Neoadjuvant Dual HER2 Blockade Research Articles

Association of HER2DX with pathological complete response and survival outcomes in HER2-positive breast cancer

The HER2DX genomic test predicts pathological complete response (pCR) and survival outcome in early-stage HER2-positive (HER2+) breast cancer. Here, we evaluated the association of HER2DX scores with (i) pCR according to hormone receptor status and various treatment regimens, and (ii) survival outcome according to pCR status. Seven neoadjuvant cohorts with HER2DX and clinical individual patient data were evaluated (DAPHNe, GOM-HGUGM-2018-05, CALGB-40601, ISPY-2, BiOnHER, NEOHER and PAMELA). All patients were treated with neoadjuvant trastuzumab (n= 765) in combination with pertuzumab (n= 328), lapatinib (n= 187) or without a second anti-HER2 drug (n= 250). Event-free survival (EFS) and overall survival (OS) outcomes were available in a combined series of 268 patients (i.e. NEOHER and PAMELA) with a pCR (n= 118) and without a pCR (n= 150). Cox models were adjusted to evaluate whether HER2DX can identify patients with low or high risk beyond pCR status. HER2DX pCR score was significantly associated with pCR in all patients [odds ratio (OR) per 10-unit increase= 1.59, 95% confidence interval 1.43-1.77; area under the ROC curve= 0.75], with or without dual HER2 blockade. A statistically significant increase in pCR rate due to dual HER2 blockade over trastuzumab-only was observed in HER2DX pCR-high tumors treated with chemotherapy (OR= 2.36 (1.09-5.42). A statistically significant increase in pCR rate due to multi-agent chemotherapy over a single taxane was observed in HER2DX pCR-medium tumors treated with dual HER2 blockade (OR= 3.11, 1.54-6.49). The pCR rates in HER2DX pCR-low tumors were ≤30.0% regardless of treatment administered. After adjusting by pCR status, patients identified as HER2DX low-risk had better EFS (P < 0.001) and OS (P= 0.006) compared with patients with HER2DX high-risk. HER2DX pCR score and risk score might help identify ideal candidates to receive neoadjuvant dual HER2 blockade in combination with a single taxane in early-stage HER2+ breast cancer.

123O Randomized phase II trial of neoadjuvant atezolizumab in combination with dual HER2 blockade plus epirubicin in early HER2-positive breast cancer (ABCSG-52/ATHENE)

For most HER2-positive early breast cancer (EBC) patients (pts), neoadjuvant dual HER2 blockade with trastuzumab (T) and pertuzumab (P) plus poly-chemotherapy is standard of care. To improve the balance between toxicity burden and treatment outcomes, chemotherapy de-escalation has been a major focus in recent years. Among other immunogenic properties, anthracyclines can trigger an immunogenic cell death that engages the adaptive immune system. Within the ABCSG-52 trial we investigated a chemotherapy de-escalation immunotherapy regimen in HER2-positive EBC. Pts with previously untreated, histologically confirmed HER2-positive EBC (clinical prognostic stage cT1c-4a-d, N0–3,M0) were randomized 1:1 to two 3-weekly cycles of a chemotherapy-free induction phase (part 1) with TP plus 1200mg atezolizumab (TP+A) or TP alone. Afterwards, all pts received 4 cycles of TP+A in combination with epirubicin (part 2). The primary endpoint was pathological complete response (pCR; ypT0/Tis ypN0) in the overall study population. A pCR rate of ≥ 40% was considered as a positive trial result. Overall, 58 pts were randomized to TP-A (n=29) or TP (n=29) in 9 Austrian study centers. Median age was 57 (range 33-82), 16 pts (27.6%) had hormone-receptor (HR)-negative and 42 (72.4%) had HR-positive tumors. 45 pts (77.6%) had stage ≤ IIA and 13 (22.4%) ≥ IIB. In 35 pts a pCR was observed (60.3%; 95%CI 47.5% - 71.9%), 19 (65.5%) in the TP-A group and 16 (55.2%) in TP group (Δ 10.3%; 95%CI -14.7% - 35.4%). Residual cancer burden (RCB) class 0 or I was seen in 44 out of 55 pts (80%) with valid RCB assessment. Treatment emergent adverse events (AEs) grade ≥ 3 were reported in 17 pts (29.3%), 9 in TP-A group (31.0%) and 8 (27.6%) in TP group. No AEs of special interest (immune-related AEs, cardiac disorders grade ≥ 2, or infusion-related reactions) grade ≥ 3 were detected. Outcome according to PD-L1 expression status is currently analyzed and will also be presented at the meeting. For HER2-positive EBC, a neoadjuvant chemotherapy de-escalation immunotherapy regimen with trastuzumab, pertuzumab, atezolizumab and epirubicin is highly effective and safe and merits further investigation.

126MO HER2DX and pathological complete response in HER2-positive breast cancer: A combined analysis of 4 neoadjuvant studies

The optimal neoadjuvant therapy for HER2-positive breast cancer patients is subject to ongoing debate and the use of biomarkers can help to personalise treatment decision. The 27-gene HER2DX test predicts pathological complete response (pCR) following neoadjuvant trastuzumab-based chemotherapy. Here, we evaluated the value of HER2DX to predict increases in pCR rate when 1) a second anti-HER2 agent is added to trastuzumab and chemotherapy, and 2) multi-agent chemotherapy is used instead of a single agent taxane in the context of dual HER2 blockade. We conducted a combined analysis of four neoadjuvant cohorts with HER2DX and clinical data (i.e., DAPHNe, GOM-HGUGM-2018-05, CALGB-40601 and ISPY-2). All patients were treated with neoadjuvant trastuzumab (n=568) in combination with multi-agent chemotherapy (n=282), a single taxane (n=286), pertuzumab (n=264), lapatinib (n=103) or without a second anti-HER2 drug (n=201). Interaction tests were performed to evaluate the predictive capacity of HER2DX to identify patients who benefit most from each treatment approach. HER2DX pCR as continuous score was significantly associated with pCR in all patients (odds-ratio [OR]=1.62, 95% CI 1.43-1.85; AUC=0.75), in patients treated with trastuzumab and chemotherapy (OR=1.48, 1.18-1.86) and in patients treated with dual HER2 blockade and chemotherapy (OR=1.69, 1.50-1.91). A statistically significant increase in pCR rate due to dual HER2 blockade over trastuzumab-only was observed in HER2DX pCR-high tumors treated with chemotherapy (OR=4.10, 1.85-9.07; interaction test p=0.03). A statistically significant increase in pCR rate due to multi-agent chemotherapy over a single taxane was observed in HER2DX pCR-medium tumors treated with dual HER2 blockade (OR=2.52, 1.18-5.52; interaction test p=0.01). The pCR rates in HER2DX pCR-low tumors were ≤30.0% regardless of type of treatment. HER2DX might help identify patients with HER2-positive breast cancer who benefit from neoadjuvant dual HER2 blockade in combination with a single taxane.

Chemotherapy Choice in Neoadjuvant Dual Her2 Blockade: Is it Really Essential to Add Anthracycline?

Chemotherapy Choice in Neoadjuvant Dual Her2 Blockade: Is it Really Essential to Add Anthracycline?

Ten-year survival of neoadjuvant dual HER2 blockade in patients with HER2-positive breast cancer

BackgroundDual anti-HER2-targeted therapy in breast cancer (BC) significantly increased the rate of pathological complete response (pCR) compared to single blockade when added to chemotherapy. However, limited data exist on the long-term impact on survival of the additional increase in pCR. MethodsNeoadjuvant lapatinib and/or trastuzumab treatment optimisation (NCT00553358) is an international, randomised, open-label, phase III study investigating the addition of lapatinib to chemotherapy plus trastuzumab in HER2-positive early BC. Ten-year event-free survival (EFS), overall survival (OS) and safety were assessed on intention-to-treat population. The association between pCR and EFS or OS was investigated in landmark population. ResultsA total of 455 patients were randomised to receive lapatinib (154), trastuzumab (149) or the combination (152). Ten-year EFS estimates were 63% (95% confidence interval [CI], 54%–71%) in the lapatinib group, 64% (95% CI, 55%–72%) in the trastuzumab group and 67% (95% CI, 58%–74%) in the combination group. Ten-year OS rates were 76% (95% CI, 67%–83%), 75% (95% CI, 66%–82%) and 80% (95% CI, 73%–86%) in the lapatinib, trastuzumab and combination groups, respectively. Women who achieved a pCR had improved EFS (hazard ratio 0.48, 95% CI, 0.31–0.73) and OS (hazard ratio 0.37, 95% CI, 0.20–0.63) compared with those who did not. The numerical difference in survival according to pCR status was greater in women treated with the combination and those with hormone-receptor-negative tumours. There were no new or long-term safety concerns. ConclusionsPatients with HER2-positive BC showed a durable survival benefit of neoadjuvant anti-HER2, irrespective of treatment arm. Patients who achieve pCR have significantly better outcomes than patients without pCR.

Targeting HER2-AXL heterodimerization to overcome resistance to HER2 blockade in breast cancer.

Anti-HER2 therapies have markedly improved prognosis of HER2-positive breast cancer. However, different mechanisms play a role in treatment resistance. Here, we identified AXL overexpression as an essential mechanism of trastuzumab resistance. AXL orchestrates epithelial-to-mesenchymal transition and heterodimerizes with HER2, leading to activation of PI3K/AKT and MAPK pathways in a ligand-independent manner. Genetic depletion and pharmacological inhibition of AXL restored trastuzumab response in vitro and in vivo. AXL inhibitor plus trastuzumab achieved complete regression in trastuzumab-resistant patient-derived xenograft models. Moreover, AXL expression in HER2-positive primary tumors was able to predict prognosis. Data from the PAMELA trial showed a change in AXL expression during neoadjuvant dual HER2 blockade, supporting its role in resistance. Therefore, our study highlights the importance of targeting AXL in combination with anti-HER2 drugs across HER2-amplified breast cancer patients with high AXL expression. Furthermore, it unveils the potential value of AXL as a druggable prognostic biomarker in HER2-positive breast cancer.

Abstract P5-13-30: Analysis of αβ and γδ circulating T cells in the PHERGain randomized phase 2 trial for patients with HER2-positive early breast cancer receiving neoadjuvant trastuzumab and pertuzumab without chemotherapy: LINGain

Abstract Background: The presence of stromal tumor-infiltrating lymphocytes (TILs) represents an independent prognostic factor in HER2-positive early-stage breast cancer (EBC) treated with trastuzumab/pertuzumab-containing regimens. Among distinct subsets of TILs, conventional CD8+ αβ T cells require TCR signaling as a part of adaptive immunity, while γδ T cells display also innate-like activity via the NKG2D receptor contributing to a very rapid tumor immunosurveillance. Specific γδ T cell subsets were associated with remission and improved overall survival of patients with triple-negative breast cancer. However, very little is known about circulating αβ and γδ T cells and their immunological status in HER2-positive breast cancer. In this substudy, we aimed to characterize the αβ and γδ T cell subsets and the association with clinical outcome in peripheral blood of patients with HER2-positive EBC enrolled in the PHERGain trial, which assessed the possibility of chemotherapy de-escalation with neoadjuvant dual HER2 blockade with trastuzumab and pertuzumab using an 18F-fluorodeoxyglucose-PET and pathological response-adapted strategy. Methods: Peripheral blood was obtained from 24 consecutive patients who were assigned to the trastuzumab and pertuzumab group (+/- endocrine therapy as per hormone receptor status) before randomization (baseline) and after 2 treatment cycles (6 weeks). Blood samples were also collected from 48 age-matched healthy donors who represented the control group. Absolute numbers of CD3+, CD3+/CD4+, CD3+/CD8+, and CD3+/CD56+ according to the TCR expression, and annexin V apoptotic rate on αβ and γδ T cells were evaluated by flow cytometry. Subset distribution of T cell differentiation within naïve, central memory, effector memory, and terminally differentiated effector memory cells was also determined. The changes in the frequency of peripheral T cells and rate of apoptotic subsets between timepoints, patients, and healthy donors were compared with Wilcoxon test. The analyses were set at two-sided 0.05 level of significance. Results: Among 24 patients with evaluable blood samples at both timepoints, median age was 50.5 years (IQR 45.8-61), 45.8% had node-positive disease, 79.2% had hormone receptor-positive status, 79.2% had tumors with HER2 IHC 3+ status, and 54.2% achieved a pathological complete response (ypT0/is ypN0) after treatment. At baseline, levels of αβ and γδ T cells in EBC patients were significantly lower than levels in healthy subjects (P ≤0.05). After 6 weeks of study treatment, these levels in EBC patients did not significantly differ from those at baseline. Baseline rates of apoptotic subsets were higher in EBC patients than rates in healthy subjects (P &amp;lt;0.01), but after 6 weeks of study treatment all apoptotic subsets were significantly reduced in EBC patients compared with those at baseline (P ≤0.05). No evidence of association was found between peripheral T cells and pathological complete response in EBC patients. Conclusions: These data suggest a potential involvement of T cell apoptosis on the mechanism of action mediated by dual HER2 blockade with trastuzumab and pertuzumab in patients with HER2-positive EBC. However, further validation is required. Additional data on the subset distribution of T cell differentiation status will be presented at the meeting. Citation Format: Juan Carlos Andreu-Ballester, José Manuel Pérez-García, Begoña Bermejo, Vicente Carañana, Vega Iranzo, Joaquín Gavilà, Ana Santaballa, María Carmen Gómez-Soler, Miguel Sampayo-Cordero, Andrea Malfettone, Javier Cortes, Antonio Llombart-Cussac. Analysis of αβ and γδ circulating T cells in the PHERGain randomized phase 2 trial for patients with HER2-positive early breast cancer receiving neoadjuvant trastuzumab and pertuzumab without chemotherapy: LINGain [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-30.

RANK signaling increases after anti-HER2 therapy contributing to the emergence of resistance in HER2-positive breast cancer

BackgroundAround 15–20% of primary breast cancers are characterized by HER2 protein overexpression and/or HER2 gene amplification. Despite the successful development of anti-HER2 drugs, intrinsic and acquired resistance represents a major hurdle. This study was performed to analyze the RANK pathway contribution in HER2-positive breast cancer and anti-HER2 therapy resistance.MethodsRANK and RANKL protein expression was assessed in samples from HER2-positive breast cancer patients resistant to anti-HER2 therapy and treatment-naive patients. RANK and RANKL gene expression was analyzed in paired samples from patients treated with neoadjuvant dual HER2-blockade (lapatinib and trastuzumab) from the SOLTI-1114 PAMELA trial. Additionally, HER2-positive breast cancer cell lines were used to modulate RANK expression and analyze in vitro the contribution of RANK signaling to anti-HER2 resistance and downstream signaling.ResultsRANK and RANKL proteins are more frequently detected in HER2-positive tumors that have acquired resistance to anti-HER2 therapies than in treatment-naive ones. RANK (but not RANKL) gene expression increased after dual anti-HER2 neoadjuvant therapy in the cohort from the SOLTI-1114 PAMELA trial. Results in HER2-positive breast cancer cell lines recapitulate the clinical observations, with increased RANK expression observed after short-term treatment with the HER2 inhibitor lapatinib or dual anti-HER2 therapy and in lapatinib-resistant cells. After RANKL stimulation, lapatinib-resistant cells show increased NF-κB activation compared to their sensitive counterparts, confirming the enhanced functionality of the RANK pathway in anti-HER2-resistant breast cancer. Overactivation of the RANK signaling pathway enhances ERK and NF-κB signaling and increases lapatinib resistance in different HER2-positive breast cancer cell lines, whereas RANK loss sensitizes lapatinib-resistant cells to the drug. Our results indicate that ErbB signaling is required for RANK/RANKL-driven activation of ERK in several HER2-positive cell lines. In contrast, lapatinib is not able to counteract the NF-κB activation elicited after RANKL treatment in RANK-overexpressing cells. Finally, we show that RANK binds to HER2 in breast cancer cells and that enhanced RANK pathway activation alters HER2 phosphorylation status.ConclusionsOur data support a physical and functional link between RANK and HER2 signaling in breast cancer and demonstrate that increased RANK signaling may contribute to the development of lapatinib resistance through NF-κB activation. Whether HER2-positive breast cancer patients with tumoral RANK expression might benefit from dual HER2 and RANK inhibition therapy remains to be elucidated.

Abstract PS5-13: Holistic artificial intelligence-driven predictor in HER2-positive (HER2+) early breast cancer (BC) treated with neoadjuvant lapatinib and trastuzumab without chemotherapy: A correlative analysis from SOLTI-1114 PAMELA

Abstract Background: Positive partial response was observed in patients with primary HER2+ early BC with dual HER2 blockade that were not treated with chemotherapy. In this context and beyond, the low (partial) response rate of chemotherapy-free treatment strategies creates the necessity for patient stratification prior to treatment selection. Here, we tackle the challenging task of evaluating the ability of clinical, gene expression and histopathology data to predict response following dual HER2 blockade without chemotherapy. Our aim is through artificial intelligence to automatically decipher the complementarity of clinical, genomic and histopathology data through an evidence-driven approach towards a low dimensional holistic signature that determines outcomes and could be subsequently used as a clinical biomarker for treatment patient inclusion. Methods: PAMELA (Lancet Oncology 2017) was a prospective study in HER2+ BC designed to evaluate the ability of the PAM50 HER2-enriched intrinsic subtype to predict pCR following 18-weeks of neoadjuvant lapatinib and trastuzumab (and hormonal therapy if hormone receptor-positive [HR+]). Clinical-pathological variables (15) were included such as tumor cellularity, tumor-infiltrating lymphocytes (TILs), the expression of BC-related genes/signatures (567) along with histopathological data from pre-treatment samples. Imaging information was obtained from H/E slides, through an unsupervised deep learning approach using an attention network. The semantic segmentation was used to derive at the patch level image and shape characteristics resulted on a pathomics-derived feature vector of (300) variables. An integrative approach that harnessed clinical, genomics and pathomics data into a unified prediction framework was used. Patients were divided into a training set 80% and a testing set 20% with proportions of pCR and non-pCR corresponding to the ones observed. A 100-fold Cross-validation (CV) was performed on the training. Linear and non-linear robust feature selection were used to recover a low dimensional holistic signature along with an ensemble learning approach to select the top 5 machine learning/artificial intelligence methods for prognosis. Results: From the high dimensional feature (882) space, a low dimensional holistic signature of 8 predictive variables was automatically retrieved through. The signature consisted of 4 genomics variables (expression levels of ERBB2, ESR1, Luminal A signature and Risk of Relapse score), 2 clinical-pathological variables (histologic grade and ER-status) and 2 imaging variables (mean Short Run Low Gray Level Emphasis of the gray level run length matrix and the mean absolute deviation). To ensure the robustness and generalizability of the results, we present results averaged over 100 splits into training and test. On all cases the same holistic signature was uses and the same prediction methods/principles. The proposed AI-driven prognosis mechanism reached 75% balanced accuracy, 69% precision, 65% sensitivity, 86% specificity and 0.84 AUC demonstrating the relevance of the approach. It was observed a successful classification of 86% for the non-pCR and 65% for the pCR cases. Ablation studies were performed to determine the relevance of the different categories of variables. Genomics variables were the most informative since their removal led to the highest decrease of the metrics (11% in average). Conclusion: The proposed method has great potentials for an effective and clinically meaningful implementation of pre-selecting patients that will not achieve a pCR after neoadjuvant dual HER2 blockade. Besides, the generality of the method used here makes it transposable to any type of cancer or therapy. Citation Format: Enzo Batistella, Laia Paré, Mihir Sahasrabudhe, Tomás Pascual, Maria Vakalopoulou, Patricia Villagrasa, Eric Deutsch, Núria Chic, Guillermo Villacampa, Paolo Nuciforo, Javier Cortes, Antonio Llombart-Cussac, Nikos Paragios, Aleix Prat. Holistic artificial intelligence-driven predictor in HER2-positive (HER2+) early breast cancer (BC) treated with neoadjuvant lapatinib and trastuzumab without chemotherapy: A correlative analysis from SOLTI-1114 PAMELA [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS5-13.

Neoadjuvant docetaxel with or without carboplatin plus dual HER2 blockade for HER2-positive breast cancer: a retrospective multi-center Chinese study

This study aimed to compare the real-world efficacy and safety of the TCbHP regimen (docetaxel, carboplatin, trastuzumab and pertuzumab) and the THP regimen (docetaxel, trastuzumab and pertuzumab) as neoadjuvant therapy for Chinese patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer. We compared efficacy and safety outcomes from 72 Chinese patients with HER2-positive breast cancer who underwent neoadjuvant dual HER2 blockade plus TCb or T chemotherapy and surgery between March 2019 and June 2020. All 72 patients were women (32-76 years old) and the overall pathological complete response (pCR) rate was 70.8% (51/72). The pCR rates were 76.1% (35/46) for the TCbHP regimen and 61.5% (16/26) for the THP regimen (P=0.28). Univariate analyses revealed that pCR was associated with clinical T classification (P=0.024), AJCC stage (P=0.042), estrogen receptor (ER) status (P=0.002), progesterone receptor (PR) status (P=0.035), Ki-67 index (P<0.001), and immunohistochemical HER2 status (P<0.001). Multivariate analyses revealed that pCR was independently predicted by ER status (OR: 0.227, 95% CI: 0.053-0.852; P=0.032) and immunohistochemical HER2 status (OR: 43.673, 95% CI: 6.801-875.86; P<0.001). The common adverse events for both regimens included neutropenia, anemia, thrombocytopenia, nausea, and diarrhea. Relative to the THP group, the TCbHP group had higher frequencies of grade 3-4 thrombocytopenia (17% vs. 0%, P=0.044) and grade 3-4 diarrhea (15% vs. 0%, P=0.044). Both regimens had very good cardiac safety. These results suggest that both TCbHP and THP regimens may be useful neoadjuvant treatments for high-risk early or locally advanced HER2-positive breast cancer. Both regimens had generally good safety outcomes, although clinicians should be aware of the risks of grade 3-4 thrombocytopenia and diarrhea during TCbHP treatment. Elderly patients who require neoadjuvant therapy may benefit from 6 cycles of THP treatment, based on its good efficacy and mild adverse events.

120P - Early on-treatment vs pre-treatment tumour transcriptomes as predictors of response to neoadjuvant therapy for HER2-positive inflammatory breast cancer

BackgroundInflammatory breast cancer (IBC) is an understudied form of breast cancer (BC). The incidence of HER2-positive disease in IBC is 2-fold greater than that in non-IBC. Several studies evaluating dual-HER2 blockade in HER2-positive BC have demonstrated an association of specific gene expression signatures with response. Those analyses were based on pretreatment tumor characteristics and did not focus specifically on IBC. We used RNA-Seq to elucidate the impact of short term neoadjuvant dual-HER2 blockade on IBC transcriptomic profile and to identify early predictors of response. MethodsWe analyzed fresh frozen tumor samples prospectively obtained from 23 patients (pts) with HER2-positive IBC, treated at a single institution in a phase 2 trial (NCT01796197) with neoadjuvant trastuzumab, pertuzumab (HP) and paclitaxel for 16 weeks (wk). Breast biopsies were performed at baseline (D1) and 1 wk later (D8) after a single dose of dual blockade with HP before adding paclitaxel. Primary endpoint was pathologic complete response (pCR) defined as no evidence of invasive disease in breast or lymph nodes. Tumors from D1 and D8 were used for RNA-Seq analysis and assessment of tumor-infiltrating lymphocytes (TILs) and CelTIL score. ResultsPaired breast tumor biopsies (D1, D8) were obtained in all pts; 2 pts did not have surgery. In the intent-to-treat analysis, 10/23 (43%) pts achieved a pCR. Across all metrics, D8 biopsies were significantly better predictors of response than D1 (p-value: 1.0X10-15). Upregulation of immune signatures by RNA-Seq was observed at D1 and D8. D8 biopsies showed a greater upregulation of anti-tumor immunity and changes in multiple signalling pathways. Neither TILs nor CelTIL were associated with pCR. ConclusionsWe identified an accurate predictor of response based on transcriptomic profiling by RNAseq, following a single dose of neoadjuvant dual-HER2 blockade in HER2-positive IBC. It outperforms a similar predictor constructed on a pretreatment profile in the same cohort. Assessing early-changes in gene expression level by RNA-seq following one dose of treatment may provide insights for the molecular mechanisms underlying response or resistance to anti-HER2 therapy. Clinical trial identificationNCT01796197. Legal entity responsible for the studyDana-Farber Cancer Institute. FundingGenentech, Inc and the Inflammatory Breast Cancer (IBC) Network. DisclosureS. Pernas: Travel / Accommodation / Expenses: Roche; Advisory / Consultancy: Polyphor. S. Goel: Advisory / Consultancy, Research grant / Funding (institution): Eli Lilly; Advisory / Consultancy, Research grant / Funding (institution): Novartis; Advisory / Consultancy: G1 Therapeutics; Research grant / Funding (institution): Merck. J.L. Guerriero: Advisory / Consultancy, Research grant / Funding (institution): Glaxo-Smith Kline; Research grant / Funding (self): Eli Lilly. E.A. Mittendorf: Advisory / Consultancy: Amgen; Advisory / Consultancy, Research grant / Funding (institution): AstraZeneca; Advisory / Consultancy, Research grant / Funding (institution): Genentech; Advisory / Consultancy: Genomic Health; Advisory / Consultancy: Merck; Advisory / Consultancy: Peregrine Pharmaceuticals; Advisory / Consultancy, Research grant / Funding (institution): Sellas Lifesciences; Advisory / Consultancy: Tapimmune. B. Overmoyer: Research grant / Funding (institution): Genentech; Research grant / Funding (institution): Incyte; Research grant / Funding (institution): Eisai. All other authors have declared no conflicts of interest.

Genomic-based predictive biomarkers to anti-HER2 therapies: A combined analysis of CALGB 40601 (Alliance) and PAMELA clinical trials.

571 Background: In HER2-positive breast cancer, new biomarkers of response are needed in order to direct multi-agent anti-HER2 combinations towards patients in whom they are truly needed. CALGB 40601 and PAMELA trials tested neoadjuvant dual HER2 blockade and included gene expression analysis aimed to evaluate different genomic biomarkers of trastuzumab and/or lapatinib benefit. Methods: Gene expression by mRNA sequencing (RNAseq) was performed on 265 and 142 pre-treatment tumors of the CALGB 40601 and the PAMELA clinical trials respectively. Intrinsic subtypes were determined by nCounter PAM50-predictor on the PAMELA samples. A new HER2-positive specific gene-centering method was trained on the PAMELA RNAseq data, and showed a higher concordance with PAM50 predictions obtained from nCounter platform. This method was then applied to CALGB 40601 samples. Results: In the combined cohort, the subtype distribution was 10% Luminal A, 8% Luminal B, 62% HER2-enriched (HER2-E), 10% Basal and 10% Normal-like. The pCR rate was significantly higher in HER2-E vs. not HER2-E subtypes (48.6% vs. 20.7%; P &lt; 0.001). HER2-E subtype correlation, ERBB2 amplicon and B-cell genomic signatures were associated with pCR, while luminal signatures were associated with non-responders. In multivariate analysis HER2-E subtype, ERBB2 mRNA and IgG signature expression were independent predictors of response to paclitaxel + trastuzumab +/-lapatinib (OR = 1.98, OR = 1.51, OR = 1.48, respectively, P &lt;0.05). The event free survival analysis at 5 years in the CALGB 40601 cohort showed a benefit of dual vs single anti-HER2-blockade (HR 0.35, P &lt;0.05). Within the HER2-E, ERBB2-high and IgG–high subpopulations, there were also a benefit of dual vs. single anti-HER2 treatment (HR = 0.32, HR = 0.15, HR =0.15, respectively, P &lt;0.05). Conclusions: Intrinsic subtype, ERBB2 mRNA levels, and IgG genomic signature are independent predictive biomarkers of response in the combined cohort. The clinical implementation of these biomarkers could help to design future escalation/de-escalation clinical trials in the HER2-positive neoadjuvant setting. Support: U10CA180821, U10CA180882, U24CA196171, P50-CA58223, GSK, SPORE, BCRF and SEOM. https://acknowledgments.alliancefound.org .

Impact of dual anti-HER2 therapy on pathologic complete response rate in breast cancer in a minority-enriched population.

e18111 Background: The addition of pertuzumab (P) to a neoadjuvant trastuzumab (H) plus chemotherapy combination has been shown to significantly improve the pathologic complete response rate (pCR) in localized HER2+ breast cancer; however, minorities have been under-represented in these trials. Racial/ethnic disparities have also been shown to affect outcomes of cancer treatment. This study is aimed to assess the impact of neoadjuvant dual HER2-blockade in an unselected minority-enriched population. Methods: A retrospective chart review was conducted of women with stage I to III HER2+ breast cancer who received neoadjuvant treatment between 2007 and 2017 at an academic institution and its affiliated safety net health system. Data on stage, chemotherapy, race/ethnicity, site of therapy (academic vs safety net hospital), and hormone receptor status were collected. All patients underwent surgery after completion of neoadjuvant chemotherapy. pCR was defined as ypT0/is, ypN0. Chi-squared test and univariate/multivariate logistic regression were used for statistical analysis. Results: The study population included 261 women with the following race/ethnic distribution: 37.7% Non-Hispanic Whites, 34.6% Hispanics, 20.6% Blacks, and 7% other racial/ethnic origin. Ninety-five patients (36%) received chemotherapy-H vs 166 patients (64%) received chemotherapy-HP. Patients at the safety net health system had higher stage at diagnosis compared to the academic site. Site of care and race/ethnicity did not impact the choice of neoadjuvant treatment. The pCR rate was significantly higher for the chemotherapy-HP group (55.4%) compared to the chemotherapy-H group (34.7%) (p = 0.001). There was no association between race/ethnicity, or site of treatment (academic vs safety net), and the probability of achieving pCR. Multivariate analysis showed only dual anti-HER2 therapy (OR: 2.67, CI: 1.55-4.59, p = 0.0004) and hormone-receptor negative status (OR: 2.18, CI: 1.30-3.67, p = 0.0031) to correlate with pCR. Conclusions: Neoadjuvant dual anti-HER2 therapy was more likely to result in a pCR in our minority enriched population. Our data also suggests the combination of chemotherapy-HP confers similar benefit irrespective of race/ethnicity or site of care.

Abstract P6-17-08: Dynamics of tumor-infiltrating lymphocytes (TILs) during neoadjuvant dual HER2 blockade in HER2-positive (HER2+) breast cancer in the absence of chemotherapy

Abstract Background: TILs in HER2+ breast cancer (BC) predict 1) prognosis in early setting, 2) complete pathological response (pCR) following neoadjuvant antiHER2-based therapy and 3) response to trastuzumab and pembrolizumab in the metastatic setting. However, less is known regarding changes in TILs during antiHER2-based treatment. Methods: Stromal TILs where evaluated centrally using H/E slides in tumor samples from the PAMELA (NCT01973660) neoadjuvant phase II trial. Briefly, 151 women with HER2+ BC were treated with lapatinib and trastuzumab, and hormonal therapy if HR positive, for 18 weeks. TIL levels were determined at baseline (n=148), after 2 weeks of treatment (n=134) and at surgery (n=137). Expression of 560 genes, including immune-related genes (e.g. CD8A, CD4, PD1 and PDL1) was measured at the same timepoints (baseline n=151, 2-weeks n=144, surgery n=144) using the nCounter platform. Intrinsic subtyping at baseline was determined using the PAM50 gene expression predictor. Changes in TILs between 2 time-points were determined by paired t-tests. Correlation of TILs with gene expression was assessed by quantitative SAM analysis using a False Discovery Rate &amp;lt;1%. All statistical tests were two-sided and considered significant when p&amp;lt;0.05. All statistical analyses were carried out using the R software. Results: Compared to baseline, a significant increase in TILs was observed at week 2 in HR- (p&amp;lt;0.001) and HER2-enriched (HER2-E) tumors (p=0.001), but not in HR+ (p=0.133) and non-HER2-E tumors (p=0.067). Within HR- and HER2-E tumors, increase in TILs at week 2 from baseline was observed regardless of pathological response at surgery (pCR and HR- [p=0.008]; RD and HR- [p=0.037]; pCR and HER2-E [p=0.010]; RD and HER2-E [p=0.056]). Compared to week 2, a significant decrease in TILs at surgery was observed in HR- (p=0.002) and HER2-E (p=0.003) tumors, but not in HR+ (p=0.616) and non-HER2-E tumors (p=0.578). Within HR- and HER2-E tumors, a significant decrease in TILs between week 2 and surgery was observed in tumors achieving pCR (p=0.004 and p=0.005), while, in tumors not achieving pCR, no significant tendency was observed (26.4% and 33.0% of tumors showed an increase and a decrease of TILs between week 2 and surgery). Nonetheless, the vast majority of residual tumors (non-pCR) at surgery had TILs above ≥5%: 34.3% 5-10%, 21.0% 10-20%, 15.2% 20-40% and 11.4% ≥40%. Finally, TILs scoring was found highly enriched (FDR&amp;lt;1%) for immune-related genes tracking activated CD8 T-cells (i.e. CD8A, CD3G, LAG3 and PD1). Expression of these immune genes consistently correlated with TIL levels across the 3 time-points. Conclusions: In early HER2+ BC, a general increase in TILs is observed following 2 weeks of dual HER2 blockade. This observation is mostly observed in HR- and HER2-E subtype, but regardless of pathological response at surgery. After 2 weeks of treatment, TILs consistently decrease in patients achieving a pCR, whereas two main patterns of TILs expression are observed in patients with residual disease at surgery. Nonetheless, most residual tumors at surgery are inflamed (i.e. TILs ≥5%) and might be good candidates for clinical trials evaluating adjuvant immune checkpoint inhibitors. Citation Format: Griguolo G, Holgado E, Cortés J, Fasani R, Pascual T, Paré L, Bermejo B, Oliveira M, Morales S, Martinez N, Vidal M, Pernas S, Lopez R, Muñoz M, Galvan P, Garau I, Manso L, Alarcón J, Martínez E, Villagrasa P, LLombart-Cussac A, Prat A, Nuciforo P. Dynamics of tumor-infiltrating lymphocytes (TILs) during neoadjuvant dual HER2 blockade in HER2-positive (HER2+) breast cancer in the absence of chemotherapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-08.

Abstract PD3-08: Assessment of the tumor immune environment in inflammatory breast cancer treated with neoadjuvant dual-HER2 blockade

Abstract Background: Inflammatory breast cancer (IBC) is an aggressive form of breast cancer that remains relatively understudied. We examined the efficacy of neoadjuvant dual-HER2 blockade (trastuzumab (H) and pertuzumab (P)) combined with paclitaxel (T) in HER2+ IBC, including a planned analysis to elucidate associations between the tumor immune microenvironment profile and response to therapy. Methods: An IRB-approved, single-arm phase II trial for patients (pts) with newly diagnosed HER2+ IBC was conducted. Pts had a pre-treatment biopsy of the affected breast (D1) followed by a loading dose of HP. A second biopsy was performed 1 week (wk) later (D8), when T (80mg/m2/wk x 16 wks) was added to HP. Responding pts underwent modified radical mastectomy (MRM) where residual disease was collected. The primary objective was to determine the rate of pathologic complete response (pCR) defined as ypT0/isN0. Residual Cancer Burden (RCB) was also determined. Tumor specimens from D1, D8 and MRM were assessed for disease cellularity and scored for percentage of tumor infiltrating lymphocytes (TILs): low=0-10%, intermediate=11-59%, high&amp;gt;60%. RNA-sequencing was performed on tumor tissue from D1 and D8 to explore the impact of short-term HP treatment on the tumor transcriptomic profile and to identify potential predictors of pCR. Results: 23 pts with HER2+ IBC were enrolled between 8/2013-6/2017. Mean age was 48 years (range 32-74); 11 pts (48%) had estrogen and progesterone receptor (ER/PR) negative disease. Matched tumor biopsies (D1, D8) were obtained in all 23 pts; 21 underwent MRM; 1 was lost to follow-up and 1 had disease progression. In the intent to treat analysis, 10/23 (43%) pts achieved a pCR and 7 (30%) had RCB-1. Ten of the 22 evaluable pts achieved a pCR (45.5%). TILs were evaluable in 20/23 (87%) matched tumor biopsies (D1, D8). Among the D1 biopsy specimens: 19 (95%) had low levels, 2 (10%) had intermediate levels, and none had high levels. When D1 TIL levels were compared with D8 levels, 3(15%) had an increase in TILs, 16(80%) had no change in TIL levels, and 1(5%) had a decrease in the level of TILs. Both samples with intermediate levels and 2 of 3 samples with high levels of TILs on D1 and D8 were seen in ER/PR negative disease. An evaluation of biopsy specimens associated with subsequent pCR using GO enrichment analysis from the RNA-Seq data showed significant upregulation of several immune-process related gene expression signatures both at D1 and D8 (e.g. antigen processing and presentation, TCR signaling, NK cell cytotoxicity, p-value: 2.99E-48 to 1.39E-16) when compared with those associated with residual disease at the time of MRM. Across the entire cohort, D8 biopsies showed evidence of upregulated anti-tumor immunity compared to D1 biopsies (p-value: 9.57E-06 to 0.012). Notably, this change from D1 to D8 was largely restricted to tumors that achieved a pCR. Conclusion: THP for 16 weeks was a highly effective treatment for HER2+ IBC. Immune activation as determined by gene expression signatures predicted pCR, and moreover upregulation of anti-tumor immunity after 1 wk of HP might further predict a complete pathologic response to therapy. ClinicalTrials.gov identifier: NCT01796197 Citation Format: Pernas S, Goel S, Harrison BT, Hu J, Johnson N, Regan M, Chichester LA, Nakhlis F, Schlosnagle EJ, Winship G, Guerriero JL, Parsons H, Mittendorf EA, Overmoyer B. Assessment of the tumor immune environment in inflammatory breast cancer treated with neoadjuvant dual-HER2 blockade [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD3-08.

Abstract P6-17-07: Gene signatures and subtype changes during HER2 dual blockade in PAM50 HER2-enriched HER2-positive breast cancer

Abstract Background: HER2-positive (HER2+) breast cancer (BC) is composed of 4 molecular subtypes: Luminal A and B, HER2-enriched (HER2-E) and Basal-like. Among them, the HER2-E is highly sensitive to anti-HER2 treatment. However, ˜60% of HER2-E tumors do not achieve a pathological complete response (pCR) following neoadjuvant dual HER2 blockade without chemotherapy. Here, we aimed to better understand the molecular changes of the HER2-E subtype during anti-HER2 treatment. Methods: Gene expression was evaluated in 101 patients with HER2-E tumors from the PAMELA neoadjuvant phase II trial (Lancet Oncol 2017). Briefly, women with HER2+ BC were treated with lapatinib and trastuzumab (and hormonal therapy if hormone receptor [HR]-positive) for 18 weeks. The median time between the last dose of treatment and surgery was 35 days (range=213; interquartile range=16). Expression of the PAM50 genes and 6 PAM50 signatures (Luminal A, Luminal B, HER2-E, Basal-like, normal-like and the PAM50 proliferation score) were determined using the nCounter platform at baseline (n=101), after 2 weeks of treatment (n=96) and in residual tumors (non-pCR) at surgery (n=57). Same analyses were done in 2 HER2+/HER2-E cell line models (BT474 [HR+] and SKBR3 [HR-]) following in vitro treatment with trastuzumab in combination with lapatinib. Biological changes between 2 time-points were determined by paired t-tests with a false discovery rate (FDR) &amp;lt;5%. Results: After 2 weeks of treatment, 85.7% and 94.6% of the 56 genes/signatures were found differentially expressed (FDR&amp;lt;5%) in HER2-E/HR+ (n=35) and HER2-E/HR- (n=61) tumors, respectively. The two gene lists were highly correlated (correlation coefficient=0.93). Overall, a significant relative increase in Luminal A and normal-like signature scores, and a relative decrease in proliferation, HER2-E and Luminal B signature scores, were observed between baseline and week 2. Interestingly, a PAM50 subtype switch to Luminal A was observed in 31.6% and 4.8% of HER2-E/HR+ and HER2-E/HR- tumors. In BT474 and SKBR3, all genes/signatures were also found differentially expressed (FDR&amp;lt;5%) following 72h of dual HER2 blockade. The in vitro findings recapitulated the in vivo findings in 80-86% of the genes/signatures. Similar to tumors, a switch to a Luminal A subtype following dual HER2 blockade was observed in BT474 but not in SKBR3. Finally, 92.9% of the 56 genes/signatures were found differentially expressed (FDR&amp;lt;5%) in residual tumors at surgery compared to week 2. Contrary to the findings in the first 2 weeks of treatment, a general rebound effect in gene expression was observed between week 2 and surgery. Similarly, a rebound effect was observed in 60% of the genes/signatures in BT474 after removing anti-HER2 therapy for 72h, leading to a subtype switch from Luminal A back to HER2-E. Conclusions: Dual HER2 blockade in the HER2-E subtype induces large biological changes that lead to a more low-proliferative Luminal A phenotype both in tumors and in vitro models, especially in HER2-E/HR+ disease. These phenotypic changes are reversible upon stopping anti-HER2 treatment. This finding supports the use of maintenance anti-HER2 treatment +/- endocrine therapy (if HR+) in advanced HER2+ BC. Citation Format: Brasó-Maristany F, Griguolo G, Llombart-Cussac A, Pascual T, Paré L, Bermejo B, Oliveira M, Morales S, Martinez N, Vidal M, Pernas S, Lopez R, Muñoz M, Galvan P, Garau I, Manso L, Alarcón J, Martínez E, Villagrasa P, Cortés J, Prat A. Gene signatures and subtype changes during HER2 dual blockade in PAM50 HER2-enriched HER2-positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-07.

Abstract P2-08-06: Standardized nCounter-based determination of estrogen receptor (ER), progesterone receptor (PR) and HER2 receptor status in breast cancer

Abstract Background: The expression of ER, PR and HER2 in breast cancer is determined by routine pathology assessment to indicate systemic treatment. Here, we investigated the ability of a standardized mRNA-based assay to predict ER, PR and HER2 status and treatment response. Methods: ESR1, PGR and ERBB2 expression was analyzed from the standardized nCounter-based PAM50 assay in 1,544 FFPE breast tumors obtained from 13 independent studies (NeoEribulin, GEICAM 2012-09, TBCRC023/006, LPT109096, EGF117165, PAMELA, PerELISA, GEICAM 2003-11, VENTANA, IBIMA and HCB). All immunohistochemical and in situ hybridization analyses followed ASCO/CAP criteria and were performed in central labs except for Neoeribulin and VENTANA studies. To explore the best cutoff for each gene, we used Monte Carlo cross validation (repeated 1000 times, 2/3 training, 1/3 testing) to achieve the highest kappa values when gene expression was compared to pathology assessment. Receiver operating characteristic analysis and area under the ROC curve (AUC) was used to evaluate the performance of each gene to predict ER, PR and HER2 status. Finally, the association of each gene (using the pre-established cutoffs) with pathological complete response (pCR) was evaluated using univariate logistic regression analyses in 2 neoadjuvant cohorts: 1) A combined HER2+ cohort using 191 tumor samples from PAMELA/PerELISA phase II trials, where patients received neoadjuvant dual HER2 blockade without chemotherapy for 15-18 weeks and 2) a combined cohort of hormone receptor-positive/HER2-negative using 205 tumor samples from IBIMA/HCB consecutive series, where patients received anthracycline/taxane-based chemotherapy. Results: Concordance between ESR1 and ER was 95.3% (95% confidence interval [95CI] 94.0-96.4%; AUC=0.98). ER+ and ER- cases were classified as ESR1- and ESR1+ in 5.5% and 4.8% of the cases, respectively. Concordance between PR and PGR was 85.2% (95CI 83.1-87.1%; AUC=0.95), and between ERBB2 and HER2 was 92.8% (95CI 91.4-94.1%; AUC=0.95). HER2+ and HER2- cases were classified ERBB2- and ERBB2+ in 16.7% and 2.9% of the cases, respectively. In the neoadjuvant HER2+ cohort, the pCR rates were 44.6% in ESR1- and 18.8% in ESR1+ (odds ratio [OR] 3.9; 95CI 1.9-8.4; p&amp;lt;0.001), 38.5 in PGR- and 15.8% in PGR+ (OR 3.2; 95CI 1.6-6.7; p=0.001), 2.6% in ERBB2- and 35.3% in ERBB2+ (OR 19.7; 95CI 2.6-149.1; p&amp;lt;0.001). In the neoadjuvant HR+/HER2- cohort, the pCR rates were 40% in ESR1- and 5.12% in ESR1+ (OR 11.5; 95IC 2.7-48.5; p&amp;lt;0.001), 15.5% in PGR- and 4.3% in PGR+ (OR 3.8; 95IC 1.3-11.7; p=0.019), 7.36% in ERBB2- and 0% in ERBB2+ (OR NA). Finally, ESR1, PGR and ERBB2 expression as continuous variables were found significantly associated with pCR in both cohorts. Conclusion: ESR1, PGR and ERBB2 standardized mRNA levels show high concordance with ER, PR and HER2, and might provide a more objective and quantitative prediction of response to chemotherapy and anti-HER2 therapy. The level of concordance between GE and pathology-based assessments is similar to 2 FDA 510(k) cleared pathology-based ER assays (e.g. SP1 versus 6F11 antibody clones), local versus central HER2 testing, and ER or PR status when determined by the ligand-binding assay versus immunohistochemistry. Citation Format: Pascual T, Tsai YS, Martín M, Lluch A, Cortes J, Llombart A, Conte P, Guarneri V, Rimawi MF, Alba E, Ruiz-Borrego M, Rojo F, de la Haba J, Schiff R, Adamo B, Vidal M, Paré L, Chic N, Muñoz M, Galvan P, Gonzalez-Farre B, Brauer HA, Sullivan A, Nuciforo P, Parker JS, Prat A. Standardized nCounter-based determination of estrogen receptor (ER), progesterone receptor (PR) and HER2 receptor status in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-08-06.

Abstract S3-03: PAM50 intrinsic subtype as a predictor of pathological complete response following neoadjuvant dual HER2 blockade without chemotherapy in HER2-positive breast cancer: First results of the PAMELA clinical trial

Abstract Background: Prior neoadjuvant studies in HER2+ breast cancer have shown that dual HER2 blockade without chemotherapy achieves pathological complete responses (pCR) rates of 6-36% (TBCRC006/TBCRC023/NeoSphere). However, a major challenge today is how to select prospectively patients who will derive the maximum benefit from dual anti-HER2 therapies without chemotherapy. In this context, we and others have previously shown that HER2+ disease is biologically heterogeneous and composed of all the intrinsic molecular subtypes (Luminal A, Luminal B, HER2-enriched [HER2-E] and Basal-like). Among them, the HER2-E subtype shows the highest activation of the EGFR/HER2 pathway. Methods: PAMELA (NCT01973660) is a non-randomized, open-label, multicentric, prospective translational research study in stage I-IIIA HER2+ breast cancer designed to evaluate the ability of the PAM50 intrinsic subtypes to predict pCR in the breast (pCRB; in situ allowed) following 18 weeks of neoadjuvant lapatinib and trastuzumab). Patients with HR+ disease received letrozole (if postmenopausal) or tamoxifen (if pre-menopausal). The primary objective was to compare the pCRB rates of the HER2-E versus the non-HER2-E subtypes in the intent-to-treat population. The study was planned with a power of 95% at a significance level of 0.05 to detect an absolute relative difference in pCRB rates between the two groups of 27% (i.e. 35% in HER2E and 8% in non-HER2-E). Day-15 formalin-fixed, paraffin-embedded tissue samples were prospectively collected and gene expression profiled using the nCounter platform. The intrinsic subtypes were identified using the research-based PAM50 predictor (Parker JCO 2009). Results: A total of 151 patients were recruited (n=77 HR+ and n=74 HR-). Patient characteristics were: mean age (55 years), mean tumor size (2.84 cm), negative axilla (63.5%) and postmenopausal (60.2%). At baseline, intrinsic subtype distribution was: HER2-E (n=101, 66.9%), Luminal A (n=22; 14.6%), Luminal B (n=16; 10.6%), Basal-like (n=9; 6%) and Normal-Like (n=3; 2%). The overall pCRB was 30.5% (46/151), 18.2% in HR+ disease and 43.2% in HR- disease. Five patients (3.3%) presented progressive disease. Rates of pCRB in HER2-E and non-HER2-E subtypes were 40.6% and 10.0% (p&amp;lt;0.0001), respectively. HER2-E subtype predicted pCRB independently of HR status. Within HR+ disease, pCRB rates were 31.6% in HER2-E subtype and 5.3% in non-HER2-E subtype (p=0.006). Within HR- disease, pCRB rates were 46.0% in HER2-E subtype and 27.3% in non-HER2-E subtypes (p=0.331). At Day-15, the majority of tumors became Normal-like (48.9%) or Luminal A (27.5%). Rates of pCRB were 46.9% in Normal-like tumors and 11.9% in non-Normal-like tumors when evaluated at day-15 (p&amp;lt;0.0001). Conclusions: The PAMELA trial met its primary endpoint. PAM50 HER2-E subtype identifies patients with HER2+ disease likely to derive a large benefit from dual anti-HER2 therapies +/- endocrine therapy, especially in HER2+/HR+ disease. In addition, early changes in gene expression indicative of a reduction of tumor cellularity are predictive of pathological complete response at surgery. Citation Format: Prat Aparicio A, Cortes Castan J, Pare L, Galvan P, Bermejo B, Martínez N, Vidal M, Pernas S, López R, Muñoz M, Nuciforo P, Fasani R, Morales S, Oliveira M, de La Peña L, Peláez A, Llombart A. PAM50 intrinsic subtype as a predictor of pathological complete response following neoadjuvant dual HER2 blockade without chemotherapy in HER2-positive breast cancer: First results of the PAMELA clinical trial [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr S3-03.

Abstract P2-11-07: Duration of fasting before taking lapatinib is associated with skin toxicity in neoadjuvant treatment of HER2 positive breast cancer: A cohort study from JBCRG-16/Neo-LaTH

Abstract Background: In neoadjuvant dual HER2 blockade, over 30% of patients fail to complete treatment as planned because of lapatinib-induced diarrhea, rash, and hepatotoxicity. Lapatinib bioavailability, which affects both efficacy and toxicity, is influenced by prandial conditions. Methods: To investigate the association between lapatinib dosage timing and toxicity, we reviewed the medical records of patients who were enrolled in the JBCRG-16/Neo-LaTH randomized phase II multicenter trial evaluating the efficacy and safety of neoadjuvant 1000 mg/day lapatinib (La) and trastuzumab (T) therapy for 6 or 12 weeks followed by 750 mg/day La, T and weekly paclitaxel for 12 weeks in Japanese patients with primary HER2 positive breast cancer. Lapatinib dosage timing was divided into three groups: after overnight fasting, between meals, and at bedtime. We also measured serum lapatinib concentrations at steady state and dosage timing on the day prior to pharmacokinetic blood sampling. The primary endpoint was to investigate the association between lapatinib dosage timing and frequency of ≥grade 2 diarrhea. The secondary endpoint was to assess the association between dosage timing and other toxicities, pharmacokinetics, efficacy, and treatment discontinuation. Statistical analyses performed included one-way ANOVA, Welch's test and logistic regression. Results: Out of 213 patients enrolled in JBCRG-16/Neo LaTH, we obtained dosage timing data from 143 (67%) patients: 16 (11%) after overnight fasting, 53 (37%) between meals, and 74 (52%) at bedtime. Serum lapatinib concentrations were obtained in 34/143 (24%) of patients. Dosage timing was not associated with ≥grade 2 diarrhea (8/16 (50%) after overnight fasting, 18/53 (34%) between meals, and 26/74 (35%) at bedtime; p = 0.48). However, multivariate analysis revealed that the after overnight fasting group is less likely to develop acne-like rash during La + T treatment regardless of age, BMI, or treatment. Multivariate logistic regression analysis of factors predicting rash during La + T treatmentFactor Adjusted odds ratio95% confidence intervalp valueAge (years)≥55Reference &amp;lt;552.671.18-6.310.018*BMI (kg/m2)≥23Reference &amp;lt;231.040.45-2.390.933La + T duration6 weeksReference 12 weeks3.621.49-9.770.004*Concurrent endocrine treatmentYesReference No2.170.94-5.150.068Dosage timingAfter overnight fastingReference Others3.681.16-11.90.027*BMI cut off is based on Asian criteria for overweight status. La: Lapatinib, T: Trastuzumab, *statistically significant In addition, serum lapatinib trough concentration and it's variability were significantly reduced in the after overnight fasting group (mean ± standard deviation (SD) = 0.35 ± 0.15 µg/ml, coefficient of variation (CV) = 42.7%) as compared to the others (mean ± SD = 0.77 ± 0.44 µg/ml, CV = 57.8%) (p&amp;lt;0.01) . The chance of pCR was not associated with dosage timing (8/16 (50%) after overnight fasting, 24/53, (45%) between meals, and 38/74 (51%) at bedtime; p = 0.79). Conclusions: These data suggest that overnight fasting stabilizes the bioavailability of lapatinib, which may aid in managing lapatinib-induced rash without diminishing its therapeutic efficacy. Citation Format: Tsuda M, Ishiguro H, Toriguchi N, Masuda N, Bando H, Ohgami M, Homma M, Morita S, Yamamoto N, Kuroi K, Takano T, Shimizu S, Toi M. Duration of fasting before taking lapatinib is associated with skin toxicity in neoadjuvant treatment of HER2 positive breast cancer: A cohort study from JBCRG-16/Neo-LaTH [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-11-07.

How to fill in and interpret an observation chart.

Background: The expression of ER, PR and HER2 in breast cancer is determined by routine pathology assessment to indicate systemic treatment. Here, we investigated the ability of a standardized mRNA-based assay to predict ER, PR and HER2 status and treatment response. Methods: ESR1, PGR and ERBB2 expression was analyzed from the standardized nCounter-based PAM50 assay in 1,544 FFPE breast tumors obtained from 13 independent studies (NeoEribulin, GEICAM 2012-09, TBCRC023/006, LPT109096, EGF117165, PAMELA, PerELISA, GEICAM 2003-11, VENTANA, IBIMA and HCB). All immunohistochemical and in situ hybridization analyses followed ASCO/CAP criteria and were performed in central labs except for Neoeribulin and VENTANA studies. To explore the best cutoff for each gene, we used Monte Carlo cross validation (repeated 1000 times, 2/3 training, 1/3 testing) to achieve the highest kappa values when gene expression was compared to pathology assessment. Receiver operating characteristic analysis and area under the ROC curve (AUC) was used to evaluate the performance of each gene to predict ER, PR and HER2 status. Finally, the association of each gene (using the pre-established cutoffs) with pathological complete response (pCR) was evaluated using univariate logistic regression analyses in 2 neoadjuvant cohorts: 1) A combined HER2+ cohort using 191 tumor samples from PAMELA/PerELISA phase II trials, where patients received neoadjuvant dual HER2 blockade without chemotherapy for 15-18 weeks and 2) a combined cohort of hormone receptor-positive/HER2-negative using 205 tumor samples from IBIMA/HCB consecutive series, where patients received anthracycline/taxane-based chemotherapy. Results: Concordance between ESR1 and ER was 95.3% (95% confidence interval [95CI] 94.0-96.4%; AUC=0.98). ER+ and ER- cases were classified as ESR1- and ESR1+ in 5.5% and 4.8% of the cases, respectively. Concordance between PR and PGR was 85.2% (95CI 83.1-87.1%; AUC=0.95), and between ERBB2 and HER2 was 92.8% (95CI 91.4-94.1%; AUC=0.95). HER2+ and HER2- cases were classified ERBB2- and ERBB2+ in 16.7% and 2.9% of the cases, respectively. In the neoadjuvant HER2+ cohort, the pCR rates were 44.6% in ESR1- and 18.8% in ESR1+ (odds ratio [OR] 3.9; 95CI 1.9-8.4; p Conclusion: ESR1, PGR and ERBB2 standardized mRNA levels show high concordance with ER, PR and HER2, and might provide a more objective and quantitative prediction of response to chemotherapy and anti-HER2 therapy. The level of concordance between GE and pathology-based assessments is similar to 2 FDA 510(k) cleared pathology-based ER assays (e.g. SP1 versus 6F11 antibody clones), local versus central HER2 testing, and ER or PR status when determined by the ligand-binding assay versus immunohistochemistry. Citation Format: Pascual T, Tsai YS, Martin M, Lluch A, Cortes J, Llombart A, Conte P, Guarneri V, Rimawi MF, Alba E, Ruiz-Borrego M, Rojo F, de la Haba J, Schiff R, Adamo B, Vidal M, Pare L, Chic N, Munoz M, Galvan P, Gonzalez-Farre B, Brauer HA, Sullivan A, Nuciforo P, Parker JS, Prat A. Standardized nCounter-based determination of estrogen receptor (ER), progesterone receptor (PR) and HER2 receptor status in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-08-06.