2014年SSO-ASTRO关于手术切缘的指南旨在减少乳腺保留手术（BCS）后不必要的再手术。本研究旨在调查指南出版是否与西澳大利亚（WA）的再手术率下降有关。在这项回顾性的人口基础队列研究中，通过WA癌症登记处确定了新诊断的乳腺癌病例。链接到住院病情数据收集中，确定了2009年1月至2018年6月间侵入性癌症的初始BCS的病例（N = 8059），以及90天内的再手术。比较了指南前（2009-2013）和指南后（2014-2018）的再手术比例，并估计了广义线性回归的时间趋势。指南前再手术比例为25.8％，而指南后为21.7％（差异为-4.0％[95％CI -5.9，-2.2，p <0.001]，比值比[OR]为0.80 [95％CI 0.72，0.89，p <0.001]）。重复BCS和乳房切除术的比较的绝对减少量相似（分别为16.3％对14.6％和9.4％对7.2％）。研究期间，再手术绝对变化率为-0.8％（95％CI -1.2，-0.5，p <0.001）。考虑到这一线性趋势，时间段之间的再手术差异为-0.5％（95％CI -4.3，3.3; p = 0.81），反映出乳房切除术的非显着减少。比较WA的指南前和指南后时期显示，再手术的减少与国际估计相似。然而，在指南之前，再手术的年度下降趋势已经存在。未考虑时间趋势的分析可能会高估与指南相关的再手术变化。

A 2014 SSO-ASTRO guideline on surgical margins aimed to reduce unnecessary reoperation after breast conserving surgery (BCS). We investigate whether publication of the guideline was associated with a reduction in reoperation in Western Australia (WA).In this retrospective, population-based cohort study, cases of newly-diagnosed breast cancer were identified from the WA Cancer Registry. Linkage to the Hospital Morbidity Data Collection identified index BCS for invasive cancer between January 2009 and June 2018 (N = 8059) and reoperation within 90 days. Pre-guideline (2009-2013) and post-guideline (2014-2018) reoperation proportions were compared, and temporal trends were estimated with generalised linear regression.The pre-guideline reoperation proportion was 25.8% compared with 21.7% post-guideline (difference -4.0% [95% CI -5.9, -2.2, p < 0.001], odds ratio [OR] 0.80 [95% CI 0.72, 0.89, p < 0.001]). Absolute reductions were similar for repeat BCS (16.3% versus 14.6%; difference -1.8% [95% CI -3.4, -0.2, p = 0.03]) and conversion to mastectomy (9.4% versus 7.2%; difference -2.2% [95% CI -3.4, -1.0, p < 0.001]). Over the study period, there was an annual absolute change in reoperation of -0.8% (95% CI -1.2, -0.5, p < 0.001). Accounting for this linear trend, the difference in reoperation between time periods was -0.5% (95% CI -4.3, 3.3; p = 0.81), reflecting a non-significant reduction in conversion to mastectomy.Comparisons of pre- versus post-guideline time periods in WA showed reductions in reoperation that were similar to international estimates; however, an annual decline in reoperation predated the guideline. Analyses that do not account for temporal trends are likely to overestimate changes in reoperation associated with the guideline.Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.