Determinants of response and molecular dynamics in HER2+ER+ breast cancers from the NA-PHER2 trial receiving HER2-targeted and endocrine therapies.

Improved outcomes in HER2+ female breast cancer have resulted from chemotherapy and anti-HER2 therapies. However, HER2+ER+ cancers exhibit lower response rates. The phase 2 NA-PHER2 trial (NCT02530424) investigated chemo-free preoperative HER2 blockade (trastuzumab + pertuzumab) and CDK4/6 inhibition (palbociclib) with or without endocrine therapy (fulvestrant) in HER2+ER+ breast cancer.

Genomic Characterization and Prognostic Significance of Human Epidermal Growth Factor Receptor 2-Low, Hormone Receptor-Positive, Early Breast Cancers From the BIG 1-98 and SOFT Clinical Trials.

Purpose: To investigate whether hormone receptor-positive, human epidermal growth factor receptor 2-low (HR+HER2-low) versus HR+HER2-zero early breast cancers have distinct genomic and clinical characteristics.

Methods: This study included HR+, HER2-negative early breast cancers from patients enrolled in the phase III, randomized BIG 1-98 and SOFT clinical trials that had undergone tumor genomic sequencing. Tumors were classified HR+HER2-low if they had a centrally reviewed HER2 immunohistochemistry (IHC) score of 1+ or 2+ with negative in situ hybridization and HR+HER2-zero if they had an HER2 IHC score of 0.

Spatial predictors of immunotherapy response in triple-negative breast cancer.

Immune checkpoint blockade (ICB) benefits some patients with triple-negative breast cancer, but what distinguishes responders from non-responders is unclear. Because ICB targets cell-cell interactions, we investigated the impact of multicellular spatial organization on response, and explored how ICB remodels the tumour microenvironment. We show that cell phenotype, activation state and spatial location are intimately linked, influence ICB effect and differ in sensitive versus resistant tumours early on-treatment.

Association of Somatic Driver Alterations With Prognosis in Postmenopausal, Hormone Receptor-Positive, HER2-Negative Early Breast Cancer: A Secondary Analysis of the BIG 1-98 Randomized Clinical Trial.

Importance: A range of somatic driver alterations has been described in estrogen receptor-positive, HER2-negative (ER+/HER2-) early breast cancer (BC); however, the clinical relevance is unknown.

Objective: To investigate associations of driver alterations with prognosis and the role of PIK3CA mutations in prediction of benefit associated with endocrine therapy in postmenopausal patients with ER+/HER2- early BC treated with tamoxifen or letrozole.

Design, Setting, And Participants: The Breast International Group (BIG) 1-98 trial randomized 8010 postmenopausal patients with hormone receptor-positive, operable, invasive BC to monotherapy with letrozole, tamoxifen, or a sequential strategy for 5 years.