Prognostic impact of HER2 biomarker levels in trastuzumab-treated early HER2-positive breast cancer

BACKGROUND

Overexpression of human epidermal growth factor receptor 2 (HER2) caused by HER2 gene amplification is a driver in breast cancer tumorigenesis. We aimed to investigate the prognostic significance of manual scoring and digital image analysis (DIA) algorithm assessment of HER2 copy numbers and HER2/CEP17 ratios, along with ERBB2 mRNA levels among early-stage HER2-positive breast cancer patients treated with trastuzumab.

METHODS

This retrospective study comprised 371 early HER2-positive breast cancer patients treated with adjuvant trastuzumab, with HER2 re-testing performed on whole tumor sections. Digitized tumor tissue slides were manually scored and assessed with uPath HER2 Dual ISH image analysis, breast algorithm. Targeted ERBB2 mRNA levels were assessed by the Xpert® Breast Cancer STRAT4 Assay. HER2 copy number and HER2/CEP17 ratio from in situ hybridization assessment, along with ERBB2 mRNA levels, were explored in relation to recurrence-free survival (RFS).

RESULTS

The analysis showed that patients with tumors with the highest and lowest manually counted HER2 copy number levels had worse RFS than those with intermediate levels (HR = 2.7, CI 1.4-5.3, p = 0.003 and HR = 2.1, CI 1.1-3.9, p = 0.03, respectively). A similar trend was observed for HER2/CEP17 ratio, and the DIA algorithm confirmed the results. Moreover, patients with tumors with the highest and the lowest values of ERBB2 mRNA had a significantly worse prognosis (HR = 2.7, CI 1.4-5.1, p = 0.003 and HR = 2.8, CI 1.4-5.5, p = 0.004, respectively) compared to those with intermediate levels.

CONCLUSIONS

Our findings suggest that the association between any of the three HER2 biomarkers and RFS was nonlinear. Patients with tumors with the highest levels of HER2 gene amplification or ERBB2 mRNA were associated with a worse prognosis than those with intermediate levels, which is of importance to investigate in future clinical trials studying HER2-targeted therapy.

Human Epidermal Growth Factor Receptor 2-Targeting [68Ga]Ga-ABY-025 PET/CT Predicts Early Metabolic Response in Metastatic Breast Cancer

Imaging using the human epidermal growth factor receptor 2 (HER2)-binding tracer 68Ga-labeled ZHER2:2891-Cys-MMA-DOTA ([68Ga]Ga-ABY-025) was shown to reflect HER2 status determined by immunohistochemistry and in situ hybridization in metastatic breast cancer (MBC). This single-center open-label phase II study investigated how [68Ga]Ga-ABY-025 uptake corresponds to biopsy results and early treatment response in both primary breast cancer (PBC) planned for neoadjuvant chemotherapy and MBC. Methods: Forty patients with known positive HER2 status were included: 19 with PBC and 21 with MBC (median, 3 previous treatments). [68Ga]Ga-ABY-025 PET/CT, [18F]F-FDG PET/CT, and core-needle biopsies from targeted lesions were performed at baseline. [18F]F-FDG PET/CT was repeated after 2 cycles of therapy to calculate the directional change in tumor lesion glycolysis (Δ-TLG). The largest lesions (up to 5) were evaluated in all 3 scans per patient. SUVs from [68Ga]Ga-ABY-025 PET/CT were compared with the biopsied HER2 status and Δ-TLG by receiver operating characteristic analyses. Results: Trial biopsies were HER2-positive in 31 patients, HER2-negative in 6 patients, and borderline HER2-positive in 3 patients. The [68Ga]Ga-ABY-025 PET/CT cutoff SUVmax of 6.0 predicted a Δ-TLG lower than -25% with 86% sensitivity and 67% specificity in soft-tissue lesions (area under the curve, 0.74 [95% CI, 0.67-0.82]; P = 0.01). Compared with the HER2 status, this cutoff resulted in clinically relevant discordant findings in 12 of 40 patients. Metabolic response (Δ-TLG) was more pronounced in PBC (-71% [95% CI, -58% to -83%]; P < 0.0001) than in MBC (-27% [95% CI, -16% to -38%]; P < 0.0001), but [68Ga]Ga-ABY-025 SUVmax was similar in both with a mean SUVmax of 9.8 (95% CI, 6.3-13.3) and 13.9 (95% CI, 10.5-17.2), respectively (P = 0.10). In multivariate analysis, global Δ-TLG was positively associated with the number of previous treatments (P = 0.0004) and negatively associated with [68Ga]Ga-ABY-025 PET/CT SUVmax (P = 0.018) but not with HER2 status (P = 0.09). Conclusion: [68Ga]Ga-ABY-025 PET/CT predicted early metabolic response to HER2-targeted therapy in HER2-positive breast cancer. Metabolic response was attenuated in recurrent disease. [68Ga]Ga-ABY-025 PET/CT appears to provide an estimate of the HER2 expression required to induce tumor metabolic remission by targeted therapies and might be useful as an adjunct diagnostic tool.

Abstract P1-02-03: Tumor-infiltrating lymphocytes but not HER2 copy number or ratio show prognostic value in trastuzumab-treated HER2-positive breast cancer

Background: Around 15% of all breast cancers are HER2+, a subtype that prior to HER2-targeted therapy was associated with a poor prognosis. With advances in treatment the survival has dramatically improved, and previous studies suggest that the level of HER2 copies are predictive of the effect of anti-HER2 therapies. However, some patients progress despite HER2-targeted therapy and routine HER2 testing is hampered by inaccuracy to discriminate patients with therapy-resistant disease. Furthermore, tumor-infiltrating lymphocytes (TILs) in the tumor stroma shows prognostic value not only in triple negative but also in HER2+ breast cancer. However, the clinical utility in the adjuvant setting for HER2+ disease needs further validation. The aim of this study was to investigate the prognostic significance of HER2/CEP17 ratio, HER2 copy numbers and TILs among early breast cancer patients treated with HER2-targeted therapy. Materials and methods: A retrospective study cohort comprising a total of 584 patients with HER2+ early breast cancer, all treated with the monoclonal antibody trastuzumab targeting HER2 during 2006-2014 in the Stockholm Region, Sweden, was identified and HER2 re-testing (silver in situ hybridization and immunohistochemistry (IHC)) was performed on 474 whole tissue sections prior to neoadjuvant (18.1%) or adjuvant therapy. Stromal TILs were manually assessed on all hematoxylin-eosin stained slides. Registry-based information on patient- and tumor characteristics including treatment were completed from medical records with a median follow-up of 8.0 years. Results: Among the 474 analyzed tumors, 11.4% were HER2 IHC score 2+ and 86.7% were 3+. In addition, 61.6% were ER+ and the median TIL score was 15%. The median HER2 copy number was 9.8 signals/cell and only 12.9% had &lt;6.0 average HER2 signals/cell and 2.5% had a HER2/CEP17 ratio &lt;2.0. Survival analysis showed no significant association between HER2 IHC score (recurrence: p=0.58; breast cancer specific death: p=0.69), HER2 signals (p=0.77; p=0.73), HER2/CEP17 ratio (p=0.73; p=0.85), ER status (p=0.55; p=0.11), PR status (p=0.97; p=0.46), Ki67 (p=0.14; p=0.77) or tumor grade (p=0.71; p=0.16) with risk of recurrence or breast cancer specific death. The hazard ratio (HR) for recurrence did not significantly differ by HER2 signals/cell (HR 1.12, CI 0.53-2.37, p=0.77) or ER status (HR 1.18, CI 0.68-2.05, p=0.55). Tumors with low TILs were independently associated with recurrence (cutoff &lt;40%: HR 4.5, CI 1.4-14.9, p=0.012) and breast cancer specific survival (cutoff &lt;30%: HR 3.5, CI 1.2-10.1, p=0.02). Among the 56 recurrences (11.8%), 37.5% had ER- primary tumors and 82.4% of the 34 HER2-analyzed recurrent tumors remained HER2+. Conclusions: This study demonstrates that routine clinicopathological data, including HER2 status, is insufficient to predict breast cancer recurrence among patients treated with HER2-targeted therapy. Neither HER2 levels, HER2/CEP17 ratio or ER status correlated to risk of recurrence. Importantly, TILs showed robust prognostic potential in trastuzumab-treated patients. Our results emphasize the need for detailed molecular analyses to understand the biology behind resistance to HER2-targeted therapy and to further tailor therapy for HER2+ breast cancer patients.

Citation Format: Stephanie Robertson, Caroline Rönnlund, Irma Fredriksson, Theodoros Foukakis, Johan Hartman. Tumor-infiltrating lymphocytes but not HER2 copy number or ratio show prognostic value in trastuzumab-treated HER2-positive breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-02-03.

Re-testing of predictive biomarkers on surgical breast cancer specimens is clinically relevant

PURPOSE

The accuracy of predictive and prognostic biomarker assessment in breast cancer is paramount since these guide therapy decisions. The aim was to investigate the concordance of biomarkers and immunohistochemical (IHC)-based surrogate tumor subtypes between core needle biopsies (CNB) and consecutive paired breast cancer surgical resections.

METHODS

This retrospective study comprised two cohorts of patients with primary breast cancer diagnosed between 2016 and 2017: one treated with primary surgery (n = 526) and one with neoadjuvant chemotherapy (NAC) (n = 216). The agreement between preoperative CNB and paired tumor specimens regarding the assessment of biomarkers and surrogate tumor subtypes was evaluated in both cohorts.

RESULTS

In the primary surgery cohort, the concordance rates and kappa values for estrogen receptor (ER), progesterone receptor (PR) and Ki67 were 98.6% (κ = 0.917), 89.3% (κ = 0.725) and 78.8% (κ = 0.529), respectively. Importantly, human epidermal growth factor receptor 2 (HER2) IHC assessment showed only moderate agreement (κ = 0.462). HER2 status combining IHC and in situ hybridization was discordant in 3.6% of cases, potentially impacting on indications for HER2-targeted therapy. The concordance rate for IHC-based surrogate tumor subtypes was only 73.2-78.3%. Generally lower concordance rates for ER, PR and HER2 were observed in the NAC cohort. Here, HER2 status was discordant in 7.4%.

CONCLUSIONS

The agreement of HER2 and Ki67 between CNB and paired surgical specimen in primary breast cancer is insufficient. Limited agreement of surrogate tumor subtypes indicates a significant clinical value of biomarker re-testing on surgical specimens.

Estrogen-dependent downregulation of hairy and enhancer of split homolog-1 gene expression in breast cancer cells is mediated via a 3' distal element

Regulation of hairy and enhancer of split homologue-1 (HES-1) by estradiol and all-trans retinoic acid affects proliferation of human breast cancer cells. Here, we identify and characterize cis-regulatory elements involved in HES-1 regulation. In the distal 5' promoter of the HES-1 gene, we found a retinoic acid response element and in the distal 3' region, an estrogen receptor alpha(ER)alpha binding site. The ERalpha binding site, composed of an estrogen response element (ERE) and an ERE half-site, is important for both ERalpha binding and transcriptional regulation. Chromatin immunoprecipitation assays revealed that ERalpha is recruited to the ERE and associates with the HES-1 promoter. We also show recruitment of nuclear receptor co-regulators to the ERE in response to estradiol, followed by a decrease in histone acetylation and RNA polymerase II docking in the HES-1 promoter region. Our findings are consistent with a novel type of repressive estrogen response element in the distal 3' region of the HES-1 gene.