Aim: The aim of the current study was to investigate time-trends in pre-operative diagnosis and surgical treatment of axillary lymph node metastases in breast cancers detected at screening mammography.Methods: We included all women who underwent screening mammography in the South of the Netherlands between 2005 and 2020. During a follow-up period of at least two years, data on clinical radiological examinations, biopsy procedures and surgical interventions were obtained. The 15 years of inclusion were divided into five cohorts of three years each.Results: Of the 4049 women with invasive breast cancer, 22.1 % (896/4049) had axillary lymph node metastasis at pathology (ALN+). Percutaneous axillary biopsy was performed in 39.6 % (355/896) of these women, with the proportions of fine needle aspiration biopsy (FNAB) decreasing from 97.6 % (40/41) in 2005-2007 to 41.6 % (37/89) in 2017-2019 and core needle biopsy (CNB) rising from 2.4 % (1/41) in 2005-2007 to 58.4 % (52/89) in 2017-2019 (P < 0.001). Sensitivity of FNAB and CNB was comparable (77.4 % (188/243, 95%CI = 71%-82 %) versus 82.4 % (103/125), 95%CI = 74%-88 %) (P = 0.26). Pre-operative confirmation of ALN + by percutaneous biopsy ranged from 27.3 % (56/205) in 2011-2013 to 39.0 % (80/205) in 2017-2019, with no significant trend changes over time (P = 0.103). The proportion of ALN + women who underwent axillary lymph node dissection (ALND) decreased from 96.0 % (97/101) in 2005-2007 to 16.6 % (34/205) in 2017-2019 (P < 0.001).Conclusion: Pre-operative confirmation of axillary lymph node metastasis by ultrasound-guided biopsy did not rise despite the increased use of CNB at the expense of less invasive FNAB. A significant reduction in ALND was observed through the years.
