Active raster scanning with carbon ions: reirradiation in patients with recurrent skull base chordomas and chondrosarcomas.

PURPOSE: To evaluate the safety and efficacy of reirradiation with carbon ions in patients with relapse of skull base chordoma and chondrosarcoma. PATIENTS AND METHODS: Reirradiation with carbon ions was performed on 25 patients with locally recurrent skull base chordoma (n = 20) or chondrosarcoma (n = 5). The median time between the last radiation exposure and the reirradiation with carbon ions was 7 years. In the past, 23 patients had been irradiated once, two patients twice. Reirradiation was delivered using the active raster scanning method. The total median dose was 51.0 GyE carbon ions in a weekly regimen of five to six fractions of 3 GyE. Local progression-free survival (LPFS) was evaluated using the Kaplan-Meier method; toxicity was evaluated using the NCI Common Terminology Criteria for Adverse Events (CTCAE v.4.03).
RESULTS: The treatment could be finished in all patients without interruption. In 80% of patients, symptom control was achieved after therapy. The 2-year-LPFS probability was 79.3%. A PTV volume of < 100 ml or a total dose of > 51 GyE was associated with a superior local control rate. The therapy was associated with low acute toxicity. One patient developed grade 2 mucositis during therapy. Furthermore, 12% of patients had tympanic effusion with mild hypacusis (grade 2), while 20% developed an asymptomatic temporal lobe reaction after treatment (grade 1). Only one patient showed a grade 3 osteoradionecrosis.
CONCLUSION: Reirradiation with carbon ions is a safe and effective method in patients with relapsed chordoma and chondrosarcoma of the skull base.