Table 1. Distribution of Patients by Characteristics and Delivery of Radiotherapy Boost.
| Characteristic | No. (%) of Patientsa | P Valueb | ||
|---|---|---|---|---|
| All (N = 4131) |
No-Boost Group (n = 1470) |
Boost Group (n = 2661) |
||
| Age, y | ||||
| Median | 56.1 | 56.2 | 56.0 | NA |
| SD | 10.9 | 10.7 | 11.0 | |
| Age, y | ||||
| <50 | 1301 (31.5) | 441 (30.0) | 860 (32.3) | .12 |
| ≥50 | 2830 (68.5) | 1029 (70.0) | 1801 (67.7) | |
| DCIS grade | ||||
| I | 694 (16.8) | 250 (17.0) | 444 (16.7) | .48 |
| II or III | 2817 (68.2) | 975 (66.3) | 1842 (69.2) | |
| Unknown | 620 (15.0) | 245 (16.7) | 375 (14.1) | |
| Tumor size, cm | ||||
| ≤1.0 | 1659 (40.2) | 608 (41.4) | 1051 (39.5) | .08 |
| >1.0 | 1680 (40.7) | 665 (45.2) | 1015 (38.1) | |
| ≤2.0 | 2685 (65.0) | 993 (67.6) | 1692 (63.6) | .006 |
| >2.0 | 654 (15.8) | 280 (19.0) | 374 (14.1) | |
| Unknown | 792 (19.2) | 197 (13.4) | 595 (22.4) | |
| NSABP-defined margin status | ||||
| Positive, ink on tumor | 168 (4.1) | 44 (3.0) | 124 (4.7) | <.001 |
| Negative, no ink on tumor | 3611 (87.4) | 1285 (87.4) | 2326 (87.4) | |
| Unknown | 352 (8.5) | 141 (9.6) | 211 (7.9) | |
| SSO/ASTRO/ASCO–defined margin status | ||||
| Positive, <2 mm | 686 (16.6) | 189 (12.9) | 497 (18.7) | <.001 |
| Negative, ≥2 mm | 3026 (73.3) | 1131 (76.9) | 1895 (71.2) | |
| Unknown | 419 (10.1) | 150 (10.2) | 269 (10.1) | |
| Comedo necrosis | ||||
| Absent | 1066 (25.8) | 262 (17.8) | 804 (30.2) | .03 |
| Present | 1301 (31.5) | 270 (18.4) | 1031 (38.7) | |
| Unknown | 1764 (42.7) | 938 (63.8) | 826 (31.0) | |
| Estrogen receptor status | ||||
| Negative | 296 (7.2) | 85 (5.8) | 211 (7.9) | .04 |
| Positive | 1242 (30.1) | 287 (19.5) | 955 (35.9) | |
| Unknown | 2593 (62.8) | 1098 (74.7) | 1495 (56.2) | |
| Tamoxifen citrate use | ||||
| Yes | 1073 (26.0) | 271 (18.4) | 802 (30.1) | <.001 |
| No | 2631 (63.7) | 1111 (75.6) | 1520 (57.1) | |
| Unknown | 427 (10.3) | 88 (6.0) | 339 (12.7) | |
Abbreviations: DCIS, ductal carcinoma in situ; NA, not applicable; NSABP, National Surgical Adjuvant Breast Project; SSO/ASTRO/ASCO, Society of Surgical Oncology/American Society of Radiation Oncology/American Society of Clinical Oncology.
a
Percentages have been rounded and may not total 100.
b
Calculated using the χ2 test.