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HER-2 and Topoisomerase II As Predictors of Response to Chemotherapy

Kathleen I. Pritchard, Hans Messersmith, Leela Elavathil, Maureen Trudeau, Frances O’Malley, Bindi Dhesy-Thind

From the Sunnybrook Odette Cancer Centre; Department of Pathology and Laboratory Medicine, Mount Sinai Hospital; Cancer Care; Departments of Medicine and Pathology and Laboratory Medicine, University of Toronto; Ontario, Toronto; McMaster University; Henderson Hospital; and Juravinski Cancer Centre, Hamilton, Ontario, Canada

Corresponding author: Kathleen I. Pritchard, MD, FRCPC, FACP, Sunnybrook Odette Cancer Centre, Department of Medicine, University of Toronto, 2075 Bayview Ave, Toronto, ON M4N 3M5; e-mail: kathy.pritchard{at}sunnybrook.ca

HER2 overexpression or amplification has been shown to be associated with a poor prognostic effect in women with breast cancer. At least eight analyses based on randomized trials have examined the relationship between HER2 and the differential effect of anthracycline compared with non–anthracycline-containing regimens. Only three of these studies were sufficiently powered to show a significant interaction between HER2 and anthracycline- versus non–anthracycline-containing treatments, but because all of the study results tended to be in the same direction, it is not surprising that three recent meta-analyses of published data have suggested that anthracycline-containing regimens provide more benefit than non–anthracycline-containing regimens in women whose tumors are overexpressed or amplified (positive) for HER2. Since topoisomerase II is a known target of the anthracyclines, it has been postulated that this relationship is actually based on the proximity of HER2 to the topoisomerase II gene (TOP2A) in the 17q chromosome. At least four recent studies have suggested that deletion and amplification of the TOP2A gene are associated with poor prognosis and are predictive of greater response to anthracycline-containing than to non–anthracycline-containing regimens. However, in at least one of those studies, HER2 positivity was as or more predictive. Although it has been suggested that HER2 positivity is predictive of better response to higher-dose anthracycline-containing regimens compared with standard anthracycline-containing regimens and to taxane- compared with non–taxane-containing regimens, these relationships have not been robust or consistent. Additional studies will be required to clarify these relationships.

Authors’ disclosures of potential conflicts of interest and author contributions are found at the end of this article.