A simple method to assess estrogen receptor gene (ESR1) amplification in paired biopsies from primary tumor and recurrence in breast cancer patients receiving endocrine therapy

Globally, Breast Cancer (BC) is the leading cause of cancer death among women. About 75% of patients are diagnosed with hormone-dependent tumors and are set to receive Endocrine Therapy (ET) targeting the estrogen receptor. Unfortunately, a significant proportion of these patients develops ET resistance. Still controversial, studies have proposed that Estrogen Receptor-Alpha Gene (ESR1) alterations may underlie ET resistance. Here, we describe the use of a Chromogenic in Situ Hybridization (CISH) assay for the assessment of ESR1 amplification in primary tumors and recurrences. This assay could be a useful clinical tool with therapeutic implications for estrogen receptor positive BC patients.
ESR1, Breast cancer, Estrogen-receptor amplification, Endocrine therapy, Endocrine therapy resistance