TABLE 3.
Univariate Cox Regression Analysis of Time to Ipsilateral Breast Tumor Recurrence
| Variable | n | Events (IBTR) | HR | 95% CI | P value |
|---|---|---|---|---|---|
| Time to Initiation of RT | |||||
| ≤ 8 weeks | 806 | 80 | 1.00 | ||
| > 8 weeks–12 weeks | 386 | 25 | 0.70 | 0.45–1.10 | 0.12 |
| > 12 weeks | 131 | 21 | 1.82 | 1.12–2.94 | 0.015 |
| Menopausal Status | |||||
| Pre/peri | 504 | 69 | 1.00 | ||
| Post | 818 | 57 | 0.50 | 0.35–0.71 | < 0.0001 |
| Family History | |||||
| No | 808 | 74 | 1.00 | ||
| Yes | 509 | 51 | 1.13 | 0.79–1.62 | 0.49 |
| Presentation | |||||
| Clinical | 140 | 23 | 1.00 | ||
| Radiologic | 1182 | 103 | 0.63 | 0.40–0.99 | 0.048 |
| Nuclear Grade | |||||
| Low | 106 | 6 | 1.00 | ||
| Intermediate | 570 | 48 | 1.61 | 0.68–3.76 | 0.27 |
| High | 609 | 62 | 1.62 | 0.70–3.74 | 0.26 |
| Necrosis | |||||
| Absent | 295 | 23 | 1.00 | ||
| Present | 1005 | 95 | 1.25 | 0.79–1.97 | 0.34 |
| Number of Excisions | |||||
| ≤ 2 | 1182 | 109 | 1.00 | ||
| ≥ 3 | 141 | 17 | 1.27 | 0.76–2.11 | 0.37 |
| Margins | |||||
| Positive/close | 276 | 28 | 1.00 | ||
| Negative | 995 | 89 | 1.08 | 0.71–0.66 | 0.71 |
| RT dose | |||||
| per 100 cGy increase in RT dose | 1.00* | 1.00–1.00 | 0.55 | ||
| Endocrine Therapy | |||||
| No | 970 | 107 | 1.00 | ||
| Yes | 348 | 19 | 0.43 | 0.26–0.70 | 0.0007 |
| Year of Surgery | |||||
| 1980–2000 | 342 | 62 | 1.00 | ||
| 2001–2010 | 981 | 64 | 0.82 | 0.56–1.21 | 0.31 |
Abbreviations: IBTR, ipsilateral breast tumor recurrence; HR, hazard ratio; CI, confidence interval; RT, radiation therapy
*
HR is expressed per 100cGy increase in RT dose