Do you continue ovarian suppression for pre-menopausal women with HR+ breast cancer after progression on ovarian suppression + AI + CDK4/6 inhibitor (i.e. when fulvestrant is the appropriate next line of therapy)?   

I do. Fulvestrant is technically an anti-estrogen receptor blocker that should work in pre or postmenopausal women. However, data in premenopausal women is limited. There would be at the least, some additional estrogen lowering effect and no harm from ovarian suppression. Therefore I would continue ...