Table 2.
Fractionated stereotactic radiotherapy (FSRT) dosimetry details and toxicity for chordoma and chondrosarcoma patients.
| Parameter | All locations (n = 20) | Skull base (n = 12) | Sacrum (n = 5) | Spine (n = 3) |
|---|---|---|---|---|
| FSRT dose (Gy) | 37.5 (25–40) | 35 (25–40) | 40 (30–40) | 40 (25–40) |
| Prescription isodose | 62.5% (52–93%) | 62% (52–92%) | 69% (63–93%) | 62% (61–62%) |
| Dmax (Gy) | 53.90 (38–68) | 53.90 (38–68) | 46.88 (38–63) | 64.52 (40–66) |
| Gross tumor volume (cm3) | 18.95 (0.65–414) | 10.29 (0.65–22) | 90.34 (75–414) | 128.00 (49–276) |
| Planning target volume (cm3) | 36.50 (7.07–424) | 14.75 (7.1–37) | 265.00 (102–424) | 226.23 (114–314) |
| Dmax optic nerve (Gy) | – | 16.79 (1.1–28) | – | – |
| Dmax chiasm (Gy) | – | 15.98 (0.93–27) | – | – |
| Dmax brainstem (Gy) | – | 28.84 (23–33) | – | – |
| Dmax spinal cord (Gy) | – | – | – | 29.43 (21–32) |
| Acute toxicity | 9 (45%) | 5 (42%) | 2 (40%) | 2 (67%) |
| Cranial neuropathy | 3 (15%) | 3 (24%) | 0 | 0 |
| Peripheral neuropathy | 2 (10%) | 0 | 1 (20%) | 1 (33%) |
| Mucositis | 2 (10%) | 0 | 0 | 2 (67%) |
| Other | – | Hearing loss (2) | Wound infection (1) | – |
| Headache (2) | ||||
| Late toxicity | 2 (10%) | 2 (17%) | 0 | 0 |
All patients received five fractions. Acute toxicity was defined as occurring within 3 months of FSRT treatment completion, and many patients reported multiple toxicities. Both cases of late toxicity involved radiation necrosis, and grade 5 radiation vasculopathy was reported in one of these patients with a prior history of proton therapy. Note both patients who experienced late toxicity also experienced acute toxicity. Data are represented as median (range) or absolute number of patients (%).