns of failure in patients with ITF carcinoma. All patients who had been surgically treated for anterolateral skull base malignancy between 1999 and 2017 at the authors' institution were retrospectively reviewed. Patient demographics, preoperative performance status, tumor stage, tumor characteristics, treatment modalities, and pathological data were collected. Primary outcomes were disease-specific survival (DSS) and local progression-free survival (LPFS) rates. Overall survival (OS) and patterns of progression were secondary outcomes. Forty ITF malignancies with skull base involvement were classified as carcinoma. Negative margins were achieved in 23 patients (58%). Median DSS and LPFS were 32 and 12 months, respectively. Five-year DSS and OS rates were 55% and 36%, respectively. The 5-year LPFS rate was 69%. The 5-year overall PFS rate was 53%. Disease recurrence was noted in 28% of patients. Age, preoperative performance status, and margin status were statistically significant prognostic factors for DSS. Lower preoperative performance status and positive surgical margins increased the probability of local recurrence. The ability to achieve negative margins was significantly associated with improved tumor control rates and DSS. Cranial base surgical approaches must be considered in multimodal treatment regimens for anterolateral skull base carcinomas.

Stereotactic Radiosurgery and Stereotactic Radiotherapy for Malignant Skull Base Tumors.

The role of stereotactic radiosurgery/stereotactic radiotherapy (SRS/SRT) for malignant skull base tumors was summarized and discussed. The treatment of skull base tumors remains challenging. Their total resection is often difficult. SRS/SRT is one useful treatment option for residual or recurrent tumors after surgical resection in cases of primary skull base tumors. If skull base metastasis and skull base invasion are relatively localized, they can be candidates for SRS/SRT. Low rates of cervical lymph node involvement in early-stage (N0M0, no lymph node involvement or distant metastasis) nasal and paranasal carcinomas (NpNCa) and external auditory canal carcinomas (EACCa) have been reported in the literature. Such cases might be good candidates for SRS/SRT as the initial therapy. We previously reported the results of SRS/SRT for various malignant extra-axial skull base tumors. In addition, treatment results of early-stage head and neck carcinomas were summarized. Those of our data and those of other reported series were reviewed here to clarify the usefulness of SRS/SRT for malignant extra-axial skull base tumors.

Ophthalmic and orbital considerations in the evaluation of skull base malignancies.

The orbital contents, afferent and efferent visual pathways, and the cranial nerves involved in eye movement, corneal sensation and eyelid closure traverse the skull base, a region bounded by the intracranial cavity, the paranasal sinuses, and the deep spaces of the face and head. As such, tumors from above or below have potential to affect some aspect of the visual system. We discuss here the clinical ophthalmologic and orbital considerations in the evaluation of patients with these tumors, as well as the ophthalmic sequelae of treatment with radiation or surgery (or both). And for the surgeon, we discuss the ophthalmic and orbital considerations in surgical planning, the role of the orbital surgeon in skull base surgery, and briefly discuss transorbital approaches to the skull base. Ophthalmic and orbital dysfunction may be the main source of disability in patients with skull base malignancy; it is thus incumbent on those who manage patients with tumors of this region to be aware of the ophthalmic, neuro-ophthalmic and orbital manifestations, so as to best tailor therapy and monitor treatment outcomes.

SABR for Skull Base Malignancies: A Systematic Analysis of Set-Up and Positioning Accuracy

PurposeHere we provide an analysis of the set-up and positioning accuracy of SABR for skull base malignancies to evaluate the use of site- or axis-specific margins to reduce field size. Methods and MaterialsData were prospectively collected on 63 patients who received 304 fractions of SABR for recurrent/previously irradiated skull base tumors. Using our custom cushion-mask-bite-block immobilization system combined with ExacTrac x-ray and cone beam computed tomography (CBCT), set-up, residual, CBCT-positioning agreement, and intrafractional errors were measured. The resulting planning target volume (PTV) margins were estimated across 4 skull base subsites: anterior (group 1), central (group 2), posterolateral (group 3), and skull base–associated sites (eg, nasopharynx/retropharyngeal, cervical vertebrae 1-2, occiput) (group 4). ResultsOn initial set-up, 66% of treatment courses required shifts of >2 mm or >2°, necessitating 4.9 mm PTV margins without image guidance. After correction, only 6 of 304 treatment sessions had residual errors >1 mm. CBCT-ExacTrac agreement was ≤1 mm in 89.1% of treatments and ≤1.5 mm in all but 1 session. Group 4 showed a higher rate of >1 mm or >1° CBCT-positioning differences compared with other groups (24.5% vs 7.8%; P = .0001), and the greatest variations occurred in the craniocaudal translational and the pitch rotational axes. Overall calculated PTV margins (based on intrafractional error) were 1.5 mm across subsites except for group 4, which required 2.0 mm margins. ConclusionsThe use of 2.0 mm PTV margins for skull base SABR appears feasible using ExacTrac x-ray as the sole imaging modality for most subsites. However, PTVs were not uniformly equal, and the use of a site-specific nonuniform margin reduction to optimize critical-organ dose sparing may be feasible for select cases. These findings warrant clinical investigation.