Immunotherapy has shown great benefit in multiple tumour types like melanoma and lung cancer. Although breast cancer was previously not considered an immunogenic disease, immunotherapy has recently demonstrated a survival benefit, combined with chemotherapy in metastatic triple negative breast cancer, as well as higher complete pathological response rates when added to chemotherapy in the neoadjuvant setting. There is currently no approval for the use of immunotherapy in endocrine responsive metastatic breast cancer. We present a case of a 34-year-old woman with stage IV endocrine responsive, Her 2 negative breast cancer, who responded to Pembrolizumab, following failure of multiple lines of hormonal blockade and chemotherapy.
Tumour infiltrating lymphocytes (TIL); checkpoint inhibitors; microsatellite instability (MSI) breast cancer; PDL 1 expression.