Reverting Estrogen-Receptor-Negative Phenotype in HER-2-Overexpressing Advanced Breast Cancer Patients Exposed to Trastuzumab Plus Chemotherapy Elisabetta Munzone; Giuseppe Curigliano; Andrea Rocca; Giuseppina Bonizzi; Giuseppe Renne; Aron Goldhirsch; Franco Nolè Abstract Introduction:The amounts of estrogen receptor (ER) and progesterone receptor (PgR) in a primary tumor are predictive of the response to endocrine therapies of breast cancer. Several patients with ER-positive primary tumors relapse after adjuvant endocrine therapy with no ER expression in the recurrent tissue; much fewer with a recurrent disease after an ER-negative primary tumor may become endocrine responsive. These sequences of events indicate that a phenotype based on ER expression may not be a permanent feature of breast cancer. Methods:Ten patients with advanced breast cancer whose tumors overexpressed HER-2, but not ER or PgR, were treated with weekly trastuzumab at standard doses with or without chemotherapy. Results:Three out of 10 patients showed overexpression of ERs first appearing after 9, 12 and 37 weeks, respectively, from the initiation of trastuzumab. Two of these patients were subsequently treated with endocrine therapy alone: one of them received letrozole for 3 years without evidence of progression. Conclusion:Therapeutic targets enabling the appearance of an endocrine responsive disease may increase treatment options for patients with breast cancer. Furthermore, these clinical data suggest that an ER-negative phenotype is a multi-step process with a reversible repression modality, and that some ER-negative tumors may either revert to an ER-positive phenotype, allowing an endocrine treatment to be effective Breast Cancer Res. 2006;8(1) ©2006 BioMed Central, Ltd. Copyright to this article is held by the author(s), licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original citation. Posted 01/30/2006 Breast Cancer Res, 1/06 Breast Cancer Res, 1/06 Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.