Efficacy and Safety of Adjuvant Proton Therapy Combined With Surgery for Chondrosarcoma of the Skull Base: A Retrospective, Population-Based Study

Proton-Based Radiation Therapy for Skull Base Chondrosarcomas in Children and Adolescents: 40-Year Experience From the Massachusetts General Hospital

PURPOSE

The literature on skull base chondrosarcoma (CHS) is scarce. We report outcomes for pediatric and young patients ≤22 years with base of skull CHSs treated with proton-based radiation therapy (PBRT).

METHODS AND MATERIALS

We retrospectively reviewed all patients treated with PBRT between 1981 and 2023. Primary endpoints were overall survival (OS), chondrosarcoma-specific survival (CSS), progression-free survival (PFS), local control, and distal control.

RESULTS

Eighty-four patients were identified. Median age at diagnosis was 19 years (range, 6-22). Most patients (n = 79, 94%) had conventional CHS, whereas 5 (6%) had mesenchymal CHS. Nine patients (11%) underwent gross total resection, 64 (76%) subtotal resection, and 11 patients (13%) underwent biopsy. Twenty-four (29%) patients progressed before radiation therapy. The median prescription dose was 70 Gy (relative biological equivalent) (range, 50-79.7). At a median follow-up of 18.0 years (IQR, 9.2-26.2) from diagnosis, 11 patients recurred (7 local, 4 distant). Six patients died of disease. Five patients died of other causes. Ten-year OS, CSS, and PFS rates for all patients were 93.3%, 94.7%, and 88%, respectively. Twenty-year OS, CSS, and PFS rates for conventional CHS (n = 79) were 93.1%, 97.1%, and 89.2%, respectively. Mesenchymal histology was significantly associated with worse OS and PFS. Preradiation therapy tumor progression portended worse OS and CSS. Eight patients (9.9 %) experienced a late toxicity grade 3 or greater.

CONCLUSIONS

This is the largest cohort of pediatric base of skull CHSs in literature to date. High-dose PBRT after surgical resection achieves excellent disease control with minimal toxicity.

Controversies in neuro-oncology: Focal proton versus photon radiation therapy for adult brain tumors

Radiation therapy (RT) plays a fundamental role in the treatment of malignant and benign brain tumors. Current state-of-the-art photon- and proton-based RT combines more conformal dose distribution of target volumes and accurate dose delivery while limiting the adverse radiation effects. PubMed was systematically searched from from 2000 to October 2023 to identify studies reporting outcomes related to treatment of central nervous system (CNS)/skull base tumors with PT in adults. Several studies have demonstrated that proton therapy (PT) provides a reduced dose to healthy brain parenchyma compared with photon-based (xRT) radiation techniques. However, whether dosimetric advantages translate into superior clinical outcomes for different adult brain tumors remains an open question. This review aims at critically reviewing the recent studies on PT in adult patients with brain tumors, including glioma, meningiomas, and chordomas, to explore its potential benefits compared with xRT.

Surgical management of skull base chordomas and chondrosarcomas: insights from a national cohort study

Objective

Skull base chordoma and chondrosarcoma are distinct sarcomas of the skull base but share significant therapeutic challenges due to their proximity to critical neurovascular structures, making surgical resection difficult. We sought to establish factors associated with outcome predictors in a national cohort of patients.

Methods and analysis

Data for all patients referred with a diagnosis of skull base chordoma or chondrosarcoma from April 2017 to December 2022 were obtained. We performed analyses of data pertaining to the first cohort of patients treated in the UK with proton beam therapy (PBT) to determine factors associated with obtaining gross total resection (GTR) and adequate clearance of the brainstem and optic apparatus.

Results

Of 230 patients with skull base chordoma or chondrosarcoma referred for PBT, 71% were accepted for PBT, with a wide regional variation between referring neurosurgical units (29%-93%). Of the first 75 consecutive patients treated with PBT, the only factor predictive of obtaining GTR was surgical resection at a unit with higher volumes of patients accepted for PBT (OR 1.32, 95% CI 1.11 to 1.63, p=0.004). Use of intraoperative MRI (OR 4.84, 95% CI 1.21 to 27.83, p=0.04) and resection at a higher volume unit (OR 1.29, 95% CI 1.07 to 1.64, p=0.013) were associated with increased rates of tumour clearance from the brainstem/optic apparatus.

Conclusions

Treatment at a higher volume centre was a key determinant of the optimal surgical outcome in this cohort. These data support the management of skull base chordomas and chondrosarcomas in higher volume centres where multidisciplinary experience can be accumulated.

A systematic review and meta-analysis of radiotherapy and particle beam therapy for skull base chondrosarcoma: TRP-chondrosarcoma 2024

Introduction

Chondrosarcoma is a rare malignant bone tumor. Particle beam therapy (PT) can concentrate doses to targets while reducing adverse events. A meta-analysis based on a literature review was performed to examine the efficacy of PT and photon radiotherapy for skull base chondrosarcoma.

Methods

The meta-analysis was conducted using 21 articles published from 1990 to 2022.

Results

After PT, the 3- and 5-year overall survival (OS) rates were 94.1% (95% confidence interval [CI]: 91.0-96.2%) and 93.9% (95% CI: 90.6-96.1%), respectively, and the 3- and 5-year local control rates were 95.4% (95% CI: 92.0-97.4%) and 90.1% (95% CI: 76.8-96.0%), respectively. Meta-regression analysis revealed a significant association of PT with a superior 5-year OS rate compared to three-dimensional conformal radiotherapy (p < 0.001). In the studies used in the meta-analysis, the major adverse event of grade 2 or higher was temporal lobe necrosis (incidence 1-18%, median 7%).

Conclusion

PT for skull base chondrosarcoma had a good outcome and may be a valuable option among radiotherapy modalities. However, high-dose postoperative irradiation of skull base chondrosarcoma can cause adverse events such as temporal lobe necrosis.

Skull-Base Chondrosarcoma: A Systematic Review of the Role of Postoperative Radiotherapy

Surgery and radiotherapy are key elements to the treatment of skull-base chondrosarcomas; however, there is currently no consensus regarding whether or not adjuvant radiotherapy has to be administered. This study searched the EMBASE, Cochrane, and PubMed databases for clinical studies evaluating the long-term prognosis of surgery with or without adjuvant radiotherapy. After reviewing the search results, a total of 22 articles were selected for this review. A total of 1388 patients were included in this cohort, of which 186 received surgery only. With mean follow-up periods ranging from 39.1 to 86 months, surgical treatment provided progression-free survival (PFS) rates ranging from 83.7 to 92.9% at 3 years, 60.0 to 92.9% at 5 years, and 58.2 to 64.0% at 10 years. Postoperative radiotherapy provides PFS rates ranging between 87 and 96.2% at 3 years, 57.1 and 100% at 5 years, and 67 and 100% at 10 years. Recurrence rates varied from 5.3% to 39.0% in the surgery-only approach and between 1.5% and 42.90% for the postoperative radiotherapy group. When considering prognostic variables, higher age, brainstem/optic apparatus compression, and larger tumor volume prior to radiotherapy were found to be significant factors for local recurrence.

PRISMA-the 100 most-cited articles on chondrosarcoma recurrence: A bibliometric analysis

BACKGROUND

Chondrosarcoma (CHS) is highly prone to recurrence and has become the most common malignant bone tumor in adults. The authors aim to identify and analyze the top 100 most-cited articles in this field, enabling researchers to quickly grasp the research focus and progress in the area of chondrosarcoma recurrence.

METHODS

A search in the Web of Science database yielded a total of 305 articles related to CHS recurrence between 2013 and 2022. Filtering was done based on the titles and abstracts of the articles in the list, and the top 100 most-cited articles were selected. The following information were analyzed using bibliometric methods: article title, first author, year of publication, journal of publication, total citations, country, institution, and keywords.

RESULTS

Among the selected 100 articles, the most frequently cited one has 224 citations. The most commonly appearing journals, institutions, and countries are as follows: "Clinical Orthopaedics Related Research" (5 times); Fudan University, University of Texas System, and Royal Orthopaedic Hospital (4 times each), with China and the USA cited the most (21 times each). The year 2018 is the most productive year (17 articles). About 97 first authors contributed one article each, and 3 had 2 articles each. Among all 229 keywords, the top 3 in frequency are CHS (20%), recurrence (4%), and surgery (3%). Twenty article topics are related to surgical treatment.

CONCLUSION

Research on CHS recurrence is citation-rich but focuses more on treatments than understanding mechanisms, indicating a need for deeper mechanistic exploration for treatment breakthroughs in the future.

Endoscopic transsphenoidal approach in resection of intracranial clivus chondrosarcoma: A case report

Intracranial primary chondrosarcomas are rare, accounting for <0.15% of all intracranial tumors, but exhibit a high risk of recurrence. Due to the rarity of this condition, it has proven difficult to establish efficacy-based treatment guidelines. The present study details a case of clivus chondrosarcoma exhibiting no recurrence following surgical resection using an endoscopic transsphenoidal approach and postoperative adjuvant radiotherapy. A 41-year-old female presented with primary symptoms of left eye esotropia, scotoma of the left nasal visual field and double vision. Preoperative cranial magnetic resonance imaging revealed a lesion on the clivus, which was initially diagnosed as chordoma. However, clivus chondrosarcoma was ultimately diagnosed based on intraoperative findings and postoperative histopathology. The tumor was totally resected and 25 doses of adjuvant radiotherapy with planning gross tumor volume (60 Gy) and planning clinical target volume (50 Gy) were administered for 5 weeks. The patient was discharged at 12 days post-surgery with no obvious postoperative complications. Over the 28-month follow-up period, there was no evidence of recurrence, which may be due to the successful use of combined gross total resection and adjuvant radiotherapy. Therefore, surgical resection using an endoscopic transsphenoidal approach and postoperative adjuvant radiotherapy is an effective method for treating intracranial clivus chondrosarcoma.

Proton Therapy for Skull Base Chondrosarcoma

Chondrosarcoma is a type of an endochondral bone malignancy that is primarily treated surgically with radiation therapy used in the adjuvant setting or in cases of unresectable disease. Proton therapy has potential advantages compared with traditional photon therapy for the treatment of tumors in close proximity to critical structures due to the theoretic lower exit dose. Studies have shown improved survival in patients with skull base chondrosarcoma who undergo proton therapy. However, there is a lack of randomized data. Further studies are needed to define the role of proton therapy in the treatment of skull base chondrosarcoma.

Pure proton therapy for skull base chordomas and chondrosarcomas: A systematic review of clinical experience

Background

Skull base chordoma and chondrosarcoma are exceptionally rare bone tumors with high propensity for local recurrence. Different postoperative radiation modalities are often used to improve the clinical efficacy. Proton therapy (PT) might be among the most promising ones because of the unique ballistic characteristics of high-energy particles. However, previous meta-analysis often included studies with combined radiation techniques. No systematic review to date has directly analyzed the survival and toxicity of pure PT for these two types of malignancies.

Methods

By following the PRISMA guidelines, a systematic search of three databases was conducted. Articles were screened and data were extracted according to a prespecified scheme. R 4.2.0 software was used to conduct the meta-analysis. Normal distribution test was used for the incidence rate of each subgroup.

Results

A total of seven studies involving 478 patients were included in this analysis. The quality of included articles ranged from moderate to high quality. All patients were histopathologically diagnosed with chordoma or chondrosarcoma, and the follow-up time of the cohort ranged from 21 to 61.7 months. For PT planning, the median target volume ranged from 15 cc to 40 cc, and the administered median dose varied from 63 to 78.4 Gy_RBE at 1.8-2.0 Gy_RBE per fraction. The 1-, 2-, 3-, 5-, and 7-year local control and overall survival rates were 100%, 93%, 87%, 78%, and 68%, and 100%, 99%, 89%, 85%, and 68%, respectively. The late grade 3 or higher toxicities were reported in only two involved articles.

Conclusions

Until now, medical centers worldwide have exerted PT to improve outcomes of skull base chordomas and chondrosarcomas. PT not combined with other radiation modalities showed favorable local control and survival with a low incidence of severe radiation-induced toxicities, which manifests promising clinical benefits. However, high-quality evidence is still limited, requiring future clinical trials and prospective studies in selected patients.

Efficacy and safety of carbon ion radiotherapy for bone sarcomas: a systematic review and meta-analysis

Objective

This study aimed to systematically evaluate and conduct a meta-analysis of the efficacy and safety of carbon ion radiotherapy for bone sarcomas.

Methods

We searched for articles using the PubMed, Embase, Cochrane Library, and the Web of Science databases from their inception to January 12, 2022. Two researchers independently screened the literature and extracted data based on the inclusion and exclusion criteria. Statistical analyses were performed using STATA version 14.0.

Results

We searched for 4378 candidate articles, of which 12 studies were included in our study according to the inclusion and exclusion criteria. Of the 897 BSs patients who received carbon ion radiotherapy in the studies, 526 patients had chordoma, 255 patients had chondrosarcoma, 112 patients had osteosarcoma, and 4 patients had other sarcomas. The local control rate at 1, 2, 3, 4, 5, and 10 years in these studies were 98.5% (95% confidence interval [CI] = 0.961–1.009, I² = 0%), 85.8% (95% CI = 0.687–1.030, I² = 91%), 86% (95% CI = 0.763–0.957, I² = 85.3%), 91.1% (95% CI = 0.849–0.974), 74.3% (95% CI = 0.666–0.820, I² = 85.2%), and 64.7% (95% CI = 0.451–0.843, I² = 95.3%), respectively. The overall survival rate at 1, 2, 3, 4, 5, and 10 years in these studies were 99.9% (95% CI = 0.995–1.004, I² = 0%), 89.6% (95% CI = 0.811–0.980, I² = 96.6%), 85% (95% CI = 0.750–0.950, I² = 89.4%), 92.4% (95% CI = 0.866–0.982), 72.7% (95% CI = 0.609–0.844, I² = 95.3%), and 72.1% (95% CI = 0.661–0.781, I² = 46.5%), respectively. Across all studies, the incidence of acute and late toxicities was mainly grade 1 to grade 2, and grade 1 to grade 3, respectively.

Conclusion

As an advanced radiotherapy, carbon ion radiotherapy is promising for patients with bone sarcomas that are unresectable or residual after incomplete surgery. The data indicated that carbon ion radiotherapy was safe and effective for bone sarcomas, showing promising results for local control, overall survival, and lower acute and late toxicity.

PROSPERO registration number

CRD42021258480.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13014-022-02089-0.

The incidence of brainstem toxicity following high-dose conformal proton therapy for adult skull-base malignancies

BACKGROUND

Dose escalation for skull-based malignancies often presents risks to critical adjacent neural structures, including the brainstem. We report the incidence of brainstem toxicity following fractionated high-dose conformal proton therapy and associated dosimetric parameters.

MATERIAL AND METHODS

We performed a single-institution review of patients with skull-base chordoma or chondrosarcoma who were treated with proton therapy between February 2007 and January 2020 on a prospective outcomes-tracking protocol. The primary endpoint was grade ≥2 brainstem toxicity. No patients received concurrent chemotherapy, and brainstem toxicity was censored for analysis if it coincided with local disease progression.

RESULTS

We analyzed 163 patients who received a minimum of 45 GyRBE to 0.03 cm³ of the brainstem. Patients were treated to a median total dose of 73.8 (range 64.5-74.4) GyRBE at 1.8 GyRBE per fraction with 17 patients undergoing twice-daily treatment at 1.2 GyRBE per fraction. With a median follow-up of 4 years, the 5-year cumulative incidence of grade ≥2 brainstem injury was 1.3% (95% CI 0.25-4.3%). There was one grade 2, one grade 3, and no grade 4 or 5 events, with all patients recovering function with medical management.

CONCLUSION

In delivering curative-intent radiotherapy for skull-base chordoma and chondrosarcoma in adults, small volumes of the brainstem can safely receive at least 64 GyRBE with minimal risk of serious brainstem injury.

Impact of Type of Treatment Center and Access to Care on Mortality and Survival for Skull Base Chordoma and Chondrosarcoma

Introduction In adults with skull base chordoma or chondrosarcoma, the impact of treatment center and access to care have not been well described in regard to perioperative mortality and survival.

Methods A query of the National Cancer Database (NCDB) and review of 1,102 adults—488 with chordomas and 614 with chondrosarcomas—was performed. The Kaplan–Meier's product limit method and chi-square analysis, respectively, assessed overall survival and 30-day (30D) and 90-day (90D) mortalities.

Results For 925 patients who had surgery and available mortality data, the 30D and 90D mortality rates were 0.9 and 1.5%. Lower education level (p = 0.0185) and treatment at a nonacademic facility (p = 0.016) were associated with increased risk of 90-day mortality. Median follow-up was 52 months and analysis was dichotomized by histology. For those with skull base chordoma, patients from a larger metro size (p = 0.002), age below the median 52 years (p ≤ 0.001), and private insurance (<0.001) were associated with prolonged survival, whereas for skull base chondrosarcoma, the factors were treatment at an academic medical center (p = 0.001), high-volume center (p = 0.007), age below the median 52 years (p ≤ 0.001), higher income (p = 0.043), higher education (p = 0.017), and private insurance (p ≤ 0.001). Comparing high-, medium-, and low-volume centers, high-volume centers were most likely to be academic, deliver radiotherapy, escalate doses >70 Gy, and utilize proton radiotherapy consistent across both disease subsets.

Conclusion Higher educational attainment and treatment at an academic facility were associated with decreased 90D mortality for patients with skull base chordoma and chondrosarcoma. For those with skull base chordoma, larger metro size, younger age, and private insurance were associated with prolonged survival; for those with chondrosarcoma, it was treatment at a high-volume or academic medical center, younger age, higher income or education, and private insurance.

Proton therapy with a fixed beamline for skull-base chordomas and chondrosarcomas: outcomes and toxicity

Aim

This study presents an analysis (efficacy and toxicity) of outcomes in patients with skull-base chordomas or chondrosarcomas treated with a fixed horizontal pencil proton beam.

Background

Chordomas (CAs) and chondrosarcomas (CSAs) are rare tumours that are usually located near the base of the skull and very close to the brain's most critical structures. Proton therapy (PT) is often considered the best radiation treatment for these diseases, but it is still a limited resource. Active scanning PT delivered via a fixed pencil beamline might be a promising option.

Methods

This is a single-centre experience describing the results of proton therapy for 31 patients with CA (n = 23) or CSA (n = 8) located near the base of the skull. Proton therapy was utilized by a fixed pencil beamline with a chair to position the patient between May 2016 and November 2020. Ten patients underwent resection (32.2%), 15 patients (48.4%) underwent R2 resection, and 6 patients had unresectable tumours (19.4%). In 4 cases, the tumours had been previously irradiated. The median PT dose was 70 GyRBE (relative biological efficacy, 1.1) [range, 60 to 74] with 2.0 GyRBE per fraction. The mean GTV volume was 25.6 cm³ [range, 4.2–115.6]. Patient demographics, pathology, treatment parameters, and toxicity were collected and analysed. Radiation-induced reactions were assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) v 4.0.

Results

The median follow-up time was 21 months [range, 4 to 52]. The median overall survival (OS) was 40 months. The 1- and 2-year OS was 100%, and the 3-year OS was 66.3%. Four patients died due to non-cancer-related reasons, 1 patient died due to tumour progression, and 1 patient died due to treatment-related injuries. The 1-year local control (LC) rate was 100%, the 2-year LC rate was 93.7%, and the 3-year LC rate was 85.3%. Two patients with CSA exhibited progression in the neck lymph nodes and lungs. All patients tolerated PT well without any treatment interruptions. We observed 2 cases of ≥ grade 3 toxicity, with 1 case of grade 3 myelitis and 1 case of grade 5 brainstem injury.

Conclusion

Treatment with a fixed proton beam shows promising disease control and an acceptable toxicity rate, even the difficult-to-treat subpopulation of patients with skull-base chordomas or chondrosarcomas requiring dose escalation.

Primary Skull Base Chondrosarcomas: A Systematic Review

Simple Summary

Primary skull base chondrosarcomas (SBCs) may carry significant tumor-burden by causing severe cranial nerve neuropathies. Current treatment strategies mainly focus on surgical resection and radiotherapy protocols, with a wide range of findings in terms of efficacy and safety. The aim of our systematic review was to comprehensively analyze the current literature on primary SBCs, describing clinical and radiological characteristics, available management strategies, treatment outcomes, and prognoses. We found that most primary SBCs show benign slow-growing patterns but may cause neurological deficits by compressing critical neurovascular structures. Open surgical approaches favor maximal resection with acceptable complication rates, but only a few studies reported the use of newer endoscopic approaches. Proton-based, photon-based, and carbon-based radiotherapy protocols may also allow safe and effective local tumor control as adjuvant treatments or stand-alone strategies in patients not eligible to undergo surgery. Overall, primary SBCs’ prognoses proved to be favorable and comparable to benign skull base neoplasms.

Abstract

Background: Primary skull base chondrosarcomas (SBCs) can severely affect patients’ quality of life. Surgical-resection and radiotherapy are feasible but may cause debilitating complications. We systematically reviewed the literature on primary SBCs. Methods: PubMed, EMBASE, Scopus, Web-of-Science, and Cochrane were searched following the PRISMA guidelines to include studies of patients with primary SBCs. Clinical characteristics, management strategies, and treatment outcomes were analyzed. Results: We included 33 studies comprising 1307 patients. Primary SBCs mostly involved the middle-fossa (72.7%), infiltrating the cavernous-sinus in 42.4% of patients. Cranial-neuropathies were reported in 810 patients (62%). Surgical-resection (93.3%) was preferred over biopsy (6.6%). The most frequent open surgical approaches were frontotemporal-orbitozygomatic (17.6%) and pterional (11.9%), and 111 patients (21.3%) underwent endoscopic-endonasal resection. Post-surgical cerebrospinal-fluid leaks occurred in 36 patients (6.5%). Radiotherapy was delivered in 1018 patients (77.9%): photon-based (41.4%), proton-based (64.2%), and carbon-based (13.1%). Severe post-radiotherapy complications, mostly hypopituitarism (15.4%) and hearing loss (7.1%) were experienced by 251 patients (30.7%). Post-treatment symptom-improvement (46.7%) and reduced/stable tumor volumes (85.4%) showed no differences based on radiotherapy-protocols (p = 0.165; p = 0.062). Median follow-up was 67-months (range, 0.1–376). SBCs recurrences were reported in 211 cases (16.1%). The 5-year and 10-year progression-free survival rates were 84.3% and 67.4%, and overall survival rates were 94% and 84%. Conclusion: Surgical-resection and radiotherapy are effective treatments in primary SBCs, with acceptable complication rates and favorable local tumor control.

Determinants of Survival in Skull Base Chondrosarcoma: A National Cancer Database Study

OBJECTIVE

Chondrosarcomas of the skull base are rare tumors most commonly treated surgically with or without adjuvant radiation therapy. Using the National Cancer Database (NCDB), we analyzed overall survival (OS), treatment modalities, and prognosticators.

METHODS

The NCDB was queried for all cases of histologically confirmed skull base chondrosarcoma treated between 2004 and 2015, excluding patients with more than 1 malignant tumor, on palliative care, receiving unrelated concurrent treatments, or having less than 1 month of follow-up. The χ² test for categorical variables, Cox proportional hazards models, and Kaplan-Meier log-rank analysis were used to test associations with the use of adjuvant radiation, OS, and survival time.

RESULTS

A total of 498 patients with skull base chondrosarcoma were identified in the NCDB. Of them, 224 (45.0%) and 198 (39.8%) were treated with either surgery alone or surgery with adjuvant radiation therapy, respectively. Patients more likely to undergo surgery with adjuvant radiation had higher tumor grade (P = 0.008), later year of diagnosis (P = 0.002), positive surgical margins (P < 0.001), and treatment at an academic institution (P = 0.02). Patient, tumor, and socioeconomic factors associated with worse OS on multivariate analysis included the Charlson/Deyo Comorbidity Score ≥2 (P = 0.017), as well as clear cell (P = 0.02) and dedifferentiated (P = 0.006) histology. Age, tumor grade, tumor size, treatment modality, insurance status, facility type, and urban/rural population did not show a statistically significant impact on OS.

CONCLUSION

The mainstay of treatment for skull base chondrosarcoma is surgery, with consideration of adjuvant radiation. This study demonstrated worse overall survival associated with more frail patients and aggressive histology types. It is important to consider these factors when planning the clinical management of these patients.

Proton Therapy in Head and Neck Cancer Treatment: State of the Problem and Development Prospects (Review)

Proton therapy (PT) due to dosimetric characteristics (Bragg peak formation, sharp dose slowdown) is currently one of the most high-tech techniques of radiation therapy exceeding the standards of photon methods.

In recent decades, PT has traditionally been used, primarily, for head and neck cancers (HNC) including skull base tumors. Regardless of the fact that recently PT application area has significantly expanded, HNC still remain a leading indication for proton radiation since PT’s physic-dosimetric and radiobiological advantages enable to achieve the best treatment results in these tumors.

The present review is devoted to PT usage in HNC treatment in the world and Russian medicine, the prospects for further technique development, the assessment of PT’s radiobiological features, a physical and dosimetric comparison of protons photons distribution. The paper shows PT’s capabilities in the treatment of skull base tumors, HNC (nasal cavity, paranasal sinuses, nasopharynx, oropharynx, and laryngopharynx, etc.), eye tumors, sialomas. The authors analyze the studies on repeated radiation and provide recent experimental data on favorable profile of proton radiation compared to the conventional radiation therapy.

The review enables to conclude that currently PT is a dynamic radiation technique opening up new opportunities for improving therapy of oncology patients, especially those with HNC.

Particle Radiotherapy for Skull Base Chondrosarcoma: A Clinical Series from Italian National Center for Oncological Hadrontherapy

Simple Summary

Skull-base chondrosarcoma is a rare locally aggressive or malignant group of cartilaginous neoplasm. The standard of care consists of surgery and high-dose radiation therapy, better if with particle, due to their radioresistance and proximity to organs at risk such as brainstem and optic pathways. Due to the rarity of the tumor and its site, outcomes in terms of local control and toxicity of patients with this malignancy after receiving particle therapy has been documented only in a limited number of series with a restricted number of patients, in particular with regard to carbon ions. The aim of our retrospective study is to assess the role of particle therapy (protons and carbon ions) after surgery in our Institute in skull-base chondrosarcomas.

Abstract

Background: The standard treatment for skull base chondrosarcoma (SB-CHS) consists of surgery and high-dose radiation therapy. Our aim was to evaluate outcome in terms of local control (LC) and toxicity of proton therapy (PT) and carbon ion (CIRT) after surgery. Materials and methods: From September 2011 to July 2020, 48 patients underwent particle therapy (67% PT, 33% CIRT) for SB-CHS. PT and CIRT total dose was 70 GyRBE (relative biological effectiveness) in 35 fractions and 70.4 GyRBE in 16 fractions, respectively. Toxicity was assessed using the Common Terminology Criteria for Adverse Events (CTCAE v5). Results: After a median follow-up time of 38 months, one local failure (2%) was documented and the patient died for progressive disease. Overall, 3-year LC was 98%. One (2%) and 4 (8%) patients experienced G3 acute and late toxicity, respectively. White-matter brain changes were documented in 22 (46%) patients, but only 7 needed steroids (G2). No patients had G3 brain toxicity. No G4–5 complications were reported. We did not find any correlation between high-grade toxicity or white-matter changes and characteristics of patients, disease and surgery. Conclusions: PT and CIRT appeared to be effective and safe treatments for patients with SB-CHS, resulting in high LC rates and an acceptable toxicity profile.

Delineation of organs at risk

The delineation of organs at risk is the basis of radiotherapy oncologists' work. Indeed, the knowledge of this delineation enables to better identify the target volumes and to optimize dose distribution, involving the prognosis of the patients but also their future. The learning of this delineation must continue throughout the clinician's career. Some contour changes have appeared with better imaging, some volumes are now required due to development of knowledge of side effects. In addition, the increasing survival time of patients requires to be more systematic and precise in the delineations, both to avoid complications until now exceptional but also because re-irradiations are becoming more and more frequent. We present the update of the recommendations of the French Society for Radiation Oncology (SFRO) on new findings or adaptations to volumes at risk.

Sinonasal Squamous Cell Carcinoma, a Narrative Reappraisal of the Current Evidence

Simple Summary

Sinonasal squamous cell carcinomas are a group of diverse tumors affecting the nasal cavity and paranasal sinuses. As a direct consequence of their rarity and heterogeneity, diagnosis is challenging, and treatment does not follow universally accepted protocols. Though surgery represents the mainstay of treatment, neoadjuvant and adjuvant therapies have pivotal roles in improving outcomes of patients treated with curative intent. Indications to endoscopic surgery have been expanding over the last three decades, but a considerable number of patients affected by sinonasal squamous cell carcinoma still need open surgical procedures. Management of the neck in patients affected by sinonasal squamous cell carcinoma is controversial. Curative-intended treatment of recurrent and/or metastatic tumors, alongside palliation of uncurable cases, represent poorly explored aspects of this disease.

Abstract

Sinonasal squamous cell carcinoma is a rare tumor affecting the nasal cavity and paranasal sinuses. Several aspects of this disease, ranging from epidemiology to biology, pathology, diagnosis, staging, treatment, and post-treatment surveillance are controversial, and consensus on how to manage this sinonasal cancer is lacking. A narrative literature review was performed to summarize the current evidence and provide the reader with available data supporting the decision-making process in patients affected by sinonasal squamous cell carcinoma, alongside the authors’ personal opinion on the unsolved issues of this tumor. The review has highlighted several advances in molecular definition of epithelial cancers of the sinonasal tract. Surgery represents the pivot of treatment and is performed through an endoscopic transnasal approach whenever feasible. Open surgery is required for a large proportion of cases. Reconstruction of the defect follows principles of skull base and cranio-maxillo-facial reconstruction. Chemotherapy is given as neoadjuvant treatment or concomitantly to radiotherapy. Photon-based radiation therapy has a crucial role in the adjuvant setting. Particle therapy is providing promising results. Management of the neck should be planned based on the presence of clinically appreciable metastases, primary tumor extension, and need for recipient vessels. Biotherapy and immunotherapy are still underexplored therapeutical modalities.

Proton Therapy for Skull-Base Chordomas and Chondrosarcomas: Initial Results From the Beaumont Proton Therapy Center

 

Background:Skull-base chordomas and chondrosarcomas are rare tumors that arise directly adjacent to important critical structures. Appropriate management consists of maximal safe resection followed by postoperative dose-escalated radiation therapy. Proton beam therapy is often employed in this context to maximize the sparing of organs at risk, such as the brainstem and optic apparatus.

Methods: This is a single-institutional experience treating skull-base chordomas and chondrosarcomas with postoperative pencil beam scanning proton therapy. We employed a simultaneous integrated boost to the gross tumor volume (GTV) for increased conformality. Demographic, clinicopathologic, toxicity, and dosimetry information were collected. Toxicity was assessed according to Common Terminology Criteria for Adverse Events (CTCAE), v. 4.0.

Results: Between 2017 and 2020, 13 patients were treated with postoperative proton therapy. There were 10 patients with chordoma (77%) and three with chondrosarcoma (23%). A gross total resection was achieved in six (60%) patients with chordoma and one patient with chondrosarcoma (33%). Nine patients (69%) received postoperative therapy, whereas four (31%) received treatment at recurrence/progression following re-excision. The median dose to the GTV was 72.4 cobalt-Gray equivalents (range, 70.0 to 75.8). The mean GTV was 3.4 cc (range, 0.2-38.7). There were no grade 3 or greater toxicities. One patient developed grade 2 temporal lobe necrosis. At 10.7 months' median follow-up (range, 2.1-30.6), the rates of local control and overall survival were 100%.

Conclusions: Proton beam therapy with pencil beam scanning and simultaneous integrated boost to the GTV affords excellent early local control with the suggestion of low morbidity. This method deserves consideration as an optimal method for limiting dose to adjacent organs at risk and delivering clinically effective doses to the treatment volume.

Proton beam therapy for children and adolescents and young adults (AYAs): JASTRO and JSPHO Guidelines

Children and adolescents and young adults (AYAs) with cancer are often treated with a multidisciplinary approach. This includes use of radiotherapy, which is important for local control, but may also cause adverse events in the long term, including second cancer. The risks for limited growth and development, endocrine dysfunction, reduced fertility and second cancer in children and AYAs are reduced by proton beam therapy (PBT), which has a dose distribution that decreases irradiation of normal organs while still targeting the tumor. To define the outcomes and characteristics of PBT in cancer treatment in pediatric and AYA patients, this document was developed by the Japanese Society for Radiation Oncology (JASTRO) and the Japanese Society of Pediatric Hematology/Oncology (JSPHO).

Early Toxicities After High Dose Rate Proton Therapy in Cancer Treatments

Background

The conventional dose rate of radiation therapy is 0.01–0.05 Gy per second. According to preclinical studies, an increased dose rate may offer similar anti-tumoral effect while dramatically improving normal tissue protection. This study aims at evaluating the early toxicities for patients irradiated with high dose rate pulsed proton therapy (PT).

Materials and Methods

A single institution retrospective chart review was performed for patients treated with high dose rate (10 Gy per second) pulsed proton therapy, from September 2016 to April 2020. This included both benign and malignant tumors with ≥3 months follow-up, evaluated for acute (≤2 months) and subacute (>2 months) toxicity after the completion of PT.

Results

There were 127 patients identified, with a median follow up of 14.8 months (3–42.9 months). The median age was 55 years (1.6–89). The cohort most commonly consisted of benign disease (55.1%), cranial targets (95.1%), and were treated with surgery prior to PT (56.7%). There was a median total PT dose of 56 Gy (30–74 Gy), dose per fraction of 2 Gy (1–3 Gy), and CTV size of 47.6 ml (5.6–2,106.1 ml). Maximum acute grade ≥2 toxicity were observed in 49 (38.6%) patients, of which 8 (6.3%) experienced grade 3 toxicity. No acute grade 4 or 5 toxicity was observed. Maximum subacute grade 2, 3, and 4 toxicity were discovered in 25 (19.7%), 12 (9.4%), and 1 (0.8%) patient(s), respectively.

Conclusion

In this cohort, utilizing high dose rate proton therapy (10 Gy per second) did not result in a major decrease in acute and subacute toxicity. Longer follow-up and comparative studies with conventional dose rate are required to evaluate whether this approach offers a toxicity benefit.

Chondrosarcoma of the Skull Base: A Case Study and Literature Review

Chondrosarcomas (CSs) are rare malignant tumors composed of cells derived from the transformed chondrocytes. Only 2% of the total cases of CS are found at the skull base, thus representing a 0.1-0.2% prevalence. We present the case of a patient with CS at the middle cranial fossa who was admitted for surgery to the Burdenko National Medical Research Center of Neurosurgery. In addition, we engage in a review of the literature to discuss the current approaches to the diagnostics and surgery of CS and delve deep into its embryo- and oncogenesis.

Dosimetric analysis of local failures in skull-base chordoma and chondrosarcoma following pencil beam scanning proton therapy

Background

Despite combined modality treatment involving surgery and radiotherapy, a relevant proportion of skull-base chordoma and chondrosarcoma patients develop a local recurrence (LR). This study aims to analyze patterns of recurrence and correlate LR with a detailed dosimetric analysis.

Methods

222 patients were treated with proton radiotherapy for chordoma (n = 151) and chondrosarcoma (n = 71) at the PSI between 1998 and 2012. All patients underwent surgery, followed by pencil-beam scanning proton therapy to a mean dose of 72.5 ± 2.2Gy_RBE. A retrospective patterns of recurrence analysis was performed: LR were contoured on follow-up MRI, registered with planning-imaging and the overlap with initial target structures (GTV, PTV_high-dose, PTV_low-dose) was calculated. DVH parameters of planning structures and recurrences were calculated and correlated with LR using univariate and multivariate cox regression.

Results

After a median follow-up of 50 months, 35 (16%) LR were observed. Follow-up MRI imaging was available for 27 (77%) of these recurring patients. Only one (3.7%) recurrence was located completely outside the initial PTV (surgical pathway recurrence). The mean proportions of LR covered by the initial target structures were 48% (range 0–86%) for the GTV, 70% (range 0–100%) for PTV_high and 83% (range 0–100%) for PTV_low. In the univariate analysis, the following DVH parameters were significantly associated with LR: GTV(V < 66Gy_RBE, p = 0.01), GTV(volume, p = 0.02), PTV_high(max, p = 0.02), PTV_high(V < 66Gy_RBE, p = 0.03), PTV_high(V < 59Gy_RBE, p = 0.02), PTV_high(volume, p = 0.01) and GTV(D95, p = 0.05). In the multivariate analysis, only histology (chordoma vs. chondrosarcoma, p = 0.01), PTV_high(volume, p = 0.05) and GTV(V < 66Gy_RBE, p = 0.02) were independent prognostic factors for LR.

Conclusion

This study identified DVH parameters, which are associated with the risk of local recurrence after proton therapy using pencil-beam scanning for patients with skull-base chordoma and chondrosarcoma.

Radiation therapy strategies for skull-base malignancies

INTRODUCTION

The management of skull base malignancies continues to evolve with improvements in surgical technique, advances in radiation delivery and novel systemic agents.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Advances in the management of primary bone sarcomas of the skull base

Skull base primary malignancies represent a heterogeneous group of histologic diagnoses and sarcomas of the skull base are specific malignant tumors that arise from mesenchymal cells and can be classified by site of origin into bony and soft tissue sarcomas. The most common bony sarcomas include: chondrosarcoma, osteosarcoma, chordoma, Ewing's sarcoma. Given the relative rarity of each histologic diagnosis, especially in the skull base, there is limited published data to guide the management of patients with skull base sarcomas. An electronic search of the literature was performed to obtain key publications in the management of bony sarcomas of the skull base published within the last decade. This article is thus a review of the multi-disciplinary management principles of primary bony sarcomas of the skull base. Of note, there have been several recent advancements in the realm of skull base sarcoma management that have resulted in improved survival. These include advances in: imaging and diagnostic techniques, surgical techniques that incorporate oncologic surgical principles, conformal radiation paradigms and targeted systemic therapies. Early access to coordinated multi-disciplinary subspecialty care immediately at suspicion of diagnosis has further improved outcomes. There are several ongoing trials in the realms of radiation therapy and systemic therapy that will hopefully provide further insight about the optimal management of bony sarcomas of the skull base.

High LET Radiation Overcomes In Vitro Resistance to X-Rays of Chondrosarcoma Cell Lines

Chondrosarcomas are malignant tumors of the cartilage that are chemoresistant and radioresistant to X-rays. This restricts the treatment options essential to surgery. In this study, we investigated the sensitivity of chondrosarcoma to X-rays and C-ions in vitro. The sensitivity of 4 chondrosarcoma cell lines (SW1353, CH2879, OUMS27, and L835) was determined by clonogenic survival assays and cell cycle progression. In addition, biomarkers of DNA damage responses were analyzed in the SW1353 cell line. Chondrosarcoma cells showed a heterogeneous sensitivity toward irradiation. Chondrosarcoma cell lines were more sensitive to C-ions exposure compared to X-rays. Using D10 values, the relative biological effectiveness of C-ions was higher (relative biological effectiveness = 5.5) with cells resistant to X-rays (CH2879) and lower (relative biological effectiveness = 3.7) with sensitive cells (L835). C-ions induced more G2 phase blockage and micronuclei in SW1353 cells as compared to X-rays with the same doses. Persistent unrepaired DNA damage was also higher following C-ions irradiation. These results indicate that chondrosarcoma cell lines displayed a heterogeneous response to conventional radiation treatment; however, treatment with C-ions irradiation was more efficient in killing chondrosarcoma cells, compared to X-rays.

The preliminary results of proton and carbon ion therapy for chordoma and chondrosarcoma of the skull base and cervical spine

Purpose

To evaluate the short-term outcomes in terms of tumor control and toxicity of patients with skull base or cervical spine chordoma and chondrosarcoma treated with intensity-modulated proton or carbon-ion radiation therapy.

Methods

Between 6/2014 and 7/2018, a total of 91 patients were treated in our Center. The median age was 38 (range, 4–70) years. Forty-six (50.5%) patients were treated definitively for their conditions as initial diagnosis, 45 (49.5%) patients had recurrent tumors including 14 had prior radiotherapy. The median gross tumor volume was 37.0 (range, 1.6–231.7) cc. Eight patients received proton therapy alone, 28 patients received combined proton and carbon ion therapy, 55 patients received carbon-ion therapy alone.

Results

With a median follow-up time of 28 (range, 8–59) months, the 2-year local control (LC), progression free (PFS) and overall survival (OS) rates was 86.2, 76.8, and 87.2%, respectively. Those rates for patients received definitive proton or carbon-ion therapy were 86.7, 82.8, and 93.8%, respectively. On multivariate analyses, tumor volume of > 60 cc was the only significant factor for predicting PFS (p = 0.045), while re-irradiation (p = 0.012) and tumor volume (> vs < 60 cc) (p = 0.005) were significant prognosticators for OS. Grade 1–2 late toxicities were observed in 11 patients, and one patient developed Grade 3 acute mucositis.

Conclusions

Larger tumor volume and re-irradiation were related to inferior survival for this group of patients. Further follow-up is needed for long-term efficacy and safety.

Radiation induced optic neuropathy: Does treatment modality influence the risk?

Radiation induced optic neuropathy (RION) is a rare but disastrous complication of radiation therapy in treatment of periorbital tumors. The objective of this study is to investigate the incidence of RION in series of patients treated from peri orbital tumors by recent photon and proton irradiation modalities. We searched the Pub Med database for studies in periorbital tumors including base of skull, sinonasal, pituitary, nasopharyngeal tumors and craniopharyngioma treated with Intensity modulated radiotherapy (IMRT) and with proton beam therapy (PBT) between 1992 and 2017 excluding metastatic tumors, lymphomas, pediatric series, those treated mainly with chemotherapy, target therapy and those written in languages other than English and French. The result retrieved 421 articles that were revised by the panel. Fourteen articles with IMRT and 27 with PBT reported usable data for the review from which 31studies that had pointed to the doses to the optic nerve (ON) and/or optic chiasm (OC) and incidence of RION have been analyzed. We have found that the incidence of RION had been reported fairly in both modalities and many other factors related to the patient, tumor, and irradiation process interplay in its development. We have concluded that proper treatment planning, good selection of treatment modality, adherence to dose constraints applied to critical structures all along with regular oncological and ophthalmological follow up, control of co-morbidities and early intervention, could help reducing its magnitude.

Proton therapy for brain tumours in the area of evidence-based medicine

ADVANCES IN KNOWLEDGE

This review details the indication of brain tumors for proton therapy and give a list of the open prospective trials for these challenging tumors.

Bystander effectors of chondrosarcoma cells irradiated at different LET impair proliferation of chondrocytes

While the dose-response relationship of radiation-induced bystander effect (RIBE) is controversial at low and high linear energy transfer (LET), mechanisms and effectors of cell-to-cell communication stay unclear and highly dependent of cell type. In the present study, we investigated the capacity of chondrocytes in responding to bystander factors released by chondrosarcoma cells irradiated at different doses (0.05 to 8 Gy) with X-rays and C-ions. Following a medium transfer protocol, cell survival, proliferation and DNA damages were quantified in bystander chondrocytes. The bystander factors secreted by chondrosarcoma cells were characterized. A significant and major RIBE response was observed in chondrocyte cells (T/C-28a2) receiving conditioned medium from chondrosarcoma cells (SW1353) irradiated with 0.1 Gy of X-rays and 0.05 Gy of C-ions, resulting in cell survivals of 36% and 62%, respectively. Micronuclei induction in bystander cells was observed from the same low doses. The cell survival results obtained by clonogenic assays were confirmed using impedancemetry. The bystander activity was vanished after a heat treatment or a dilution of the conditioned media. The cytokines which are well known as bystander factors, TNF-α and IL-6, were increased as a function of doses and LET according to an ELISA multiplex analysis. Together, the results demonstrate that irradiated chondrosarcoma cells can communicate stress factors to non-irradiated chondrocytes, inducing a wide and specific bystander response related to both doses and LET.

Proton therapy for skull-base chondrosarcoma, a single-institution outcomes study

BACKGROUND

We sought to evaluate the effectiveness of definitive or adjuvant external-beam proton therapy on local control and survival in patients with skull-base chondrosarcoma.

METHODS

We reviewed the medical records of 43 patients with a median age of 49 years (range, 23-80 years) treated with double-scattered 3D conformal proton therapy for skull-base chondrosarcomas between January 2007 and February 2016. Proton therapy-related toxicities were scored using CTCAE v4.0.

RESULTS

The median radiotherapy dose was 73.8 Gy(RBE) (range, 64.5-74.4 Gy[RBE]). Thirty-six (84%) and 7 (16%) patients underwent surgical resection or biopsy alone. Tumor grade distribution included: grade 1, 19 (44%) patients; grade 2, 22 (51%); and grade 3, 2 (5%). Forty patients had gross disease at the time of radiotherapy and 7 patients were treated for locally recurrent disease following surgery. The median follow-up was 3.7 years (range, 0.7-10.1 years). There were no acute grade 3 toxicities related to RT. At 4 years following RT, actuarial rates of overall survival, cause-specific survival, local control, and RT-related grade 3 toxicity-free survival were 95%, 100%, 89%, and 95%.

CONCLUSION

High-dose, double-scattered 3D conformal proton therapy alone or following surgical resection for skull-base chondrosarcoma is an effective treatment with a high rate of local control with no acute grade 3 radiation-related toxicity. Further follow-up of this cohort is necessary to better characterize long-term disease control and late toxicities.

The role of dose escalation and proton therapy in perioperative or definitive treatment of chondrosarcoma and chordoma: An analysis of the National Cancer Data Base

BACKGROUND

Chordomas and chondrosarcomas are a rare but challenging subset of tumors to treat; however, previous studies have shown benefits from proton therapy, which are thought to be primarily driven by prescription conformality permitting homogeneous tumor dosing and the allowance of higher doses. No retrospective studies to date have directly compared the outcomes of conventional and particle therapy or examined the role of high doses (specifically ≥70 Gy) in definitive radiotherapy (DRT) or perioperative radiotherapy (PRT) for both types of malignancies.

METHODS

A total of 863 patients with chondrosarcoma and 715 patients with chordoma treated with nonpalliative proton or conventional radiation therapy with a dose range of 20 to 80 Gy and at least 15 months of follow-up were identified from the National Cancer Data Base for the years 2003-2014. The primary endpoint of overall survival (OS) was evaluated, and clinical features, including age, sex, grade, clinical stage, and Charlson-Deyo comorbidity index, were compared.

RESULTS

Patients receiving DRT were older and had more advanced disease. In DRT for chondrosarcoma, a high dose (40.6% vs 16.9%; P = .006) and proton therapy (75.0% vs 19.1%; P = .046) were associated with improved OS at 5 years in a multivariate analysis. In DRT for chordoma, proton therapy was associated with improved OS at 5 years in a multivariate analysis (100% vs 34.1%; P = .031), and a high dose for chordoma was significant for improved OS in a univariate analysis with both DRT (79.0% vs 54.1%; P = .027) and PRT (83.3% vs 77.4%; P = .007).

CONCLUSIONS

In the largest retrospective series to date, dose escalation and proton radiotherapy were associated with improved OS in patients with chondrosarcoma and chordoma despite limited follow-up and access to particle therapy.

Surgery and protontherapy in Grade I and II skull base chondrosarcoma: A comparative retrospective study

Objective

Skull base chondrosarcoma is a rare tumour usually treated by surgery and proton therapy. However, as mortality rate is very low and treatment complications are frequent, a less aggressive therapeutic strategy could be considered. The objective of this study was to compare the results of surgery only vs surgery and adjuvant proton therapy, in terms of survival and treatment adverse effects, based on a retrospective series.

Methods

Monocentric retrospective study at a tertiary care centre. All patients treated for a skull base grade I and II chondrosarcoma were included. We collected data concerning surgical and proton therapy treatment and up-to-date follow-up, including Common Terminology Criteria for Adverse Events (CTCAE) scores.

Results

47 patients (23M/24F) were operated on between 2002 and 2015; mean age at diagnosis was 47 years-old (10–85). Petroclival and anterior skull base locations were found in 34 and 13 patients, respectively. Gross total resection was achieved in 17 cases (36%) and partial in 30 (64%). Adjuvant proton therapy (mean total dose 70 GyRBE,1.8 GyRBE/day) was administered in 23 cases. Overall mean follow-up was 91 months (7–182). Of the patients treated by surgery only, 8 (34%) experienced residual tumour progression (mean delay 51 months) and 5 received second-line proton therapy. Adjuvant proton therapy was associated with a significantly lower rate of relapse (11%; p = 0.01). There was no significant difference in 10-year disease specific survival between patients initially treated with or without adjuvant proton therapy (100% vs 89.8%, p = 0.14). Difference in high-grade toxicity was not statistically significant between patients in both groups (25% (7) vs 11% (5), p = 0.10). The most frequent adverse effect of proton therapy was sensorineural hearing loss (39%).

Conclusion

Long-term disease specific survival was not significantly lower in patients without adjuvant proton therapy, but they experienced less adverse effects. We believe a surgery only strategy could be discussed, delaying as much as possible proton therapy in cases of relapse. Further prospective studies are needed to validate this more conservative strategy in skull base chondrosarcoma.

Proton beam therapy for cancer in the era of precision medicine

Precision radiotherapy, which accurately delivers the dose on a tumor and confers little or no irradiation to the surrounding normal tissue and organs, results in maximum tumor control and decreases the toxicity to the utmost extent. Proton beam therapy (PBT) provides superior dose distributions and has a dosimetric advantage over photon beam therapy. Initially, the clinical practice and study of proton beam therapy focused on ocular tumor, skull base, paraspinal tumors (chondrosarcoma and chordoma), and unresectable sarcomas, which responded poorly when treated with photon radiotherapy. Then, it is widely regarded as an ideal mode for reirradiation and pediatrics due to reducing unwanted side effects by lessening the dose to normal tissue. During the past decade, the application of PBT has been rapidly increasing worldwide and gradually expanding for the treatment of various malignancies. However, to date, the role of PBT in clinical settings is still controversial, and there are considerable challenges in its application. We systematically review the latest advances of PBT and the challenges for patient treatment in the era of precision medicine.

Protons vs Photons for Brain and Skull Base Tumors

The physical characteristics of proton therapy result in steeper dose gradients and superior dose conformality compared to photon therapy. These properties render proton therapy ideal for skull base tumors requiring dose escalation for optimal tumor control, and may also be beneficial for brain tumors as a means of mitigating radiation-related adverse effects. This review summarizes the literature regarding the role of proton therapy compared to photon therapy in the treatment of adult brain and skull base tumors.

The Differences Between Intracranial Mesenchymal Chondrosarcoma and Conventional Chondrosarcoma in Clinical Features and Outcomes

OBJECTIVE

To report differences in clinical features and outcomes between intracranial mesenchymal chondrosarcoma (MCS) and conventional chondrosarcoma (CCS).

METHODS

Clinical data of patients with primary intracranial MCS and CCS were retrospectively extracted and analyzed to compare differences between MCS and CCS.

RESULTS

Seventy-four patients with intracranial chondrosarcoma (61 cases with MCS and 13 cases with CCS) were included. Compared with patients with CCS, patients with MCS presented at a younger mean age (21.1 years vs. 34.5 years, P < 0.001) and had a poor mean preoperative Karnofsky performance scale score (64.6 vs. 77.8, P = 0.014). Compared with CCS, MCS was less often located in the skull base (38.5% vs. 96.7%, P < 0.001) and had a larger tumor volume (87.8 cm³ vs. 26.7 cm³, P < 0.001). Rates of gross total resection in MCS and CCS subgroups were 41.1% (n = 25) and 46.2% (n = 6), respectively; rates of adjuvant radiotherapy postoperatively were 44.2% (n = 27) and 46.2% (n = 6), respectively. After mean follow-up of 41.7 months, 1-year, 3-year, and 5-year overall survival and progression-free survival of MCS were significantly shorter than overall survival and progression-free survival of CCS. Multivariate analysis revealed that tumor pathology and extent of surgery were independent predictors for tumor recurrence.

CONCLUSIONS

Clinical features of MCS are quite different from CCS. Treatment strategies used for CCS do not yield satisfactory outcomes for MCS. Treatment of MCS should be aggressive and individualized.

[Technical aspects and indications of extracranial stereotactic radiotherapy]

Extracranial stereotactic radiotherapy has developed considerably in recent years and is now an important part of the therapeutic alternatives to be offered to patients with cancer. It offers opportunities that have progressively led physicians to reconsider the therapeutic strategy, for example in the case of local recurrence in irradiated territory or oligometastatic disease. The literature on the subject is rich but, yet, there is no real consensus on therapeutic indications. This is largely due to the lack of prospective, randomized studies that have evaluated this technique with sufficient recoil. We propose a review of the literature on the technical aspects and indications of extracranial stereotactic radiotherapy.

Three-year results after radiotherapy for locally advanced sinonasal adenoid cystic carcinoma, using highly conformational radiotherapy techniques proton therapy and/or Tomotherapy

PURPOSE

We report the patient outcomes of a treatment combining proton therapy and Tomotherapy in sinonasal adenoid cystic carcinoma involving skull base.

MATERIALS AND METHODS

We included patients treated at Curie Institute, Paris, France, between March 2010 and February 2014 for an advanced adenoid cystic carcinoma involving skull base. Patients received Tomotherapy, proton therapy or both. We evaluated treatment toxicity (according to CTCAE V4), local control, distant metastasis-free survival and overall survival.

RESULTS

Thirteen patients were included, with a median follow-up of 34 months. Radiation therapy followed surgery for 77% of the patients and margins were positive in all those cases. Median dose was 73.8Gy. Local control, distant metastasis-free survival and overall survival at 3 years were respectively 60%, 48% and 60%. One-sided grade 3 hearing impairment occurred in 46% of the patients.

CONCLUSION

Combining high-dose proton therapy and Tomotherapy is effective and has moderate toxicity in the treatment of T4 sinonasal adenoid cystic carcinoma involving skull base.

Proton Therapy for Head and Neck Cancers

Because of its sharp lateral penumbra and steep distal fall-off, proton therapy offers dosimetric advantages over photon therapy. In head and neck cancer, proton therapy has been used for decades in the treatment of skull-base tumors. In recent years the use of proton therapy has been extended to numerous other disease sites, including nasopharynx, oropharynx, nasal cavity and paranasal sinuses, periorbital tumors, skin, and salivary gland, or to reirradiation. The aim of this review is to present the physical properties and dosimetric benefit of proton therapy over advanced photon therapy; to summarize the clinical benefit described for each disease site; and to discuss issues of patient selection and cost-effectiveness.

The EPTN consensus-based atlas for CT- and MR-based contouring in neuro-oncology

PURPOSE

To create a digital, online atlas for organs at risk (OAR) delineation in neuro-oncology based on high-quality computed tomography (CT) and magnetic resonance (MR) imaging.

METHODS

CT and 3 Tesla (3T) MR images (slice thickness 1 mm with intravenous contrast agent) were obtained from the same patient and subsequently fused. In addition, a 7T MR without intravenous contrast agent was obtained from a healthy volunteer. Based on discussion between experienced radiation oncologists, the clinically relevant organs at risk (OARs) to be included in the atlas for neuro-oncology were determined, excluding typical head and neck OARs previously published. The draft atlas was delineated by a senior radiation oncologist, 2 residents in radiation oncology, and a senior neuro-radiologist incorporating relevant available literature. The proposed atlas was then critically reviewed and discussed by European radiation oncologists until consensus was reached.

RESULTS

The online atlas includes one CT-scan at two different window settings and one MR scan (3T) showing the OARs in axial, coronal and sagittal view. This manuscript presents the three-dimensional descriptions of the fifteen consensus OARs for neuro-oncology. Among these is a new OAR relevant for neuro-cognition, the posterior cerebellum (illustrated on 7T MR images).

CONCLUSION

In order to decrease inter- and intra-observer variability in delineating OARs relevant for neuro-oncology and thus derive consistent dosimetric data, we propose this atlas to be used in photon and particle therapy. The atlas is available online at www.cancerdata.org and will be updated whenever required.

High control rates of proton- and carbon-ion-beam treatment with intensity-modulated active raster scanning in 101 patients with skull base chondrosarcoma at the Heidelberg Ion Beam Therapy Center

BACKGROUND

The current study compares the results of irradiation with protons and irradiation with carbon ions via a raster scan technique in patients with G1 and G2 skull base chondrosarcomas.

METHODS

Between 2009 and 2014, a total of 101 patients (40 men and 61 women) with a median age of 44 years (range, 19-77 years) were irradiated with carbon ions (79 patients) or protons (22 patients) via a raster scan technique at the Heidelberg Ion Beam Therapy Center. The median total dose was 60 Gy (relative biological effectiveness [RBE]) at 3 Gy per fraction for carbon ions and 70 Gy (RBE) at 2 Gy per fraction for protons. The median boost planning target volume was 38 cm³ (range, 8-133 cm³ ). Overall survival (OS) and local control (LC) were evaluated with the Kaplan-Meier method.

RESULTS

The median follow-up period was 40 months (range, 0.8-78.1 months). At the start of the irradiation, all patients had residual macroscopic tumors. Five patients (5%) developed a local recurrence during the follow-up. The 1-, 2-, and 4-year LC rates were 100%, 100%, and 100%, respectively, for protons and 98.6%, 97.2%, and 90.5%, respectively, for carbon ions. The OS rates during the same periods of time were 100%, 100%, and 100%, respectively, for protons and 100%, 98.5%, and 92.9%, respectively, for carbon ions. An age ≤ 44 years was associated with a trend for a better outcome. No toxicity worse than Common Toxicity Criteria grade 3 was observed after treatment.

CONCLUSIONS

No significant difference between carbon ions and protons in the therapy of skull base chondrosarcoma could be detected in these initial retrospective results. Cancer 2018;124:2036-44. © 2018 American Cancer Society.

Proton beam therapy for skull base chordomas in 106 patients: A dose adaptive radiation protocol

BACKGROUND AND PURPOSE

To evaluate clinical results and safety of a dose adaptive protocol based on tumor volume coverage and critical structure constraints, for the treatment of skull base chordomas.

MATERIAL AND METHODS

Between May 2006 and October 2012, 106 patients with skull base chordoma were treated by combined photon and proton irradiation. Prescribed dose levels were 68.4, 70.2, 72 and 73.8 Gy(RBE) in once daily fractionation of 1.8 Gy(RBE). Dose level and dosimetric constraints to organs at risk depended on postoperative residual Gross Tumor Volume (GTV) coverage. Local control (LC) and overall survival (OS) were evaluated using the Kaplan-Meier method.

RESULTS

With a median follow-up of 61 months, the 2-year, 4-year, and 5-year LC rates were 88.6%, 78.3%, and 75.1%, respectively. GTV > 25 mL (p = 0.034, HR = 2.22; 95%CI 1.06-4.62) was an independent unfavorable prognostic factor of LC. The 2-year, 4-year, and 5-year OS rates were 99%, 90.2%, and 88.3%, respectively. Grade 3-5 late toxicity was observed in 7 patients, resulting in 93% 5-year freedom from high-grade toxicity.

CONCLUSIONS

This study suggests that the probability of LC of skull base chordomas depends on postoperative GTV. The dose adaptive protocol achieves acceptable local control. Future studies should investigate whether further dose escalation to doses in excess of 74 Gy(RBE) would achieve better results.