Background: The expanding treatment landscape for patients with hormone receptor-positive, HER2-negative (HR+/HER2-) metastatic breast cancer (mBC) has led to the emergence of new “grey areas” not covered by international guidelines, where treatment decision making is particularly challenging. Methods: Sixteen relevant statements regarding the management of HR+ /HER2- mBC were formulated by an Executive Board and validated by a Scientific Board, composed by internationally recognized experts in the field of BC. Subsequently, 50 Italian oncologists were surveyed between May 2024 and June 2024 through the modified Delphi method, in order to capture their rate of agreement and disagreement on the proposed statements. Results: The consensus was reached for all 16 statements: 4 were related to resistance and sensitivity to CDK4/6 inhibitors and endocrine therapy, 6 to biomarkers for HR+ /HER2- mBC, and 6 to treatment algorithm of HR+ /HER2- mBC. The Panel critically and comprehensively discussed the most relevant results, especially regarding the statements with lower level of agreement (which ranged from 85.4 % to 100 %). Conclusions: The treatment of HR+ /HER2- mBC is currently being reshaped due to the expansion of its pharmacopoeia, the better understanding of its molecular determinants and the validation of biomarkers for patient selection. This consensus addressed the most controversial questions related to treatment decision and reached the agreement in all statements.
