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Table of Contents    
Year : 2020  |  Volume : 68  |  Issue : 1  |  Page : 42-44

Introduction of Image‑Guided Pencil Beam for Skull Base Tumors in India: A Report of Two Cases and a Brief Review of the Literature

Department of Radiation Oncology, Apollo Proton Cancer Centre, Chennai, Tamil Nadu, India

Date of Web Publication28-Feb-2020

Correspondence Address:
Dr. Rakesh Jalali
Apollo Proton Cancer Centre, 4/661, Dr Vikram Sarabai Instronic Estate 7th St, Dr. Vasi Estate, Phase II, Tharamani, Chennai - 600 096, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0028-3886.279680

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 » Abstract 

Chordoma and chondrosarcoma are locally aggressive tumors occurring in one-third cases at the base of the skull. These tumors often recur locally with significant morbidity and mortality. The mainstay of treatment is maximal safe tumor debulking. However, in spite of gross total resection, these tumors are likely to recur. Hence, adjuvant radiation is provided to reduce the risk of local recurrence and to improve outcomes. These tumors are considered relatively radioresistant; hence, high doses of radiation are generally required during treatment. However, the presence of several important structures around the lesion poses a major challenge with respect to covering the target with the prescribed high dose. In this regard, protons, for their physical and dosimetric advantages, have become the accepted modality of treatment in these tumors. With the evolution of proton beam therapy (PBT) over the years, especially pencil beam scanning techniques; which result in an extremely high conformal intensity-modulated proton beam therapy (IMPT), robust and Monte Carlo optimization, computational algorithms, and biological modelling are the significant advances which have further enhanced the value of this technology and have improved outcomes. Herein, we would like to report our experience of two cases of skull base tumors treated with intensity-modulated proton therapy at our center along with a review of the literature.

Keywords: Chondrosarcoma, chordoma, intensity-modulated proton beam therapy, proton beam therapy
Key Messages: PBT has been one of the classic indications for management of skull base tumors. Modern IMPT has the potential to further improve outcomes in skull base tumors.

How to cite this article:
Tonse R, Chilikuri S, Shamurailatpam D, Jalali R. Introduction of Image‑Guided Pencil Beam for Skull Base Tumors in India: A Report of Two Cases and a Brief Review of the Literature. Neurol India 2020;68:42-4

How to cite this URL:
Tonse R, Chilikuri S, Shamurailatpam D, Jalali R. Introduction of Image‑Guided Pencil Beam for Skull Base Tumors in India: A Report of Two Cases and a Brief Review of the Literature. Neurol India [serial online] 2020 [cited 2022 Sep 27];68:42-4. Available from: https://www.neurologyindia.com/text.asp?2020/68/1/42/279680

Chordomas account for 1–4% of all bone malignancies that arise from the primitive notochord, whereas chondrosarcomas are primary bone tumors of cartilaginous origin.[1],[2] Chordomas exhibit a locally destructive growth with recurrence as the characteristic hallmark. Gross total resection is the current treatment of choice for skull base chordomas and chondrosarcomas. In addition, radiation therapy can improve local control and overall survival.[3],[4],[5],[6] Since these tumors are relatively radioresistant, high-dose radiation often exceeding 60 Gy offers the best chance at local control. Proton beam therapy (PBT) is usually administered to these tumors as it can deliver high-dose radiation while sparing organs at risk (OARs) in the direct vicinity of the target volume. In the present study, we report two cases of skull base tumors treated with intensity-modulated proton therapy at our center.

 » Case Report Top

Case 1

A 24-year-old woman presented with a history of diplopia and severe headache since January 2016. Her MRI brain revealed a mass of size 2.8 × 2.1 × 2.1 cm arising from the left side of the body of sphenoid eroding the left post clinoid process involving left cavernous sinus and optic recess. She further underwent transnasal endoscopic excision and biopsy which revealed a chondrosarcoma. She was kept on a regular follow-up. Later in August 2018, she suffered an unbearable headache, vomiting, altered sensorium, and giddiness. Subsequent MRI brain revealed a large ill-defined enhancing mass of size 55 × 39 × 37 mm arising from the left parasellar region involving the posterior aspect of the left cavernous sinus with extension. She later underwent right craniotomy and partial excision of tumor and HPR was chondrosarcoma. MRI of the brain further revealed a 3.6 × 4.2 × 3.2 cm mass lesion in the left side of the superior part of dorsum sellae. The patient was immobilized with a brain aquaplast mask and mold care was done, planning CT scan was acquired and registered with volumetric planning MRI for delineation of target volumes and OARs. A 3-field single field optimization (SFO) plan was generated and the planned dose was 68.2 GyE in 31 fractions at 2.2 GyE per fraction (with 1.1 relative biologic effectiveness) [Figure 1]. Baseline quality of life questionnaire was assessed before treatment. The patient tolerated treatment well with no treatment interruptions and is doing well clinically. Response assessment MRI brain scan after 3 months of treatment showed a very good response [Figure 2].
Figure 1: Representative images showing the field arrangement and dose wash in axial, coronal and sagittal view of intensity-modulated proton therapy (IMPT) plan for a case of skull base chondrosarcoma

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Figure 2: (a) T1 contrast image pre-proton beam therapy, (b) T1 contrast image 3 months post-proton beam therapy

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Case 2

A 45-year-old man was presented with complaints of headache and nasal obstruction in December 2015. He underwent endoscopic excision of the lesion and histopathology showed it to be chordoma. He was asymptomatic till May 2018, when he developed nasal obstruction and headache. His MRI showed a lytic lesion in the sphenoid bone with soft tissue component extending into the posterior wall of the nasopharynx. He underwent transnasal endoscopic excision for the same. On follow-up after 3 months MRI showed soft tissue mass lesion with bony destruction along the ventral surface of clivus, extending to the posterosuperior wall of the nasopharynx, reaching oropharynx up to the level of the soft palate in the posterior pharyngeal wall. He underwent transnasal endoscopic re-excision of the lesion. Histopathology (HPE) showed clival chordoma, immunohistochemistry (IHC) positive for brachyury, AE1/AE3, focally positive for p53 and Mib1 index 10–12%. He was advised adjuvant radiation therapy with PBT. The residual disease was labelled as high-risk CTV (HRCTV) and the entire postoperative bed was labelled as low-risk CTV (LRCTV). He was put on a total dose of 70.4 GyE in 32 fractions at 2.2 Gy E per fraction to the HRCTV and 57.6 GyE in 32 fractions to the LRCTV using 3-field multifield optimization (MFO) technique [Figure 3]. He tolerated treatment well with no treatment interruptions and was kept on regular follow-up. A follow-up scan after 3 months was suggestive of disease stability.
Figure 3: Representative images of pencil beam proton therapy plan showing dose-wash in axial, sagittal, and coronal view of a case of a skull base chordoma. Planning is based on Monte Carlo optimization algorithms

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 » Discussion Top

A systematic review of the literature in patients with chordomas analyzed seven retrospective studies that included a total of 416 patients who were treated either with protons or with a combination of protons plus photons.[5] The radiation doses and schedules varied within and between series but generally, the total radiation dose was 70 Gy equivalents or higher. In patients with chondrosarcoma, the largest series comprised 200 patients treated at a single institution. The median total dose of radiation in that series was 72 Gy equivalents. The 10-year local control and survival rates were 98% and 99%, respectively.[7]

With the evolution of PBT, there have been several technical refinements in the proton machinery and methods of delivery in the last few years, which includes incorporation of pencil beam scanning techniques with a resultant extremely highly conformal intensity-modulated proton beam therapy (IMPT), robust and Monte Carlo optimization and routine use of modern cone beam based highly precise daily image guidance. The impact of the modern conformal proton therapy was seen from the Paul Scherrer Institute in chordoma (n = 151) where the mean dose delivered was 72.5 Gy RBE with 7-year local control found to be 70.9% and overall survival (OS) to be 81.7%.[8] In the same series, patients with chondrosarcoma (n = 71) were found to have a 7-year local control of 93.6%.[8] Another long term outcome data of chondrosarcoma showed the median dose delivered 70.2 Gy RBE. The median follow-up of 88.0 months with the 7-year local control of 93.1%., the 7-year OS was 93.6% and 7-year toxicity free survival was 84.2%.[9] Some of the results of PBT in chordoma and chondrosarcoma reported in the literature are summarized in [Table 1].[10],[11],[12],[13],[14]
Table 1: Series of skull base chordoma and chondrosarcoma treated by proton beam therapy

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At our center, in both chordoma and chondrosarcoma, we could safely deliver high doses of radiation with significant sparing of normal brain tissues. Quality of life and response assessment are prospectively captured and will be published once we have a longer follow-up.

 » Conclusion Top

PBT is the standard adjuvant treatment post-surgery in the management of chordomas and chondrosarcomas. Modern pencil beam proton therapy has the potential to further reduce the toxicity and improve outcomes in these challenging skull base tumors.


We thank our colleagues from neurosurgery, radiation oncology and medical physics for patient referrals and treatment planning.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

 » References Top

McMaster ML, Goldstein AM, Bromley CM. Chordoma: Incidence and survival patterns in the United States. Cancer Causes Control 2001;12:1-11.  Back to cited text no. 1
Rosenberg AE, Nielsen GP, Keel SB, Renard LG, Fitzek MM, Munzenrider JE, et al. Chondrosarcoma of the base of the skull: A clinicopathologic study of 200 cases with emphasis on its distinction from chordoma. Am J Surg Pathol 1999;23:1370-8.  Back to cited text no. 2
Stacchiotti S, Sommer J. Chordoma Global Consensus Group. Building a global consensus approach to chordoma: A position paper from the medical and patient community. Lancet Oncol 2015;16:71-83.  Back to cited text no. 3
Amichetti M, Cianchetti M, Amelio D, Enrici RM, Minniti G. Proton therapy in chordoma of the base of the skull: A systematic review. Neurosurg Rev 2009;32:403-16.  Back to cited text no. 4
Amichetti M, Amelio D, Cianchetti M, Enrici RM, Minniti G. A systematic review of proton therapy in the treatment of chondrosarcoma of the skull base. Neurosurg Rev 2010;33:155-65.  Back to cited text no. 5
Munzenrider JE, Liebsch NJ. Proton therapy for tumors of the skull base. Strahlenther Onkol 1999;175(Suppl 2):57-63.  Back to cited text no. 6
Rosenberg AE, Nielsen GP, Keel SB, Renard LG, Fitzek MM, Munzenrider JE, et al. Chondrosarcoma of the base of the skull: A clinicopathologic study of 200 cases with emphasis on its distinction from chordoma. Am J Surg Pathol 1999;23:1370-8.  Back to cited text no. 7
Weber DC, Malyapa R, Albertini F, Bolsi A, Kliebsch U, Walser M, et al. Long term outcomes of patients with skull-base low-grade chondrosarcoma and chordoma patients treated with pencil beam scanning proton therapy. Radiother Oncol 2016;120:169-74.  Back to cited text no. 8
Weber DC, Murray F, Combescure C, Calugaru V, Alapetite C, Albertini F, et al. Long term outcome of skull-base chondrosarcoma patients treated with high-dose proton therapy with or without conventional radiation therapy. Radiother Oncol 2018;129:520-6.  Back to cited text no. 9
Hug EB, Loredo LN, Slater JD, DeVries A, Grove RI, Schaefer RA, et al. Proton radiation therapy for chordomas and chondrosarcomas of the skull base. J Neurosurg 1999;91:432-9.  Back to cited text no. 10
Noel G, Feuvret L, Ferrand R, Boisserie G, Mazeron JJ, Habrand JL. Radiotherapeutic factors in the management of cervical-basal chordomas and chondrosarcomas. Neurosurgery 2004;55:1252-60. discussion 60-2.  Back to cited text no. 11
Ares C, Hug EB, Lomax AJ, Bolsi A, Timmermann B, Rutz HP, et al. Effectiveness and safety of spot scanning proton radiation therapy for chordomas and chondrosarcomas of the skull base:First long-term report. Int J Radiat Oncol Biol Phys 2009;75:1111-8.  Back to cited text no. 12
Yasuda M, Bresson D, Chibbaro S, Cornelius JF, Polivka M, Feuvret L, et al. Chordomas of the skull base and cervical spine: Clinical outcomes associated with a multimodal surgical resection combined with proton- beam radiation in 40 patients. Neurosurg Rev 2012;35:171-82.  Back to cited text no. 13
Deraniyagala RL, Yeung D, Mendenhall WM, Li Z, Morris CG, Mendenhall NP, et al. Proton therapy for skull base chordomas: An outcome study from the university of Florida proton therapy institute. J NeurolSurg B Skull Base 2014;75:53-7.  Back to cited text no. 14


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1]

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