OBJECTIVES:

The Estrogen Receptor, Progesterone Receptor and Human Epidermal growth factor Receptor 2 (ER/PR/HER2) status are essential to guide treatment and provide insight in the prognosis of breast cancer (BC) patients. In many patients, this ER/PR/HER2 status is tested multiple times; on tissue biopsies and tumor resection material. For patients receiving neo-adjuvant therapy or having tumor mutations over time, there might be discrepancies in receptor status between test results. Therefore, this study identifies the discordance and budget impact of multiple ER/PR/HER2 determinations using Dutch individual patient data.

METHODS:

Standardized records of all excerpts (i.e. biopsy or tissue material) of 11,054 BC patients was extracted from the network and registry of histo- and cytopathology in the Netherlands. Discordance in test results was calculated for multiple combinations of the ER/PR/HER2 receptor status. Potential influence of patient- and tumor characteristics on test results and discordance were estimated using multinomial regression.

RESULTS:

Most patients (n=8,881; 80.3%) had records of two excerpts: one from tumor biopsy and one from tumor resection. For 1,691 patients (19.0%), at least one of the receptors (ER/PR/HER2) was determined on both excerpts whilst only for 261 patients (2.9%) all receptors were determined twice. Results were concordant in 183 patients (70.1%) and discordant in 1 patient (0.4%). Remaining patients (n=77; 29.5%) had concordant HER2 test results but differences in the percentages of cells positive for ER/PR. Several patient- and tumor characteristics influence concordance in test results. Total potential cost savings of omitting the second test for patients with concordant test results can be up to €561,230 yearly.

CONCLUSIONS:

Concordance in ER/PR/HER2 test results is high, thereby implying that potential cost-savings of omitting one of the ER/PR/HER2 tests can be substantial. However, to address whether tests indeed can potentially be omitted, treatment decisions and patient outcomes based on these test results should be taken into account.