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

The "lows": Update on ER-low and HER2-low breast cancer

ER-low and HER2-low breast cancers have emerged as clinically significant subtypes that challenge traditional diagnostic categories and treatment paradigms. These subtypes, representing a spectrum of disease, exhibit distinct biological behaviors, therapeutic responses, and prognostic outcomes. HER2-low breast cancer, defined by low HER2 protein expression (IHC score of 1+ or 2+ without HER2 gene amplification), has achieved clinical significance, particularly following the DESTINY-Breast trials, which demonstrated the efficacy of trastuzumab deruxtecan (T-DXd) in the population of patients with advanced HER2-low disease. Similarly, ER-low breast cancer, characterized by low estrogen receptor expression (in 1%-10 % invasive tumor cells), poses unique challenges due to its intermediate biological behavior and uncertain response to endocrine therapies. The identification of these subtypes is further complicated by inconsistencies in testing methodologies, which can lead to misclassification and impact treatment decisions. As our understanding of these subtypes improves, the need for standardized diagnostic approaches and individualized therapeutic decisions becomes increasingly urgent. Ongoing research and collaboration between pathologists and oncologists are essential for refining diagnostic criteria and improving outcomes for patients with breast cancers characterized by low expression of these theragnostic biomarkers. This review aims to consolidate current knowledge on HER2-low and ER-low breast cancers, focusing on the challenges associated with their identification, the implications for treatment, and future directions in clinical management. By examining recent studies and interlaboratory assessments, this review emphasizes the critical need for accurate and reproducible testing and reporting, and for the development of tailored therapeutic strategies for these "low" expression cancers.

HER2 Antibody-Drug Conjugates Are Active against Desmoplastic Small Round Cell Tumor

PURPOSE

Desmoplastic small round cell tumor (DSRCT) is a rare but highly aggressive soft tissue sarcoma that arises in the abdominopelvic cavity of young males. Since the discovery of EWSR1::WT1 fusion as the driver of DSRCT, no actionable genomic alterations have been identified, limiting disease management to a combination of surgery, chemotherapy, and radiation, with very poor outcomes. Herein, we evaluated ERBB2/HER2 expression in DSRCT as a therapeutic target.

EXPERIMENTAL DESIGN

ERBB2/HER2 expression was assessed in clinical samples and patient-derived xenografts (PDX) using RNA sequencing, RT-qPCR, and a newly developed HER2 IHC assay (clone 29D8). Responses to HER2 antibody-drug conjugates (ADC)-trastuzumab deruxtecan (T-DXd) and trastuzumab emtansine-were evaluated in DSRCT PDX, cell line, and organoid models. Drug internalization was demonstrated by live microscopy. Apoptosis was evaluated by Western blotting and caspase activity assays.

RESULTS

ERBB2/HER2 was detectable in DSRCT samples from patients and PDXs, with higher sensitivity RNA assays and improved IHC detectability using clone 29D8. Treatment of ERBB2/HER2-expressing DSRCT PDX, cell line, and organoid models with T-DXd or trastuzumab emtansine resulted in tumor regression. This therapeutic response was long-lasting in T-DXd-treated xenografts and was mediated by rapid HER2 ADC complex internalization and cytotoxicity, triggering p53-mediated apoptosis and growth arrest. Xenograft regression was associated with bystander payload effects triggering global tumor niche responses proportional to HER2 status.

CONCLUSIONS

ERBB2/HER2 is a therapeutic target in DSRCT. HER2 ADCs may represent novel options for managing this exceptionally aggressive sarcoma, possibly fulfilling an urgent and historically unmet need for more effective clinical therapy.

Healthcare Systems and Artificial Intelligence: Focus on Challenges and the International Regulatory Framework

BACKGROUND

Nowadays, healthcare systems are coping with the challenge of countering the exponential growth of healthcare costs worldwide, to support sustainability and to guarantee access to treatment for all patients.

METHODS

Artificial Intelligence (AI) is the technology able to perform human cognitive functions through the creation of algorithms. The value of AI in healthcare and its ability to address healthcare delivery issues has been a subject of discussion within the scientific community for several years.

RESULTS

The aim of this work is to provide an overview of the primary uses of AI in the healthcare system, to discuss its desirable future uses while shedding light on the major issues related to implications within international regulatory processes. In this manuscript, it will be described the main applications of AI in various aspects of health care, from clinical studies to ethical implications, focusing on the international regulatory framework in countries in which AI is used, to discuss and compare strengthens and weaknesses.

CONCLUSIONS

The challenges in regulatory processes to facilitate the integration of AI in healthcare are significant. However, overcoming them is essential to ensure that AI-based technologies are adopted safely and effectively.

HER2-Low Expression in Male Breast Cancer: Results from a Multicenter Series in Italy

In the field of breast cancer care, a significant breakthrough has occurred with the recognition of HER2-low expression as a target for novel anti-HER2 antibody-drug conjugates (ADC). This discovery is reshaping the treatment landscape, challenging previous perceptions that considered HER2-low as clinically insignificant. The ability to target HER2-low expression is expected to have substantial clinical implications, irrespective of gender, including in cases of male breast cancer (MBC). However, an estimate of the prevalence of the HER2-low subtype in MBC is missing. This retrospective, observational, multicenter study was aimed at characterizing the HER2-low subtype in MBC. For the purpose of this study, the three-tiered categorization of HER2 (HER2-0, HER2-low, and HER2-positive) was used to reclassify the HER2-negative group into HER-0 or HER2-low subtypes. In the whole series of 144 invasive MBCs, 79 (54.9%) were HER2-0 (IHC scores of 0), 39 (27.1%) HER2-low (IHC scores of 1+/2+ with negative ISH), and 26 (18.0%) HER2-positive (IHC scores of 3+/2+ with positive ISH). Specifically, among hormone receptor-positive (HR+) HER2-negative invasive MBCs, 34.8% were HER2-low and 65.2% HER2-0. Compared with HER2-0, HER2-low subtype was associated with a positive lymph node involvement (p = 0.01). Other pathologic characteristics including histology, staging, and grading did not show notable variations between the two subtypes. The presence of germline BRCA1/2 pathogenic variants (PVs) did not significantly differ between HER2-0 and HER2-low MBCs. However, about 13% of HER2-low MBCs had germline PVs in BRCA1/2 genes, mainly BRCA2, a clinically relevant observation in the context of combined target therapy. Overall, our data, which focused on the largest gender-specific breast cancer series, to our knowledge, confirm that the emerging three-tiered categorization of HER2 (HER2-0, HER2-low, and HER2-positive) can also be considered in MBC, to mitigate both the gender gap and the underrepresentation of males in clinical trials.