Characteristics and management of women with a new breast cancer diagnosis after previous breast cancer in Australia and New Zealand.

[INTRODUCTION] Women previously treated for breast cancer are at higher risk of developing second primary breast cancer. This study investigates the diagnosis method, demographics, tumour characteristics and management of women who developed a subsequent breast cancer after previous primary breast cancer treatment.

[MATERIALS & METHODS] Australian and New Zealand women diagnosed with breast cancer between June 2023 and December 2024 were identified using the BreastSurgANZ Quality Audit database. A multivariable Poisson model with robust error variance was performed to compare the two groups (previous breast cancer and no previous breast cancer) versus a number of a priori predictors: age at diagnosis and detection method, invasive breast cancer tumour size, histological grade and node positivity, Sentinel Lymph Node biopsy, referral source, axillary surgery as well as type of surgery, reconstruction type and use of adjuvant radiotherapy.

[RESULTS] 11,474 women were diagnosed with breast cancer between June 2023 to December 2024. 13.9% had undergone previous breast cancer surgery. Second primary breast cancers were smaller (p < 0.001), more likely to be node negative (p < 0.002) and asymptomatic (p < 0.001). Women with no previous breast cancer surgery were more likely to undergo breast conservation than mastectomy (70.58% vs 29.42%). Patient subgroups that opted for immediate reconstruction were highest in those presenting with their first breast cancer (27% vs 21%)).

[CONCLUSIONS] Second primary breast cancers diagnosed after previous breast cancer are commonly smaller, asymptomatic and node negative. There is a need for an evidence based personal surveillance approach for women who have had previous breast cancer based on known risk factors.