Chordoma of the Skull Base: Initial Results in a Series of Patients Treated by Particle Therapy at the Italian National Center for Oncological Hadron Therapy (CNAO)

Objective: To assess the clinical results of spot scanning particle beam radiation therapy (PT) in the treatment of skull base chordomas.

Methods and Materials: Between September 2011 and May 2015, a total of 79 patients (49 males, 30 females, median age 60 years, range 14–81) with histologically proven skull base chordomas were treated at National Center for Hadron Therapy (CNAO) with proton or carbon ion radiotherapy and spot scanning technology. Forty patients were treated by carbon ion and 39 by proton therapy. We based our choice of particle type upon the amount of residual disease after surgery.

The median prescription dose was 74 cobalt Gy equivalent (2 Gy/Fr) and 70.4 cobalt Gy equivalent (4.4 Gy/Fr), for proton and for carbon ion RT, respectively. Median gross tumor volume (GTV) was 34.6 mL (range, 0.5–127 mL). The median follow-up time was 20 months (range, 6–43 months). Toxicity was assessed using the Common Terminology Criteria for Adverse Events (CTCAE, v4.0) grading system.

Results: Local control rate was 89.8%. We observed eight failures; in seven patients, the tumor was in close proximity to the brainstem; one patient had histologically confirmed cervical node relapse. Radiation-induced pituitary dysfunction was observed in 6 (7.5%) patients (CTCAE Grade 2), temporal lobe radionecrosis G2 was found in 11 patients (13.9%). No patient presented with post-RT unexpected dysfunction of optic pathways.

Conclusion: Spot-scanning particle therapy offers high tumor control rates of skull base chordoma. Results compare favorably to other particle irradiation series. These preliminary results are encouraging but should be confirmed during a longer follow-up.