HER2-Positive Lobular Versus Ductal Carcinoma of the Breast: Pattern of First Recurrence and Molecular Insights

Molecular and Clinical Portrait of HER2-low Invasive Lobular Carcinomas

Invasive lobular carcinomas (ILCs) have a low frequency of ERBB2 amplification, therefore restricting the use of conventional anti-HER2 therapies for this histologic special type. Conversely, ILCs with low HER2 overexpression may represent a broader target for the use of emerging antibody drug conjugate therapies targeting HER2, since these treatments have proven effective in HER2-low breast cancers. Very scarce data about HER2-low ILCs have been so far published, although these tumors could have different prevalence and histomolecular specificities compared with invasive breast carcinoma of no special type (IBC-NST). Our aims in that context were to decipher the clinicopathological and molecular features of a large series of HER2-low ILCs. Comparative evaluation of HER2-low prevalence was done based on a retrospective series of 7970 patients from Institut Curie, with either primary invasive lobular (N = 1103) or no special type (N = 6867) invasive carcinoma. Clinicopathological and molecular analyses of HER2-zero, HER2-low, and HER2-positive ILCs were performed on a subgroup of 251 patients who underwent surgery for a primary ILC between 2005 and 2008. The mutational profile of these 251 cases was determined from RNAseq data. Compared with HER2-negative IBC-NSTs, the HER2-negative ILCs were found to display a higher frequency of HER2-zero cases (59.4% vs 53.7%) and a lower frequency of HER2-low (40.6% vs 46.3%) (P < .001). Clinicopathological features associated with HER2-low status (vs HER2-zero) in ILC were older age, postmenopausal status, nonclassic ILC histological types, higher grade, proliferation, and estrogen receptor expression levels. Survival curve analysis showed a significantly lower risk of local recurrence for HER2-low (vs HER2-zero) ILCs, but no association was found between HER2 status and either breast cancer-specific survival or distant metastasis-free interval. ERBB3 was the unique mutated gene exclusively associated with HER2-low ILCs yet being mutated at a low frequency (7.1%) (false discovery rate < 0.05). In conclusion, HER2-low ILCs exhibit their own particularities, both on clinical-pathological and molecular levels. Our findings call for larger multicenter validation studies.

ERBB2-amplified lobular breast carcinoma exhibits concomitant CDK12 co-amplification associated with poor prognostic features

Most invasive lobular breast carcinomas (ILBCs) are luminal-type carcinomas with an HER2-negative phenotype (ERBB2 or HER2 un-amplified) and CDH1 mutations. Rare variants include ERBB2-amplified subtypes associated with an unfavorable prognosis and less response to anti-HER2 targeted therapies. We analyzed the clinicopathological and molecular features of ERBB2-amplified ILBC and compared these characteristics with ERBB2-unamplified ILBC. A total of 253 patients with ILBC were analyzed. Paraffin-embedded formalin-fixed tumor samples from 250 of these patients were added to a tissue microarray. Protein expression of prognostic, stem cell and breast-specific markers was tested by immunohistochemistry (IHC). Hybrid capture-based comprehensive genomic profiling (CGP) was performed for 10 ILBCs that were either fluorescent in situ hybridization (FISH) or IHC positive for HER2 amplification/overexpression and 10 ILBCs that were either FISH or IHC negative. Results were compared with a CGP database of 44,293 invasive breast carcinomas. The CGP definition of ERBB2 amplification was five copies or greater. A total of 17 of 255 ILBC (5%) were ERBB2 amplified. ERBB2-amplified ILBC had higher tumor stage (p < 0.0001), more frequent positive nodal status (p = 0.00022), more distant metastases (p = 0.012), and higher histological grade (p < 0.0001), and were more often hormone receptor negative (p < 0.001) and more often SOX10 positive (p = 0.005). ERBB2 short variant sequence mutations were more often detected in ERBB2-unamplified tumors (6/10, p = 0.027), whereas CDH1 mutations/copy loss were frequently present in both subgroups (9/10 and 7/10, respectively). Amplification of pathogenic genes were more common in HER2-positive ILBC (p = 0.0009). CDK12 gene amplification (≥6 copies) was detected in 7 of 10 ERBB2-amplified ILBC (p = 0.018). There were no CDK12 gene amplifications reported in 44,293 invasive breast carcinomas in the FMI Insights CGP database. ERBB2-amplified ILBC is a distinct molecular subgroup with frequent coamplification of CDK12, whereas ERBB2 sequence mutations occur only in ERBB2-unamplified ILBC. CDK12/ERBB2 co-amplification may explain the poor prognosis and therapy resistance of ERBB2-amplified ILBC.

Digital mammography and digital breast tomosynthesis for detecting invasive lobular and ductal carcinoma

PURPOSE

Invasive lobular carcinoma (ILC) is a distinct histological subtype of breast cancer that can make early detection with mammography challenging. We compared imaging performance of digital breast tomosynthesis (DBT) to digital mammography (DM) for diagnoses of ILC, invasive ductal carcinoma (IDC), and invasive mixed carcinoma (IMC) in a screening population.

METHODS

We included screening exams (DM; n = 1,715,249 or DBT; n = 414,793) from 2011 to 2018 among 839,801 women in the Breast Cancer Surveillance Consortium. Examinations were followed for one year to ascertain incident ILC, IDC, or IMC. We measured cancer detection rate (CDR) and interval invasive cancer rate/1000 screening examinations for each histological subtype and stratified by breast density and modality. We calculated relative risk (RR) for DM vs. DBT using log-binomial models to adjust for the propensity of receiving DBT vs. DM.

RESULTS

Unadjusted CDR per 1000 mammograms of ILC overall was 0.33 (95%CI: 0.30-0.36) for DM; 0.45 (95%CI: 0.39-0.52) for DBT, and for women with dense breasts- 0.33 (95%CI: 0.29-0.37) for DM and 0.54 (95%CI: 0.43-0.66) for DBT. Similar results were noted for IDC and IMC. Adjusted models showed a significantly increased RR for cancer detection with DBT compared to DM among women with dense breasts for all three histologies (RR; 95%CI: ILC 1.53; 1.09-2.14, IDC 1.21; 1.02-1.44, IMC 1.76; 1.30-2.38), but no significant increase among women with non-dense breasts.

CONCLUSION

DBT was associated with higher CDR for ILC, IDC, and IMC for women with dense breasts. Early detection of ILC with DBT may improve outcomes for this distinct clinical entity.

Clinical outcomes in patients with triple negative or HER2 positive lobular breast cancer: a single institution experience

PURPOSE

Invasive lobular carcinomas (ILC) are characterised by loss of the cell adhesion molecule E-cadherin. Approximately 15% of ILC are ER negative at the time of breast cancer diagnosis, or at relapse due to loss of ER expression. Less than 5% of classical ILC but up to 35% of pleomorphic ILC are HER2 positive (HER2+).

METHODS

Retrospective analysis of clinic-pathological data from patients with Triple negative (TN) or HER2+ ILC diagnosed 2004-2014 at the Royal Marsden Hospital. The primary endpoint was median overall survival (OS) in patients with metastatic disease. Secondary endpoints included response rate to neo-adjuvant chemotherapy (NAC), median disease-free interval (DFI) and OS for patients with early disease.

RESULTS

Three of 16 patients with early TN ILC and 7/33 with early HER2+ ILC received NAC with pCR rates of 0/3 and 3/5 patients who underwent surgery, respectively. Median DFI was 28.5 months [95% Confidence interval (95%CI) 15-78.8] for TN ILC and not reached (NR) (111.2-NR) for HER2+ early ILC. Five-year OS was 52% (95%CI 23-74%) and 77% (95%CI 58-88%), respectively. Twenty-three patients with advanced TN ILC and 14 patients with advanced HER2+ ILC were identified. Median OS was 18.3 months (95%CI 13.0-32.8 months) and 30.4 months (95%CI 8.8-NR), respectively.

CONCLUSIONS

In our institution we report a high relapse rate after treatment for early TN ILC, but median OS from metastatic disease is similar to that expected from TN IDC. Outcomes for patients with advanced HER2+ ILC were less favourable than those expected for IDC, possibly reflecting incomplete exposure to anti-HER2 therapies.

CLINICAL TRIAL REGISTRATION

ROLo (ClinicalTrials.gov Identifier: NCT03620643), ROSALINE (ClinicalTrials.gov Identifier: NCT04551495).

Invasive lobular carcinoma of the breast: the increasing importance of this special subtype

Invasive lobular carcinoma (ILC) is the most common of the breast cancer special types, accounting for up to 15% of all breast cancer cases. ILCs are noted for their lack of E-cadherin function, which underpins their characteristic discohesive growth pattern, with cells arranged in single file and dispersed throughout the stroma. Typically, tumours are luminal in molecular subtype, being oestrogen and progesterone receptor positive, and HER2 negative. Since last reviewing the lobular literature (McCart Reed et al., Breast Cancer Res 17:12, 2015), there has been a considerable increase in research output focused on this tumour type, including studies into the pathology and management of disease, a high-resolution definition of the genomic landscape of tumours as well as the evolution of several potential therapeutic avenues. There abounds a huge amount of new data, which we will review herein.

Tumor-infiltrating lymphocytes are associated with poor prognosis in invasive lobular breast carcinoma

The prognostic impact of tumor-infiltrating lymphocytes (TILs) within invasive lobular carcinoma (ILC) remains to be better characterized. In estrogen receptor (ER)-negative invasive ductal carcinomas of no special type (IDC-NST), TILs are associated with good prognosis. The aim of this study was to examine TILs in ILC, with particular focus on prognostic and clinicopathologic features. A cohort comprising 459 consecutive ILCs diagnosed in a single institution from 2005 to 2008 met the eligibility criteria for this study. The percentage of tumor area occupied by TILs was quantified by two breast pathologists and categorized into three groups: no TILs, ≤5%, >5%. Clinicopathologic features were tested by Fisher's exact tests or Chi² tests. Overall survival (OS) and invasive disease-free survival (iDFS) were estimated by Kaplan-Meier and Cox proportional hazard statistics. There were 239 TIL-negative cases, 185 cases with ≤5% TILs, and 35 cases with >5% TILs. TILs were associated with younger age, larger tumors, lymph node involvement, poor Nottingham prognostic index, HER2 amplification, multinucleation, and prominent nucleoli (p < 0.05). Poor OS was significantly associated with increasing TILs in the univariate Cox proportional hazards model (p < 0.001) and Kaplan-Meier estimator (p < 0.05, log-rank test). Similar results were observed for iDFS (p = 0.004 for Cox univariate and p = 0.005 for log-rank test). Notably, TILs can identify a subset of ILC patients with poor OS independently of molecular subtype and lymph node metastases (multivariate Cox, p < 0.001, OS hazard ratio (HR) = 4.38 and HR = 6.15, for ≤5% and >5% TILs, respectively, vs. absence of TILs). Prominent nucleoli was the only nuclear feature associated with poor OS (p = 0.05) and iDFS (p = 0.05) in univariate Cox survival analysis. TILs represent a promising new morphologic biomarker associated with poor outcome of ILC, in contrast with that observed in ER-negative IDC-NST.

Human epidermal growth factor receptor 2 positive rates in invasive lobular breast carcinoma: The Singapore experience

BACKGROUND

Invasive lobular carcinomas (ILC) form 5%-10% of breast cancer and rarely show overexpression of human epidermal growth factor receptor 2 (HER2).

AIM

To describe the prevalence and prognostic factors of HER2 positive (HER2+) ILC in an Asian population.

METHODS

A retrospective review of patients with ILC seen between January 1985 and March 2018 at various SingHealth medical institutions was conducted. Demographic and clinical data were collected from medical records. We examined clinicopathological characteristics and survival in relation to HER2 status.

RESULTS

A total of 864 patients were included. Prevalence of HER2 positivity was 10.1% (87 patients). Compared with HER2 negative (HER2-) ILC, HER2+ ILC was associated with a higher proportion of estrogen receptor negative (24.4% vs 5.9%, P < 0.001), progesterone receptor negative (PR-) (40.2% vs 24%, P = 0.002) and grade 3 tumours (Grade 3, 29.0% vs 10.2%, P < 0.001). Overall survival rate was poorer in patients with HER2+ compared to HER2- ILC (56.7% vs 72.9% alive at 10 years; hazard ratio 1.87, 95% confidence interval: 1.21-2.90, P = 0.004). Based on multivariate analysis, negative prognostic factors for overall survival included HER2 positivity, PR negativity, older age, Indian ethnicity and higher tumour stage.

CONCLUSION

Prevalence of HER2+ ILC was 10.1%. HER2+ ILC was more likely to have poorer prognostic features such as estrogen receptor negative, PR- and higher tumour grade, and have a poorer survival.

Impact of FDG PET Imaging for Expanding Patient Eligibility and Measuring Treatment Response in a Genome-Driven Basket Trial of the Pan-HER Kinase Inhibitor, Neratinib

PURPOSE

To determine whether FDG PET can expand eligibility in biomarker-selected clinical trials by providing a means to quantitate response in patients with non-assessable disease by RECIST.

EXPERIMENTAL DESIGN

SUMMIT (NCT01953926) is a multicenter phase II "basket" trial of the Pan-HER kinase inhibitor, neratinib. Patients had advanced ERBB2 (HER2)-mutant solid tumors, ≥1 measurable lesion, preferably defined unidimensionally by RECIST v1.1, or alternatively metabolically by PET Response Criteria (PRC). The primary aim was to determine the proportion of additional breast cancer patients accrued using PRC who would have otherwise been ineligible based on RECIST criteria alone. The secondary aim was to determine the concordance of response versus non-response between RECIST and PRC.

RESULTS

Eighty-one patients with HER2-mutant metastatic breast cancer were accrued; 77 were evaluable for response by RECIST and/or PRC. 63 (82%) were RECIST-evaluable and 14 (18%) were accrued using PRC alone. Bone-only disease (n = 11; 79%) was the most common reason for classification as non-measurable by RECIST. Twenty-nine patients were accrued and followed using both criteria, of which 25 (86%; 95% confidence interval, 68%-96%) were concordant for response versus non-response as defined by RECIST and PRC.

CONCLUSIONS

PRC allowed patients with non-RECIST measurable disease access to therapy and facilitated more rapid accrual of patients to this trial of a rare biomarker. PRC and RECIST both provided methods of response assessment and were generally concordant. Thus, PRC was useful as a supplement to RECIST criteria. This provides a rationale for including FDG PET measurements in future clinical trials involving rare tumors or rare genomically defined subpopulations of more common cancers.