Supplementary Material for: Breast Conservation Therapy vs. Mastectomy Survival in Young Breast Cancer Patients: Systematic Review & Meta-Analysis

Background: While young breast cancer patients exhibit lower overall survival (OS) than older groups, it remains unclear whether OS differs between breast-conserving therapy (BCT) and mastectomy specifically in this younger population. Although BCT carries a higher recurrence risk than mastectomy in young patients, OS appears similar across all ages. This meta-analysis therefore directly compares OS and breast cancer specific survival (BCSS) in young patients treated with BCT versus mastectomy.
Methods: Our review included 6 studies that compared OS between BCT and mastectomy in patients aged 40 years or younger diagnosed with stage I-III breast cancer. The endpoint was OS/BCSS, and only studies presenting hazard ratios (HRs) were included in the analysis. Meta-analyses used inverse-variance random effects (REML with Hartung–Knapp CIs); heterogeneity was assessed with Q and I². Leave-one-out, fixed-effect, and DerSimonian–Laird models tested robustness; Egger’s test explored small-study effects. Analyses were performed in RevMan 5.3 and Stata 17, with p<0.05 or 95% CIs excluding 1.00 considered significant.
Results: OS showed no difference between BCT and mastectomy (pooled HR =0.99, 95% CI 0.88–1.10, I²= 54%). BCSS favored BCT with a small but significant reduction in mortality (HR 0.92, 95% CI 0.86–0.98, I²=0%). Subgroup analyses of OS suggested stage dependence: benefit with T1–2 (HR 0.93, 0.87–0.99) and N0–1 (HR 0.93, 0.87–0.99), but no advantage in T1–3 or N2–3 disease (both HR 1.19, 0.99–1.44). Leave-one-out and model checks did not change inference; unadjusted estimates suggested benefit but this attenuated after adjustment.
Conclusion: In women ≤40 years with stage I–III breast cancer, BCT with radiotherapy achieves OS comparable to mastectomy and may yield a modest BCSS benefit, particularly in lower-burden disease (T1-2 or N0–1). Given the observational nature of the evidence and residual heterogeneity, results should be interpreted cautiously and individualized clinical decision-making is recommended; randomized or prospectively adjusted data are still needed.

背景：相较于老年乳腺癌患者，年轻乳腺癌患者的总生存期（Overall Survival, OS）更短，但目前尚不清楚在该年轻人群中，保乳治疗（breast-conserving therapy, BCT）与乳房切除术的总生存期是否存在差异。尽管年轻患者接受保乳治疗后的复发风险高于乳房切除术，但各年龄段患者的总生存期似乎并无显著差异。因此本项荟萃分析直接对比了年轻乳腺癌患者接受保乳治疗与乳房切除术的总生存期及乳腺癌特异性生存期（breast cancer specific survival, BCSS）。
方法：本综述纳入了6项针对40岁及以下、确诊为I~III期乳腺癌的患者，对比保乳治疗与乳房切除术总生存期的研究。分析仅纳入报告了风险比（hazard ratios, HR）的研究，以总生存期/乳腺癌特异性生存期作为终点指标。荟萃分析采用逆方差随机效应模型（采用Hartung-Knapp置信区间的限制最大似然法，Restricted Maximum Likelihood, REML）；异质性通过Q检验与I²值进行评估。通过留一法、固定效应模型及德西蒙尼-莱尔德（DerSimonian–Laird）模型检验结果的稳健性；采用Egger检验探索小样本研究偏倚。分析在RevMan 5.3与Stata 17软件中完成，以P<0.05或95%置信区间不包含1.00作为显著性判定标准。
结果：保乳治疗与乳房切除术的总生存期无显著差异（合并风险比=0.99，95%置信区间0.88~1.10，I²=54%）。乳腺癌特异性生存期方面，保乳治疗组的死亡风险呈小幅且具有统计学意义的降低（HR=0.92，95%置信区间0.86~0.98，I²=0%）。总生存期的亚组分析显示存在分期依赖性：在T1~2期（HR=0.93，0.87~0.99）及N0~1期（HR=0.93，0.87~0.99）患者中，保乳治疗存在获益，但在T1~3期或N2~3期患者中无显著优势（两组HR均为1.19，0.99~1.44）。留一法检验与模型验证未改变推论；未校正的估算值显示存在获益，但校正后该获益有所减弱。
结论：对于≤40岁的I~III期乳腺癌女性患者，联合放疗的保乳治疗的总生存期与乳房切除术相当，且可能带来适度的乳腺癌特异性生存期获益，尤其在肿瘤负荷较低的患者（T1~2期或N0~1期）中更为明显。鉴于现有证据为观察性研究且存在残余异质性，解读结果时应谨慎，并推荐进行个体化临床决策；目前仍需随机对照研究或前瞻性校正数据来进一步验证。