The hormone receptor status of an invasive breast carcinoma may predict response to endocrine therapy. Different thresholds are currently being discussed to categorise a tumour as hormone receptor positive and to recommend endocrine therapy to those patients.
The aim of this question was to determine which is the most appropriate threshold to use.
Should a threshold of 10% or more vs. 1% or more of cells showing progesterone receptor positivity be used for providing endocrine therapy in women with invasive breast cancer?
In women with invasive breast cancer, the ECIBC's Guidelines Development Group (GDG) suggests administration of adjuvant endocrine therapy if 1% or greater of tumour cells show progesterone receptor positivity rather than applying a threshold of 10% tumour cell progesterone receptor positivity.
Conditional recommendation against the intervention
Very low certainty of the evidence
Considerations for implementation and policy making
The comparison, using a threshold of 1%, is already current practice, therefore no implementation considerations were identified.
- New research using ideally modern progesterone receptor (PR) immunohistochemical techniques on tumour tissue primarily fixed in 10% neutral buffered formalin.
- The GDG suggested additional observational studies to provide evidence on the current threshold used in practice, ideally using modern immunohistochemical techniques.
Monitoring and evaluation
The GDG suggested monitoring low (1-9%) and high (10% and above) PR positivity in relation to patient outcomes to better assess PR thresholds for treatment.