Early Stage HER2-Positive Breast Cancers Not Achieving a pCR From Neoadjuvant Trastuzumab- or Pertuzumab-Based Regimens Have an Immunosuppressive Phenotype.

BACKGROUND: Stromal tumor-infiltrating lymphocytes (TILs) might predict pathologic complete response (pCR) in patients with HER2-positive (HER2+) breast cancer treated with trastuzumab (H). Docetaxel (T), carboplatin (C), H, and pertuzumab (P) have immune-modulating effects. Pre- and post-treatment immune biomarkers in cancers treated with neoadjuvant TCH with or without P are lacking. In this study we quantified baseline and changes in TILs, cluster of differentiation (CD) 4+, CD8+, FoxP3+, and PD-L1+ cells using immunohistochemistry (IHC) and quantified productive T-cell receptor ß (TCRß) rearrangements and TCRß clonality using next-generation sequencing (NGS) in 30 HER2+ breast cancer tissues treated with neoadjuvant H with or without P regimens. MATERIALS AND METHODS: Thirty pre- and post-neoadjuvant TCH (n = 4) or TCHP (n = 26) breast cancer tissues were identified. TILs were quantified manually using hematoxylin and eosin. CD4, CD8, FoxP3, and PD-L1 were stained using IHC. TCRß was evaluated using NGS. Immune infiltrates were compared between pCR and non-pCR groups using the Wilcoxon rank sum test. RESULTS: A pCR occurred in 15 (n = 15; 50%) cancers (TCH n = 2; TCHP, n = 13). Pretreatment TILs, CD4+, CD8+, FoxP3+, and PD-L1+ cells were not associated with response (P = .42, P = .55, P = .19, P = .66, P = .87, respectively. Pretreatment productive TCRß and TCRß clonality did not predict response, P = .84 and P = .40, respectively). However, post-treatment CD4+ and FoxP3+ cells (T-regulatory cells) were elevated in the non-pCR cohort (P = .042 and P = .082, respectively). CONCLUSION: An increase in regulatory T cells in non-pCR tissues suggests the development of an immunosuppressive phenotype. Further investigation in a larger cohort of samples is warranted to validate these findings.

HR+, HER2- Advanced Breast Cancer and CDK4/6 Inhibitors: Mode of Action, Clinical Activity, and Safety Profiles.

BACKGROUND: Cyclin-dependent kinase (CDK) 4/6 inhibitor-based therapies have shown great promise in improving clinical outcomes for patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer. OBJECTIVES: 1. Discuss the mode of action of the three CDK4/6 inhibitors in late clinical development: palbociclib (PD-0332991; Pfizer), ribociclib (LEE011; Novartis), and abemaciclib (LY2835219; Lilly). 2. Describe the efficacy and safety data relating to their use in HR+, HER2- advanced breast cancer. 3. Discuss the key side effects associated with CDK4/6 inhibitors along with considerations for adverse event management and patient monitoring. METHOD: Relevant information and data were assimilated from manuscripts, congress publications, and online sources. RESULTS: CDK4/6 inhibitors have demonstrated improved progression-free survival in combination with endocrine therapy compared with endocrine therapy alone. The side-effect profile of each agent is described, along with implications for patient monitoring, and considerations for patient care providers and pharmacists. CONCLUSION: Addition of a CDK4/6 inhibitor to endocrine therapy increases efficacy and delays disease progression. Insight into the unique side-effect profiles of this class of agents and effective patient monitoring will facilitate the successful use of CDK4/6 inhibitor-based therapies in the clinic.