Table 1.
Baseline Characteristics of Original and Weighted Cohorts.
| Variables | All (n = 173) | 45 Gy/30 Fractions BID (n = 110) | 40 Gy/15 Fractions (n = 63) | p-Value *** | Pre-Weighting SMD * | Post-Weighting SMD * |
|---|---|---|---|---|---|---|
| Age (mean, SD) | 66.7 (9.7) | 65.7 (8.9) | 68.5 (10.8) | 0.12 | 0.33 | 0.001 |
| Gender (n, %) | 0.59 | 0.04 | 0 | |||
| Male | 98 (57) | 64 (58) | 34 (54) | |||
| Female | 75 (43) | 46 (42) | 29 (46) | |||
| Surgery (n, %) | 0.03 | 0.09 | 0 | |||
| Yes | 12 (7) | 4 (4) | 8 (13) | |||
| No | 161 (93) | 106 (96) | 55 (87) | |||
| ECOG (n, %) | 0.80 | 0.65 | 0 | |||
| 0 | 47 (27) | 29 (26) | 18 (29) | |||
| 1 | 84 (49) | 56 (51) | 28 (44) | |||
| 2 | 33 (19) | 19 (17) | 14 (22) | |||
| 3 | 9 (5) | 6 (6) | 3 (5) | |||
| Stage (n, %) | 0.13 | 0.13 | 0 | |||
| IA | 16 (9) | 5 (4) | 11 (17) | |||
| IB | 5 (3) | 1 (2) | 3 (5) | |||
| IIA | 5 (3) | 3 (3) | 2 (3) | |||
| IIB | 11 (6) | 8 (8) | 3 (5) | |||
| IIIA | 51 (29) | 35 (32) | 16 (25) | |||
| IIIB | 58 (34) | 39 (36) | 19 (30) | |||
| IIIC | 27 (16) | 18 (16) | 9 (14) | |||
| Year of Treatment (median, IQR) | 2013 (2009–2016) | 2014 (2010–2016) | 2011 (2008–2016) | 0.02 | 0.17 | 0 |
| Smoking Status (n, %) | 1.0 | 0.005 | 0 | |||
| Never/Not Documented | 6 (3) | 4 (4) | 2 (3) | |||
| Former | 112 (65) | 71 (64) | 41 (65) | |||
| Current | 55 (32) | 35 (32) | 20 (31) | |||
| Pack Years (mean, SD) | 43.34 (21.52) | 41.91 (21.66) | 45.84 (21.22) | 0.16 | 0.18 | 0 |
| Paraneoplastic Syndrome (n, %) | 0.89 | 0.007 | 0.003 | |||
| Yes | 20 (12) | 13 (12) | 7 (11) | |||
| No | 153 (88) | 97 (88) | 56 (89) | |||
| mCCI Score (n, %) | 0.79 | 0.05 | 0 | |||
| 0 | 114 (66) | 74 (67) | 40 (64) | |||
| 1 | 47 (27) | 28 (25) | 19 (30) | |||
| 2+ | 12 (7) | 8 (7) | 4 (6) | |||
| PET-CT scan (n, %) | <0.01 | 0.25 | 0 | |||
| Yes | 96 (55) | 71 (65) | 25 (40) | |||
| No | 77 (45) | 39 (35) | 38 (60) | |||
| Pre-treatment Brain Imaging (n, %) | 0.35 | 0.06 | 0 | |||
| None | 1 (1) | 0 (0) | 1 (1) | |||
| CT | 45 (26) | 27 (25) | 18 (29) | |||
| MRI | 127 (73) | 83 (75) | 44 (70) | |||
| 4D-CT Utilization (n, %) | 0.48 | 0.01 | 0 | |||
| Yes | 158 (91) | 101 (92) | 57 (90) | |||
| No | 15 (9) | 9 (8) | 6 (10) | |||
| Treatment Technique (n, %) | 0.01 | 0.20 | 0 | |||
| 3D-CRT | 22 (13) | 9 (8) | 13 (21) | |||
| IMRT | 135 (76) | 92 (84) | 40 (63) | |||
| VMAT | 19 (11) | 9 (8) | 10 (16) | |||
| IGRT Utilization (n, %) | <0.01 | 0.24 | 0 | |||
| Non-IGRT | 39 (23) | 16 (15) | 23 (37) | |||
| CBCT | 134 (77) | 94 (85) | 40 (63) | |||
| ** PCI Utilization (n, %) | 0.29 | |||||
| Yes | 121 (70) | 80 (73) | 41 (65) | |||
| No | 52 (30) | 30 (27) | 22 (35) | |||
| Chemotherapy (n, %) | <0.01 | 0.15 | 0 | |||
| Concurrent | 154 (89) | 104 (95) | 50 (79) | |||
| Sequential | 19 (11) | 6 (5) | 13 (21) | |||
| Cycles of Chemotherapy (n, %) | 0.12 | 0.36 | 0.03 | |||
| 0 | 1 (1) | 0 (0) | 1 (2) | |||
| 1 | 3 (2) | 1 (1) | 2 (3) | |||
| 2 | 9 (5) | 6 (5) | 3 (5) | |||
| 3 | 9 (5) | 3 (3) | 6 (10) | |||
| 4 | 63 (36) | 37 (34) | 26 (41) | |||
| 5 | 18 (10) | 13 (12) | 5 (8) | |||
| 6 | 70 (40) | 50 (45) | 20 (32) | |||
| Chemotherapy to RT Time in Days (mean, SD) | 56.05 (36.80) | 50.71 (32.37) | 65.38 (42.14) | 0.05 | 0.31 | 0 |
Abbreviations: BID—twice daily, ECOG—Eastern Cooperative Oncology Group, mCCI—modified Charlson Comorbidity Index, IQR—interquartile range, PET—positron emission tomography, 4D-CT—4-dimensional computed tomography, VMAT—volumetric modulated arc therapy, IMRT—intensity modulated radiotherapy, 3D-CRT—3-dimensional conformal radiotherapy, IGRT—image guided radiotherapy, KV-KV—orthogonal kV films, CBCT—cone beam CT, PCI—prophylactic cranial irradiation, SMD—standardized mean difference; * Note that for non-continuous covariates, the displayed SMD is the largest applied across all categorical levels. ** PCI was not included in covariate balancing since its utilization is determined after the treatment variable, thoracic radiotherapy, has been administered; *** p-values determined from Mann–Whitney U test and Fisher’s exact test for continuous and categorical variables respectively.