Chordomas of the base of the skull and upper cervical spine. One hundred patients irradiated by a 3D conformal technique combining photon and proton beams

Abstract

To define the prognostic factors for local control and overall survival among 100 consecutive patients with chordoma of the base of skull or upper cervical spine treated by fractionated irradiation combining proton and photon beams. Between December 1993 and August 2002, 100 patients (median age: 53 years [8 - 85], M/F sex ratio: 3/2) were treated by a combination of high-energy photons and protons. The proton component was delivered at the Centre de Protonthérapie d'Orsay (CPO) by a 201 MeV beam. The median total dose delivered to the tumor volume was 67 GyECo. With a median follow-up of 31 months [range: 0 - 87], 25 tumours relapsed locally. The 2- and 4-year local control rates were 86.3% (+/-3.9%) and 53.8% (+/-7.5%), respectively. According to multivariate analysis, at least 95% of the tumor volume encompassed by the 95% isodose (p = 0.048; RR: 3.4 95%CI [1.01 - 11.8]) and a minimal dose delivered into the tumor volume <56 GyECo (p = 0.042; RR: 2.3 95%CI [1.03 - 5.2]) were independent prognostic factors of local control. Ten patients died. The 2- and 5-year overall survival rates were 94.3% (+/-2.5%) and 80.5% (+/-7.2%), respectively. According to multivariate analysis, local tumor control (p = 0.005; RR: 21 95%CI [2.2 - 200]) was a prognostic factor of overall survival. For chordomas of the base of the skull and upper cervical spine treated by surgery and irradiation combining photons and protons, the quality of irradiation, reflected by homogeneity of the dose into the tumor volume, is a major factor of local control. Close attention must be paid to minimize the underdosed areas close to critical organs. The role of surgical resection remains paramount, and a trial of dose escalation would have to consider an increase in the dose to critical organs, especially as current results indicate the low toxicity of this treatment.

Chordoma

“…Chordomas are relatively radiation-resistant tumors; however, high-dose radiation such as is possible with particle-based therapy has been shown to offer improved local control and survival [10,11]. The goal of radiation is to sterilize the bed of the tumor from invisible, microscopic tumor nests.…”

Reprint of “Chordoma in children: Case-report and review of literature”

“…[45][46][47][48]51,53 Pediatric CHs seem to fare better compared with their adult counterparts: 60-100% and 80-100%, respectively. 13,30,50,54,55 Nonetheless, younger children were frequently excluded in earlier series dealing with protons (since they require special attention, such as general anesthesia).…”

“…45 This favorable outcome has been reproduced by multiple teams in US, Europe and Japan. [46][47][48] Doses were progressively upgraded to 75 Gy (EBR) (Gy (EBR) = physical dose × an estimated mean 1.1 RBE) and more, conventionally fractionated, at the price of an acceptable toxicity. Recently, carbon ions have also been advocated in place of protons.…”

Review of photon and proton radiotherapy for skull base tumours

“…A few articles describe also the use of a mixed proton/photon beam (Table 5 [9][10][11][91][92][93][94][95][96][97][98][99][100][101][102]. From the methodological point of view, the large majority of the studies are retrospective and may include different tumour types: chordoma, chondrosarcoma, and meningioma of grade I-III.…”