International, multicenter, randomized, open-label, phase II clinical trial to evaluate the efficacy and safety of continuation of palbociclib

Full title: International, multicenter, randomized, open-label, phase II clinical trial to evaluate the efficacy and safety of continuation of palbociclib in combination with second-line endocrine therapy in hormone receptor-positive/her2-negative advanced breast cancer patients who have achieved clinical benefit during first-line palbociclib-based treatment