Table 3. Multivariable Models: Radiation Therapy Duration, Continuous (N = 509 Patients).
| Variablea | OS (n = 409 deaths) | DFS (n = 445 failures) | LRF (n = 288 failures) | DF (n = 219 failures) | ||||
|---|---|---|---|---|---|---|---|---|
| HR (95% CI) | P valueb | HR (95% CI) | P valueb | HR (95% CI) | P valueb | HR (95% CI) | P valueb | |
| RT duration (continuous; unit increase = 7 d) | 1.08 (0.97-1.22) | .17 | 1.14 (1.01-1.28) | .03 | 1.13 (0.99-1.28) | .07 | 0.87 (0.72-1.03) | .11 |
| NRG Oncology trial | ||||||||
| RTOG 0436 | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA |
| RTOG 8501 | 1.11 (0.85-1.46) | .45 | 1.06 (0.80-1.40) | .71 | 1.21 (0.91-1.62) | .19 | 0.76 (0.52-1.11) | .15 |
| RTOG 9405 | 0.96 (0.73-1.26) | .76 | 1.08 (0.82-1.42) | .59 | 1.33 (0.99-1.78) | .05 | 0.99 (0.68-1.44) | .95 |
| Age (continuous; unit increase = 10 y) | NA | NA | 0.86 (0.77-0.97) | .01 | 0.84 (0.73-0.97) | .02 | ||
| Sex | ||||||||
| Female | 1 [Reference] | NA | 1 [Reference] | NA | NA | NA | NA | NA |
| Male | 1.50 (1.14-1.96) | .004 | 1.31 (1.01-1.70) | .045 | NA | NA | ||
| Race and ethnicityc | ||||||||
| White | NA | NA | NA | NA | NA | NA | NA | NA |
| Otherd | NA | NA | NA | NA | NA | NA | NA | NA |
| Zubrod score | ||||||||
| 0 | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA | NA | NA |
| 1 or 2 | 1.26 (1.04-1.53) | .02 | 1.27 (1.05-1.53) | .01 | 1.30 (1.05-1.62) | .02 | NA | NA |
| Tumor size, cm | ||||||||
| <5 | 1 [Reference] | NA | 1 [Reference] | NA | NA | NA | 1 [Reference] | NA |
| ≥5 | 1.43 (1.15-1.78) | .001 | 1.30 (1.06-1.60) | .01 | NA | 1.36 (1.02-1.81) | .04 | |
| N category | ||||||||
| N0 | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA | NA | NA |
| NX or N1 | 1.36 (1.10-1.69) | .005 | 1.35 (1.10-1.67) | .005 | 1.36 (1.07-1.73) | .01 | NA | |
| Histological subtype | ||||||||
| Adenocarcinoma | NA | NA | 1 [Reference] | NA | NA | NA | 1 [Reference] | NA |
| Squamous | NA | NA | 0.76 (0.61-0.95) | .02 | NA | NA | 0.60 (0.45-0.81) | <.001 |
| ≥80% Of protocol-specified concurrent chemotherapy | ||||||||
| No | NA | NA | 1 [Reference] | NA | NA | NA | NA | NA |
| Yes | NA | NA | 0.68 (0.49-0.95) | .02 | NA | NA | NA | NA |
Abbreviations: DF, distant failure; DFS, disease-free survival; HR, hazard ratio; LRF, local-regional failure; NA, not applicable; OS, overall survival; RT, radiation therapy; RTOG, Radiation Therapy Oncology Group.
RT duration and NRG Oncology trial were included in each model, and other variables were included if P < .05.
P values were from the Cox proportional hazards regression model (OS/DFS) or the Fine-Gray regression model (LRF/DF).
Race and ethnicity were derived from electronic health records.
Other category included Black, Asian, and other in the RTOG 8501 trial; Black or African American, Hispanic, Native American (Aleutian, American Indian, and Eskimo), Native Hawaiian or other Pacific Islander, and Asian (Chinese, Japanese, Korean, and Southeast Asian) in the RTOG 9405 trial; and American Indian or Alaska Native, Asian, Black or African American, more than 1 race, and unknown in the RTOG 0436 trial.