Table 2.
Risk of subsequent mastectomy at 5- and 10-years with and without radiation therapy
| No RT Group (%) | RT Group (%) | P-value* | |||
|---|---|---|---|---|---|
| Clinical Variable | 5-year (95% CI) |
10-year (95% CI) |
5-year (95% CI) |
10-year (95% CI) |
|
| Entire Cohort | 3.5 (2.5–5.1) | 6.3 (4.6–8.6) | 0.94 (0.73–1.2) | 3.2 (2.6–3.9) | <0.001 |
| Demographic Characteristics | |||||
| Age (years) | |||||
| 70 – 74 | 4.3 (2.5–7.1) | 7.6 (5.0–11.5) | 1.2 (0.85–1.6) | 3.8 (3.0–4.7) | <0.001 |
| 75 – 79 | 3.1 (1.9–5.0) | 5.4 (3.4–8.6) | 0.68 (0.43–1.1) | 2.5 (1.7–3.5) | <0.001 |
| Race | |||||
| White | 3.2 (2.1–4.7) | 5.6 (4.0–7.9) | 0.95 (0.73–1.2) | 3.1 (2.6–3.8) | <0.001 |
| Hispanic | 9.1 (1.3–49.2) | 9.1 (1.3–49.2) | 0.0 (0.0–0.0) | 4.2 (1.1–16.1) | 0.206 |
| Black | 6.5 (2.5–16.3) | 14.8 (7.0–29.5) | 1.8 (0.70–4.8) | 6.8 (3.4–13.1) | 0.030 |
| Asian | 8.3 (1.2–46.1) | 8.3 (1.2–46.1) | 0.0 (0.0–0.0) | 0.0 (0.0–0.0) | 0.001 |
| Other/unknown | 0.0 (0.0–0.0) | 0.0 (0.0–0.0) | 0.0 (0.0–0.0) | 1.9 (0.26–12.4) | 0.739 |
| Comorbidity | |||||
| 0 | 4.1 (2.5–6.6) | 7.1 (4.7–10.6) | 0.99 (0.72–1.3) | 2.9 (2.3–3.7) | <0.001 |
| 1 | 2.6 (1.2–5.7) | 4.5 (2.1–9.3) | 0.93 (0.54–1.6) | 3.4 (2.2–5.2) | 0.077 |
| 2 or more | 4.5 (2.0–9.7) | 10.2 (5.4–19.1) | 0.71 (0.29–1.7) | 4.9 (2.7–8.8) | 0.001 |
| Unknown | 1.4 (0.20–9.5) | 1.4 (0.20–9.5) | 0.84 (0.12–5.8) | 4.6 (1.7–12.2) | 0.432 |
| Tumor Characteristics | |||||
| Tumor histology | |||||
| Invasive ductal | 3.8 (2.4–5.8) | 6.8 (4.7–9.8) | 0.98 (0.73–1.3) | 3.5 (2.8–4.3) | <0.001 |
| Invasive lobular | 4.5 (1.5–13.3) | 4.5 (1.5–13.3) | 0.40 (0.10–1.6) | 1.0 (0.38–2.8) | 0.005 |
| Other/unknown | 2.7 (1.2–5.9) | 5.4 (2.9–10.0) | 1.0 (0.57–1.8) | 3.0 (1.9–4.6) | 0.021 |
| Tumor Grade | |||||
| Low | 2.4 (1.1–4.9) | 5.4 (2.9–9.7) | 0.76 (0.46–1.3) | 2.9 (1.9–4.2) | 0.010 |
| Intermediate | 3.2 (1.7–5.8) | 5.5 (3.3–9.1) | 0.85 (0.56–1.3) | 3.3 (2.5–4.3) | 0.001 |
| High | 8.8 (4.3–17.6) | 11.2 (5.6–21.7) | 1.8 (1.1–2.9) | 4.5 (3.0–6.6) | 0.002 |
| Unknown | 4.0 (1.7–9.3) | 7.6 (3.8–14.9) | 0.80 (0.33–1.9) | 2.3 (1.2–4.4) | 0.001 |
| Treatment characteristics | |||||
| Axillary lymph node status | |||||
| Clinical node negative | 4.1 (2.7–6.2) | 6.8 (4.7–9.8) | 0.62 (0.31–1.2) | 1.9 (1.1–3.0) | <0.001 |
| Pathologic node negative | 2.6 (1.3–5.1) | 5.6 (3.2–9.7) | 1.0 (0.78–1.3) | 3.6 (2.9–4.5) | 0.017 |
| Receipt of chemotherapy | |||||
| No | 3.6 (2.5–5.2) | 6.4 (4.7–8.7) | 0.96 (0.74–1.2) | 3.2 (2.6–3.9) | <0.001 |
| Yes | 0.0 (0.0–0.0) | 0.0 (0.0–0.0) | 0.60 (0.15–2.4) | 3.5 (1.6–7.6) | 0.566 |
Abbreviations: RT (Radiation therapy), CI (Confidence interval)
*
P-value from log-rank test comparing risk of mastectomy for RT vs no RT groups through 10 years follow-up.
†
10-year estimates could not be provided for this group with maximum follow-up of 7 years