AB219. SOH26AB_0183. Hormone replacement therapy and breast cancer trends: a case-control study insight

Background: Hormone replacement therapy (HRT) is commonly used for menopausal symptom management; nonetheless, its relationship with breast cancer risk and tumour biology remains complex. Combined oestrogen-progestogen therapy is linked with an elevated breast cancer risk compared to oestrogen-only regimens, with risk impacted by duration and route of administration. Emerging evidence suggests that exposure to HRT could affect tumour phenotype at diagnosis. This study aimed to investigate associations between HRT use and breast cancer characteristics within a case-control cohort.

Methods: A retrospective case-control study was conducted using the University Hospital Limerick breast cancer database. Matched cohorts of HRT users and non-users were established. Data gathered comprised the type of HRT (combined or oestrogen-only), duration, and route of administration, family history, tumour stage, hormone receptor status (progesterone receptor, oestrogen receptor, and human epidermal growth factor receptor 2), tumour size, and nodal involvement. Descriptive analyses and statistical tests were conducted to evaluate correlations between HRT exposure and tumour characteristics.

Results: Women using combined or longer-duration HRT more often presented with early-stage breast cancers and exhibited higher rates of hormone receptor–positive tumours than non-users. Additional factors, including route of administration and family history of breast cancer, were incorporated into the assessment of clinical and pathological features.

Conclusions: Our study shows that HRT is associated with early-stage breast cancer, and this is concordant with previous studies published in the literature.

Keywords: Hormone replacement therapy (HRT); breast cancer; tumour stage; receptor status; hormone receptors