Human Epidermal Growth Factor Receptor 2 Testing by Fluorescent In Situ Hybridization: Positive or Negative? ASCO/College of American Pathologists Guidelines 2007, 2013, and 2018

The journey of patients affected by metastatic hormone receptor-positive/HER2-negative breast cancer from CDK 4/6 inhibitors to second-line treatment: A real-world analysis of 701 patients enrolled in the GIM14/BIOMETA study

PURPOSE

The aim of this study was to evaluate the effectiveness of CDK 4/6 inhibitors (CDK 4-6i) according to HER2 status (low/zero), and endocrine resistance/sensitivity, as well as the efficacy of second-line treatments, in a large real-world cohort.

METHODS

The GIM14/BIOMETA study (NCT02284581) is a retrospective/prospective study of the Gruppo Italiano Mammella evaluating treatment patterns and survival outcomes in patients with metastatic breast cancer (MBC). We retrieved data on patients with hormone receptor-positive/HER2-negative MBC receiving first-line CDK 4/6i.

RESULTS

Among 3832 patients enrolled in the GIM14-BIOMETA study, 701 were eligible. At a median follow-up of 24.80 months, no significant differences were found between HER2-zero and HER2-low subgroups in terms of first-line time to treatment discontinuation (TTD) (26.16 months [IQR 12.84-NR] vs. 27.60 months [IQR 12.12-64.44], p = 0.972) or overall survival (OS) (mOS>60 months for both groups, p = 0.398). Median TTD was 33.24 months (IQR 16.32-NR) for the endocrine sensitive subgroup, 19.92 months (IQR 8.88-51.24) for the secondary endocrine resistant subgroup and 17.40 months (IQR 7.44-24.72) for the primary endocrine resistant subset, respectively (p < 0.001). Among 239 patients receiving second-line treatment, no significant difference (p = 0.188) was found in terms of second-line TTD between those treated with capecitabine (6.11 months, IQR 2.96-11.47), taxane-based chemotherapy (5.06 months, IQR 2.99-9.99), everolimus plus exemestane (5.39 months, IQR 2.53-9.03) or fulvestrant (6.44 months, IQR 3.38-NR).

CONCLUSIONS

Endocrine therapy plus CDK 4/6i represents an effective treatment, regardless of HER2 status (low/zero). Second-line agents did not differ significantly in terms of TTD. Endocrine resistant cancers exhibit poor response to CDK 4/6i.

Evolving treatments and outcomes in HER2-Positive metastatic breast cancer: Data from the GIM14/BIOMETA study

BACKGROUND

Treatment for HER2-positive (+) metastatic breast cancer has improved in the last decade. We analyzed treatment changes over time and their impact on patients outcomes in a real-world dataset.

METHODS

Data from 637 HER2+ patients with metastatic breast cancer enrolled in the multicenter Italian GIM14/BIOMETA study were retrieved. Progression-free survival (PFS) over time was evaluated according to the type of anti-HER2 therapy, disease onset (de novo vs. relapsing), metastatic site, and year of treatment (2000-2013 vs. 2014-2020).

RESULTS

Median follow-up was 64.4 months. Overall, for first-line therapies, mPFS was 16.5 vs 19.5 months for patients treated in 2000-2013 vs 2014-2020 (HR: 0.78, 95% CI:0.65-0.94, P = 0.008). mPFS improved over time in all patients except for those with brain metastasis. Interestingly mPFS was 17.4 vs13.4 months (HR, 1.49; 95% CI, 1.13-1.98, P = 0.005) in 2000-2013 and 24.4 vs 20.9 months (HR 1.04; 95% CI 0.78-1.40 p = 0.77) in 2014-2020 in pts without vs with liver metastases. For second line therapies, the overall median PFS was 9.6 months (95% CI, 8.31-10.97) and did not change over time.

CONCLUSION

Median first-line PFS improved since 2014, mainly due to the introduction of pertuzumab. The outcome of patients with liver metastases appears to have improved in recent years. Patients with brain metastases had the worst PFS, which also did not improve over time.

The spectrum of HER2 expression in breast cancer: linking immunohistochemistry quantification with in situ hybridization assay

We aimed to document the pathological characteristics of breast cancer (BC) cases with different scores of HER2 by immunohistochemistry (IHC), as well as to establish a relationship between HER2 expression and HER2 amplification by in situ hybridization (ISH). A cohort of 258 primary BC cases was evaluated for HER2 gene amplification with bright-field ISH. All HER2-negative and HER2-positive cases by IHC were concordant with the ISH classification. BC cases with score of 0 had lower average of HER2 copy number compared to cases with score of 1 + . HER2-equivocal cases by IHC had intermediate pathological characteristics between HER2-negative and HER2-positive cases. About 12% of HER2-equivocal cases were classified as ISH-positive. HER2-equivocal cases with HER2 gene amplification had proliferation index, HER2/CEP17 ratio, and average of HER2 copy number between HER2-equivocal cases without HER2 gene amplification and HER2-positive cases by IHC. Additionally, HER2-equivocal cases with HER2 amplification had score of 2 + in at least 50% of the total tumor area, with a proportion of ISH-positive cases increasing with the amount of score of 2 + present in the tumor. The quantification of score of 2 + in the tumor predicted the ISH classification with an AUC of 0.902. A logistic regression model using the same HER2 quantification and the nuclear score was able to increase the abovementioned prediction to an AUC of 0.929. As such, we were able to link HER2 quantification by IHC and morphological analysis with HER2 amplification by ISH.

Detection of ERBB2 amplification in uterine serous carcinoma by next-generation sequencing: an approach highly concordant with standard assays

Uterine serous carcinoma is an aggressive subtype of endometrial cancer that accounts for fewer than 10% of endometrial carcinomas but is responsible for about half of deaths. A subset of cases has HER2 overexpression secondary to ERBB2 gene amplification, and these patients may benefit from anti-HER2 therapies, such as trastuzumab. HER2 protein overexpression is currently assessed by immunohistochemistry (IHC) and ERBB2 gene amplification by fluorescence in situ hybridization (FISH). Targeted next-generation sequencing (NGS) is increasingly used to routinely identify predictive and prognostic molecular abnormalities in endometrial carcinoma. To investigate the ability of a targeted NGS panel to detect ERBB2 amplification, we identified cases of uterine serous carcinoma (n = 93) and compared HER2 expression by IHC and copy number assessed by FISH with copy number status assessed by NGS. ERBB2 copy number status using a combination of IHC and FISH was interpreted using the 2018 ASCO/CAP guidelines for breast carcinoma. ERBB2 amplification by NGS was determined by the relative number of reads mapping to ERBB2 in tumor DNA compared to control nonneoplastic DNA. Cases with copy number ≥6 were considered amplified and copy number <6 were non-amplified. By IHC, 70 specimens were classified as negative (0 or 1+), 19 were classified as equivocal (2+), and 4 were classified as positive (3+). Using combined IHC/FISH, ERBB2 amplification was observed in 8 of 93 cases (9%). NGS identified the same 8 cases with copy number ≥6; all 85 others had copy number <6. In this series, NGS had 100% concordance with combined IHC/FISH in identifying ERBB2 amplification. NGS is highly accurate in detecting ERBB2 amplification in uterine serous carcinoma and provides an alternative to measurement by IHC and FISH.

Impact of the Updated 2018 American Society of Clinical Oncology/College of American Pathologists Guideline for Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer

CONTEXT.—

The updated American Society of Clinical Oncology/College of American Pathologists guideline for human epidermal growth factor receptor 2 (HER2) testing in breast cancer requires pathologists to re-evaluate HER2 status.

OBJECTIVE.—

To define HER2 status of breast cancer using immunohistochemistry and fluorescence in situ hybridization.

DESIGN.—

Diagnostic reports of invasive breast cancers made between 2014 and 2018 with HER2 immunohistochemistry and fluorescence in situ hybridization results were retrieved. HER2 status was re-defined using the updated recommendations.

RESULTS.—

Of 2514 tumors, 89.7% (2254 of 2514) suggested for fluorescence in situ hybridization assay were HER2 immunohistochemistry 2+. Approximately 8.9% (225 of 2514) and 1.4% (35 of 2514) of tumors were of immunohistochemistry 0/1+ and 3+, respectively. Based on the average HER2 copy number and HER2:CEP17 ratio, tumors were assigned into 5 groups, including 13.1% (330 of 2514) group 1 tumors, 2.1% (52 of 2514) group 2 tumors, 1.1% (27 of 2514) group 3 tumors, 7.0% (175 of 2514) group 4 tumors, and 76.8% (1930 of 2514) group 5 tumors. In combination with immunohistochemistry, all tumors in group 2 and group 4 changed HER2 status, from positive and equivocal into negative, respectively, while group 3 tumors remained positive. Comparative analyses of clinicopathologic features of tumors in different groups revealed that group 2 and 4 tumors displayed worse clinicopathologic features than those of group 5, while group 3 tumors shared similar clinicopathologic features to those of group 1.

CONCLUSIONS.—

Following the updated guideline, HER2 status is clearly designated. Significant differences regarding clinical features were observed between tumors in different groups but they share the same HER2 status, suggesting further validation of the accuracy of this diagnostic approach is warranted.

Implementation of the 2018 American Society of Clinical Oncology/College of American Pathologists Guidelines on HER2/neu Assessment by FISH in breast cancers: predicted impact in a single institutional cohort

The 2018 American Society of Clinical Oncology (ASCO) and College of American Pathologists (CAP) update modified the interpretation guidelines for human epidermal growth factor receptor 2 (HER2) testing by incorporating immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) results in a subset of cases. Importantly, the new guidelines eliminate "equivocal" results, as well as the use of alternative chromosome 17 probes as the primary strategy for resolving the indeterminate FISH results. Herein, we investigate the predicted impact of implementing the 2018 ASCO/CAP guidelines on HER2 assessment by FISH in breast cancers, using data from a single institution. We compared the HER2 status of 1542 consecutive cases of breast carcinoma, interpreted by 2013 and 2018 ASCO/CAP guidelines. In total, 10.7% (165/1542) of the cases had a different final interpretation by 2018 guidelines compared with 2013 guidelines, including 70 previously HER2-positive cases reclassified as negative, four previously negative cases reclassified as positive, and 91 previously equivocal cases reclassified as negative. Overall, the number of HER2-positive cancers was reduced by 66 cases (4.3% reduction in the HER2 positivity rate). The newly HER2-negative cases were mostly estrogen receptor positive (90%), progesterone receptor positive (80%), stage 1 (60.9%), and grade 1-2 (59.4%) cancers; 70% of them had been designated as HER2 positive only after the use of an alternative chromosome 17 FISH probe after an intially equivocal result from the standard CEP17 probe. Overall, implementing the revised 2018 HER2 guidelines is predicted to change the HER2 results of 10.7% of breast cancers, mainly by reclassifying previously equivocal to negative results.

Assessing the impact of the 2018 American Society of Clinical Oncology/College of American Pathologists recommendations on human epidermal growth factor receptor 2 testing by fluorescence in situ hybridization in breast carcinoma

The American Society of Clinical Oncology/College of American Pathologists recently updated their recommendations on human epidermal growth factor receptor 2 (HER2) testing by fluorescence in situ hybridization (FISH) in invasive breast cancer, with a focus on the clarification of less common test patterns of ISH. We assessed the impact of the updated ASCO/CAP guidelines on 1044 FISH tested tumors by comparing categorization according to the 2007, 2013, and 2018 ISH classification criteria. The 2013 guidelines increased the number of positive cases (17.4% vs 10.7%) identifying 70 (6.7%) additional patients who met the eligibility criteria for consideration for HER2-targeted therapy compared with the 2007 guidelines. There was a reduction in equivocal tumors (7.7%) with tumors classified as equivocal by the 2007 guidelines (n = 136) redistributed into positive (74, 54.4%) and negative (49, 36.0%) groups. The 2018 guidelines reclassified 10.8% of tumors in our series with a reduction in the number of positive tumors (7.1%). While the proportion of positive tumors (10.2%) was similar to that in 2007 (10.7%), the composition of this group was significantly altered. HER2 equivocal cases, a group which under the 2013 guidelines caused diagnostic and treatment difficulties, were largely eliminated. Our findings suggest that the 2018 update represents a potentially significant change in therapeutic options for a substantial proportion of patients with 2.9% of FISH-positive tumors according to the 2007 and 2013 guidelines now categorized as HER2 negative and, thus, ineligible for HER2-targeted therapy.

What to expect from the 2018 ASCO/CAP HER2 guideline in the reflex in situ hybridization test of immunohistochemically equivocal 2+ cases?

To evaluate the effect of the 2018 ASCO/CAP guideline in the identification of HER2-positive breast carcinomas (BC) in reflex in situ hybridization (ISH) test. A total of 592 primary invasive BC cases from before and after the publication of the updated ASCO/CAP guideline were evaluated for HER2 amplification by silver ISH according to the 2013 and 2018 guidelines. Cases were mostly (95%) HER2 equivocal by immunohistochemistry (IHC), not centrally reviewed. Other reasons for referring cases were IHC confirmation, IHC discordancy (either between needle-core-biopsy (NCB) and surgical excision specimen (SES) or between different laboratories) and IHC result unexpected for histopathologic features. Cases evaluated with the 2013 guideline (1st cohort) were 14.6% HER2-positive, decreasing significantly after the reclassification with the 2018 guideline due to the exclusion of group 2 cases without HER2 protein overexpression. Cases studied after the implementation of the 2018 guideline (2nd cohort) were 8.7% HER2-positive, a frequency that was not significantly different from the reclassification of the 1st cohort with the 2018 guideline. All cases referred for IHC confirmation had the expected ISH result. Cases with IHC discordancy between NCB and SES were ISH concordant. Only one out of 14 cases with an IHC score 3+ and classified as histological grade 1 or with a Ki67 below 10% was classified as ISH HER2-positive. The 2018 ASCO/CAP guideline resulted in a decrease of HER2-positive cases in reflex ISH test, selecting less patients for anti-HER2-targeted therapy.