Fig. 4
Local control in dependence of PTVhigh volume and GTV volume receiving less than 66GyRBE separately for both chordoma and chondrosarcoma patients. Apart from tumor histology (chordoma vs chondosarcoma, p = 0.009), both PTVhigh volume (p = 0.045) and GTV (V < 66GyRBE, p = 0.022) were significant independent prognostic factors of local failure in the multivariate analysis. The PTV volume could differentiate between a 5-year local control rate of 57% (PTV > 120 cc) and 78% (PTV < 120 cc) for chordoma (a) and between 73% (PTV > 120 cc) and 97% (PTV < 120 cc) for chondrosarcoma patients (c). The GTV volume receiving less than 66GyRBE could differentiate between a 5-year local control rate of 65% (GTV < 66GyRBE > 3 cc) and 77% (GTV < 66GyRBE < 3 cc) for chordoma (b) and between 86% (GTV < 66GyRBE > 3 cc) and 97% (GTV < 66GyRBE < 3 cc) for chondrosarcoma patients (d)