antibody–drug conjugate
trastuzumab emtasine plus endocrine therapy
es-BC - HR positive - (neo)adjuvant (NA) 2   
es-BC - HR-positive - 1st line (L1) 1
la/mBC - HR positive 2
la/mBC - HR positive - (neo)adjuvant (NA) 3
la/mBC - HR positive - NA - PIK3CA mutant
la/mBC - HR-positive - 1st line (L1) 13
la/mBC - HR positive - L1 - PIK3CA mutant 1
la/mBC - HR-positive - 2nd line (L2) 20
la/mBC - HR positive - L2 - all population 1
la/mBC - HR positive - L2 - PIK3CA mutant 1
Comparator:  vs trastuzumab plus endocrine therapy; 
Risk of bias:  low;   some concerns;   high;  NA;