Table 1.
Overall cohort characteristics and comparison of proton therapy and IMRT cohorts
| Variable | Overall (N = 633) | Proton (n = 508) | IMRT (n = 125) | P-valuea |
|---|---|---|---|---|
| Demographic | ||||
| Age (years) | ||||
| Mean ± SD | 66.3 ± 7.2 | 65.8 ± 7.0 | 68.0 ± 7.6 | .004 |
| Race | ||||
| White (%) | 444 (70.1) | 380 (74.8) | 64 (51.2) | <.001 |
| Black (%) | 132 (20.9) | 85 (16.7) | 47 (37.6) | |
| Other (%) | 57 (9.0) | 43 (8.5) | 14 (11.2) | |
| Povertyb | ||||
| Mean ± SD | 10.0 ± 11.8 | 9.2 ± 10.9 | 13.4 ± 14.5 | <.001 |
| Distance (miles) | ||||
| Mean ± SD | 76.7 ± 226.4 | 90.2 ± 250.6 | 21.7 ± 24.7 | .002 |
| Primary Insurance | ||||
| Private (%) | 286 (45.3) | 233 (46.0) | 53 (42.4) | .474 |
| Non-private (%) | 346 (54.7) | 274 (54.0) | 72 (57.6) | |
| Clinical | ||||
| PSA | ||||
| Mean ± SD | 6.4 ± 6.1 | 6.0 ± 3.0 | 8.1 ± 12.1 | <.001 |
| Gleason Score | ||||
| 3 + 3 = 6 (%) | 264 (41.7) | 218 (42.9) | 46 (36.8) | .275 |
| 3 + 4 = 7 (%) | 264 (41.7) | 211 (41.5) | 53 (42.4) | |
| 4 + 3 = 7 (%) | 105 (16.6) | 79 (15.6) | 26 (20.8) | |
| Clinical Tumor (T) Stage | ||||
| Missing (%) | 4 (0.6) | 4 (0.8) | 0 (0.0) | .432 |
| T1 (%) | 529 (83.6) | 421 (82.9) | 108 (86.4) | |
| T2 (%) | 100 (15.8) | 83 (16.3) | 17 (13.6) | |
| Risk Group | ||||
| Low (%) | 250 (39.5) | 206 (40.6) | 44 (35.2) | .273 |
| Intermediate (%) | 383 (60.5) | 302 (59.4) | 81 (64.8) | |
| Prostate Volume (cc) | ||||
| Mean ± SD | 42.0 ± 22.4 | 40.6 ± 19.0 | 47.9 ± 32.9 | .006 |
| IPSS | ||||
| Mean ± SD | 7.8 ± 6.2 | 7.8 ± 6.2 | 7.7 ± 6.4 | .969 |
| IPSS QoL | ||||
| Mean ± SD | 1.7 ± 1.4 | 1.6 ± 1.4 | 1.9 ± 1.3 | .276 |
| IIEF | ||||
| Mean ± SD | 17.9 ± 6.8 | 18.5 ± 6.5 | 15.7 ± 7.5 | .002 |
| Bowel Botherc | ||||
| Mean ± SD | 92.1 ± 9.4 | 91.9 ± 9.8 | 92.8 ± 7.1 | .597 |
| Bowel Functionc | ||||
| Mean ± SD | 93.6 ± 11.5 | 93.3 ± 12.1 | 95.2 ± 8.4 | .367 |
| Treatment | ||||
| Androgen Deprivation | ||||
| (%) | 130 (20.5) | 94 (18.5) | 36 (28.8) | .011 |
| Dose (Gy RBE) | ||||
| 70 (%) | 183 (28.9) | 170 (33.5) | 13 (10.4) | <.001 |
| 79.2 (%) | 450 (71.1) | 338 (66.5) | 112 (89.6) | |
| Physician | ||||
| 1 (%) | 146 (23.1) | 108 (21.3) | 38 (30.4) | .018 |
| 2 (%) | 122 (19.3) | 97 (19.1) | 25 (20.0) | |
| 3 (%) | 142 (22.4) | 127 (25.0) | 15 (12.0) | |
| 4 (%) | 177 (28.0) | 138 (27.2) | 39 (31.2) | |
| Other (%) | 46 (7.3) | 38 (7.5) | 8 (6.4) | |
| Treatment Year | ||||
| 2010 (%) | 94 (14.8) | 61 (12.0) | 33 (26.4) | <.001 |
| 2011 (%) | 141 (22.3) | 126 (24.8) | 15 (12.0) | |
| 2012 (%) | 125 (19.7) | 115 (22.6) | 10 (8.0) | |
| 2013 (%) | 118 (18.6) | 89 (17.5) | 29 (23.2) | |
| 2014 (%) | 89 (14.1) | 76 (15.0) | 13 (10.4) | |
| 2015 (%) | 66 (10.4) | 41 (8.1) | 25 (20.0) | |
IMRT, intensity modulated radiation therapy; IIEF, International Index of Erectile Function; IPSS, International Prostate Symptom Score; PSA, prostate-specific antigen; QoL, quality of life; RBE, relative biological effectiveness; SD, standard deviation.
a
P-value is from the t test for continuous variables and the χ2 test for categorical variables.
b
Geocoded census tract for the percentage of those residing below the federal poverty line.
c
Bowel bother and function scores are from the Expanded Prostate Cancer Index Composite.