Despite Advances, Repeat Breast-Conserving Surgery Rates Persist: A 25-Year National Analysis of Breast-Conserving Surgery in Australia

Using Australian Medicare Benefits Schedule data from 2000-2024, this national study examined repeat breastconserving surgery after initial excision for breast cancer. Repeat procedures remained persistently high (18. 6%) despite evolving margin guidelines and surgical advances, with marked interstate variation. Younger patients had higher repeat surgery rates, and estimated annual system costs exceeded AUD 12 million. BACKGROUND: Re-excision following breast-conserving surgery (BCS) remains a key indicator of surgical quality. Although adoption of the 2014 Society of Surgical Oncology and American Society for Radiation Oncology (SSO-ASTRO) "no tumor on ink" margin guideline, advances in imaging and oncoplastic techniques were expected to substantially reduce re-excision, national trends in Australia have not been well studied. METHODS: We performed a retrospective population-based analysis using publicly available Medicare Benefits Schedule (MBS) procedural data from 2000 to 2024. Initial BCS procedures (MBS 31512 and, from 2023, 31513-31514) were used as denominators and re-excisions (MBS 31515) as numerators to calculate annual and state-based re-excision proportions. Demographic variation was assessed by age group and jurisdiction. Health-system costs were estimated using 2024 to 2025 National Weighted Activity Unit pricing. RESULTS: Over 25 years, 171, 715 BCS procedures and 31, 987 repeat BCS were recorded, yielding a national repeat BCS proportion of 18. 6%. Following publication of the SSO-ASTRO guideline, repeat BCS decreased modestly from 19. 5% (2003-2013) to 18. 1% (2014-2024; P <. 001) but remained persistently high. Younger patients exhibited higher re-excision proportions, while substantial geographic variation was observed across states and territories (range 12. 1%-24. 1%). Mastectomy volumes stabilized over time while BCS volumes continued to rise. System-level costs attributable to re-excision exceeded AUD 12 million in 2024 alone. CONCLUSIONS: Despite technical advances and consensus margin guidelines, national re-excision proportions after BCS have shown only marginal improvement over 25 years and remain geographically heterogeneous. Though our data cannot describe the true national re-excision rate, these findings indicate persistent system-level barriers to optimal margin clearance and highlight opportunities for national quality improvement.