Table 1. Patient Characteristics for High vs Low Average Cumulative Facility Volume.
| Covariate and level information | Patients, No. (%) | P valuea | ||
|---|---|---|---|---|
| Total (N = 25 219) | Average cumulative facility volume | |||
| Low (n = 18 781 [74.5%]) | High (n = 6438 [25.5%]) | |||
| Facility type | ||||
| Nonacademic/research program | 17 522 (69.5) | 14 249 (75.9) | 3273 (50.8) | <.001 |
| Academic/research program | 7697 (30.5) | 4532 (24.1) | 3165 (49.2) | |
| Age, y | ||||
| <70 | 12 578 (49.9) | 9289 (49.5) | 3289 (51.1) | .02 |
| ≥70 | 12 641 (50.1) | 9492 (50.5) | 3149 (48.9) | |
| Race | ||||
| Black | 4311 (17.1) | 3198 (17.0) | 1113 (17.3) | <.001 |
| White | 19 859 (78.7) | 14 892 (79.3) | 4967 (77.2) | |
| Otherb | 1049 (4.2) | 691 (3.7) | 358 (5.6) | |
| Zip code median income, $ | ||||
| ≥68 000 | 7876 (31.2) | 5292 (28.2) | 2584 (40.1) | <.001 |
| 48 000-67 999 | 6641 (26.3) | 5137 (27.4) | 1504 (23.4) | |
| 38 000-47 999 | 5916 (23.5) | 4648 (24.7) | 1268 (19.7) | |
| <38 000 | 4693 (18.6) | 3634 (19.3) | 1059 (16.4) | |
| Zip code without high school degree, % | ||||
| <7.0 | 6046 (24.0) | 4245 (22.7) | 1801 (28.1) | <.001 |
| 7.0-12.9 | 8361 (33.2) | 6208 (33.1) | 2153 (33.4) | |
| 13.0-20.9 | 6569 (26.0) | 5026 (26.8) | 1543 (24.0) | |
| ≥21 | 4171 (16.5) | 3250 (17.43 | 921 (14.3) | |
| Insurance type | ||||
| Medicaid/uninsured | 2545 (10.1) | 2060 (11.0) | 485 (7.5) | <.001 |
| Private | 6756 (26.8) | 4679 (24.9) | 2077 (32.3) | |
| Medicare | 15 918 (63.1) | 12 042 (64.1) | 3876 (60.2) | |
| Charlson-Deyo Comorbidity Index score | ||||
| 0 | 20 907 (82.9) | 15 375 (81.9) | 5532 (85.9) | <.001 |
| 1 | 3322 (13.2) | 2628 (14.0) | 694 (10.8) | |
| ≥2 | 990 (3.9) | 778 (4.1) | 212 (3.3) | |
| AJCC Clinical T category | ||||
| T1 | 9351 (37.1) | 7132 (38.0) | 2219 (34.5) | <.001 |
| T2 | 9052 (35.9) | 6800 (36.2) | 2252 (35.0) | |
| T3-4 | 6816 (27.0) | 4849 (25.8) | 1967 (30.6) | |
| PSA, ng/mL | ||||
| <10 | 10 225 (40.5) | 7534 (40.1) | 2691 (41.8) | .03 |
| 10-20 | 5413 (21.5) | 4027 (21.4) | 1386 (21.5) | |
| >20 | 9581 (38.0) | 7220 (38.4) | 2361 (36.7) | |
| Gleason score | ||||
| 6-7 | 1571 (6.2) | 1085 (5.8) | 486 (7.5) | <.001 |
| 8-10 | 23 483 (93.1) | 17 571 (94.2) | 5912 (91.8 | |
| Total radiation dose, Gy | ||||
| <74 | 4995 (19.8) | 3352 (17.8) | 1643 (25.5) | <.001 |
| ≥74 | 20 224 (80.2) | 15 429 (82.2) | 4795 (74.5) | |
| Chemotherapy | ||||
| No | 25 011 (99.2) | 18 643 (99.3) | 6368 (98.9) | .007 |
| Yes | 208 (0.8) | 138 (0.7) | 70 (1.1) | |
| Brachytherapy boost | ||||
| No | 22 707 (90.0) | 17 379 (92.5) | 5328 (82.8) | <.001 |
| Yes | 2512 (10.0) | 1402 (7.5) | 1110 (17.2) | |
| Radiation treatment volume | ||||
| Unknown | 2741 (10.9) | 2261 (12) | 480 (7.5) | <.001 |
| Prostate with whole pelvis | 11 675 (46.3) | 8508 (45.3) | 3167 (49.2) | |
| Prostate only | 10 803 (42.8) | 8012 (42.7) | 2791 (43.4) | |
| Radiation modality | ||||
| 3DCRT | 931 (3.7) | 668 (3.6) | 263 (4.1) | <.001 |
| IMRT | 16 915 (67.1) | 12 829 (68.3) | 4086 (63.5) | |
| Proton | 160 (0.6) | 51 (0.3) | 109 (1.7) | |
| Unknown | 7213 (28.6) | 5233 (27.9) | 1980 (30.8) | |
| Year of diagnosis | ||||
| ≥2004 to ≤2009 | 12 125 (48.1) | 9211 (49.0) | 2914 (45.3) | <.001 |
| >2009 to ≤2011 | 10 353 (41.1) | 7309 (38.9) | 3044 (47.3) | |
| >2011 to ≤2014 | 8758 (34.7) | 6688 (35.6) | 2070 (32.2) | |
| >2014 to ≤2016 | 3555 (14.1) | 2892 (15.4) | 663 (10.3) | |
| Distance to facility (miles) | ||||
| ≥0 to ≤4.1 | 6302 (25.1) | 4983 (26.5) | 1319 (20.5) | <.001 |
| >4.1 to ≤9.1 | 6372 (25.3) | 4704 (25.0) | 1668 (25.9) | |
| >9.1 to ≤19.8 | 6197 (24.6) | 4545 (24.2) | 1652 (25.7) | |
| >19.8 to ≤2914.7 | 6285 (24.9) | 4504 (24.0) | 1781 (27.7) | |
Abbreviations: AJCC, American Joint Committee on Cancer; 3DCRT, 3-dimensional conformal radiotherapy; IMRT, intensity-modulated radiation therapy; PSA, prostate-specific antigen.
SI conversion: To convert PSA to μg/L, multiply by 1.0.
a
The parametric P value was calculated by the χ2 test.
b
Other includes Native American, Asian, Pacific Islander, or unknown race; groups were collapsed because of small sample sizes.