Reporting from ASCO 2023, Catherine HarperWynne discusses the results from three important studies in HR+, HER2 Breast Cancer. The NATALEE trial investigating the addition of ribociclib to Endocrine Therapy (ET) in the adjuvant setting, shows promising but still early DFS results. In the metastatic setting, the SONIA study explores the possibility of using in firstline ET alone and then switching to CDK4/6 inhibitors with ET, vs the opposite. Addressing the issue of CDK4/6 inhibitors' efficacy as maintenance in secondline treatment, the PALMIRA study provides insights into their effectiveness in this context.

Abstracts discussed:
LBA1000: Primary outcome analysis of the phase 3 SONIA trial (BOOG 201703) on selecting the optimal position of cyclindependent kinases 4 and 6 (CDK4/6) inhibitors for patients with hormone receptorpositive (HR+), HER2negative (HER2) advanced breast cancer (ABC).
LBA500: Phase III NATALEE trial of ribociclib + endocrine therapy as adjuvant treatment in patients with HR+/HER2− early breast cancer.
Abstract 1001: Secondline endocrine therapy (ET) with or without palbociclib (P) maintenance in patients (pts) with hormone receptorpositive (HR[+])/human epidermal growth factor receptor 2negative (HER2[]) advanced breast cancer (ABC): PALMIRA trial.

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