Resection Of Skull Base Chordoma Research Articles

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.

Endoscopic endonasal approach for skull base chordoma

BackgroundChordoma is a rare slow-growing malignant bone tumor that arises from embryonic notochordal remnants in the axial skeleton. Clival chordomas have a high propensity for extension through the skull base and a high proclivity for recurrence. Recently, resection of skull base chordomas through the endoscopic transnasal approach has become the standard way of managing these lesions with the new advancements in neuronavigation and reconstructive techniques in skull base surgery.MethodsIt is a retrospective study of all patients with clival chordoma that were operated upon using endoscopic endonasal resection at the Main Alexandria University Hospital during the period from March 2008 to April 2013. The extent of surgical resection was assessed intraoperatively and confirmed by the postoperative MRI study performed 8–12 weeks, 6 months, and yearly after the surgery.ResultsTwelve patients with clival chordoma were managed by endoscopic transnasal resection. Gross total resection confirmed by postoperative MRI was achieved in four cases, subtotal resection in six cases, and partial resection in two cases of clival chordoma. In cases where gross total resection was not achieved, residual tumors were adherent to vital neurovascular structures as confirmed with the utilization of an intraoperative imaging navigation device. A study of postoperative complications and possible recurrence was done for all cases.ConclusionsThe findings of this study highlight the significance of gross total resection as a major determinant for preventing the recurrence of chordoma. Our findings also support the validity of the endoscopic approach for the management of clival chordoma especially when the approach is tailored based on the site and extent of the tumor.

Outcomes of the Endoscopic Endonasal Approach for the Treatment of Clival Chordomas: A Single-Center Experience

Abstract Objective Chordoma is a low-grade malignant tumor that originates from the remnant tissue of the embryonic notochord. Postoperative or definitive radiotherapy (RT) has been used to enhance local control. This study aims to assess the outcomes of the expanded endoscopic endonasal approach (EEA) for maximal removal of clival chordomas followed by RT for visualized residual or tumor recurrence. Materials and Methods A retrospective review was performed on consecutive patients with clival chordoma who underwent endoscopic endonasal resection in the otorhinolaryngology and neurosurgery departments, between 2016 and 2021. We included all patients with pathologically confirmed clival chordoma who were treated using the EEA. Patients who underwent combined external and endoscopic approaches or transcranial surgery were excluded. Results Seventeen patients were included in this study. Most of them had tumors located in the middle clivus. Regarding RT, the majority of patients underwent postoperative RT. Almost half of them underwent CyberKnife (CK) RT. None of them had severe toxicities (grade 3 or higher). Three patients died, resulting in a mortality rate of 17.6% none of them related to radiation side effect. The 2-year overall survival was 82.4% (mean standard error [SE] = 1.765, 95% confidence interval [CI] = 1.505–2.024), and the progression-free survival (PFS) was 76.5% (mean SE = 3.403, 95% CI = 2.791–4.016). No distal metastasis was reported in our series. Conclusion This series demonstrates that expanded endoscopic endonasal approach (EEA) for the resection of skull base chordomas, followed by CyberKnife radiosurgery, presents a viable alternative to proton beam therapy; however, further research is necessary to directly compare these modalities.

SURG-33. LATERAL VERSUS MIDLINE APPROACHES TO RESECTION OF SKULL BASE CHORDOMAS: A META-ANALYSIS

Abstract INTRODUCTION Though it remains a rare and devastating tumor, great strides have been taken to improve prognostication and treatment paradigms for patients with skull base chordoma. With respect to surgical techniques, lateral transcranial (TC) approaches have traditionally been used, however endoscopic endonasal approaches (EEA) have been advocated for midline lesions. However, due to the rarity of this tumor (0.2% of all intracranial neoplasms), investigations within the literature remain limited to small retrospective series. METHODS Accordingly, we performed a systematic review and meta-analysis in order to profile surgical outcomes for midline versus lateral approaches to resection of skull base chordoma. Meta-analysis of pooled mortality rates and sub-analyses of operative margin and surgical complications were used to compare midline versus lateral approaches via the Mantel-Haenszel method. We considered all p-values < 0.05 to be statistically significant. RESULTS Fifty studies published between 1993-2022 reporting data for 2252 patients remained eligible for analysis. Average age at diagnosis was 42.4 ± 12.5 years, while average age of treatment initiation was 43.0 ± 10.6 years. The relative risk for mortality (Figure 2) in patients undergoing surgical intervention was -0.93 [-1.03,-0.97], I^2=95%, (p < 0.001), indicating low surgery-related mortality rates. From the seven studies eligible for formal meta-analysis, we found that there was no statistically significant difference between midline and lateral approaches with respect to rates of GTR or recurrence. Nor was there a significant difference between rates of postoperative cranial nerve dysfunction, although the result trended toward favoring midline approaches. Finally, midline approaches exhibited a lower odds for peri- and post-operative complications, including CSF leak (OR 0.59 [0.35, 0.97], I^2 = 0%, p = 0.04). CONCLUSION Ultimately, there are no striking differences between midline versus lateral approaches to resection of skull base chordoma, particularly as they relate to operative margins, recurrence, or rates of cranial nerve palsy.

Radiotherapy After Gross Total Resection of Skull Base Chordoma: A Surveillance, Epidemiology, and End Results Database Analysis of Survival Outcomes.

Skull base chordoma is a rare and locally destructive malignancy which presents unique therapeutic challenges. While achieving gross total resection (GTR) confers the greatest survival advantage, the role of adjuvant radiotherapy (RT) for patients who receive GTR remains unclear in the absence of prospective trials. Here, we aim to assess the effect of RT on survival outcomes in skull base chordoma patients who receive GTR by utilizing the Surveillance, Epidemiology, and End Results (SEER) database. Patients with diagnostic, primary site, and resection codes specific for chordoma, skull base, and GTR, respectively, were queried in the SEER database (2000-2018). Kaplan-Meier curves (log-rank test) were constructed and Cox proportional hazards models were used to assess survival outcomes. A total of 115 skull base chordomas undergoing GTR were identified, of which 37 (32%) received no RT and 78 (68%) received RT. Median follow-up was 55.00months (range: 0.00-227.00). Overall survival (OS) of patients with GTR was 85% and 70% at 5 and 10years, respectively. Multivariate Cox proportional hazard analysis among chordoma patients undergoing GTR found age ≥65 (P < 0.01) was associated with poorer OS outcomes. RT appeared to trend toward offering benefit in terms of OS in patients after GTR, however this did not achieve statistical significance in the adjusted model (HR= 0.51, CI= 0.23-1.16, P= 0.09). When comparing, disease-specific survival was also not improved in patients undergoing RT (HR= 0.58, CI= 0.23-1.46, P= 0.25). It remains unclear whether RT after GTR of chordoma improved survival outcomes among SEER database patients.

The prognostic significance of different degrees of resection of skull base chordoma.

Complete resection combined with postoperative radiotherapy is ideal for skull base chordomas. The recent literature suggests that the degree of surgical resection is the most important prognostic factor. We retrospectively analyzed the clinical data of 16 patients with initial chordoma treated at our center between August 2015 and December 2021 and conducted a retrospective study on the prognosis of surgical treatment of skull base chordoma between 2013 and 2022. According to the Kaplan-Meier method, there was a significant difference in PFS between patients aged > 50years and < 50years, and no significant difference was observed in PFS for tumor involvement of the internal carotid artery, dura, or superior or inferior clivus. However, there was still a correlation with prognosis. As observed in the included literature, the 5-year overall survival rate was significantly higher in patients undergoing total skull base chordoma resection than in those undergoing subtotal resection (STR), which in turn was significantly higher than in those undergoing partial resection (PR). Patients undergoing subtotal resection had significantly better 5-year PFS rates than those undergoing PR. Our study shows that gross total resection and STR have better survival in patients with skull base chordomas compared to PR.

Contemporary surgical management of skull base chordomas-Anatomical reflections on a single center experience retrospective case series.

Chordoma, a rare, locally aggressive tumor can affect the central skull base, usually centered at the midline. Complete surgical resection remains mainstay of therapy in case of primary as well as recurrent tumors. Owing to their secluded location, surgical resection of skull base chordomas remains a challenge, even though the recent advancement of endoscopic endonasal approaches has had a significant positive impact on the management of these patients. Endoscopic endonasal approaches have been shown to significantly reduce surgical morbidity when compared to traditional open approaches; however, the classical endoscopic transclival midline approach fails to sufficiently expose parts of many skull base chordomas. More recent refinements of the technique, such as the interdural pituitary transposition and posterior clinoidectomy, the transpterygoid plate approach and the transcondylar far medial approach enable the surgeon the increase the resection rate in these patients. This retrospective case series focuses on anatomical aspects in the surgical management of patients with skull base chordomas. We outline the surgical anatomy of contemporary endoscopic approaches to the skull base based intraoperative illustrations as well as pre- and postoperative 3D reconstructed CT and MR images if our patients. This article should help the clinical choose the most appropriate approach and be aware of relevant anatomy as well as potential shortcomings of a given approach.

Intraoperative Magnetic Resonance Imaging Assisted Endoscopic Endonasal Resection of Clival Chordomas.

BackgroundCranial base chordomas are typically indolent and usually appear as encapsulated tumors. They slowly grow by infiltrating the bone, along with the lines of least resistance. Due to its relationship with important neurovascular structures, skull base chordoma surgery is challenging.ObjectiveThe usefulness of intraoperative magnetic resonance imaging (IO-MRI) in achieving the goal of surgery, is evaluated in this study.MethodsBetween March 2018 and March 2020, 42 patients were operated on for resection of skull base chordomas in our institution. All of them were operated on under IO-MRI. Patients were analyzed retrospectively for identifying common residue locations, complications and early post-operative outcomes.ResultsIn 22 patients (52,4%) gross total resection was achieved according to the final IO-MRI. In 20 patients (47,6%) complete tumor removal was not possible because of extension to the petrous bone (8 patients), pontocerebellar angle (6 patients), prepontine cistern (4 patients), temporobasal (1 patient), cervical axis (1 patient). In 13 patients, the surgery was continued after the first IO-MRI control was performed, which showed a resectable residual tumor. 7 of these patients achieved total resection according to the second IO-MRI, in the other 6 patients all efforts were made to ensure maximal resection of the tumor as much as possible without morbidity. Repeated IO-MRI helped achieve gross total resection in 7 patients (53.8%).ConclusionsOur study proves that the use of IO-MRI is a safe method that provides the opportunity to show the degree of resection in skull base chordomas and to evaluate the volume and location of the residual tumor intraoperatively. Hence IO-MRI can improve the life expectancy of patients because it provides an opportunity for both gross total resection and maximal safe resection in cases where total resection is not possible.

Surgical Management of Skull Base and Spine Chordomas

Management of chordoma along the cranial-spinal axis is a major challenge for both skull base and spinal surgeons. Although chordoma remains a rare tumor, occurring in approximately 1 per 1 million individuals, its treatment poses several challenges. These tumors are generally poorly responsive to radiation and chemotherapy, leading to surgical resection as the mainstay of treatment. Due to anatomic constraints and unique challenges associated with each primary site of disease, gross total resection is often not feasible and is associated with high rates of morbidity. Additionally, chordoma is associated with high rates of recurrence due to the tumor's aggressive biologic features, and postoperative radiation is increasingly incorporated as a treatment option for these patients. Despite these challenges, modern-day surgical techniques in both skull base and spinal surgery have facilitated improved patient outcomes. For example, endoscopic endonasal techniques have become the mainstay in resection of skull base chordomas, improving the ability to achieve gross total resection, while reducing associated morbidity of open transfacial techniques. Resection of spinal chordomas has been facilitated by emerging techniques in preoperative imaging, intraoperative navigation, spinal reconstruction, and radiotherapy. Taken collectively, the treatment of chordoma affecting the skull base and spinal requires a multidisciplinary team of surgeons, radiation oncologists, and medical oncologists who specialize in the treatment of this challenging disease.

Endovascular Approach to Ruptured Sphenopalatine Artery: A Case Report and Literature Review

Epistaxis is a rare complication following the endonasal approach of skull base surgery. Conservative methods like anterior and posterior nasal packing can be useful, but when these fail, a neuro-interventional technique can be used as a last-resort measure in cases of severe bleeding. The authors identify a 22-year-old female patient with recurrent epistaxis following resection of skull-base chordoma through an endonasal approach. An endovascular catheter digital subtraction angiogram identified the cause of epistaxis as a rupture of the left sphenopalatine artery branch of the left external carotid artery. A large dissecting aneurysm in the right intracerebral artery was also incidentally found. The unique co-occurrence of vascular problems was successfully managed by neuro-interventional techniques.

The Significance of Intraoperative Magnetic Resonance Imaging in Resection of Skull Base Chordomas

Skull base chordoma can be a challenging surgical entity because of its invasive nature. In this study, the role of intraoperative magnetic resonance imaging (iMRI) to optimize the resection of skull base chordomas is evaluated. We performed a retrospective analysis of operated patients with skull base chordomas in the setting of iMRI. The clinical records, operative notes, radiologic images, tumor volumetry, location of the residual tumor, and surgical outcome were evaluated. Fifteen patients were operated on for resection of skull base chordomas between 2010 and 2017 in our institution. Gross total resection was planned and achieved in 8 patients and partial resection in 7 patients. In 8 patients (53.3%), the preoperatively planned volume of resection was achieved and confirmed in the first iMRI control. In 7 patients, repeated iMRI controls were required to achieve the surgical target. In 3 patients, the tumor residual requiring further resection was located in the clivus and in 4 patients in the intradural space. The improvement of the preoperative deficits showed a significant statistical association with the resection of the intradural component and decompression of the brainstem. This study shows that iMRI is a safe method for intraoperative assessment of the degree of resection and the volume and location of residual tumor when resecting skull base chordomas. When gross total resection of the tumor is not feasible, iMRI can be a useful tool for targeted tumor resection.

Adjuvant Stereotactic Radiosurgery Improves Local Control After Surgical Resection of Skull Base Chordomas and Chondrosarcomas

Adjuvant Stereotactic Radiosurgery Improves Local Control After Surgical Resection of Skull Base Chordomas and Chondrosarcomas

Tumour seeding in the surgical pathway after resection of skull base chordoma

AimThe aim of this study is to review the clinical series in which tumour seeding was reported after skull base surgery for chordomas. BackgroundThe occurrence of implantation of cancer cells during surgical procedures for the removal of chordoma is a rare event described by a number of authors in a few patient series and case reports. Materials and methodsLiterature search was performed by PubMed and Scopus by using the words “surgical tumour seeding, tumour implantation, surgical pathway recurrence, skull base chordoma, and clivus chordoma”. ResultsSix retrospective series and 7 case reports were included in the analysis. In total, 34 patients are described with pathway recurrence, 30 at a single site and 4 at multiple sites.In the 5 largest chordoma series, the rate of occurrence of surgical seeding ranged from 1.3% to 7.3% (3.9%). In the 34 patients diagnosed with tumour seeding, the most frequent surgical approach was trans-nasal/trans-sphenoidal, that was used in 12 cases. The median time from primary treatment to surgical pathway tumour seeding ranged from 7 to 78 months. Data of the treatment of seeding are available in 26/34 patients. All of them underwent a new surgery, 6 received additional external beam radiotherapy, and 2 intraoperative radiotherapy. ConclusionsThe risk of surgical seeding should be taken into consideration when deciding on the surgical approach and the planning treatment volume for postoperative radiation therapy. The surgical pathway should be included in follow-up studies to diagnose this peculiar type of treatment failure possibly at an early phase.

Classification and surgical approaches for transnasal endoscopic skull base chordoma resection: a 6-year experience with 161 cases.

The aim of this study is to retrospectively analyze 161 cases of surgically treated skull base chordoma, so as to summarize the clinical classification of this tumor and the surgical approaches for its treatment via transnasal endoscopic surgery. Between August 2007 and October 2013, a total of 161 patients (92 males and 69 females) undergoing surgical treatment of skull base chordoma were evaluated with regard to the clinical classification, surgical approach, and surgical efficacy. The tumor was located in the midline region of the skull base in 134 cases, and in the midline and paramedian regions in 27 cases (extensive type). Resection was performed via the transnasal endoscopic approach in 124 cases (77%), via the open cranial base approach in 11 cases (6.8%), and via staged resection combined with the transnasal endoscopic approach and open cranial base approach in 26 cases (16.2%). Total resection was achieved in 38 cases (23.6%); subtotal resection, 86 cases (53.4%); partial resection of 80-95%, 29 cases (18%); and partial resection <80%, 8 cases (5%). The clinical classification method used in this study seems suitable for selection of transnasal endoscopic surgical approach which may improve the resection degree and surgical efficacy of skull base chordoma. Gross total resection of skull base chordoma via endoscopic endonasal surgery (with addition of an open approach as needed) is a safe and viable alternative to the traditional open approach.

Skull base reconstruction after endoscopic endonasal resection of skull base chordomas

Objective To describe the techniques for the reconstruction of skull base defects after minimally invasive endoscopic resection of skull base chordomas.Methods The records of 146 patients who presented with skull base chordomas between Aug.2007 and Oct.2013 were retrospectively reviewed.The skull base defects after endoscopic endonasal resection of the chordomas were classified according to the dimensions of the dural defects as the following:(Type Ⅰ) The dura of skull base was intact after the tumour resection (113 cases) ; (Type Ⅱ) The dural defect was equal or less than 1 cm (12 cases) ; (Type Ⅲ) The dural defect was greater than 1 cm (21 cases).Three different reconstruction methods were utilized according to the classification of the skull base defects.The reconstruction of the type Ⅰ defect was performed mainly using artificial material; type Ⅱ in a multilayer fashion,mainly using an array of autologous free material including fat,muscle,muscle fascia and artificial material; type Ⅲ using vascular pedicle nasoseptal flap and autologous free material.Results There was no case of postoperative cerebrospinal fluid (CSF) leakage occurred following the reconstruction of type Ⅰ.One case of postoperative CSF leak (8.3％) occurred following the reconstruction of type Ⅱ and two (9.5％) occurred following the reconstruction of type Ⅲ.The rate of postoperative CSF leakage of all the cases is 2.1％.Conclusions Different reconstruction methods should be chosen according to different types of skull base defects.Reducing the use of vascular pedicle nasoseptal flap as much as possible could minimize the trauma of nasal cavity,increase the degree of comfort of the patients and offer convenience for the next skull base reconstruction after the resection of recurrent chordomas. Key words: Chordoma; Endoscopic ; Skull base reconstruction

Endoscopic Endonasal Resection of Skull Base Chordoma I: Case Series and Review of Literature

Endoscopic Endonasal Resection of Skull Base Chordoma I: Case Series and Review of Literature

Endoscopic endonasal resection of skull base chordoma: Case series and review of literature

Background and Objective: Skull base chordoma is a rare tumor with slow and progressive growth. Significance of this tumor is it’s difficult to access location in skull base. This is the reason for various proposed techniques for resection of the tumor. Endoscopic endonasal technique is a minimally invasive approach that gives surgeons opportunity of total resection of tumor and low morbidity. Total resection of the tumor is the main determining factor of prognosis. Material and methods: In this article we retrospectively studied 18 patients with pathological diagnosis of skull base chordoma treated in Amiralam hospital, Loghman-Hakim hospital and Day general hospital, Tehran, Iran, between 2005 and 2012. All patients underwent endoscopic endonasal surgery. Thirteen patients were primary cases but 3 and 2 cases were referred respectively after radiation failure and recurrence after craniotomy. Mean follow-up time was 23 months. Difficulty in swallowing and speech, diplopia and nasal obstruction was common presenting symptoms. Results: Gross tumor resection was feasible in 13 cases. Subtotal resection was done in 5 cases. During follow-up, 1 case died from disease and tumor recurred in other 8 cases. Nine patients are disease free. Eight recurrences and 1 mortality were in cases that underwent subtotal resection or referred to us after radiation failure. The major operative complication was a case of pneumocephalus. Conclusion: Endoscopic endonasal resection of skull base chordoma is a low morbidity approach, advisable in most cases. We think that total resection is the best surgical strategy. We recommend postoperative radiation in all patients.

Modified transoral approach for resection of skull base chordomas in children

Chordomas are rare slow growing, locally destructive tumours originating from remnants of the primitive notocord and are found most commonly in the clivus and saccrococcygeal region. These tumours usually present in early adult life but on occasion can present in childhood. The combination of the skull base location and paediatric patient size makes access to these tumours particularly challenging. We report a multidisciplinary technique used in two cases in children where a modified extended palatal split was undertaken to allow greater access for tumour excision. This approach allows for good access to the skull base region to allow for maximal tumour resection. This technique also appears to have minimal impact on palatal function and no adverse effects on the upper airway management.

Modified Transoral Approach for Resection of Skull Base Chordoma in Children

Introduction: Chordomas are rare, slow-growing tumors arising from the remnants of the notochord and are found in close association with the axial skeleton. These tumors usually present in early adult life but on occasion present in childhood. Pediatric skull base tumors are particularly challenging to access to allow for maximal surgical resection. We report a multidisciplinary technique used in 2 cases in children, where an extended palatal split was undertaken to allow neurosurgical access for excision to be attempted.

Optimal Treatment Planning for Skull Base Chordomas: Photons, Protons or a Combination of Both?

Skull base chordomas are challenging tumors to treat due to their complex shape and proximity to critical structures. We compared the dosimetry of proton (PR), intensity modulated radiation therapy (IMRT) photon (PH), and combined proton and IMRT photon (PP) irradiation of skull-based chordomas to determine the best technique based on a scoring system comprised of several dosimetric parameters. We acquired the CT simulation scans of five patients who received irradiation to gross residual disease following resection of skull base chordoma. Four plans were generated per patient: an IMRT PH plan with a 1 mm PTV (PH1), used in stereotactic treatment, an IMRT PH plan with a 3 mm PTV (PH3), used in routine treatment, a PR plan with a 3 mm smearing, and a PP plan with 3 mm smearing for proton treatment and 1 mm PTV for the photon segment. All plans were prescribed 74 Gy or CGE to the PTV. In the PP plans, 50 CGE plus a 24 Gy PH boost was prescribed. To facilitate comparison, the primary objective of all plans was ≥95% PTV coverage with the prescribed dose. Plans were optimized to limit dose to organs at risk without sacrificing coverage. Plans were compared via mean values calculated from DVH data of clinically significant parameters. Plans were ranked 1 (best)–4 (worst) for each parameter and rank scores were summated (Table). Target volumes ranged from 4.4–36.7 cc (mean 21.58). The mean % PTV receiving 74 Gy was highest in the PP plan (98.35, range 96.5–99.2), followed by the PR plan (97.3, range 96.1–99.3), the PH1 plan (96.4, range 95.4–97.4), and the PH3 plan (96.1, range 95.1–96.7). The PR plan was the least homogeneous and conformal. Brain mean %V30 Gy was highest for PH3 plans (7.08, range 5.2–9.1) and lowest for PR plans (4.2, range 2.8–6.2). PH3 plans had the highest mean %V of brainstem, chiasm and temporal lobes above tolerance doses. The PH1 plan had the lowest brainstem mean %V67 Gy (2.25, range 0–7.8) and temporal lobes mean %V65 Gy (4.3, range 0.1–7.7). Global evaluation of the plans based on their total ranks scores revealed that PH1 plans and PP plans were more optimal than either single modality PR or PH3 plans (Table). Due to scheduling constraints, some proton centers have used a combination of photon and proton treatment in skull base chordomas. There may be a dosimetric advantage for using PP, as such plans appear to be the most conformal and give the best target coverage. Further investigation of this approach is underway.Tabled 1Dosimetric Parameters and Treatment PlansParameterPH3PH1PPPRPTV74 Gy4312Inhomogeneity Coefficient (D5%-D95%)/D95%2134Conformality Index (V95%/PTV)3214Brain V30 Gy4231Brainstem V67 Gy4132Chiasm V60 Gy4312Temporal Lobes V65 Gy4123Total25131418 Open table in a new tab