Margin status after breast-conserving surgery for breast cancer in the Netherlands from 2009 to 2022.

BACKGROUND

Tumour-positive margins after breast-conserving surgery (BCS) for breast cancer increase the risk of local recurrence and require additional therapy. Intraoperative imaging techniques in high-risk patients could improve margin determination. This study describes margin status after BCS in the Netherlands between 2009 and 2022, focusing on trends in surgical margin status and identifying subgroups at higher risk of tumour-positive margins.

METHODS

All patients undergoing BCS for non-metastatic breast cancer in the Netherlands from 2009 to 2022 were selected from the Netherlands Cancer Registry. Data included patient and tumour characteristics, treatment details, and surgical margin status. Descriptive statistics and trend analyses were performed. Univariate and multivariable analyses were performed to identify risk factors and patient subgroups at higher risk of margin involvement. Marginal effects analyses quantified tumour-positive margin risks.

RESULTS

In total, 109 475 women were included in the study. The mean tumour-positive margin rate was 10.8%. An extensively positive margin (> 4 mm involvement) occurred in 3.9% of patients, with a decreasing trend seen until 2013. Risk factors for a positive margin were invasive lobular carcinoma, multifocal disease, clinical tumour (cT) category 2 or 3, and neoadjuvant chemo- or hormonal systemic therapy without pathological complete response (pCR), with odds ratios (ORs) ranging from 1.56 to 2.96. One or more of these risk factors was present in 44 772 patients (40.9% of total cohort). The probability of positive margins increased with the number of risk factors, from 6.8% (no risk factors) to 49.1% (all four risk factors). Preoperative understaging (cT<pathological tumour) was also associated with an increased margin risk (OR 3.69). Two prediction tools were developed based on these outcomes (for total positive margins and for extensively positive margins only).

CONCLUSION

Over the past decade, tumour-positive margin rates in the Netherlands have remained stable at 10.8%. Patients with invasive lobular carcinoma, cT2/3 tumours, multifocal disease, or those receiving neoadjuvant chemotherapy or hormonal systemic therapy without pCR remain at substantially higher risk. There is room for improvement in these patient subgroups, highlighting the need for intraoperative imaging innovations to reduce positive margins.