ESR1 and breast cancer: On the other hand, in all meta-analyses involving taxane-based regimens or anthracycline-based regimens [62], the proportional reductions in early recurrence, any recurrence, and breast cancer mortality appeared largely independent of age, nodal status, tumor diameter, tumor differentiation (poorly or moderately differentiated, relatively few were well differentiated) or ER status (ER-poor or ER-positive).