PIK3CA testing in hormone receptor-positive/HER2-negative metastatic breast cancer: real-world data from Italian molecular pathology laboratories.

Introduction: PIK3CA gene mutations occur in approximately 40% of hormone receptor-positive/HER2-negative (HR+/HER2-) metastatic breast cancers (MBCs), electing them to targeted therapy. Testing PIK3CA status is complex due to selection of biological specimen and testing method. Materials & methods: This work investigates real-life experience on PIK3CA testing in HR+/HER2- MBC. Clinical, technical and molecular data on PIK3CA testing were collected from two referral laboratories. Additionally, the results of a nationwide PIK3CA survey involving 116 institutions were assessed. Results: Overall, n = 35 MBCs were PIK3CA-mutated, with mutations mostly occurring in exons 9 (n = 19; 51.4%) and 20 (n = 15; 40.5%). The nationwide survey revealed significant variability across laboratories in terms of sampling methodology, technical assessment and clinical report signing healthcare figures for PIK3CA molecular testing in diagnostic routine practice. Conclusion: This study provides insights into the real-world routine of PIK3CA testing in HR+/HER2- MBC and highlights the need for standardization and networking in predictive pathology.

Think "HER2" different: integrative diagnostic approaches for HER2-low breast cancer.

This work explores the complex field of HER2 testing in the HER2-low breast cancer era, with a focus on methodological aspects. We aim to propose clear positions to scientific societies, institutions, pathologists, and oncologists to guide and shape the appropriate diagnostic strategies for HER2-low breast cancer. The fundamental question at hand is whether the necessary tools to effectively translate our knowledge about HER2 into practical diagnostic schemes for the lower spectrum of expression are available. Our investigation is centered on the significance of distinguishing between an immunohistochemistry (IHC) score 0 and score 1+ in light of the clinical implications now apparent, as patients with HER2-low breast cancer become eligible for trastuzumab-deruxtecan treatment. Furthermore, we discuss the definition of HER2-low beyond its conventional boundaries and assess the reliability of established diagnostic procedures designed at a time when therapeutic perspectives were non-existent for these cases. In this regard, we examine potential complementary technologies, such as gene expression analysis and liquid biopsy. Ultimately, we consider the potential role of artificial intelligence (AI) in the field of digital pathology and its integration into HER2 testing, with a particular emphasis on its application in the context of HER2-low breast cancer.

Palbociclib added to ongoing endocrine therapy for hormone receptor-positive HER2-negative metastatic breast cancer: A case report series.

Palbociclib is a potent cyclin-dependent kinase (CDK)4/6 inhibitor that disrupts cell cycle progression and has been recently approved in combination with an aromatase inhibitor or fulvestrant as first- and second-line treatment in hormone receptor (HR)+, human epidermal growth factor receptor (HER)2- metastatic breast cancer. There is evidence that palbociclib may reverse endocrine therapy resistance and that it may also be added to ongoing endocrine therapy beyond progression to obtain clinical benefit. The aim of the present study was to explore this possibility in 5 patients who received palbociclib + fulvestrant following disease progression while under treatment with fulvestrant alone. The median progression-free survival was not reached during a median follow-up of 25 months, and the most frequent best response was stable disease. Three patients remained under treatment on the last re-evaluation. All patients had highly endocrine-sensitive disease and had previously received fulvestrant for ≥12 months. The hypothesis that a selected subpopulation of patients with HR+/HER2- metastatic breast cancer may benefit from the addition of palbociclib to ongoing endocrine therapy beyond disease progression merits further investigation.