Table 2. (A) Concordance calculation between RT-qPCR and IHC for the biomarkers studied, (B) Methodologic discrepancies in receptor conversion recognition.

A) Concordance of RT-qPCR and IHC	ER/ESR1	PR/PGR
Primary breast cancer (PT)	81% κ 0.51	70% κ 0.10
Metastatic breast cancer (MT)	84% κ 0.34	78% κ−0.32
B) Hormone receptor conversion	RT-qPCR	IHC
Total:	19 (20)*/55°	21 (22)*/53†
Both neg to both pos	0	1
Both pos to both neg	4	4
ER neg to pos/PR neg	1	1
ER neg to pos/PR pos	1	3
ER pos to neg/PR neg	2	0
ER pos to neg/PR pos	1	1
PR neg to pos/ER neg	(1)*	1
PR neg to pos/ER pos	0	1
PR pos to neg/ER neg	0	1
PR pos to neg/ER pos	8	8 (9)*

*One patient had 2 MT biopsies for one PT, but only one MT biopsy showed a shift, thus the value including the shifting sample in brackets.

°RT-qPCR total comprises 55 patients as % tumor cells were insufficient for accurate statement of hormone receptor positivity/negativity in 11 MT and 1 PT.

†IHC total comprises 53 samples as immunohistochemistry was missing for 14 samples.