Figure 2.

Event-free survival in selected patient subgroups relative to time of fractionated stereotactic radiotherapy (FSRT). (A) When separating FSRT in the upfront (solid line) versus recurrent (dashed line) setting, a minority of patients (n = 5) received FSRT for recurrent disease, and this group encompassed all patients with significant events (3/5). (B) Considering prior history of radiation therapy (protons or EBRT) (n = 6), all patients with reported events (3/6) received radiation therapy before undergoing FSRT. (C) With respect to definitive (solid line) versus preoperative (dashed line) versus postoperative FSRT (dotted line), the majority of patients (n = 14) received FSRT in the postoperative setting, including all patients with significant events (4/14). (D) Based on anatomic site of the tumor, one local recurrence was in a sacral tumor (dashed line), and the second recurrence was in a tumor in the cervical spine (dotted line). For skull base tumors (black), one death but no local recurrences were observed. (E) With regard to histological subtype, the majority of patients were diagnosed with chordoma (n = 16, black line) compared to chondrosarcoma (n = 4, dashed), and all three events occurred in chordoma patients. Significant events were defined as tumor recurrence (local, regional, or distant) or death, and reported p-values are from the log-rank (Mantel–Cox) test.