The Clinicopathologic and Prognostic Value of Altered Chromosome 17 Centromere Copy Number in HER2 Fish Equivocal Breast Carcinomas

HER2-directed antibodies, affibodies and nanobodies as drug-delivery vehicles in breast cancer with a specific focus on radioimmunotherapy and radioimmunoimaging

PURPOSE

The aim of the present paper is to review the role of HER2 antibodies, affibodies and nanobodies as vehicles for imaging and therapy approaches in breast cancer, including a detailed look at recent clinical data from antibody drug conjugates and nanobodies as well as affibodies that are currently under development.

RESULTS

Clinical and preclinical studies have shown that the use of monoclonal antibodies in molecular imaging is impaired by slow blood clearance, associated with slow and low tumor uptake and with limited tumor penetration potential. Antibody fragments, such as nanobodies, on the other hand, can be radiolabelled with short-lived radioisotopes and provide high-contrast images within a few hours after injection, allowing early diagnosis and reduced radiation exposure of patients. Even in therapy, the small radioactively labeled nanobodies prove to be superior to radioactively labeled monoclonal antibodies due to their higher specificity and their ability to penetrate the tumor.

CONCLUSION

While monoclonal antibodies are well established drug delivery vehicles, the current literature on molecular imaging supports the notion that antibody fragments, such as affibodies or nanobodies, might be superior in this approach.

Clinicopathologic features of breast cancer reclassified as HER2-amplified by fluorescence in situ hybridization with alternative chromosome 17 probes

OBJECTIVE

Dual probe fluorescence in situ hybridization (FISH) assays for determination of human epidermal growth factor receptor 2 (HER2) gene amplification in breast cancer provide a ratio of HER2 to chromosome 17. The ratio may be skewed by copy number alterations (CNA) in the control locus for chromosome 17 (CEP17). We analyzed the impact of alternative chromosome 17 control probes on HER2 status in a series of breast cancers with an emphasis on patients reclassified as amplified.

METHODS

Breast cancer patients with equivocal HER2 immunohistochemistry (2+) and equivocal FISH with CEP17 were included. Reclassification of HER2 status was assessed with alternative chromosome 17 control probes (LIS1 and RARA).

RESULTS

A total of 40 unique patients with 46 specimens reflexed to alternative chromosome 17 probe testing were identified. The majority (>80%) of patients had pT1-2, hormone receptor-positive tumors with an intermediate or high combined histologic grade. There were 34/46 (73.9%) specimens reclassified as amplified with alternative probes, corresponding to 29/40 (72.5%) patients. Of the patients reclassified as amplified with alternative probes, 34.5% (10/29) received HER2-targeted therapy.

CONCLUSION

In this series, the majority of breast cancers tested with alternative chromosome 17 control probes under the 2013 ASCO/CAP Guidelines were converted to HER2-amplified. The treatment data and the clinicopathologic profile of the tumors suggest that most of these patients will neither receive nor benefit from HER2-targeted therapy. The findings support the recommendation in the 2018 ASCO/CAP HER2 Guidelines to discontinue the use of alternative chromosome 17 probes.

Amplification of Chromosome 17 Centromere (CEP17) in Breast Cancer Patients with a Result of HER2 2± by Immunohistochemistry

Background: Amplification of the centromeric region of chromosome 17 (CEP17) as measured by In Situ Hybridization (ISH) of the CEP17 probe is used clinically as part of the ISH assay for HER2 status determination in breast cancer. The value of amplification of CEP17 beyond its use in the HER2 ISH test has not been fully explored.Methods: A retrospective review of patients with breast cancer that had a dual probe HER2/CEP17 FISH test during an eight-year period was performed. Data on demographic and cancer-specific characteristics of the included patients were extracted. The group of patients with an amplified CEP17 defined as mean copy number of ≥3 per nucleus was compared with the group without amplification.Results: Two hundred and twelve patients were eligible and included in the analysis. Amplification of CEP17 was observed in 39 patients (18.4%). All patients in the amplified group had a concomitant amplification of HER2 (mean copy number ≥3 per nucleus). In the CEP17 non-amplified group 82 of 172 patients (47.7%) had an amplified HER2 status. More patients in the amplified group had a clinical HER2+ status according to the 3-protein classifier (30.8% versus 12.3% in the non-amplified group) and fewer patients in the amplified group had a clinical ER+/HER2- status (66.7% versus 81.3% in the non-amplified group, x² p = .01). Other significant differences between the amplified and CEP17 non-amplified groups were observed in their lymph node (LN) status (56.4% of patients in the amplified group versus 38.8% in the non-amplified group were lymph node positive, p = .04) and in the nuclear heterogeneity component of grade (91.2% of patients in the amplified group were nuclear grade 3 versus 67.1% in the non-amplified group, p = .005). There were no statistically significant differences between the groups in overall stage, grade, menopause status or histology. Recurrence Free Survival (RFS) was shorter in stage I to III patients with an amplified CEP17 compared with the non-amplified group.Conclusion: Patients with amplification of CEP17 had a co-amplified HER2 and were more commonly HER2+, LN positive and grade 3 in the nuclear component of grade.

Impact of repeat HER2 testing after initial equivocal HER2 FISH results using 2013 ASCO/CAP guidelines

PURPOSE

The updated 2013 American Society of Clinical Oncology/College of American Pathologists guideline recommendations for human epidermal growth factor receptor 2 (HER2) testing have made some major changes in HER2 fluorescence in situ hybridization (FISH) interpretation criteria with additional FISH equivocal cases. Repeat HER2 testing is recommended after initial HER2 FISH equivocal results; however, little is known about its impact on final HER2 status. The aim of this study is to investigate whether reflex test clarifies HER2 status, and to characterize clinicopathological features of the newly defined HER2 equivocal group.

METHODS

A total of 886 consecutive cases of primary invasive breast cancer conducted with dual-probe HER2 FISH testing between November 2013 and December 2015 were reviewed. HER2 immunohistochemistry (IHC) and FISH testing were performed on a different tissue block or a new specimen after initial HER2 FISH equivocal results.

RESULTS

Compared to 2007 guideline, 85 (9.6%) cases changed their category by using 2013 guideline. The major change of the 85 cases is that 57 (6.4%) cases in HER2 FISH-negative category changed to equivocal, and the equivocal category cases increased from 36 to 67. HER2 FISH equivocal was significantly associated with HER2 IHC equivocal (2+) and chromosome 17 polysomy (P < 0.01). Repeat testing by IHC and FISH clarified HER2 status in 33 and 42% of HER2 equivocal cases, respectively. Overall 32 (48%) initial HER2 equivocal cases stayed HER2 equivocal after repeat FISH and or IHC testing. These tumors were ER/PR+, with high KI-67 index.

CONCLUSION

New guidelines classify more HER2 FISH equivocal cases. Repeat HER2 testing clarifies HER2 status in about 50% of initial HER2 FISH equivocal cases. In addition, HER2 equivocal cases merit further study as there is limited information about prognosis and optimal treatment strategy for this population.

Prognostic significance of centromere 17 copy number gain in breast cancer depends on breast cancer subtype

Increased copy number of chromosome enumeration probe (CEP) targeting centromere 17 is frequently encountered during HER2 in situ hybridization (ISH) in breast cancer. The aim of this study was to clarify the clinicopathologic significance of CEP17 copy number gain in a relatively large series of breast cancer patients. We analyzed 945 cases of invasive breast cancers whose HER2 fluorescence ISH reports were available from 2004 to 2011 at a single institution and evaluated the association of CEP17 copy number gain with clinicopathologic features of tumors and patient survival. We detected 186 (19.7%) cases of CEP17 copy number gain (CEP17≥3.0) among 945 invasive breast cancers. In survival analysis, CEP17 copy number gain was not associated with disease-free survival of the patients in the whole group. Nonetheless, it was found to be an independent adverse prognostic factor in the HER2-negative group but not in the HER2-positive group. In further subgroup analyses, CEP17 copy number gain was revealed as an independent poor prognostic factor in HER2-negative and hormone receptor-positive breast cancers, and it was associated with aggressive histologic variables including high T stage, high histologic grade, lymphovascular invasion, p53 overexpression, and high Ki-67 proliferative index. In conclusion, we found that elevated CEP17 count can serve as a prognostic marker in luminal/HER2-negative subtype of invasive breast cancer. We advocate the use of the dual-colored fluorescence ISH using CEP17 rather than the single-colored one because it gives additional valuable information on CEP17 copy number alterations.