Immunohistochemical markers predict response to neoadjuvant chemotherapy
MedWire News: Simple immunohistochemistry (IHC)-based categorization of breast tumors can help predict the extent of tumor response to neoadjuvant chemotherapy (NACT), US study findings indicate.
“The predictive power of IHC criteria appears to be similar to that of gene expression analysis,” report Rohit Bhargava (University of Pittsburgh Medical Center, Pennsylvania) and co-authors in the journal Cancer.
Bhargava and team explain that breast cancer can be classified into four distinct molecular classes, luminal A, luminal B, ERBB2, and basal-like. Complete pathologic response to NACT is predominantly seen in ERBB2 and basal-like tumors.
To investigate whether a similar response could be predicted using semiquantitative IHC for estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), the researchers studied 359 tumors treated with NACT.
The tumors were classified into six groups on the basis of IHC findings. These were luminal A (strong ER-positive, HER2-negative), luminal B (weak to moderate ER-positive, HER2-negative), triple negative (negative for ER, PR, and HER2), ERBB2 (negative for ER and PR, but HER2-positive), luminal A- HER2 hybrid (strong ER-positive and HER2-positive), and luminal B-HER2 hybrid (weak to moderate ER-positive and HER2-positive).
The team reports that 48 (13%) tumors demonstrated complete pathologic response to NACT. The highest rate of complete pathologic response was seen in ERBB2 and triple-negative tumor classes at 33% (19 of 57) and 30% (24 of 79), respectively
Among the ER-positive groups, the highest rate of complete pathologic response was observed among luminal B-HER2 hybrid tumors, at 8% (two of 24). Only 1.5% (three of 198) of the remaining ER-positive tumors demonstrated a complete pathologic response.
The 5-year survival for patients achieving complete pathologic response was 96% compared with 75% in patients that failed to achieve complete pathologic response. However, despite the best response to NACT, ERBB2 and triple-negative tumors showed the worst overall survival because of higher relapse among those with residual disease.
Bhargava et al conclude: “By using the simple IHC criteria, the study findings suggest that routine hormone receptor and HER2 analysis can act as a substitute for expression analysis in predicting complete pathologic response to NACT.”
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By Laura Dean