Expression of ER-α36, a novel variant of estrogen receptor-α, and resistance to tamoxifen treatment in breast cancer
Shi L et al. - In a study to investigate the association between ER-α36 expression and tamoxifen resistance in pts with breast cancer, it was reported that women with ER-α66–positive tumors that also express high levels of ER-α36 are less likely to benefit from tamoxifen treatment. Methods- ER-α36 protein expression in tumors from 896 women (2 independent cohorts, 1 and 2) with operable primary breast cancer was assessed using an immunohistochemistry assay.
Results- In the first cohort of 710 consecutive pts, overexpression of ER-α36 was associated with poorer disease-free survival (DFS) and disease-specific survival (DSS) in pts with ER-α66–positive tumors who received tamoxifen treatment (chemotherapy plus tamoxifen or tamoxifen alone, n=307).
- ER-α36 was not associated with survival in pts with ER-α66–positive tumors who did not receive tamoxifen (chemotherapy alone, n=129) and in pts with ER-α66–negative tumors whether they received tamoxifen (n = 73) or not (n = 149).
- In the second cohort of 186 pts who only received tamoxifen as adjuvant therapy, overexpression of ER-α36 was significantly associated with poorer DFS and DSS in 156 ER-α66–positive pts from this cohort, and ER-α36 remained an independent unfavorable factor for both DFS and DSS in these 156 pts by a multivariate analysis.
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