Fractionated proton radiation therapy of chordoma and low-grade chondrosarcoma of the base of the skull

Abstract

Sixty-eight patients with chordoma or low-grade chondrosarcoma at the base of the skull received fractionated high-dose postoperative radiation delivered with a 160-MeV proton beam. Protons have favorable physical characteristics which allow the delivery of high doses of radiation to these critically located tumors. The methods employed for these treatments are described. These patients have been followed for at least 17 months and for a median of 34 months. The median tumor dose was 69 CGE (cobalt Gy equivalent): CGE is the dose in proton Gy multiplied by 1.1, which is the relative biological effectiveness for protons compared to cobalt-60. The daily dose was 1.8 to 2.1 CGE. For this group the 5-year actuarial local control rate is 82% and disease-free survival rate is 76%. The incidence of treatment-related morbidity has been acceptable.

Visual complications of proton beam therapy for clival chordoma

“…1 Bilateral loss of vision developing concurrently with radiographically proven tumour progression in the upper clivus has been described. 9 There has been no evidence of this in our patients.…”

“…Combining maximal surgical resection with high-dose proton radiation therapy has been reported to be currently the best management of these patients. 1 We are unaware that the neurovisual outcome of patients treated for clival chordoma with proton-photon therapy has been reported in detail in the ophthalmic literature.…”

Clinical Benefits of Proton Beam Therapy for Tumors of the Skull Base

“…[25][26][27][28] Protons have also been instrumental in the dose escalation of chordomas (> 70 Gy); a steep dose-gradient limits toxicity to critical normal tissues. 5 Long-term follow-up of patients with chordomas whose conditions were managed with proton beam therapy has also been reported. 29 With a median dose of 72.1 Gy for combined proton/photon beam therapy, a 5-year local control rate of 73% has been reported.…”

“…1 There are proven benefits to proton treatment in select patients, including those with chordomas, skull-base tumors, and in the setting of childhood malignancies where doses initiated in proximity to adjacent normal structures are of critical importance. [2][3][4][5] The potential therapeutic benefit of proton beam therapy is being investigated in many other disease sites, including tumors of the lung, pancreas, esophagus, prostate, and cervix. [6][7][8][9][10] In this review, we summarize the unique properties of protons that make them particularly beneficial for the treatment of skull-base lesions and review the results of clinical studies supporting their use.…”

External Radiotherapy Plus Intracavitary Brachytherapy for Recurrent Chordoma of the Nasopharynx

“…Proton beams have been used in a few centres to treat skullbase chordomas. The spreadout of the Bragg peak of proton beams allows optimal coverage of the target volume with very limited irradiation of surrounding tissues (9). At the Massachusetts General Hospital and Harvard Cyclotron Laboratory in Boston, a combination of photons and protons was used in a series of 194 patients to a total dose of 56.8-79.2 cobalt Gray equivalent (CGE) and a median dose of 68.4 CGE (considering the relative biological effectiveness, RBE, of protons 1.1, compared with 1.0 for cobalt k-rays).…”