The Diminishing Impact of Margin Definitions and Width on Local Recurrence Rates following Breast-Conserving Therapy for Early-Stage Invasive Cancer: A Meta-Analysis.

BACKGROUND

The optimal tumor-free margin definition and width following breast-conserving therapy (BCT) for early-stage invasive cancers has been evaluated in previous meta-analyses and guidelines. We performed an updated meta-analysis to assess how improvements in treatment over time have affected the impact of margins on local recurrence (LR) rates over time.

METHODS

A systematic literature review identified 38 eligible studies comprising 54,502 patients treated between 1968 and 2010. Inclusion criteria included patients treated with BCT and minimum follow-up of 50 months, pathologic definitions of margin status explicitly stated, and LR data in relation to margin status. Data were pooled using a Bayesian logistic regression model to evaluate the risk of LR in relation to both margin status and study enrollment periods.

RESULTS

Median follow-up was 7.25 years. Absolute LR rates decreased over time for each margin width cohort, with maximum differences between negative margin groups of less than 1% for the most recent enrollment period. However, relative rates of LR between different margin groups remained stable over time.

CONCLUSIONS

With an additional 22,000 patients compared with the previous meta-analysis, this updated meta-analysis supports the consensus guideline of "no tumor on ink" for the majority of patients. Additionally, while concerns exist regarding a benefit with wider margins from previous studies, the analysis demonstrates the impact of margin width on LR rates has declined substantially over time, with very small differences between the narrowest and widest margin groups in the most recent cohort. Hence, older studies appear to have limited value to inform current management guidelines.