[Comment] SERDs for primary breast cancer

In The Lancet Oncology, Sara A Hurvitz and colleagues1 report their randomised phase 2 trial, investigating neoadjuvant palbociclib plus giredestrant, a potent selective oestrogen receptor antagonist and degradant (SERD), or anastrozole, an aromatase inhibitor, in postmenopausal women with oestrogen receptor-positive and HER2-negative early breast cancer. The authors found that the addition of giredestrant suppressed the Ki67 index, a marker of cell-cycle activation, more potently than the aromatase inhibitor anastrozole.