Table 2.
Baseline and dosimetric characteristics grouped according to treatment modality*
| Characteristic | Total (n = 84) | Protons (n = 28) | Photons (n = 56) | P-value |
|---|---|---|---|---|
| Sex, n (%) | 1 | |||
| Male | 47 (56.0) | 16 (57.1) | 31 (55.4) | |
| Female | 37 (44.0) | 12 (42.9) | 25 (44.6) | |
| Age, mean (SD) | 52.6 (12.4) | 55.1 (10.7) | 51.3 (13) | 0.177 |
| BMI, mean (SD) | 28.3 (7.5) | 30 (8.6) | 27.5 (6.8) | 0.139 |
| GTV, mean (SD) | 47.0 (35.3) | 41.7 (28.1) | 49.6 (38.4) | 0.339 |
| CTV, mean (SD) | 231.1 (93.5) | 215.1 (83.0) | 239.2 (98.0) | 0.264 |
| PTV-50, mean (SD) | 331.4 (125.2) | 295.4 (96.1) | 349.4 (134.7) | 0.058 |
| PTV-60, mean (SD) | 91.6 (65.7) | 74.0 (41.0) | 100.4 (73.9) | 0.079 |
| Baseline ALC, mean (SD) | 1.6 (0.6) | 1.5 (0.6) | 1.6 (0.6) | 0.675 |
| Baseline WBC, mean (SD) | 8.5 (3.8) | 8.2 (4.2) | 8.6 (3.6) | 0.663 |
| G3+L, n (%) | 0.024* | |||
| No | 58 (69.0) | 24 (85.7) | 34 (60.7) | |
| Yes | 26 (31.0) | 4 (14.3) | 22 (39.3) | |
| Location, n (%) | 0.916 | |||
| Left | 37 (44.0) | 13 (46.4) | 24 (42.9) | |
| Right | 44 (52.4) | 14 (50.0) | 30 (53.6) | |
| Bilateral | 3 (3.6) | 1 (3.6) | 2 (3.6) | |
| Preradiation steroids | 1 | |||
| No | 43 (51.2) | 14 (50.0) | 29 (51.8) | |
| Yes | 41 (48.8) | 14 (50.0) | 27 (48.2) | |
| Whole brain DVH, mean (SD) | ||||
| Mean, Gy(RBE) | 24.7 (6.8) | 20.1 (5.7) | 27.0 (6.1) | <0.001* |
| V5 (%) | 76.8 (21.1) | 51.9 (13.3) | 89.2 (10.8) | <0.001* |
| V10 (%) | 68 (20.3) | 46.2 (13) | 78.9 (13.3) | <0.001* |
| V15 (%) | 58 (18.1) | 42 (12.7) | 66.1 (14.8) | <0.001* |
| V20 (%) | 48.2 (15.2) | 37.4 (11) | 53.6 (14.2) | <0.001* |
| V25 (%) | 40.9 (12.8) | 35.3 (10.7) | 43.8 (13) | 0.003* |
| V30 (%) | 35.7 (11.1) | 32.5 (9.9) | 37.3 (11.5) | 0.059 |
| V40 (%) | 29 (9.6) | 27.6 (8.9) | 29.7 (9.9) | 0.363 |
| V50 (%) | 22.1 (8.2) | 21.1 (7.2) | 22.6 (8.6) | 0.410 |
Abbreviations: BMI, body mass index; GTV, gross tumor volume; CTV, clinical target volume; PTV-50 and PTV-60, planning target volumes receiving higher than 50 and 60 Gy respectively; ALC: absolute lymphocyte count; WBC, white blood cells count (in units of 100 cells per liter); G3+L, grade 3+ lymphopenia; DVH, dose-volume histogram; V5, V10, . . . , brain volumes receiving greater than 5, 10, . . . Gy(RBE) dose.