HER2 in Uterine Serous Carcinoma: Testing platforms and implications for targeted therapy

Human epidermal growth factor 2 (HER2) amplification in uterine serous carcinoma: an analysis of prognosis and immune microenvironment

Uterine serous carcinoma (USC) is a biologically aggressive subtype of endometrial cancer. Anti-human epidermal growth factor receptor 2 (HER2) therapy has demonstrated its promising effects on HER2-positive USC. However, data on prognostic relevance and immune microenvironment are limited in HER2-positive USC. This study aimed to determine the clinicopathologic features, prognosis, and the immune microenvironment trait in HER2 status in USC. We applied immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and multi-color immunofluorescence to investigate HER2 expression and amplification, PD-L1 expression, and tumor infiltration lymphocytes (TIL) in 77 USC (61 pure and 16 mixed-type USC). HER2 IHC 1 + , 2 + , and 3 + were found in 26, 18, and 10 USC, respectively. HER2 staining frequently had an incomplete membrane (basolateral or "U"-shaped) pattern. Twenty-three cases (23/54, 42.6%) showed an intra-tumor heterogeneous staining. HER2 amplification was present in 16/77 (20.8%) USC. HER2 amplification was significantly associated with deep myometrial invasion (> 1/2), and increased intra-epithelial and stromal density of CD20 + or CD8 + TIL (all P < 0.05), but not with USC subtypes (pure versus mixed-type), PD-L1 expression, CD4 + TIL, CD68 + histiocytes, or the CD4 + /CD8 + ratio (p > 0.05). HER2 amplification was associated with poor overall and progression-free survival in USC, but lost the prognostic significance on multivariate analysis. We concluded that HER2 amplified USC had adverse clinical outcomes, but showed the potential active immune microenvironment. Our findings raised the possibility of the combined anti-HER2 and immunotherapy for HER2-positive USC in the future.

Top advances of the year: Uterine cancer

Endometrial cancer continues to be the only gynecologic malignancy with a rising incidence and mortality, with both regional and global implications. Combination carboplatin and paclitaxel has been the recognized chemotherapy backbone for the treatment of advanced-stage or recurrent disease, with modest clinical outcomes. Over the last year, significant advances were achieved in improving oncologic outcomes by capitalizing on the molecular characterization of this heterogenous disease. These advances include incorporation of immunotherapy, identification of effective hormonal approaches, the evolution of antibody drug conjugates, and utilization of alternate targeted therapies. PLAIN LANGUAGE SUMMARY: The molecular characterization of endometrial cancer has been critical in informing novel treatment strategies. Over the past year, significant gains have been made via the incorporation of immunotherapy, hormonal combinations as well as antibody drug conjugates.

Implementation of HER2 Testing in Endometrial Cancer, a Summary of Real-World Initial Experience in a Large Tertiary Cancer Center

HER2-targeted therapies have transformed the management of advanced or recurrent serous endometrial cancer (EC), leading to an increased clinical demand for HER2 testing. Despite its adoption in select academic centers, the global extent of such tumor testing is unclear. In this study, we report on the initial two-year experience of HER2 testing at a major academic center with a reference gynecologic oncology service and biomarker reference laboratory. All patients who underwent HER2 testing based on physician discretion, reflex HER2 testing, and reference laboratory requests were included. From February 2021 to October 2023, HER2 testing was performed on 192 tumor tissue samples from 180 EC patients. Serous carcinoma constituted 52% of samples, reflecting diagnostic challenges and limited therapeutic options for advanced EC. HER2 positivity was found in 28% of all cases and 30% of p53-aberrant cases. An immunohistochemistry (IHC) score of 3+ was found in 15% of samples, while IHC 2+ was found in 45% (13% IHC 2+/ISH+ and 32% IHC 2+/ISH-). The newly identified 'HER2-low' category comprised 46% of the samples. Heterogeneity was noted in 42% of HER2-positive cases, with complex patterns in 3%. NGS and HER2 IHC-FISH showed a 24% discordance, attributed to intratumoral heterogeneity, tumor cellularity, a small number of amplified cells, and the HER2/CEP17 ratio near the cut-off. This study offers real-world insights into HER2 testing in EC, highlighting the challenges and underscoring the need for standardized guidelines in specimen handling, proficiency testing, and scoring criteria to enhance patient management and therapeutic decision-making.

Predictive and prognostic biomarkers in female genital tract tumours: an update highlighting their clinical relevance and practical issues

The evaluation of biomarkers by molecular techniques and immunohistochemistry has become increasingly relevant to the treatment of female genital tract tumours as a consequence of the greater availability of therapeutic options and updated disease classifications. For ovarian cancer, mutation testing for BRCA1/2 is the standard predictive biomarker for poly(ADP-ribose) polymerase inhibitor therapy, while homologous recombination deficiency testing may allow the identification of eligible patients among cases without demonstrable BRCA1/2 mutations. Clinical recommendations are available which specify how these predictive biomarkers should be applied. Mismatch repair (MMR) protein and folate receptor alpha immunohistochemistry may also be used to guide treatment in ovarian cancer. In endometrial cancer, MMR immunohistochemistry is the preferred test for predicting benefit from immune checkpoint inhibitor (ICI) therapy, but molecular testing for microsatellite instability may have a supplementary role. HER2 testing by immunohistochemistry and in situ hybridisation is applicable to endometrial serous carcinomas to assess trastuzumab eligibility. Immunohistochemistry for oestrogen receptor and progesterone receptor expression may be used for prognostication in endometrial cancer, but its predictive value for hormonal therapy is not yet proven. POLE mutation testing and p53 immunohistochemistry (as a surrogate for TP53 mutation status) serve as prognostic markers for favourable and adverse outcomes, respectively, in endometrial cancer, especially when combined with MMR testing for molecular subtype designation. For cervical cancer, programmed death ligand 1 immunohistochemistry may be used to predict benefit from ICI therapy although its predictive value is under debate. In vulvar cancer, p16 and p53 immunohistochemistry has established prognostic value, stratifying patients into three groups based on the human papillomavirus and TP53 mutation status of the tumour. Awareness of the variety and pitfalls of expression patterns for p16 and p53 in vulvar carcinomas is crucial for accurate designation. It is hoped that collaborative efforts in standardising and optimising biomarker testing for gynaecological tumours will contribute to evidence-based therapeutic decisions.

HER2 Oncogene as Molecular Target in Uterine Serous Carcinoma and Uterine Carcinosarcoma

Uterine serous carcinoma (USC) and uterine carcinosarcoma (UCS) are two rare histologic variants of uterine carcinoma, with distinct molecular profiles and aggressive metastatic potential. As the effectivity of traditional platinum-based chemotherapy for USC and UCS is low, and there are high rates of resistance and recurrence, the development of novel targeted therapeutics is needed. Human epidermal growth factor receptor 2 (HER2) has proven to be an oncogene of increasing interest in these cancers, as HER2 protein overexpression and/or c-ERBB2 gene amplification ranges from ~30 to 35% in USC, and between ~15 and 20% in UCS. This review summarizes the existing clinical and preclinical evidence, as well as ongoing clinical trials of HER2-targeting therapeutics, and identifies potential areas of further development and inquiry.