Table 3.
Comparison of treatment characteristics
| Treatment characteristics | Total | HVC | LVC | MVA | |
|---|---|---|---|---|---|
| n (%) | n (%) | n (%) | P value | OR (95% CI) | |
| RT duration (wk) | |||||
| ≤7 | 938 (49) | 715 (52) | 223 (40) | <0.001 | REF |
| >7 | 951 (49) | 647 (47) | 304 (54) | <0.001 | 0.31 (0.22‐0.43) |
| Unknown duration | 41 (2) | 6 (0) | 35 (6) | <0.001 | 0.08 (0.02‐0.26) |
| Total RT dose | |||||
| <66/60 Gy | 158 (8) | 75 (6) | 83 (15) | <0.001 | REF |
| ≥66/60 Gy | 1673 (87) | 1289 (94) | 384 (68) | <0.001 | 4.12 (2.42‐7.02) |
| Unknown dose | 99 (5) | 4 (0) | 95 (17) | 0.001 | 0.11 (0.03‐0.39) |
| IMRT | |||||
| IMRT (−) | 490 (25) | 399 (29) | 91 (16) | <0.001 | REF |
| IMRT (+) | 1038 (54) | 880 (64) | 158 (28) | 0.007 | 0.59 (0.4‐0.87) |
| Unknown IMRT status | 402 (21) | 89 (7) | 313 (56) | <0.001 | 0.05 (0.03‐0.08) |
| Chemotherapy | |||||
| Chemo (+) | 748 (39) | 421 (31) | 327 (58) | <0.001 | 2.79 (1.91‐4.07) |
| Chemo (−) | 1182 (61) | 947 (69) | 235 (42) | ||
| DTI (d) | |||||
| ≤45 | 971 (50) | 715 (52) | 256 (46) | 0.447 | — |
| 46+ | 959 (50) | 653 (48) | 306 (54) | ||
| Type of RT | |||||
| Definitive RT | 1228 (64) | 1018 (74) | 210 (37) | <0.001 | 3.3 (2.1‐5.0) |
| Adjuvant RT | 702 (36) | 350 (26) | 352 (63) | ||
95% CI, 95% confidence interval; DTI, diagnosis to treatment initiation; HVC, high‐volume center; HPV, human papillomavirus; IMRT, intensity‐modulated radiotherapy; LVC, low‐volume center; MVA, multivariate analysis; n, number of patients; OR, odds ratio; REF, reference variable; RT, radiation.