Novel imaging technique to determine PD-L1 expression in breast cancer
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Abstract
Breast cancer continues to be the most common cancer in women and a leading cause of mortality amongst cancers despite developments in screening and targeted therapies. Triple negative breast cancer is the most aggressive subtype with the poorest survival. Studies have found an increased progression free survival in patients with triple negative breast cancer when treated with PD-L1 inhibitor pembrolizumab in the neoadjuvant and adjuvant phase of treatment. However, this result was independent of PD-L1 expression of the tumor as measured by immunohistochemistry (IHC). Studies also have found that IHC measurement of PD-L1 expression may be inaccurate due to heterogeneity of expression within the tumor. Another proposed option for determination of PD-L1 expression is PET/CT imaging utilizing radiolabeled atezolizumab. To date, only one clinical trial with low enrollment studied if PET/CT imaging could have a stronger predictive power for treatment response in patients with breast cancer. This proposed study is a five-year prospective clinical trial that aims to determine if PET/CT based imaging will be a more accurate predictor for response to pembrolizumab based therapy as compared to IHC in patients with triple negative breast cancer. In addition, the study will allow future studies to evaluate whether PET/CT imaging could be useful to monitor PD-L1 expression during treatment.