72224 - Characteristics and management of locally advanced breast cancer – a retrospective register study from Breast Cancer DataBase Sweden (BCBaSe) 3.0

Introduction Locally advanced breast cancer (LABC) refers to large primary breast tumours (T3), tumours of any size with chest wall/skin involvement (T4), and/or extensive lymph node involvement (N2-3). LABC may be a consequence of delayed presentation or aggressive tumour biology. The aim of the study was to explore patient characteristics, treatment, and time trends of LABC in a Swedish population-based cohort. Method The study cohort was retrieved from BCBaSe 3.0 including 94 271 patients with invasive breast cancer diagnosed 2008-2019 after exclusion of those with distant metastasis at diagnosis or within 3 months. Comparisons were made between non-LABC (T0-2N0-1) and LABC subcategorized by T-stage (T≥3) and N-stage (N≥2). Result Of all BC, 6565 (7.0 %) were LABC, with a fairly constant proportion over time. A higher proportion of LABC was seen both among the youngest (<40 y; 11.9 %) and among the oldest (80+ y; 15.7 %), and in those with a low level of education (9.5 %). Lobular BC was overrepresented among LABC (16.0 % vs 11.1 % in non-LABC), as were the Her2-positive (17.3 % vs 10.2 %) and triple-negative subtypes (11.0 % vs 7.3 % in non-LABC). On average, 47.2 % of LABC underwent primary surgery, 44.2 % received neoadjuvant treatment ranging from 26.7 % for T0-2N2 to 83.0 % for inflammatory BC, whereas 8.6 % received no treatment. Of those undergoing neoadjuvant treatment, 71.8 % proceeded to surgery. Discussion LABC encompasses a wide range of tumours, comprising both primarily operable and non-operable tumours, with notable distinctions observed between different subgroups of LABC.