2016 - Esther J Campbell

The Combined Endocrine Receptor (CER) is a better discriminator of patient outcome than ER and PR alone

Aim: To determine the prognostic power of the combined endocrine receptor (CER), a surrogate marker of oestrogen receptor (ER) and progesterone receptor (PR) functional cross talk and validate in a separate breast cancer patient cohort.

Methods: ER and PR were centrally retested for 557 early breast cancer patients by immunohistochemistry with accurate follow up. Tumour Allred ER and PR scores were reclassified as negative, low and high and the CER calculated as the average of the reclassified ER and PR scores, resulting in 3 groups: CER negative, impaired and high.

Results: In multivariate analysis the CER was independently prognostic for 5 years DFS (HR 0.393, CI 0.283-0.548, P=0.00001) and BCSS (HR 0.553, CI 0.423-0.722, P=2.506 x10^-8). In ER+ patients impaired CER was an independent marker of poor outcome in multivariate analysis which included all recognised prognostic indices for 5 years DFS (HR 2.469 CI 1.049-5.810, P=0.038) and BCSS (HR 1.946 CI 1.054-3.596 P=0.033) These results were validated in a separate cohort of patients.

Conclusion: CER is a more powerful discriminator of patient outcome than either ER or PR. Economical and simple, it can identify risk in ER+ early breast cancer and potentially be utilised for adjuvant cytotoxic chemotherapy decision-making.