HER2gene copy number and breast cancer-specific survival

Advances in cancer genomics and precision oncology

BACKGROUND

Next-generation sequencing has revolutionized genome science over the last two decades. Indeed, the wealth of sequence information on our genome has deepened our understanding on cancer. Cancer is a genetic disease caused by genetic or epigenetic alternations that affect the expression of genes that control cell functions, particularly cell growth and division. Utilization of next-generation sequencing in cancer gene panels has enabled the identification of actionable gene alterations in cancer patients to guide personalized precision medicine.

OBJECTIVE

The aim is to provide information that can identify actionable gene alterations, enabling personalized precision medicine for cancer patients.

RESULTS & DISCUSSION

Equipped with next-generation sequencing techniques, international collaboration programs on cancer genomics have identified numerous mutations, gene fusions, microsatellite variations, copy number variations, and epigenetics changes that promote the transformation of normal cells into tumors. Cancer classification has traditionally been based on cell type or tissue-of-origin and the morphological characteristics of the cancer. However, interactive genomic analyses have currently reclassified cancers based on systemic molecular-based taxonomy. Although all cancer-causing genes and mechanisms have yet to be completely understood or identified, personalized or precision medicine is now currently possible for some forms of cancer. Unlike the "one-size-fits-all" approach of traditional medicine, precision medicine allows for customized or personalized treatment based on genomic information.

CONCLUSION

Despite the availability of numerous cancer gene panels, technological innovation in genomics and expansion of knowledge on the cancer genome will allow precision oncology to manage even more types of cancers.

Pertuzumab as second‑ or later‑line therapy for human epidermal growth factor receptor 2‑positive metastatic breast cancer: A clinical experience

Trastuzumab and pertuzumab with taxane-based chemotherapy are considered the first-line standard therapy for human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (mBC). Pertuzumab is also a later-line therapy for mBC in Switzerland, although limited safety and efficacy data are available. The present study assessed the therapeutic regimens, toxicities and clinical outcomes after second- or later-line pertuzumab therapy in patients with mBC who did not receive pertuzumab as a first-line therapy. Physicians from nine major Swiss oncology centers retrospectively completed a questionnaire for each pertuzumab-naive patient who was treated with pertuzumab as a second- or later-line therapy. Of 35 patients with HER2-positive mBC (median age, 49 years; range, 35-87 years), 14 received pertuzumab as a second-line therapy, 6 as a third-line therapy, and 15 as a fourth- or later-line therapy. A total of 20 patients (57%) died during the study period. The median overall survival was 74.2 months (95% confidence interval, 47.6-139.8 months). Grade (G) 3/4 adverse events (AEs) were reported in 14% of patients, with only 1 patient discontinuing therapy due to pertuzumab-related toxicities. The most common AE was fatigue (overall, 46%; G3, 11%). Overall, congestive heart disease occurred in 14% of patients (G3, 6%), nausea in 14% of patients (all G1), and myelosuppression in 12% of patients (G3, 6%). In conclusion, the median overall survival of patients who underwent second- or later-line pertuzumab treatment was similar to that reported for patients who underwent first-line pertuzumab treatment, and the safety profile was acceptable. These data support the use of pertuzumab for second- or later-line therapy when it was not administered as first-line therapy.

HER2 in situ hybridization test in breast cancer: quantifying margins of error and genetic heterogeneity

The aim of the present study was to evaluate the effect of counting increasing number of invasive cancer cells in the result of the HER2 in situ hybridization (ISH) test in breast cancer as well as to compare two different approaches of measuring genomic heterogeneity (single cell and population based). A cohort of 100 consecutive breast cancer cases (primary and metastatic) were evaluated for HER2 gene amplification with bright-field ISH. The evaluation of the samples included scoring 20 nuclei, in five different areas, measuring the margins of error for each case. Genomic heterogeneity (GH) was defined by the 2018 ASCO/CAP guideline as a discrete population of tumor cells with HER2 amplification. We also evaluated GH as single tumor cells with HER2 amplification. The stabilization of the coefficient of variation of HER2/CEP17 ratio requires about 60 invasive cancer cells. The average margin of error of HER2/CEP17 ratio and of HER2 copy number was 0.40 and 0.53, respectively, when counting 20 cells, decreasing to 0.20 and 0.26 when counting 100 cells. Population GH was observed in 1% of the cases, while single cell GH was observed in 27% of the cases, reaching its maximum value in cases near the thresholds of positivity. Therefore, margins of error in HER2 ISH test are high, and the minimal cell number recommended in current guidelines should be raised to at least 60 cells. Population GH is a rare event and single cell GH is maximal in cases near the thresholds.

The Dilemma of HER2 Double-equivocal Breast Carcinomas: Genomic Profiling and Implications for Treatment

Supplemental Digital Content is available in the text.

The American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) 2013 guidelines for HER2 assessment have increased the number of HER2 equivocal breast carcinomas following in situ hybridization reflex testing, that is, HER2 “double equivocal” (equivocal protein expression and equivocal gene copy number). Forty-five double-equivocal carcinomas were subjected to Prosigna analysis. Twenty-seven cases were investigated for the expression of genes found to be differentially expressed between estrogen receptor (ER)-positive/HER2-positive (N=22) and ER-positive/HER2-negative (N=22) control cases. Twenty-nine of the 45 cases were also analyzed by targeted sequencing using a panel of 14 genes. We then explored the pathologic complete response rates in an independent series of double-equivocal carcinoma patients treated with trastuzumab-containing chemotherapy. All cases were ER-positive, with a mean Ki67 of 28%. Double-equivocal carcinomas were predominantly luminal B (76%); 9 cases (20%) were luminal A, and 2 cases (4%) HER2-enriched. The majority (73%) showed a high risk of recurrence by Prosigna, even when the carcinomas were small (<2 cm), node-negative/micrometastatic, and/or grade 2. Double-equivocal carcinomas showed TP53 (6/29, 20%), PIK3CA (3/29, 10%), HER2 (1/29, 3%), and MAP2K4 (1/29, 3%) mutations. Compared with grade-matched ER-positive/HER2-negative breast carcinomas from METABRIC, double-equivocal carcinomas harbored more frequently TP53 mutations and less frequently PIK3CA mutations (P<0.05). No significant differences were observed with grade-matched ER-positive/HER2-positive carcinomas. Lower pathologic complete response rates were observed in double-equivocal compared with HER2-positive patients (10% vs. 60%, P=0.009). Double-equivocal carcinomas are preferentially luminal B and show a high risk of recurrence. A subset of these tumors can be labeled as HER2-enriched by transcriptomic analysis. HER2 mutations can be identified in HER2 double-equivocal cases.

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.

Human epidermal growth factor receptor 2 amplification as a biomarker for treatment in patients with lymph node-metastatic penoscrotal extramammary Paget's disease

The role of human epidermal growth factor receptor 2 (HER2) amplification as a biomarker for treatment in patients with lymph node (LN)-metastatic penoscrotal extramammary Paget's disease (EMPD) was investigated in the present study. A total of 11 male patients with LN-metastatic penoscrotal EMPD were retrospectively reviewed. Positron emission tomography/computed tomography (PET/CT) was conducted prior to surgery. Immunohistochemistry and fluorescence in situ hybridization were used to evaluate HER2 gene amplification in LN samples. Sanger sequencing was used to investigate HER2 mutations. A literature review of the prevalence of HER2 amplification in EMPD and the efficacy of HER2-targeted therapy was also undertaken. PET/CT is effective in detecting metastatic sites. The sensitivity and specificity of PET/CT was 90.9 and 100.0% for inguinal LNs, and 85.7 and 80.0% for pelvic LNs, respectively. The median time from LN dissection to disease progression was 15.9±1.5 months. Of the 11 patients, 3 (27.3%) indicated HER2 amplification. Patients with HER2 amplification showed shorter median times from disease discovery to LN metastasis (HER2 amplification vs HER2 non-amplification; 15.6 vs. 10.0 months; P=0.50) and from LN dissection to disease progression (HER2 amplification vs. HER2 non-amplification, 16.2 vs. 13.6 months; P=0.11). However, the aforementioned observations were not indicated to be statistically significant. No HER2 mutations were identified. Trastuzumab, a HER2-targeted monoclonal antibody, was administered to 2 of the patients with HER2 amplification. A literature review of the prevalence of HER2 amplification in EMPD and the efficacy of HER2-targeted therapy showed similar results. Altogether, 485 cases of EMPD were reported, 35 of which had metastases. The results in the present study suggest that PET/CT should be used on all metastatic EMPD patients. EMPD may be effectively treated with trastuzumab. The present study and case reports from the literature provide evidence for the benefit of testing for HER2 amplification in this rare disease and highlight the requirement for a multicenter clinical trial to assess the impact of trastuzumab therapy in treating this disease.

Equivocal (HER2 IHC 2+) breast carcinomas: gene-protein assay testing reveals association between genetic heterogeneity, individual cell amplification status and potential treatment benefits

AIMS

Genetic heterogeneity can pose a challenge to identifying eligible cases for targeted therapy in the human epidermal growth factor receptor 2 (HER2) immunohistochemistry (IHC) 2+ breast carcinoma group. In this study, we characterised this subset of tumours according to clinicopathological parameters.

METHODS AND RESULTS

We assessed 1000 tumour cells per case and recorded the number of HER2 and chromosome enumeration probe 17 (CEP17) copies using gene-protein assay slides. HER2 status was determined based on ASCO/CAP 2013 guidelines. Tumours with 5-50% of cancer cells with amplification were considered to be heterogeneous, whereas those with >50% were considered to be non-heterogeneous. In a study cohort of 110 HER2 IHC 2+ carcinomas, 93 (84.5%) were non-amplified, 12 (10.9%) were amplified and five (4.5%) were ISH-equivocal. All the HER2-amplified and two of ISH-equivocal cases (12.7%) corresponded to non-heterogeneous tumours, with highly significant differences evident in the average HER2/CEP17 ratio (P = 0.0002) and the proportion of cells with HER2 >6 copies (P < 0.0001) compared with heterogeneous lesions. NST grade 3 and HER2-amplified carcinomas average HER2/CEP17 ratio correlated with an increased number of cells with HER2/CEP17 ≥2.0 (P < 0.014). Triple-negative CEP17 polysomic carcinomas showed increased metastatic capacity (P = 0.003) compared with other tumour types.

CONCLUSION

Non-heterogeneous HER2 IHC 2+ tumours tend to be HER2-amplified. Adding the percentage of cells with HER2 >6 copies to the average HER2/CEP17 ratio may facilitate assessment of amplification status in ISH-equivocal cases. The proportion of cells with HER2/CEP17 ≥2.0 contributes information concerning the actual average HER2/CEP17 ratio, depending on tumour type.

Benefit of everolimus as a monotherapy for a refractory breast cancer patient bearing multiple genetic mutations in the PI3K/AKT/mTOR signaling pathway

A postmenopausal patient with a diagnosis of estrogen receptor (ER) (+), progesterone receptor (PR) (+), and human epidermal growth factor receptor-2 (HER2) (-) breast cancer was reported. The patient refused surgery and was resistant to conventional chemotherapy regimens. Computed tomography and the circulating tumor cell test indicated that the patient’s tumor burden increased rapidly even after several chemotherapy sessions. Multiple genetic aberrances in the phosphatidylinositol3-kinases (PI3K) signaling pathway were detected via next-generation sequencing (NGS)-based liquid biopsy, including a p. G1007R missense mutation in exon 21 of PIK3CA (33.61%), a p.L70fs frameshift mutation in exon 3 of phosphatase and tension homolog deleted on chromosome ten (PTEN) (49.14%), and a p. D1542Y missense mutation in exon 32 of mammalian target of rapamycin (mTOR) (1.66%). Therefore, only the mTOR inhibitor everolimus was administered to the patient. Partial remission (PR) was observed after 2 months, and sustained stable disease (SD) was observed after a year and a half. Subsequent sequencing showed that the mutation ratio of PIK3CA decreased to 4.17%, and that the PTEN and mTOR mutations disappeared, which revealed the significant curative effect of everolimus. We report the first case of successful monotherapy treatment using everolimus in a patient with advanced breast cancer bearing mutations in genes involved in the PI3K/ARK/mTOR signaling pathway. The success of this case highlights the invaluable clinical contribution of NGS-based liquid biopsy, as it successfully provided an optimal therapeutic target for the patient with advanced breast cancer.

Counting invasive breast cancer cells in the HER2 silver in-situ hybridization test: how many cells are enough?

AIM

To evaluate the intraobserver and interobserver reproducibility of the HER2 in-situ hybridization (ISH) test in breast cancer by measuring the impact of counting different numbers of invasive cancer cells.

METHODS AND RESULTS

A cohort of 101 primary invasive breast cancer cases were evaluated for HER2 gene amplification by silver ISH, and the concordance among four observers with different levels of experience, counting different numbers of invasive cancer cells, was determined. The evaluation of the samples included scoring 20 nuclei, in three different areas. The cases were scored twice, with a washout interval of at least 2 weeks. We observed an increase in the intraobserver concordance rate between the first and second evaluations with an increase in cell count. A count of 60 invasive cells was needed to obtain a concordance rate near 95% and an agreement rate greater than 0.80 by all observers. The interobserver concordance rate of the HER2 test also increased with the increase in cell count, reaching at least a 90% concordance rate with a count of 60 invasive cells. The median variability of both the HER2/CEP17 ratio and the average HER2 copy number between different evaluations decreased with the increase in cell count, being statistically higher in HER2-positive cases.

CONCLUSIONS

The minimal cell number recommended in current guidelines should be raised to at least 40, and preferably 60, invasive cells. Moreover, cases with amplification levels close to the threshold should be subjected to a dual count from an experienced observer.