Table 2.
Change in organ at risk parameters
| Patient no. | OAR | Dose constraint | Before SSP | Before the initiation of PT | At the initiation of PT | 4 wk after SSP | 6 wk after SSP | 8 wk after SSP | At the end of PT |
|---|---|---|---|---|---|---|---|---|---|
| 1 | SB | Dmax ≤53 Gy (RBE) | 53.0 | 19.8 | 18.5 | 18.3 | 19.9 | 20.3 | 27.3 |
| 2 | LB | Dmax ≤59 Gy (RBE) | 57.1 | 3.3 | 3.9 | 4.6 | 6.0 | 2.9 | 8.9 |
| Rectum | V65 ≤ 17% | 1.7 | 0.2 | 0.6 | 2.0 | 6.0 | 6.2 | 6.0 | |
| V40 ≤ 35% | 29.0 | 7.8 | 8.4 | 9.0 | 13.2 | 13.9 | 12.3 | ||
| 3 | Rectum | V65 ≤ 17% | 9.4 | 8.3 | 2.8 | 8.1 | 3.1 | 13.1 | 12.9 |
| V40 ≤ 35% | 34.1 | 29.8 | 20.4 | 26.6 | 23.5 | 33.0 | 33.6 | ||
| 4 | SB | Dmax ≤53 Gy (RBE) | 51.4 | 23.0 | 22.8 | 29.2 | 39.7 | 19.9 | 48.5 |
| LB | Dmax ≤59 Gy (RBE) | 58.5 | 58.9 | 58.1 | 47.7 | 63.9∗ | 65.6∗ | 66.0∗ | |
| Rectum | V65 ≤ 17% | 2.6 | 2.0 | 1.1 | 0.8 | 4.2 | 12.6 | 11.5 | |
| V40 ≤ 35% | 33.8 | 27.9 | 22.6 | 25.1 | 29.1 | 36.0 | 31.9 | ||
| 5 | Rectum | D2cc < 44 Gy (RBE) | 43.5 | 30.7 | 40.8 | 27.2 | 58.2∗ | − | 60.6∗ |
Abbreviations: Dmax = maximum dose; D2cc = dose for the most exposed 2-mL volume; LB = large bowel; OAR = organ at risk; PT = particle therapy; RBE = relative biological effectiveness; SB = small bowel; SSP = surgical spacer placement; Vx = volume receiving ≥ x Gy (RBE).
∗
Violation of the dose constraints.