Table 1.
Baseline clinical and treatment characteristics.
| Entire Cohort (N = 202) | Matched Cohort (N = 74) | ||||||
|---|---|---|---|---|---|---|---|
| Overall (n = 202) |
Photon SBRT (n = 168) |
Proton SBRT (n = 34) |
p value | Photon SBRT (n = 46) |
Proton SBRT (n = 28) |
p value | |
| Age (years, median, IQR) | 75 (70–79) | 76 (70–79) | 72.5 (68–76) | 0.288 | 75 (70–78) | 73 (68–76) | 0.411 |
| Sex | 0.963 | 0.667 | |||||
| Male | 161 (79.7%) | 134 (79.8%) | 27 (79.4%) | 38 (82.6%) | 22 (78.6%) | ||
| Female | 41 (20.3%) | 34 (20.2%) | 7 (20.6%) | 8 (17.4%) | 6 (21.4%) | ||
| ECOG PS | 0.151 | 0.113 | |||||
| 0–1 | 167 (82.7%) | 136 (81.0%) | 31 (91.2%) | 35 (76.1%) | 26 (92.9%) | ||
| 2- | 35 (17.3%) | 32 (19.0%) | 3 (8.8%) | 11 (23.9%) | 2 (7.1%) | ||
| Pathology | 0.241 | 0.589 | |||||
| Adenocarcinoma | 77 (38.1%) | 66 (39.3%) | 11 (32.4%) | 16 (34.8%) | 10 (35.7%) | ||
| Squamous cell carcinoma | 47 (23.3%) | 38 (22.6%) | 9 (26.5%) | 12 (26.1%) | 8 (28.6%) | ||
| Other | 13 (6.4%) | 13 (7.7%) | 0 (0.0%) | 3 (6.5%) | 0 (0.0%) | ||
| Unproven | 65 (32.2%) | 51 (30.4%) | 14 (41.2%) | 15 (32.6%) | 10 (35.7%) | ||
| Location | 0.176 | 0.479 | |||||
| LLL | 34 (16.8%) | 25 (14.9%) | 9 (26.5%) | 5 (10.9%) | 7 (25.0%) | ||
| LUL | 55 (27.2%) | 48 (28.6%) | 7 (20.6%) | 12 (26.1%) | 6 (21.4%) | ||
| RLL | 41 (20.3%) | 31 (18.5%) | 10 (29.4%) | 11 (23.9%) | 8 (28.6%) | ||
| RML | 7 (3.5%) | 6 (3.6%) | 1 (2.9%) | 3 (6.5%) | 1 (3.6%) | ||
| RUL | 65 (32.2%) | 58 (34.5%) | 7 (20.6%) | 15 (32.6%) | 6 (21.4%) | ||
| Tumor size (mm, mean ± SD) | 21.77 ± 8.52 | 21.62 ± 8.22 | 22.50 ± 10.00 | 0.584 | 22.00 ± 9.60 | 23.32 ± 9.96 | 0.573 |
| T stage | 0.178 | 0.667 | |||||
| T1 | 170 (84.2%) | 144 (85.7%) | 26 (76.5%) | 38 (82.6%) | 22 (78.6%) | ||
| T2 | 32 (15.8%) | 24 (14.3%) | 8 (23.5%) | 8 (17.4%) | 6 (21.4%) | ||
| COPD | 85 (42.1%) | 61 (36.3%) | 24 (70.6%) | <0.001 | 25 (54.3%) | 18 (64.3%) | 0.401 |
| COPD GOLD grade | 0.001 | 0.645 | |||||
| Grade 1 | 22 (10.8%) | 18 (10.7%) | 4 (11.8%) | 6 (13.0%) | 3 (10.7%) | ||
| Grade 2 | 46 (22.7%) | 33 (19.6%) | 13 (38.2%) | 13 (28.3%) | 12 (42.9%) | ||
| Grade 3 | 16 (7.9%) | 9 (5.4%) | 7 (20.6%) | 6 (13.0%) | 3 (10.7%) | ||
| Grade 4 | 1 (0.5%) | 1 (0.6%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | ||
| ILD | 25 (12.4%) | 18 (10.7%) | 7 (20.6%) | 0.149 | 9 (19.6%) | 6 (21.4%) | 0.847 |
| ILD GAP stage | 0.065 | 0.845 | |||||
| Stage 1 | 6 (3.0%) | 6 (3.6%) | 0 (0.0%) | 1 (2.2%) | 0 (0.0%) | ||
| Stage 2 | 17 (8.4%) | 11 (6.5%) | 6 (17.7%) | 7 (15.2%) | 5 (17.9%) | ||
| Stage 3 | 2 (1.0%) | 1 (0.6%) | 1 (2.9%) | 1 (2.2%) | 1 (3.6%) | ||
| Baseline FEV1 (% predicted, mean ± SD) |
77.85 ± 24.74 | 80.19 ± 25.24 | 67.38 ± 19.44 | 0.006 | 71.46 ± 22.71 | 71.25 ± 16.45 | 0.967 |
| Baseline DLCO (% predicted, mean ± SD) |
68.98 ± 22.82 | 72.42 ± 21.87 | 54.52 ± 21.29 | <0.001 | 60.28 ± 17.51 | 57.68 ± 21.40 | 0.571 |
| Operability | <0.001 | 0.001 | |||||
| Operable | 47 (23.3%) | 47 (28.0%) | 0 (0.0%) | 13 (28.3%) | 0 (0.0%) | ||
| Inoperable | 155 (76.7%) | 121 (72.0%) | 34 (100.0%) | 33 (71.7%) | 28 (100.0%) | ||
| SBRT technique | <0.001 | <0.001 | |||||
| 3D-CRT | 130 (64.4%) | 130 (77.4%) | 0 (0.0%) | 29 (63.0%) | 0 (0.0%) | ||
| IMRT | 38 (18.8%) | 38 (22.6%) | 0 (0.0%) | 17 (37.0%) | 0 (0.0%) | ||
| Passive scattering | 4 (2.0%) | 0 (0.0%) | 4 (11.8%) | 0 (0.0%) | 4 (14.3%) | ||
| IMPT | 30 (14.8%) | 0 (0.0%) | 30 (88.2%) | 0 (0.0%) | 24 (85.7%) | ||
| Respiratory motion control | <0.001 | <0.001 | |||||
| Free breathing | 187 (92.6%) | 167 (99.4%) | 20 (58.8%) | 46 (100.0%) | 16 (57.1%) | ||
| Gating | 1 (0.5%) | 0 (0.0%) | 1 (2.9%) | 0 (0.0%) | 1 (3.6%) | ||
| DIBH | 14 (6.9%) | 1 (0.6%) | 13 (38.2%) | 0 (0.0%) | 11 (39.3%) | ||
| Dosimetric parameters | |||||||
| ITV (cc, mean ± SD) | 14.44 ± 18.73 | 13.39 ± 15.07 | 19.44 ± 30.55 | 0.274 | 12.48 ± 13.63 | 19.68 ± 32.38 | 0.189 |
| PTV (cc, mean ± SD) | 38.57 ± 34.74 | 36.00 ± 29.07 | 51.28 ± 53.62 | 0.115 | 34.38 ± 27.77 | 52.61 ± 55.59 | 0.064 |
| Lung V40Gy (%, mean ± SD) | 4.07 ± 2.66 | 4.06 ± 2.72 | 4.12 ± 2.38 | 0.907 | 4.16 ± 3.68 | 4.49 ± 2.40 | 0.674 |
| Lung V20Gy (%, mean ± SD) | 8.74 ± 4.33 | 8.90 ± 4.45 | 7.93 ± 3.61 | 0.233 | 9.28 ± 5.51 | 8.51 ± 3.45 | 0.513 |
| Lung V10Gy (%, mean ± SD) | 13.78 ± 5.52 | 14.28 ± 5.52 | 11.33 ± 4.90 | 0.004 | 14.72 ± 6.09 | 12.07 ± 4.68 | 0.053 |
| Lung V5Gy (%, mean ± SD) | 20.40 ± 7.90 | 21.69 ± 7.61 | 14.04 ± 6.09 | <0.001 | 22.02 ± 7.79 | 14.90 ± 5.86 | <0.001 |
SBRT, stereotactic body radiation therapy; ECOG PS, Eastern Cooperative Oncology Group performance status; LLL, left lower lobe; LUL, left upper lobe; RLL, right lower lobe; RML, right middle lobe; RUL, right upper lobe; COPD, chronic obstructive pulmonary disease; GOLD, Global Initiative for Chronic Obstructive Lung disease; ILD, interstitial lung disease; GAP, gender (G), age (A), and 2 lung physiology variables (P); FEV1, forced expiratory volume in 1 s; DLCO, diffusion capacity of lung for carbon monoxide; 3D-CRT, three dimensional conformal radiation therapy; IMRT, intensity modulated radiation therapy; IMPT, intensity modulated proton therapy; DIBH, deep inspiration breath hold; ITV, internal target volume; PTV, planning target volume; IQR, interquartile range; SD, standard deviation.