[Carbon ion irradiation of skull base tumors at GSI. First clinical results and future perspectives].

BACKGROUND: Radiobiological and physical examinations suggest clinical advantages of heavy ion irradiation. We report the results of 23 women and 22 men (median age 48 years) with skull base tumors irradiated with carbon ion beams at the Gesellschaft für Schwerionenforschung (GSI), Darmstadt, from December 1997 until September 1999.

PATIENTS AND METHODS: The study included patients with chordomas (17), chondrosarcomas (10) and other skull base tumors (Table 1). It is the first time that the intensity-controlled rasterscan-technique and the application of positron-emission tomography (PET) for quality assurance was used. All patients had computed tomography for three-dimensional-treatment planning (Figure 1). Patients with chordomas and chondrosarcomas underwent fractionated carbon ion irradiation in 20 consecutive days (median total dose 60 GyE). Other histologies were treated with a carbon ion boost of 15 to 18 GyE delivered to the macroscopic tumor after fractionated stereotactic radiotherapy (median total dose 63 GyE).

RESULTS: Mean follow-up was 9 months. Irradiation was well tolerated by all patients. Partial tumor remission was seen in 7 patients (15.5%) (Figure 2). One-year local control rate was 94%. One patient (2.2%) deceased. No severe toxicity and no local recurrence within the treated volume were observed.

CONCLUSION: Clinical effectiveness and technical feasibility of this therapy modality could clearly be demonstrated in our study. To evaluate the clinical relevance of the different beam modalities studies with larger patient numbers are necessary. To continue our project a new heavy ion accelerator exclusively for clinical use is planned to be constructed in Heidelberg.