her2+ breast cancer seems to have different pathways driving it and may not act the same way as "generic" breast cancer--that which comprises all breast cancers lumped together, most of which are her2- and skew the statistics/results:
Progesterone status provides important information in breast cancer
MedWire News: Women with breast cancer are more likely to respond well to adjuvant hormone therapy if their tumors express the estrogen and progesterone receptors (ER+/ PgR+), rather than the estrogen receptor alone (ER+/ PgR-), suggests a study.
Emad Rakha (University of Nottingham, UK) and colleagues also report that single hormone receptor positive tumors - ER+/PgR- or ER-/PgR+ - are "clinically and biologically distinct groups of breast cancer" that require different treatment strategies.
The team of researchers investigated 1944 women under the age of 70 years who presented with primary invasive breast carcinoma between 1986 and 1998. Information on clinical and biological characteristics was collected and women were monitored for a median of 9 years.
Noting that the significance of the single receptor-positive breast cancer phenotype is poorly understood, the researchers stratified patients according to ER and PgR expression.
In total, 272 (15.6%) women had tumors that were ER+/PgR-, 60 (3.4%) had tumors that were ER-/PgR+, while 963 and 448 women had double-positive (ER+/PgR+) and double-negative (ER-/PgR-) tumors, respectively.
Among 503 women receiving adjuvant hormone therapy, those with tumors that were ER+/PgR- had a 1.9-fold decrease in both overall survival and disease-free interval, compared with women with double-positive tumors.
Rakha et al comment in the Journal of Clinical Oncology: "We believe that assessment of PgR can provide important prognostic information and prediction of response to adjuvant hormone therapy in estrogen receptor positive tumors."
The researchers found that older, postmenopausal women tended to have ER+/PgR- tumors that were moderately differentiated.
In contrast, most of the ER-/PgR+ tumors occurred in younger, premenopausal women and were poorly differentiated. These tumors also tended to have biomarkers of poor prognosis such as positive expression of p53 and basal cytokeratins, and reduced E-cadherin expression.
This, say the researchers, shows that the single hormone receptor positive tumors are biologically distinct, with ER-/PgR+ tumors the most aggressive subtype.
"The differences observed suggest that consideration be given to exploring the behavioral characteristics of these tumors with respect to treatment response in more detail," they say.
J Clin Oncol 2007; Advance online publication
http://jco.ascopubs.org/
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