HER2-Low Luminal Breast Carcinoma Is Not a Homogenous Clinicopathological and Molecular Entity.

BACKGROUND: With the development of some new antibody-drug conjugates, the HER2 classification of breast carcinomas now includes the HER2-low (H2L) category: IHC 1+, 2+ non-amplified by ISH, and double-equivocal carcinomas, mostly luminal, expressing hormone receptors (HR+). METHODS: We analyzed mutational status and transcriptomic activities of three HER2 effector pathways: PI3K-AKT, MAPK, and JAK-STAT, in association with clinicopathologic features, in 62 H2L carcinomas compared to 43 HER2-positive and 20 HER2-negative carcinomas, all HR+. RESULTS: H2L carcinomas had significantly lower histoprognostic grades and mitotic and Ki67 proliferation indexes than HER2-positive carcinomas. Their PIK3CA mutation rates were close to those of HER2-negative and significantly higher than in HER2-positive carcinomas, contrary to TP53 mutations. At the transcriptomic level, we identified three distinct groups which did not reflect the new HER2 classification. H2L and HER2-negative carcinomas shared most of clinicopathological and molecular characteristics, except HER2 membrane expression (mRNA levels). The presence of a mutation in a signaling pathway had a strong pathway activation effect. PIK3CA mutations were more prevalent in H2L carcinomas, leading to a strong activation of the PI3K-AKT signaling pathway even in the absence of HER2 overexpression/amplification. CONCLUSION: PIK3CA mutations may explain the failure of conventional anti-HER2 treatments, suggesting that new antibody-drug conjugates may be more effective.

Prognostic stratification ability of the CPS+EG scoring system in HER2-low and HER2-zero early breast cancer treated with neoadjuvant chemotherapy.

BACKGROUND: The CPS+EG scoring system was initially described in unselected early breast cancer (eBC) patients treated with neoadjuvant chemotherapy (NAC), leading to refined prognostic stratification, and thus helping to select patients for additional post-NAC treatments. It remains unknown whether the performance is the same in new biological breast cancer entities such as the HER2-low subtype. PATIENTS AND METHODS: Outcomes (disease-free (DFS) and overall survival OS)) of 608 patients with HER2-non amplified eBC and treated with NAC were retrospectively analyzed according to CPS-EG score. We compared the prognostic stratification abilities of the CPS+EG in HER2-low and HER2-0 eBC, analyzing ER+ and ER- tumors separately. RESULTS: In ER+ eBC, the CPS+EG scoring system seems to retain a prognostic value, both in HER2-low and HER2-0 tumors, by distinguishing populations with significantly different outcomes (good: score 0-1, poor: score 2-3, and very poor: score 4-5). Using C-indices for DFS and OS, CPS+EG provided the highest prognostic information in ER+ eBC, especially in HER2-0 tumors. In contrast, in ER- eBC, the CPS+EG does not appear to be able to distinguish different outcome groups, either in HER2-low or HER2-0 tumors. In ER- eBC, C-indices for DFS and OS were highest for pathological stage, reflecting the predominant prognostic importance of residual disease in this subtype. CONCLUSIONS: HER2-low status does not influence the prognostic performance of the CPS+EG score. Our results confirm the usefulness of the CPS+EG score in stratifying the prognosis of ER+ eBC after NAC, for both HER2-0 and HER2-low tumors. For ER- eBC, HER2-low status does not influence the performance of the CPS+EG score, which was lower than that of the pathological stage alone.

Pathologic complete response and survival in HER2-low and HER2-zero early breast cancer treated with neoadjuvant chemotherapy.

BACKGROUND: Breast cancers without HER2 amplification but still expressing this membrane protein constitute a new entity called HER2-low tumors. It is important to characterize them in terms of sensitivity to treatment and prognosis. PATIENTS AND METHODS: To investigate chemosensitivity and long-term prognosis of HER2-low early breast cancer (eBC), compared to HER2-0 tumors, we retrospectively retrieved clinicopathological characteristics, response to treatment, and survival data from 511 patients treated for eBC with neoadjuvant chemotherapy (NAC) in a French cancer center between 2007 and 2018. Factors associated with the achievement of pathologic complete response (pCR) and survival were studied among hormone receptor positive (HR+) and negative (HR-) eBC. RESULTS: A total of 280 HR+ (61% HER2-low), and 231 HR- (28% HER2-low) eBC were included. We found classical clinicopathological factors usually associated with chemosensitivity and prognosis, in both HR+ and HR- eBC. By uni- and multivariable analysis, HER2 status (low vs 0) was not independently associated with pCR, either in HR+ or HR- eBC. Relapse free (RFS) and overall survival (OS) were not significantly different between HER2-low and HER2-0 among HR+ tumors. In contrast, among HR- negative tumors, RFS and OS were slightly better in HER2-0 eBC by univariable but not by multivariable analysis. CONCLUSIONS: In eBC patients treated with NAC, taking into account HR expression subtype and other current clinicopathological features, HER2-low tumors did not appear to have different chemosensitivity or prognosis, compared to their HER2-0 counterparts.

Anticipating changes in the HER2 status of breast tumours with disease progression-towards better treatment decisions in the new era of HER2-low breast cancers.

BACKGROUND: HER2 expression is often negative or low in primary breast cancers (BCs) but its changes with disease progression remain poorly known. We aimed to estimate them between primary and recurrent tumours, and identify predictive factors. METHODS: We compared the HER2 status, and clinical and pathological characteristics by its evolution category (stable or changed), between all primary BCs and matched recurrences registered in our database in 2000-2020 (n = 512). RESULTS: HER2-low tumours were the most prevalent at diagnosis (44.9%), followed by HER2-negative tumours (39.3%). HER2 status significantly changed in 37.3% of recurrences, mainly of HER2-negative and HER2-low tumours. HER2-negative tumours which relapsed as HER2-low significantly more frequently expressed oestrogen receptors (ER) and recurred later than stably HER2-negative tumours. Changed HER2 status in distant metastases correlated with lower proliferation rates and higher ER expression in primary tumours, and among metastases of hormone receptor-positive (HR+) tumours-with weak progesterone receptor (PR) expression in primary tumours. CONCLUSIONS: HER2 status changes with BC progression, with enrichment of HER2-low tumours in advanced stages. The ER+/PR- status, low proliferation index and time to late recurrence correlated with these changes. These findings highlight the need of retesting recurrences, especially of HR + primary tumours, to identify candidates for new anti-HER2 therapies.

Idylla EGFR assay on extracted DNA: advantages, limits and place in molecular screening according to the latest guidelines for non-small-cell lung cancer (NSCLC) patients.

AIMS: Idylla epidermal growth factor receptor (EGFR) is a fast and fully automated mutation assay that is easy to implement. However, under the Biocartis-recommended technical conditions, tissue sections are directly introduced into the cartridge, at the risk of exhausting the tumour sample. In this study, we evaluate the performance of Idylla EGFR on extracted DNA and discuss its place within the global non-small-cell lung cancer (NSCLC) screening strategy. METHODS: 577 comparative tests between Idylla EGFR on extracted DNA and next-generation sequencing (NGS) were performed across two centres. RESULTS: Preanalytical thresholds were established (20% tumour cell content, 50 ng DNA input) and challenged prospectively in routine practice. 16.8% of samples referred for screening were considered non eligible for Idylla EGFR testing. Due to discordant by design cases, Idylla EGFR sensitivity was 86.9% for currently actionable EGFR mutations. Idylla EGFR specificity was 100% in first-line screening. NGS was always feasible on the same DNA. CONCLUSION: Idylla EGFR on extracted DNA is feasible and enables tumour material to be saved compared with tissue section use. It is not necessary to replace the analytical thresholds of the Biocartis algorithm. Due to both the limits of the mutational repertoire and the high increase of targetable genes in NSCLC, the use of Idylla EGFR should be restricted to clinical emergency situations accompanied by NGS.

Molecular intrinsic subtypes, genomic, and immune landscapes of BRCA-proficient but HRD-high ER-positive/HER2-negative early breast cancers.

PURPOSE: The vast majority of research studies that have described the links between DNA damage repair or homologous recombination deficiency (HRD) score, and tumor biology, have concerned either triple negative breast cancers or cancers with mutation of BRCA 1/2. We hypothesized that ER + /HER2- early breast tumors without BRCA 1/2 mutation could have high HRD score and aimed to describe their genomic, transcriptomic, and immune landscapes. PATIENTS AND METHODS: In this study, we reported BRCA 1/2 mutational status, HRD score, and mutational signature 3 (S3) expression, in all early breast cancer (eBC) subtypes from the TCGA database, with a particular focus in ER + /HER2-. In this subtype, bioinformatics analyses of tumor transcriptomic, immune profile, and mutational landscape were performed, according to HRD status. Overall survival (OS), progression free-interval (PFI), and variables associated with outcome were also evaluated. RESULTS: Among the 928 tumor samples analyzed, 46 harbored BRCA 1/2 mutations, and 606 were ER + /HER2- (of which 24 were BRCA 1/2 mutated). We found a subset of BRCA-proficient ER + /HER2- eBC, with high HRD score. These tumors displayed significantly different immune, mutational, and tumor molecular signatures landscapes, compared to BRCA-mutated and BRCA-proficient HRD-low tumors. Outcome did not significantly differ between these 3 groups, but biological factors associated with survival are not the same across the 3 entities. CONCLUSION: This study highlights possible novel biological differences among ER + /HER2- breast cancer related to HRD status. Our results could have important implications for translational research and/or the design of future clinical trials, but require prospective clinical evaluation.

Efficacy of platinum-based chemotherapy in metastatic breast cancer and HRD biomarkers: utility of exome sequencing.

Metastatic breast cancer (MBC) is frequently managed by platinum-based chemotherapy during the disease course. The real benefit of these treatments is uncertain at advanced stages of the disease and in non-triple-negative subtypes. Since homologous recombination deficiency (HRD) could inform about tumor sensitivity to DNA-damaging agents, we aimed to determine biomarkers of genomic instability, and their link with platinum efficacy. In this single-center study, we report BRCA1/2 mutational status, HRD score and signature 3 levels, all obtained by tumor exome sequencing, in 86 patients with various subtypes of MBC and who received platinum-based chemotherapy. Overall response rate, disease control rate, PFS and PFS2/PFS1 ratio were evaluated to assess platinum-based chemotherapy efficacy. Among the 86 tumor samples analyzed, 7 harbored BRCA1/2 mutations. We found a subset of BRCA-proficient MBC with high HRD score or high S3 levels, comparable to BRCA-mutated tumors. However, these patients with high HRD score or high S3 tumor level do not seem to benefit more from platinum-based chemotherapy than the others, in terms of response rates and/or PFS, regardless of BC molecular subtype. By multivariate analysis, only the absence of liver metastases was independently associated with significantly better PFS on platinum-based chemotherapy. However, some of our exploratory analyses reveal that certain methods, when optimized, seem to associate with platinum benefit. Tumor exome sequencing methodology for quantifying HRD has to be approached systematically, and further validated and standardized prior to its clinical use. Further studies are warranted to confirm these results to guide platinum use in MBC.

Association of Anti-EGFR Antibody and MEK Inhibitor in Gynecological Cancer Harboring RAS Mutation: A Case Series.

Low-grade serous carcinoma represents a minority of serous carcinoma. Although they have better prognosis than high-grade serous carcinoma, they respond poorly to chemotherapy. Thus, it appears necessary to find other treatments such as targeted therapies. Since RAS or RAF mutations occur frequently in low-grade serous carcinoma and lead to constitutively activated MAPK cascade, MEK inhibition should be effective in the treatment of low-grade serous carcinoma. So, we wanted to evaluate the clinical benefit of MEK inhibitors in the management of advanced-stage low-grade serous carcinoma harboring KRAS or NRAS mutation. We report a case series of three women with advanced-stage low-grade serous carcinoma harboring RAS mutation who had stabilization of their disease during several months under targeted therapy combining anti-EGFR antibody and MEK inhibitor. We performed in vitro experiments, confirming the effectiveness of MEK inhibitor on the KRAS-mutated OVCAR-5 cell line, and the constitutively activation of MAPK cascade in RAS-mutated carcinoma. However, it seems that the anti-EGFR antibody does not provide any additional benefit. After whole exome analysis is carried out on the patient with the shortest response, we observed the appearance of RB1 loss-of-function mutation that could be a mechanism of resistance to MEK inhibitors in RAS- of RAF-mutated cancers. The MEK inhibitor is effective in the advanced stages of low-grade serous carcinoma harboring RAS mutation with acceptable tolerance. RB1 loss could be a mechanism of resistance to MEK inhibitors in RAS-mutated low-grade serous carcinoma.

Triple-negative breast lobular carcinoma: a luminal androgen receptor carcinoma with specific ESRRA mutations.

Primary triple-negative invasive lobular breast carcinomas (TN-ILCs), which do not express hormone receptors and HER2 at diagnosis, are rare and poorly known. In this study, we analyzed the largest TN-ILC series ever reported in the literature, in comparison to phenotypically similar breast tumor subtypes: triple-negative invasive ductal carcinoma (TN-IDC) and hormone receptor-positive invasive lobular carcinoma (HR + ILC). All primary TN-ILCs registered in our database between 2000 and 2018 (n = 38) were compared to tumors from control groups, matched by stage and Elston/Ellis grade, with regard to clinical, pathologic, and immunohistochemical characteristics. A comparative molecular analysis (whole-exome and RNA sequencing using next-generation technology) was also performed. We found that TN-ILC patients were older than those with HR + ILC (P = 0.002) or TN-IDC (P < 0.001). Morphologically, TN-ILCs had aggressive phenotypes, with more pleomorphism (P = 0.003) and higher nuclear grades than HR + ILCs (P = 0.009). Immunohistochemistry showed that TN-ILCs less frequently expressed basal markers (CK5/6, EGFR and SOX10) than TN-IDCs (P < 0.001), while androgen receptor (AR) positivity was more prevalent (P < 0.001). Survival curves analysis did not show differences between TN-ILC and TN-IDC patients, while overall and distant metastasis-free survival were significantly worse compared to those with HR + ILCs (P = 0.047 and P = 0.039, respectively). At a molecular level, we found that TN-ILCs had particular transcriptomic profiles, characterized by increased AR signaling, and associated with frequent alterations in the PI3K network and ERBB2. Interestingly, whole-exome analysis also identified three specific recurrent ESRRA hotspot mutations in these tumors, which have never been described in breast cancer to date and which were absent in the other two tumor subtypes. Our findings highlight that TN-ILC is a unique aggressive breast cancer associated with elderly age, which belong to the luminal androgen receptor subtype as determined by immunohistochemistry and transcriptomic profiling. Moreover, it harbors specific molecular alterations (PI3K, ERBB2 and ESRRA) which may pave the way for new targeted therapeutic strategies.

ER-/PR+ breast cancer: A distinct entity, which is morphologically and molecularly close to triple-negative breast cancer.

Determining the status of steroid hormone receptors [oestrogen (ER) and progesterone receptors (PR)] is a crucial part of the breast cancer workup. Thereby, breast cancers can be classified into four subtypes. However, the existence of ER-/PR+ tumours, often reported to be ill-classified due to technical errors, remains controversial. In order to address this controversy, we reviewed the hormone receptor status of 49 breast tumours previously classified as ER-/PR+ by immunohistochemistry, and compared clinical, pathological and molecular characteristics of confirmed ER-/PR+ tumours with those of ER+ and triple-negative tumours. We unequivocally confirmed the ER-/PR+ status in 27 of 49 tumours (0.3% of all breast cancers diagnosed in our institution between 2000 and 2014). We found that ER-/PR+ were morphologically and histologically similar to triple-negative tumours, but very distinct from ER+ tumours, with more aggressive phenotypes and more frequent basal marker expression than the latter. On the molecular level, RNA sequencing revealed different gene expression profiles between the three groups. Of particular interest, several genes controlled by the suppressor of zest 12 (SUZ12) were upregulated in ER-/PR+ tumours. Overall, our results confirm that ER-/PR+ breast cancers are an extremely rare but 'real' tumour subtype that requires careful diagnosis and has distinct features warranting different responsiveness to therapies and different clinical outcomes. Studies on larger cohorts are needed to further characterise these tumours. The likely involvement of SUZ12 in their biology is an interesting finding which may - in a long run - give rise to the development of new therapeutic alternatives.

An exceptional metaplastic lobular breast carcinoma diagnosed through exome sequencing.

Metaplastic breast carcinoma is a rare subtype of breast cancer. This subtype is mostly found in association with poorly differentiated ductal breast carcinomas and rarely with other breast carcinoma types. We report the case of a 69-year-old woman with an exceptional invasive lobular breast carcinoma associated with metaplastic squamous cell bone metastasis occurring 2 years after the initial breast cancer diagnosis. Whole-exome sequencing and subsequent immunohistochemistry of the lesions were used to link the squamous cell bone metastasis of unknown origin to the primary breast carcinoma initially diagnosed. Searching for primary carcinoma when metastatic lesions of unknown origin occur can be complex. Current molecular biology techniques may help pathologists in associating metastasis with the primary carcinoma by identifying shared specific gene mutations, even when different morphological and immunohistochemical profiles are observed between the tumours.