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

Abstract

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.

Upright proton therapy for esthesioneuroblastoma: a single-institution experience

“…With new technological advances in the image guidance, patient positioning, beam delivery, etc., the approach is gaining a renewed interest ( 21 ). Our own clinical practice comprises a positive experience of upright PT for similarly complicated tumors including skull base chordomas and chondrosarcomas ( 34 ).…”

Risk Factors for Radiation Necrosis and Local Recurrence after Proton Beam Therapy for Skull Base Chordoma or Chondrosarcoma

“…However, an escalated dose to the skull base leads to risks of brain necrosis or vision loss [36], and several reports have suggested necrosis of the temporal lobe in particular. Gordon et al treated 31 patients with chordoma or chondrosarcoma with PBT and found 2 cases with Grade 2 or higher temporal lobe necrosis [37]. Similarly, Pehlivan et al used PBT in 62 patients with basilar chordoma or chondrosarcoma and found 7 cases with temporal lobe necrosis, of which 2 were Grade 2 or higher [38].…”

Beam Position Projection Algorithms in Proton Pencil Beam Scanning

“…This allows for the effective sparing of surrounding healthy tissue and organs at risk and thus reducing treatment toxicity. Proton therapy is routinely used for the treatment of various tumor sites [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ] and is a dynamically developing form of radiotherapy [ 20 ].…”