Comparison of Estrogen receptors, Progesterone receptors and HER2-neu immunohistochemistry results in breast cancer with those of Oncotype Dx

Abstract

Oncotype Dx (ODx) recurrence score (RS) is used in early breast cancer to guide the use of adjuvant therapy. In addition to RS the test produces results of reverse transcriptase-polymerase chain reaction (RT-PCR) of Estrogen receptors (ER), Progesterone receptors (PgR) and Human epidermal growth factor receptor 2 (HER2-neu). Our goal was to determine the correlation between immunohistochemistry (IHC) and RT-PCR testing of ER, PgR and HER2-neu and to correlate the results of ODx RS with tumors' grade, age and PgR status.113 patients with ER+, HER2-neu- breast cancers that underwent ODx testing were analyzed for receptors correlation and concordance rates by the 2 methods.A total of 104 patients had ER+/PgR+ tumors and 9 patients had ER+/PgR- tumors by IHC, the average RS were 17.5 ± 9.1 and 31.2 ± 8.7 (P < 0.001) respectively.The Spearman correlation coefficient between IHC and ODx results were 0.5 (95% CI 0.34–0.62) for ER and 0.78 (95% CI 0.7–0.84) for PgR.The concordance rate between IHC and ODx was 98.2% for ER, 89.4%.for PgR and 99.1% for HER2-neu. Most of the discordant cases (9 out of 13) were low positive (1–10%) by IHC and negative by RT-PCR. In addition higher tumor grade was associated with a higher ODx RS.Our data show that the IHC results were highly concordant with RT-PCR for ER, PgR and Her2-neu. In addition low positive (1–10%) ER/PgR might indicate a real negative status. Our study shows that ER+/PgR- breast cancers are associated with a significantly higher ODx RS.