Table 3.
Dosimetric results with SS-IMRT, CDR-VMAT and VDR-VMAT for organs at risk (OARs).
| Mean range | ||||
|---|---|---|---|---|
| SS-IMRT | CDR-VMAT | VDR-VMAT | p Value | |
| Mandible | ||||
| D1cc | 50.5 Gy (32.2–62.9) | 52.15 (34.6–61.7) | 51.45 (32–63) | IMRT vs. CDR-VMAT p > 0.9999 IMRT vs. VDR-VMAT p = 0.0133 CDR-VMAT vs. VDR-VMAT p = 0.0133 |
| Right parotid | ||||
| Dmean | 23.6 Gy (16.2–27.6) | 22.7 Gy (14.8–25.9) | 21.5 Gy (12.9–25.4) | IMRT vs. CDR-VMAT p < 0.0001 IMRT vs. VDR-VMAT p < 0.0001 CDR-VMAT vs. VDR-VMAT p < 0.001 |
| V30Gy | 39% (30–46) | 34.50% (19–40) | 31.50% (17–37) | IMRT vs. CDR-VMAT p = 0.0057 IMRT vs. VDR-VMAT p < 0.0001 CDR-VMAT vs. VDR-VMAT p = 0.0057 |
| Left parotid | ||||
| Dmean | 23.6 Gy (19.8–26.4) | 22.6 Gy (15.4–24.7) | 21.2 Gy (15.1–24.5) | IMRT vs. CDR-VMAT p < 0.0001 IMRT vs. VDR-VMAT p < 0.0001 CDR-VMAT vs. VDR-VMAT p < 0.001 |
| V30Gy | 40% (27–46) | 33.50% (18–37) | 29.50% (21–36) | IMRT vs. CDR-VMAT p < 0.0001 IMRT vs. VDR-VMAT p < 0.0001 CDR-VMAT vs. VDR-VMAT p = 0.0065 |
| Right submandibular gland | ||||
| Dmean | 44.2 Gy (24.7–62) | 37.6 Gy (24.1–61.3) | 34.5 Gy (24.1–63.1) | IMRT vs. CDR-VMAT p < 0.0001 IMRT vs. VDR-VMAT p < 0.0001 CDR-VMAT vs. VDR-VMAT p = 0.0663 |
| Left submandibular gland | ||||
| Dmean | 44.1 Gy (24.8–61.7) | 36.7 Gy (24.6–67.9) | 32.9 Gy (25.1–50.3) | IMRT vs. CDR-VMAT p = 0.0003 IMRT vs. VDR-VMAT p < 0.0001 CDR-VMAT vs. VDR-VMAT p = 0.0237 |
| Spinal cord | ||||
| D0.1cc | 40.8 Gy (36–55) | 40.1 Gy (38.1–58.1) | 39.5 Gy (37.8– 60.8) | IMRT vs. CDR-VMAT p = 0.5807 IMRT vs. VDR-VMAT p = 0.2735 CDR-VMAT vs. VDR-VMAT p = 0.5807 |
| Brainstem | ||||
| D0.1cc | 35.4 Gy (2.9–43.3) | 30.9 Gy (5–45.1) | 32.2 Gy (5–44.6) | IMRT vs. CDR-VMAT p = 0.8965 IMRT vs. VDR-VMAT p = 0.3708 CDR-VMAT vs. VDR-VMAT p = 0.3088 |
| Larynx | ||||
| Dmean | 46.5 Gy (38.9–59.1) | 43.1 Gy (35.4–51.3) | 39.5 Gy (35.2–46) | IMRT vs. CDR-VMAT p = 0.0045 IMRT vs. VDR-VMAT p < 0.0001 CDR-VMAT vs. VDR-VMAT p = 0.0045 |
| D1cc | 63.5 Gy (53.3–67.7) | 64.2 Gy (53.6–68.2) | 65.7 Gy (52.9–67.5) | IMRT vs. CDR-VMAT p = 0.8965 IMRT vs. VDR-VMAT p = 0.3708 CDR-VMAT vs. VDR-VMAT p = 0.3088 |
| Thyroid | ||||
| V45Gy | 72.5% (20–100) | 55% (6–100) | 38% (7–100) | IMRT vs. CDR-VMAT p = 0.056 IMRT vs. VDR-VMAT p = 0.0005 CDR-VMAT vs. VDR-VMAT p = 0.56 |
| Esophagus | ||||
| D1cc | 40.5 Gy (20.7–61) | 41 Gy (31.3–60.3) | 34.9 Gy (23.9–58.8) | IMRT vs. CDR-VMAT p > 0.9999 IMRT vs. VDR-VMAT p = 0.0133 CDR-VMAT vs. VDR-VMAT p = 0.0133 |
Abbreviations: SS-IMRT: step and shoot intensity-modulated radiotherapy; VDR-VMAT: varying dose rates volumetric-modulated arc therapy; CDR-VMAT: constant dose rate volumetric-modulated arc therapy.