Table 1 –
Study sample characteristics (n = 25,723).
| Characteristics | Group 1: radiation (n = 20,328) | Group 2: no radiation (n = 5395) | P value* |
|---|---|---|---|
| Age group, y | <0.0001 | ||
| 70–74 | 7887 (38.80) | 1109 (20.56) | |
| 75–79 | 7406 (36.43) | 1648 (30.55) | |
| 80–84 | 3908 (19.22) | 1564 (28.99) | |
| 85+ | 1127 (5.54) | 1074 (19.91) | |
| Race | 0.0612 | ||
| White | 18,399 (90.51) | 4928 (91.34) | |
| Other | 1929 (9.49) | 467 (8.66) | |
| Marital status | <0.0001 | ||
| Single/Other | 10,463 (51.47) | 3271 (60.63) | |
| Married | 9865 (48.53) | 2124 (39.37) | |
| Tumor size, cm | <0.0001 | ||
| 0–1 | 7920 (38.96) | 2400 (44.49) | |
| 1–2 | 12,408 (61.04) | 2995 (55.51) | |
| Lymph node status | 0.3926 | ||
| Negative | 120,316 (99.94) | 5390 (99.91) | |
| Unknown | 12 (0.06) | 5 (0.09) | |
| Geographic region | <0.0001 | ||
| Midwest | 2557 (12.58) | 543 (10.06) | |
| Northeast | 4824 (23.73) | 1077 (19.96) | |
| South | 4079 (20.07) | 1120 (20.76) | |
| West | 8868 (43.62) | 2655 (49.21) | |
| Socioeconomic status | 0.0207 | ||
| 1st quartile | 5690 (27.99) | 1517 (28.12) | |
| 2nd quartile | 4970 (24.45) | 1215 (22.52) | |
| 3rd quartile | 4831 (23.77) | 1316 (24.39) | |
| 4th quartile | 4837 (23.79) | 1347 (24.97) | |
| Year of diagnosis | <0.0001 | ||
| 2004 | 1699 (8.36) | 282 (5.23) | |
| 2005 | 1607 (7.91) | 361 (6.69) | |
| 2006 | 1674 (8.23) | 368 (6.82) | |
| 2007 | 1697 (8.35) | 359 (6.65) | |
| 2008 | 1687 (8.30) | 408 (7.56) | |
| 2009 | 1764 (8.68) | 387 (7.17) | |
| 2010 | 1729 (8.51) | 421 (7.80) | |
| 2011 | 1806 (8.88) | 484 (8.97) | |
| 2012 | 1651 (8.12) | 494 (9.16) | |
| 2013 | 1688 (8.30) | 525 (9.73) | |
| 2014 | 1651 (8.12) | 627 (11.62) | |
| 2015 | 1675 (8.24) | 679 (12.59) | |
| CCI | <0.001 | ||
| 0 | 12,757 (62.76) | 2969 (55.03) | |
| 1 | 4747 (23.35) | 1387 (25.71) | |
| 2+ | 2824 (13.89) | 1039 (19.26) | |
*
P value is for a χ2 test between each covariate and group.