Table 3. Univariable and Multivariable Analyses for Overall Survival and Progression-Free Survival.
| Variable | Overall survival | Progression-free survival | ||||||
|---|---|---|---|---|---|---|---|---|
| Univariable | Multivariablea | Univariable | Multivariablea | |||||
| HR (95% CI) | P value | HR (95% CI) | P value | HR (95% CI) | P value | HR (95% CI) | P value | |
| RT modality | ||||||||
| IMRT | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA |
| IMPT | 2.29 (0.36-14.67) | .38 | 9.21 (0.26-328.37) | .22 | 0.86 (0.28-2.68) | .80 | 0.71 (0.19-2.68) | .62 |
| Sex | ||||||||
| Female | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA |
| Male | 1.76 (0.20-15.79) | .61 | 5.93 (0.12-287.48) | .37 | 1.93 (0.63-5.89) | .25 | 5.84 (1.19-28.72) | .03 |
| Age | 1.08 (0.99-1.19) | .10 | 1.05 (0.92-1.20) | .48 | 1.03 (0.98-1.07) | .23 | 1.01 (0.96-1.06) | .72 |
| Smoking history | ||||||||
| No | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA |
| Yes | 8.73 (0.97-78.24) | .05 | 24.43 (0.86-698.07) | .06 | 2.29 (0.91-5.79) | .08 | 2.21 (0.73-6.71) | .16 |
| KPS | 0.92 (0.76-1.10) | .34 | NA | NA | 0.95 (0.86-1.04) | .28 | 0.97 (0.89-1.07) | .60 |
| T stage | ||||||||
| T3-T4 | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA |
| T1-T2 | 1.09 (0.18-6.62) | .92 | 0.33 (0.02-5.32) | .43 | 0.40 (0.15-1.04) | .06 | 0.20 (0.06-0.66) | .008 |
| N stage | ||||||||
| N2-N3 | 1 [Reference] | NA | NA | NA | [Reference] | NA | NA | NA |
| N0-N1 | 0.98 (0.16-5.92) | .99 | NA | NA | 1.08 (0.42-2.80) | .87 | NA | NA |
| AJCC eighth edition stage | ||||||||
| III-IVA | 1 [Reference] | NA | NA | NA | 1 [Reference] | NA | NA | NA |
| I-II | 1.35 (0.22-8.07) | .74 | NA | NA | 0.80 (0.28-2.25) | .67 | NA | NA |
| EBV status | ||||||||
| Negative or unknown | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] | NA |
| Positive | 0.05 (0.01-0.39) | .004 | 0.04 (0.00-2.25) | .12 | 0.14 (0.04-0.51) | .003 | 0.03 (0.00-0.27) | .002 |
| HPV status | ||||||||
| Negative or unknown | 1 [Reference] | NA | NA | NA | 1 [Reference] | NA | NA | NA |
| Positive | 42.95 (3.81-483.75) | .002 | NA | NA | 22.67 (4.35-118.22) | <.001 | NA | NA |
| Concurrent chemotherapy | ||||||||
| No | 1 [Reference] | NA | NA | NA | 1 [Reference] | NA | NA | NA |
| Yes | 0.24 (0.02-2.27) | .21 | NA | NA | 0.41 (0.09-1.83) | .24 | NA | NA |
| Type of concurrent chemo | ||||||||
| Weekly cisplatin | 1 [Reference] | NA | NA | NA | 1 [Reference] | NA | NA | NA |
| High-dose cisplatin | 0.76 (0.08-7.17) | .81 | NA | NA | 1.79 (0.68-4.73) | .24 | NA | NA |
Abbreviations: AJCC, American Joint Committee on Cancer; EBV, Epstein-Barr virus; HR, hazard ratio; HPV, human papillomavirus; IMPT, intensity-modulated proton therapy; IMRT, intensity-modulated radiation therapy; KPS, Karnofsky Performance Score; NA, not applicable; RT, radiotherapy.
a
Multivariable Cox proportional hazard model included a panel of covariates determined a priori, as follows: RT modality, sex, age, smoking history, KPS, EBV status, and disease stage.