Table 3.
Univariate analysis of factors associated with in-field failure
| P-value | HR (95% CI) | |
|---|---|---|
| Technique | ||
| SBRT | 1.0 (Ref) | |
| CFRT | <.01 | 6.79 (3.69-12.49) |
| Age at RT (y) | .33 | 1.02 (.98-1.05) |
| Gleason | .63 | |
| 6 | 1.0 (Ref) | |
| 7 | .18 | .50 (.18-1.39) |
| 8 | .28 | .52 (.16-1.70) |
| 9 | .38 | .63 (.22-1.77) |
| 10 | .94 | .95 (.24-3.74) |
| PSA at RT (ng/mL) | .04 | |
| <5 | 1.0 (Ref) | |
| 5-10 | .64 | .80 (.30-2.09) |
| 11-20 | .31 | 1.66 (.62-4.41) |
| >20 | <.01 | 3.16 (1.36-7.32) |
| Castrate-resistant | ||
| No | 1.0 (Ref) | |
| Yes | .74 | .90 (.48-1.68) |
| No. of metastases at RT | ||
| 1-3 | 1.0 (Ref) | |
| ≥4 | <.01 | 2.92 (1.59-5.34) |
| PTV | <.01 | 1.15 (1.08-1.23) |
| BED | <.01 | .18 (.09-.37) |
| Site treated | ||
| Spine | .70 | 1.0 (Ref) |
| Pelvis | .99 | 1.00 (.49-2.04) |
| Extremity | .21 | 1.72 (.74-4.03) |
| Sternum | .69 | .66 (.08-5.17) |
| Rib | .91 | .93 (.28-3.10) |
| Pre-RT systemic therapy | ||
| H + C | .11 | 1.0 (Ref) |
| H | .03 | .49 (.25-.95) |
| C | .99 | 1.00 (.06-17.80) |
| None | .10 | .47 (.19-1.16) |
| Peri-RT systemic therapy | ||
| H + C | .84 | 1.0 (Ref) |
| H | .53 | 1.61 (.36-7.13) |
| C | .91 | 1.15 (.09-14.77) |
| None | .76 | 1.27 (.27-5.84) |
| SBRT dose (Gy) | ||
| ≤18 | 1.0 (Ref) | |
| >18 | .16 | 2.03 (.75-5.46) |
| CFRT dose (Gy) | ||
| ≤10 | 1.0 (Ref) | |
| >10 | .10 | .49 (.21-1.14) |
Abbreviations: BED = biologically effective dose; C = chemotherapy; CFRT = conventionally fractionated radiation therapy; CI = confidence interval; H = hormonal therapy; HR = hazard ratio; PTV = planning target volume; RT = radiation therapy; SBRT = stereotactic body radiation therapy.