Analysis of molecular subtypes for the increased HER2 equivocal cases caused by application of the updated 2013 ASCO/CAP HER2 testing guidelines in breast cancer

Invasive Breast Cancer with HER2 ≥4.0 and <6.0: Risk Classification and Molecular Typing by a 21-Gene Expression Assay and MammaPrint Plus BluePrint Testing

PURPOSE

To investigate the HER2 status and clinicopathological features in invasive breast cancer with HER2 ≥4.0 and <6.0, which has always been controversial.

METHODS

Forty breast cancer cases with HER2 ≥4.0 and <6.0 by fluorescence in situ hybridization (FISH) were collected and classified into two groups based on the HRE2/CEP17 ratio (Group A: ≥2.0, n=22; Group B: <2.0, n=18). Clinicopathological characteristics, HER2 status, risk classification, and molecular typing were further analyzed and compared by 21-Gene expression assay and MammaPrint plus BluePrint test.

RESULTS

The majority of cases in both groups were invasive carcinoma (NOS), with histological grade II, HR+, Ki-67 ≥20%, HER2 2+, and a high risk of recurrence, although younger patients and lymph node metastases were more common in Group A. Surprisingly, all HR+ breast cancers in both groups were classified as luminal-type, HR- cases were all basal-type or unknown, and the index of HER2 in all cases was <0.000 using the BluePrint test, which indicated that HER2 status should be negative. Furthermore, the level of HER2 mRNA expression in all cases of both groups was <10.7, which was defined as HER2 negative by the 21-Gene expression assay. In addition, 10 patients of Group A received anti-HER2 neoadjuvant therapy; only one patient with HR- achieved Grade 5 based on the Miller-Payne system, whereas none of the patients achieved pathological complete response (pCR) based on the Residual Cancer Burden system.

CONCLUSION

Group A breast cancer, which has always been unquestionably diagnosed as HER2 amplification, was more likely to be HER2 negative and derived less benefit from anti-HER2 neoadjuvant chemotherapy. Group A breast cancer should be distinguished from classical HER2-positive breast cancers when assessing HER2 FISH, and a larger cohort of Group A patients should be included in further studies.

Characteristics of HER2-negative breast cancers with FISH-equivocal status according to 2018 ASCO/CAP guideline

BACKGROUND

According to 2018 ASCO/CAP guideline, HER2 FISH-equivocal breast cancers will be categorized as HER2 negative except those with IHC 3+. However, whether or not HER2 FISH-equivocal breast cancers was a heterogeneous group has not been well illustrated.

METHODS

195 HER2 FISH-equivocal breast cancer samples were collected from 2014 to 2018. The molecular subtype was identified according to 2013 St Gallen consensus, and HER2 status was also re-determined following 2018 ASCO/CAP guideline. All samples were classified into 4 groups according to the average HER2 copy number (4.0-4.4, 4.5-4.9, 5.0-5.4, 5.5-5.9 signals/cell). The relationship between HER2 copy number and clinicopathological parameters was analyzed.

RESULTS

183 (93.8%) of 195 FISH-equivocal cases were classified as luminal-like subtype, while the other 12 (6.2%) were undetermined. Following 2018 ASCO/CAP guideline, all FISH-equivocal cases were recategorized as HER2 negative. Therefore, 31(15.9%) cases were luminal A-like, 152 (77.9%) were luminal B-like (HER2 negative) and 12 (6.2%) were triple negative. The average HER2 copy number showed a positive correlation with chromosome 17 polysomy, but had no significant association with other clinicopathological parameters as well as prognosis. 17 (8.7%) patients were treated with trastuzumab, but showed no difference in prognosis with those who didn't receive targeted therapy.

CONCLUSIONS

In this study, all HER2 FISH-equivocal breast cancers were recategorized as HER2 negative according to 2018 ASCO/CAP guideline. Most of these patients were luminal B-like (HER2 negative). The average HER2 copy number had no significant association with clinicopathological parameters, as well as prognosis.

Precise discrimination of Luminal A breast cancer subtype using an aptamer in vitro and in vivo

Precise discrimination of breast cancer remains a challenge in clinical medicine, which depends on the development of novel specific molecular probes. However, the current technologies and antibodies cannot achieve precise discrimination of breast cancer subtypes very well. To address this problem, a novel truncated DNA aptamer MF3Ec was developed in this work. Aptamer MF3Ec exhibited high specificity and binding affinity against MCF-7 breast cancer cells with a K_d value of 18.95 ± 2.9 nM which is four times lower than that of the original aptamer, and could work at 4 °C, 25 °C and 37 °C with no obvious differences. Besides, aptamer MF3Ec displayed better stability in serum samples with a long existence time of about 12 h. Moreover, fluorescence imaging experiments indicated that aptamer MF3Ec was able to distinguish MCF-7 breast cancer cells from SK-BR-3, MDA-MB-231 and MCF-10A breast cancer cell subtypes, and differentiate the tumor-bearing mice and xenografted tissue sections of MCF-7 breast cancer cells from those of MDA-MB-231 and SK-BR-3 breast cancer cells in vivo and in vitro, respectively. Finally, clinical experiments indicated that aptamer MF3Ec could distinguish Luminal A breast cancer subtype from Luminal B (HER2+), HER2-enriched, and triple-negative breast cancer subtypes, para-carcinoma tissues and normal breast tissues. Collectively, all these results suggest that aptamer MF3Ec is a promising probe for precise discrimination and targeted therapy of Luminal A breast cancer molecular subtype.

Impact of 2013 ASCO/CAP guidelines on various HER2 reporting categories in breast cancer by fluorescentin-situhybridization and Immunohistochemistry: A meta-analysis with systematic review

Objective:

The ASCO/CAP guidelines for reporting HER2 in breast cancer, first released in 2007, aimed to standardize the reporting protocol, and were updated in 2013 and 2018, to ensure right treatment. Several studies have analyzed the changes attributed to 2013 updated guidelines, and majority of them found increase in positive and equivocal cases. However, the precise implication of these updated guidelines is still contentious, in spite of the latest update (2018 guidelines) addressing some of the issues. We conducted systematic review and meta- analysis to see the impact of 2013 guidelines on various HER2 reporting categories by both FISH and IHC.

Materials and Methods:

After extensively searching the pertinent literature, 16 studies were included for the systematic review. We divided our approach in three strategies: (1) Studies in which breast cancer cases were scored for HER2 by FISH or IHC as a primary test concurrently by both 2007 and 2013 guidelines, (2) Studies in which HER2 results were equivocal by IHC and were followed by reflex-FISH test by both 2007 and 2013 guidelines, and (3) Studies in which trends of HER2 reporting were compared in the two periods before and after implementation of updated 2013 guidelines. All the paired data in these respective categories was pooled and analyzed statistically to see the overall impact of the updated guidelines.

Results:

In the first category, by pooled analysis of primary FISH testing there has been a significant increase in the equivocal cases (P< 0.001) and positive cases (P= 0.037). We also found 8.3% and 0.8% of all the negative cases from 2007 guidelines shifted to equivocal and positive categories, respectively. Similarly by primary IHC testing there has been a significant increase in both equivocal cases (P< 0.001) and positive cases (P= 0.02). In the second category of reflex-FISH testing there was a substantial increase in the equivocal cases (P< 0.0001); however there is insignificant decrease (10% to 9.7%;P= 0.66) in the amplified cases. In the third approach for evaluating the trend, with the implementation of 2013 guidelines, there was increase in the equivocal category (P= 0.025) and positive category (P= 0.0088) by IHC. By FISH test also there was significant increase in the equivocal category (P< 0.001) while the increase in the positive category was non-significant (P= 0.159).

Conclusions:

The updated 2013 guidelines has significantly increased the positive and equivocal cases using primary FISH or IHC test and with further reflex testing, thereby increasing the double equivocal cases and increasing the cost and delaying the decision for definite management. However, whether the additional patients becoming eligible for HDT will derive treatment benefit needs to be answered by further large clinical trials.

The FDA-Approved Breast Cancer HER2 Evaluation Kit (HercepTest; Dako) May Miss Some HER2-Positive Breast Cancers

OBJECTIVES

Accurate evaluation of human epidermal growth factor receptor 2 (HER2) in breast cancer is critical.

METHODS

HER2 fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) tests were performed on 52 cases using a US Food and Drug Administration (FDA)-approved kit (HercepTest, FDA kit) and a laboratory-developed test (LDT) with the HercepTest antibody and a Leica Bond automated stainer.

RESULTS

By FISH, 22 were HER2 positive, 29 were negative, and one was equivocal. Of the 22 HER2 FISH-positive cases, five were negative by the FDA kit and none by LDT. The five discrepant cases were retested using the same FDA kit in another Clinical Laboratory Improvement Amendments-certified laboratory, and all five cases were still negative. None of the 29 HER2 FISH-negative cases were positive by the FDA kit or LDT. The overall IHC-FISH concordance rate was 90.4% for the FDA kit and 100% for the LDT.

CONCLUSIONS

The FDA kit may miss some HER2-positive cases. The LDT has a higher sensitivity and a higher concordance rate with FISH results.