Tamoxifen is a potent and effective drug reducing the risk of dying from breast cancer in the
adjuvant setting. Although more modern drugs have partly replaced tamoxifen, it is helpful in
the neoadjuvant and metastatic settings as a single drug. Despite that, in the adjuvant
setting, it is a valuable drug.
This study aims to validate and study the feasibility of serial assessments, including
therapeutic drug monitoring of tamoxifen, 4-hydroxytamoxifen and Z-endoxifen by capillary
blood sampling, combined with patient-reported symptom scores. This will provide preliminary
data to allow us to develop a future multicentre randomised clinical trial of personalised
dose monitoring and adjustment of adjuvant tamoxifen therapy to enhance the quality of life
and breast cancer outcomes.