Comparative Overall Survival of Breast Conservation Therapy and Mastectomy in Young Women with Breast Cancer: A Comprehensive Systematic Review and Meta-Analysis
Authors: Ma Xiaowen , Sun Yiming 
Published: August 2024

Young age is recognized as an independent risk factor for local recurrence following breast-conserving therapy (BCT) and whole-breast radiotherapy (WBRT) for patients with breast cancer. The objective of this meta-analysis was to evaluate and compare the 5-year and 10-year overall survival (OS) rates between patients who underwent BCT and those who underwent mastectomy for the treatment of breast cancer. The analysis is meticulously stratified by tumor stage (T1, T1-2, T1-3) and lymph node stage (N0-1, N0-3) to offer a more detailed understanding of the long-term outcomes associated with these two surgical interventions. Materials and Methods: Our review included 8 studies that compared OS between BCT and mastectomy in young patients (< 40 years) diagnosed with stage I-IV breast cancer. The endpoint was OS, and only studies presenting fully adjusted hazard ratios (HRs) were included in the analysis. Summary odds ratios (ORs) were calculated via random effects models. We assessed publication bias and heterogeneity through sensitivity analyses and meta-regression models. Results: Eight population-based studies encompassing a total of 49,285 patients aged 40 years or younger were included: 23,280 patients received BCT, while 26,005 underwent mastectomy. For the 5-year OS, the combined effect size OR was 1.45 [0.89, 2.37], which was not statistically significant. For the 10-year OS, the OR was 1.30 [1.00, 1.69], which was statistically significant and was accompanied by notable heterogeneity (I2 = 95.1%). The overall effect size, which combines both follow-up durations, was OR = 1.33 [1.07, 1.65], indicating a superior OS for patients who underwent BCT compared with mastectomy, albeit with considerable heterogeneity (I2 = 94.2%, p = 0.000). In the forest plot analysis by tumor stage, for T1 tumors, the combined effect size OR was 1.49 [1.23, 1.80], with no significant heterogeneity (I2 = 0.0%). Tumor Stage T1-2: Combined effect size OR = 1.09 [0.84, 1.34], with significant heterogeneity (I2 = 92.7%). Tumor Stage T1-3: Combined effect size OR = 1.73 [0.92, 3.25], with significant heterogeneity (I2 = 95.7%). Forest plot analysis by lymph node stage: The combined effect size OR = 1.19 [0.99, 1.44], with significant heterogeneity (I2 = 91.1%). Lymph node stage N0–3: Combined effect size OR = 1.73 [0.92, 3.25], with significant heterogeneity (I2 = 95.7%). The OS of the T1 subgroup in the BCT group was significantly greater than that in the mastectomy group, whereas the difference in OS among the other subgroups was not statistically significant. Leave-One-Out Sensitivity Analysis: The leave-one-out sensitivity analysis demonstrated that the overall odds ratio remained robust, indicating that the results were not disproportionately swayed by any single study. This analysis ensures the reliability and consistency of the findings across the included studies. Meta-regression analysis: To delve into the potential sources of heterogeneity, a meta-regression analysis was conducted, scrutinizing study-level covariates, including 'Nstage' (node stage) and 'Tstage' (tumor stage). The findings are as follows: 'Nstage': the coefficient is -0.1317, with a p value of 0.844, which implies that there is no significant effect on the magnitude of the outcome. 'Tstage': The coefficient is 0.2857, with a p value of 0.512, also indicating that there is no significant influence on the effect size. Egger’s test for publication bias: The outcomes of Egger’s test for publication bias are as follows: Beta1 = -2.20, standard error (SE) = 1.172, z score = -1.88, p value = 0.0599. The p value hovers near the threshold for significance, hinting at a marginal suggestion of small-study effects. However, it does not provide definitive evidence of publication bias, thus maintaining the integrity of the reported results. Conclusion: The combined effect size from both follow-up periods had an OR of 1.33 [1.07, 1.65], which signifies a noteworthy 33% reduction in risk for BCT compared with mastectomy. These findings suggest that patients who undergo BCT experience superior overall survival, particularly in terms of 10-year overall survival. Subgroup Analysis for T1 Stage: The data suggest that BCT may confer a higher overall survival rate, with an OR of 1.49 [95% CI: 1.23–1.80]. The I2 statistic of 0 indicates the absence of heterogeneity, implying that patients receiving BCT demonstrate a 49% enhancement in overall survival compared with those undergoing mastectomy. Leave-one-out sensitivity analysis indicated that the results are not unduly influenced by any single study, thereby reinforcing the reliability of the findings. Meta-regression analysis indicated that neither the nodal stage (N stage) nor the tumor stage (T stage) significantly affected the effect size. Egger’s test shows that the findings remain robust and free from the influence of potential publication biases.