Chromosome 17 polysomy without HER2 amplification does not predict response to lapatinib in metastatic breast cancer--letter

Prognostic significance of equivocal human epidermal growth factor receptor 2 results and clinical utility of alternative chromosome 17 genes in patients with invasive breast cancer: A cohort study

BACKGROUND

The 2013 testing guidelines for determining the human epidermal growth factor receptor 2 (HER2) status include new cutoff points for the HER2/chromosome enumeration probe 17 (CEP17) ratio and the average HER2 copy number per cell, and they recommend using a reflex test with alternative chromosome 17 probes (Ch17Ps) to resolve equivocal HER2 results. This study sought to determine the clinical utility of alternative Ch17Ps in equivocal cases and the effects of equivocal results and/or a change in the HER2 status on patients' outcomes.

METHODS

The University of Texas MD Anderson Cancer Center database of HER2 dual-probe fluorescence in situ hybridization results from 2000 to 2010 was searched for cases of invasive breast cancer with HER2/CEP17 ratios < 2 and average HER2 copy numbers < 6 per cell. Cases with HER2 copy numbers of 4 to < 6 (the definition of equivocal HER2 results) were analyzed with alternative Ch17Ps for Smith-Magenis syndrome and retinoic acid receptor α genes. Disease-free survival (DFS) and overall survival (OS) were evaluated with respect to the HER2 copy number with multivariate Cox proportional hazards regression.

RESULTS

Among the 3630 patients meeting the inclusion criteria, 137 (4%) had equivocal HER2 results. With alternative Ch17Ps, 35 of 57 equivocal HER2 cases (61%) were upgraded to a positive HER2 status, and 22 cases (39%) remained unchanged. The 5-year DFS and OS adjusted hazard ratios (HRs) for copy numbers of 4 to < 6 versus < 4 were 0.6 (95% confidence interval [CI], 0.3-1.2) and 0.5 (95% CI, 0.2-1.0) with P values of .16 and .66, respectively. In comparison with HER2-negative cases, these CIs indicated that equivocal HER2 results were associated with either a protective effect (HR, < 0.5) or no effect (HR, 1.0).

CONCLUSIONS

These findings rule out a significant deleterious effect of equivocal HER2 results. Alternative Ch17Ps may erroneously upgrade the HER2 status; therefore, they cannot be considered reliable in clinical practice. Cancer 2017;123:1115-1123. © 2016 American Cancer Society.

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

Chromosome 17 centromere (CEP17) gain is frequently observed in breast cancer by fluorescence in situ hybridization (FISH). To address the biologic characteristics and clinical significance of CEP17 gain in a large population of breast cancer patients, we performed FISH on a series of 770 breast cancer tissues to evaluate the status of human epidermal growth factor receptor 2 (HER2) gene and CEP17 by immunohistochemistry (IHC) and FISH. Among the 770 specimens, 184 cases showed CEP17 gain (23.9%). Histological grade, nodal status, HER2 by IHC, Ki 67 index, and p53 expression were significantly different between CEP17 gain tumors and HER2-positive tumors. In contrast with HER2-negative tumors, CEP17 gain tumors showed higher histological grade, higher HER2 score by IHC, and higher Ki 67 index. The patients with CEP17 gain tumors had an intermediate survival between HER2-negative and HER2-positive patients. By comparison to HER2-negative and HER2-positive patients, survival in luminal B patients with CEP17 gain tumors also fell in between. In conclusion, CEP17 gain tumors show specific differences compared with HER2-negative and HER2-positive tumors in clinical parameters and prognosis.

Comparison of the 2007 and 2013 ASCO/CAP evaluation systems for HER2 amplification in breast cancer

It has been proven that chromosome 17 centromere (CEP17) amplification causes misleading human epidermal growth factor receptor 2 (HER2) gene fluorescence in situ hybridization (FISH) results, precluding anti-HER2-based therapy in some patients with breast carcinoma. We used the 2013 American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) scoring criteria to evaluate HER2 amplification status in 175 cases of breast carcinoma with chromosome 17 polysomy. We used immunohistochemistry (IHC) to determine the HER2 amplification status, and 2-color FISH to detect CEP17, and reviewed the results of initial evaluation using the 2007 ASCO/CAP criteria. Of the 175 cases, 17, 95, and 63 were IHC 0/1+, 2+, and 3+, respectively. Evaluation of IHC HER2 status according to the 2013 ASCO/CAP criteria identified significantly more HER2-positive cases compared to cases evaluated using the 2007 criteria (p<0.05). When the FISH results were evaluated in parallel with the 2013 criteria, we found that 22 cases were not HER2-negative despite the presence of polysomy 17, which, according to the 2013 criteria, indicates HER2-positive status. Our findings indicate that in breast carcinoma, HER2 status in the presence of polysomy 17 may vary with the scoring criteria used. In turn, performing FISH and evaluating samples using the 2013 ASCO/CAP criteria means that more patients with breast cancer may be appropriate for targeted treatment with trastuzumab, potentially improving their outcome.

Concomitant detection of HER2 protein and gene alterations by immunohistochemistry (IHC) and silver enhanced in situ hybridization (SISH) identifies HER2 positive breast cancer with and without gene amplification

Introduction

HER2 status assessment became a mandatory test assay in breast cancer, giving prognostic and predictive information including eligibility for adjuvant anti-HER2 therapy. Precise and reliable assessment of HER2 status is therefore of utmost importance. In this study we analyzed breast cancer samples by a novel technology for concomitant detection of the HER2 protein and gene copy number.

Methods

Tissue microarrays containing 589 invasive breast cancer samples were analyzed with a double immunohistochemistry (IHC) and silver labeled in situ hybridization (SISH) assay simultaneously detecting HER2 protein and gene copy number in the same tumor cells. This bright-field assay was analyzed using scores according to the modified ASCO guidelines and the results were correlated with patient prognosis.

Results

Overall concordance rate between protein expression and the presence of gene amplification was 98%. Fifty-seven of 60 tumors (95%) with IHC score 3+, 6 of 10 tumors with IHC score 2+ (60%) and only 3 of 519 tumors (0.6%) with IHC score 0/1+ were amplified by SISH. Patients with gene amplification despite IHC score 0/1+ had a tendency for worse overall survival (p = 0.088, reaching nearly statistical significance) compared to IHC score 0/1+ without amplification. In contrast, there was no difference in overall survival in IHC score 3+/2+ tumors with and without gene amplification.

Conclusions

The novel double IHC and SISH assay for HER2 is efficient in the identification of breast cancer with discordant HER2 protein and HER2 gene status, especially for the prognostically relevant groups of HER2 protein negative tumors with HER2 amplification and HER2 protein positive tumors without HER2 amplification. Breast cancer without HER2 amplification among IHC score 2+/3+ tumors (10% in our cohort) suggests that other mechanisms than gene amplification contribute to protein overexpression in these cells.

Assessment of HER2 status in breast cancer: overall positivity rate and accuracy by fluorescence in situ hybridization and immunohistochemistry in a single institution over 12 years: a quality control study

Background

The gold standard of HER2 status assessment in breast cancer is still debated. Immunohistochemistry (IHC) and in-situ technology as fluorescent-labeled methodology (FISH) can be influenced by pre-analytical factors, assay-conditions and interpretation of test results. We retrospectively conducted this quality control study and analyzed HER2 test results in breast cancer within the routine diagnostic service in a single institution over a period of 12 years. We addressed the question how stable and concordant IHC and FISH methods are and whether HER2 positivity rate has changed over this period.

Methods

Data of 7714 consecutive HER2-FISH-assays in a period of 12 years (2001–2012) on breast cancer biopsies and excision specimens were retrospectively analyzed. From 2001 to 2004, FISH tests were performed from all cases with IHC score 3+ and 2+ (and in some tumors with IHC score 1+ and 0). From 2005–2010, HER2 status was only determined by FISH. From 2011–2012, all breast carcinomas were analyzed by both IHC and FISH. Scoring and cut-off-definition were done according to time-current ASCO-CAP and FDA-guidelines.

Results

Between 2001–2004, IHC score 3+ was diagnosed in 22% of cases, 69% of these 3+ cases were amplified by FISH. 6% of IHC score 0/1+ cases were amplified by FISH. There was a mean amplification rate of 15.8% (range 13 -19%) using FISH only HER2-assays (2005–2010). Starting 2008, a slight drop in the amplification rate from 17% to 14% was noticed due to the modified ASCO-criteria in 2007. From 2011–2012, 12% of cases were 3+ by IHC, 84% of them were amplified by FISH. Less than 1% of IHC score 0/1+ cases were amplified by FISH. Concordance between FISH and IHC increased from 83% to 97%.

Conclusions

Our quality control study demonstrates that HER2 positivity rate remained stable by FISH-technology but showed a significant variation by IHC over the analyzed 12 years. Improvement in concordance rate was due to standardization of pre-analytical factors, scoring and interpretation.

Chromosome 17 polysomy: correlation with histological parameters and HER2NEU gene amplification

Aims

HER2NEU gene amplification is present in the majority of invasive breast carcinomas that have HER2 protein overexpression. A subset of breast cancers harbour an increased chromosome 17 (CEP17) copy number (polysomy 17). We investigated the clinicopathologic significance of polysomy 17 in correlation with various histological parameters and HER2NEU gene amplification.

Methods

We collected the surgical specimens of 266 consecutive cases of primary invasive breast carcinomas. HER2NEU gene status and CEP17 copy numbers were assessed by fluorescent in situ hybridisation (FISH). Chromosome 17 polysomy was determined by the presence of ≥3 average CEP17 signals per nucleus.

Results

63 tumours (23.7%) harboured polysomy 17. Carcinomas with polysomy 17 were associated with adverse histological indicators including high histological grade, high nuclear grade, poor Nottingham Prognostic Index, advanced local tumour extent and progesterone receptor negativity. Polysomy 17 was common to HER2NEU amplified and unamplified tumours, and more frequently observed in HER2NEU unamplified (71.4%) cases.

Conclusions

In the absence of the gene amplification, HER2 protein overexpression may be explained by other mechanisms including polysomy 17.

Oncogene amplification in male breast cancer: analysis by multiplex ligation-dependent probe amplification

Gene amplification is an important mechanism for oncogene activation, a crucial step in carcinogenesis. Compared to female breast cancer, little is known on the genetic makeup of male breast cancer, because large series are lacking. Copy number changes of 21 breast cancer related genes were studied in 110 male breast cancers using multiplex ligation-dependent probe amplification. A ratio of >1.3 was regarded indicative for gene copy number gain and a ratio >2.0 for gene amplification. Data were correlated with clinicopathological features, prognosis and 17 genes were compared with a group of female breast cancers. Gene copy number gain of CCND1, TRAF4, CDC6 and MTDH was seen in >40 % of the male breast cancer cases, with also frequent amplification. The number of genes with copy number gain and several single genes were associated with high grade, but only CCND1 amplification was an independent predictor of adverse survival in Cox regression (p = 0.015; hazard ratio 3.0). In unsupervised hierarchical clustering a distinctive group of male breast cancer with poor prognosis (p = 0.009; hazard ratio 3.4) was identified, characterized by frequent CCND1, MTDH, CDC6, ADAM9, TRAF4 and MYC copy number gain. Compared to female breast cancers, EGFR (p = 0.005) and CCND1 (p = 0.041) copy number gain was more often seen in male breast cancer, while copy number gain of EMSY (p = 0.004) and CPD (p = 0.001) and amplification in general was less frequent. In conclusion, several female breast cancer genes also seem to be important in male breast carcinogenesis. However, there are also clear differences in copy number changes between male and female breast cancers, pointing toward differences in carcinogenesis between male and female breast cancer and emphasizing the importance of identifying biomarkers and therapeutic agents based on research in male breast cancer. In addition CCND1 amplification seems to be an independent prognosticator in male breast cancer.