TABLE 2.
OS and BCSS of BCS Compared With Mx—Meta-analyses of Results of Studies Using Data From Population-based Samples
| BCS vs Mx | K* | Heterogeneity | Pooled effect size | 95% PI # | |||||
|---|---|---|---|---|---|---|---|---|---|
| Q† | P | I 2 ‡ | Tau2 § | HR∥ | 95% CI | P ¶ | |||
| OS** | 13 | 1045.7 | <0.001 | 98.9 | 0.042 | 1.34 | 1.20–1.51 | <0.001 | 0.84–2.15 |
| OS, Mx– RT ** †† ‡‡ | 10 | 137.4 | <0.001 | 93.4 | 0.011 | 1.46 | 1.36–1.57 | <0.001 | 1.13–1.89 |
| OS, Mx+ RT ** †† ‡‡ | 7 | 18.2 | 0.006 | 67.0 | 0.007 | 1.32 | 1.22–1.42 | <0.001 | 1.04–1.67 |
| OS, N0§§ | 10 | 45.6 | <0.001 | 80.3 | 0.004 | 1.39 | 1.33–1.46 | <0.001 | 1.19–1.63 |
| OS, N+∥∥ | 7 | 39.5 | <0.001 | 84.8 | 0.011 | 1.38 | 1.26–1.50 | <0.001 | 1.02–1.85 |
| OS, age <50 | 6 | 42.1 | <0.001 | 88.1 | 0.048 | 1.27 | 1.05–1.54 | 0.015 | 0.65–2.47 |
| OS, age ≥50 | 5 | 68.1 | <0.001 | 94.1 | 0.009 | 1.40 | 1.28–1.54 | <0.001 | 1.00–1.97 |
| OS, North America | 7 | 581.6 | <0.001 | 99.0 | 0.045 | 1.22 | 1.04–1.43 | 0.017 | 0.68–2.19 |
| OS, Europe | 5 | 73.6 | <0.001 | 94.6 | 0.011 | 1.44 | 1.31–1.59 | <0.001 | 0.99–2.09 |
| OS, TNBC | 2 | 0.0 | 0.873 | 00 | 0.0 | 1.48 | 1.37–1.60 | <0.001 | NA |
| OS, Low study quality (score 0–6) | 3 | 219.4 | <0.001 | 96.4 | 0.049 | 1.04 | 0.80–1.35 | 0.773 | 0.04–27.7 |
| OS, High study quality (score 7–10) | 10 | 229.5 | <0.001 | 96.1 | 0.014 | 1.44 | 1.33–1.55 | <0.001 | 1.08–1.92 |
| Breast cancer–specific survival (BCSS) ** | 14 | 81.1 | <0.001 | 84.0 | 0.011 | 1.38 | 1.29–1.47 | <0.001 | 1.09–1.75 |
| BCSS, Mx–RT †† ‡‡ | 9 | 54.0 | <0.001 | 85.2 | 0.027 | 1.43 | 1.27–1.62 | <0.001 | 0.94–2.16 |
| BCSS, Mx + RT†† ‡‡ | 8 | 26.5 | <0.001 | 73.6 | 0.014 | 1.36 | 1.22–1.51 | <0.001 | 0.99–1.87 |
| BCSS, N0§§ | 8 | 15.1 | 0.034 | 53.8 | 0.004 | 1.30 | 1.21–1.39 | <0.001 | 1.09–1.55 |
| BCSS, N+∥∥ | 7 | 10.1 | 0.120 | 40.6 | 0.002 | 1.31 | 1.23–1.39 | <0.001 | 1.13–1.52 |
| BCSS, age <50 | 5 | 9.8 | 0.044 | 59.1 | 0.006 | 1.16 | 1.05–1.28 | 0.002 | 0.75–1.79 |
| BCSS, age ≥50 | 5 | 21.1 | <0.001 | 81.0 | 0.009 | 1.24 | 1.11–1.38 | <0.001 | 0.88–1.75 |
| BCSS, North America | 7 | 8.2 | 0.222 | 27.1 | 0.002 | 1.32 | 1.24–1.40 | <0.001 | 1.15–1.52 |
| BCSS, Europe | 5 | 37.6 | <0.001 | 89.4 | 0.009 | 1.38 | 1.26–1.51 | <0.001 | 0.99–1.93 |
| OS, Low study quality (score 0–6) | 3 | 4.4 | 0.018 | 55.0 | 0.023 | 1.19 | 0.94–1.49 | 0.145 | 0.10–13.33 |
| OS, High study quality (score 7–10) | 11 | 75.3 | <0.001 | 86.7 | 0.011 | 1.40 | 1.31–1.50 | <0.001 | 1.09–1.80 |
*K = number of studies/independent samples in the analysis.
†Q statistic: P values <0.1 taken to suggest heterogeneity.
‡I2 statistic: the proportion of the variance explained by differences in effect sizes beyond random error (heterogeneity).
§Tau2: the between-study variance in effect sizes.
∥Pooled effect size (random-effects model): HR.
¶P values (2-tailed): Statistically significant (P < 0.05) in bold. HR > 1 indicates an association in the hypothesized direction, that is, BCS is associated with improved survival compared with mastectomy.
#95% PI, that is, the interval in which 95% of future observations from the same family of studies will fall, given the observed data, calculated for heterogeneous ESs (I2 > 0).
**For pooled estimates from K ≥ 10, the possibility of publication bias was explored with funnel plots and Egger’s test. No indications of publication bias were found (Egger’s test > 0.05).
††Mx ± RT = Mastectomy with and without radiotherapy.
‡‡Number of studies/independent samples for Mx ± RT do not add up with overall OS and BCSS analyses due to omission of overlapping samples to ensure independence.
§§N0 = lymph node-negative breast cancer.
∥∥N+ = lymph node-positive breast cancer.
95% PI, 95% prediction interval; BCS, breast-conserving surgery; HR, hazard ratio; Mx, mastectomy; OS, overall survival.