HER-2 amplification + HR-positive

CCND1 amplification is a recurring event in breast cancer, occurring most frequently in luminal B-like and HER2-amplified subtypes. A trend toward less favorable outcomes was observed among CCND1-amplified HR-positive, HER2-negative tumors.

Within HR + HER2- breast cancer, HER2-low tumors are associated with high RS, especially for histologically invasive ductal carcinoma. A prognostic influence of HER2-low expression among HR + HER2- breast cancer remains as an area that requires further study.

In this study, we analyzed the intrinsic subtype of HR positive, HER2 positive breast cancer based on prediction analysis of microarray 50 (PAM50) and Breast Cancer 360 panel (nanostring) between durable and poor responder in first-line docetaxel + trastuzumab + pertuzumab (THP) treated patients. Conclusions Other than HER2 pathway, ER pathway and inflammatory signal may influence the tumor response of HR(+), HER2 (+) breast cancer. Further clinical trials should be designed based not only on HER2 status, ER status and other molecular subtypes should be considered to maximize the clinical benefit.

TIL levels are higher in early-stage HR-positive breast carcinomas with a high recurrence risk. These tumors also harbor targetable genomic alterations, suggesting that TIL measurement and genomic profiling could enhance risk stratification and identify patients who might benefit from targeted therapies. Her-2 low expression in high-risk patients provides a consideration for including novel ADC therapies in this subset of patients.

In this study, we analyzed a subset of patients from the Dallas Metastatic Breast Cancer Study comprised of patients with HR+, HER2 non-amplified, mBC who underwent treatment with a CDK4/6 inhibitor (palbociclib, ribociclib, abemaciclib) and ET, became resistant to therapy, and had ctDNA testing (n=102). There is an urgent need to develop predictive biomarkers that capture real-time changes in tumor biology. Tissue analyses from patients resistant to CDK4/6 inhibitors have demonstrated a 14%-28% expression of CCNE1, 16% of MYC mutations, and 9%-10% expression of RB mutations. In our study, we observe a lower rate of detection in ctDNA of each gene.

HER2 expression in primary and recurrent breast cancer samples was highly unstable. Discordance was more frequently observed in the HR-positive population.

HER-2 zero to low conversion was associated with better DFS in patients who are HER-2 zero. These results provide a valuable reference for the potential application of anti-HER-2 ADC in an adjuvant setting for patients with residual disease after NAC.

Early-stage HR-positive breast carcinomas have low TIL levels regardless of the recurrence risk, molecular subtype, and HER2- low status. These cancers are markedly enriched by HER2-low phenotype, which might have therapeutic implications due to the recently approved anti-HER2 antibody-drug conjugate.