Updated results of tucatinib versus placebo added to trastuzumab and capecitabine for patients with pretreated HER2+ metastatic breast cancer with and without brain metastases (HER2CLIMB)

1043

Background: Tucatinib (TUC) is an oral tyrosine kinase inhibitor (TKI) highly specific for HER2. TUC is approved for use in combination with trastuzumab (T) and capecitabine (C) in patients (pts) with and without brain metastases (BM) who have received 1 or more prior anti-HER2–based regimens in the metastatic setting. In the primary analysis from the pivotal HER2CLIMB trial, the addition of TUC to T and C in pts with HER2+ metastatic breast cancer showed a statistically significant and clinically meaningful prolongation of progression-free (PFS) (HR = 0.54 [95% CI: 0.42, 0.71]; P < 0.001) and overall survival (OS) (HR = 0.66 [95% CI: 0.50, 0.88]; P = 0.005) (Murthy, et al. NEJM 2020). TUC in combination with T and C was well tolerated with few discontinuations other than for disease progression. Based on these data, the protocol was amended for unblinding of sites to treatment assignment to allow for crossover from the placebo arm to receive TUC in combination with T and C. Methods: HER2CLIMB (NCT02614794) is a global, randomized, double-blind, placebo-controlled trial in pts with unresectable locally advanced or metastatic HER2+ breast cancer previously treated with T, pertuzumab, and T-emtansine (T-DM1), including pts with untreated, treated stable, or treated and progressing BM. Overall 612 pts were randomized 2:1 to receive TUC 300 mg BID or placebo, each in combination with T and C. Randomization was stratified by BM, ECOG performance status, and geographic region. Protocol prespecified analysis of OS, PFS (by investigator assessment) and safety in the total study population will be performed at approximately 2 years from the last patient randomized. Results: Updated Kaplan-Meier time-to-event analysis of OS and PFS with hazard ratios and 95% confidence intervals for TUC arm vs placebo arm will be presented overall, as well as for OS in the prespecified subgroups reported previously (Murthy, et al. NEJM 2020). Safety and tolerability assessments will include frequency of adverse events by severity, dose modifications and discontinuation of study medications. Conclusions: Conclusions will be presented in the presentation. Clinical trial information: NCT02614794 .

Pharmacokinetic (PK) analyses in CSF and plasma from TBCRC049, an ongoing trial to assess the safety and efficacy of the combination of tucatinib, trastuzumab and capecitabine for the treatment of leptomeningeal metastasis (LM) in HER2 positive breast cancer

1044

Background: Tucatinib is a potent and highly selective HER2-targeted tyrosine kinase inhibitor approved for use in combination with trastuzumab and capecitabine for patients with metastatic HER2+ breast cancer (MBC) who have received ≥1 prior HER2-based regimen in the metastatic setting, including patients with brain metastases (BM). TBCRC049 (NCT03501979) is an investigator-initiated phase 2 single-arm study currently enrolling to evaluate the safety and efficacy of tucatinib, trastuzumab and capecitabine in HER2+ BC with newly diagnosed LM. Here, we report the pre-specified pharmacokinetic (PK) analysis for the first 15 patients to determine bioavailability of tucatinib and its predominant metabolite, ONT-993, in the CSF. Methods: Eligible patients included adults with HER2+ MBC, KPS > 50, and newly diagnosed, untreated LM (defined as positive CSF cytology and/or radiographic evidence of LM, plus clinical signs/symptoms). Patients with treated or concurrent/new BM were allowed. The primary endpoint is overall survival with an accrual goal of 30 pts. Parallel PK samples were collected in plasma and CSF via Ommaya reservoir on day 1 of cycles 1 and 2 at 0h (baseline), 2-3h, 5-7h and 24h (optional) following initiation of tucatinib 300 mg BID. Tucatinib and ONT-993 were quantified in plasma (n=15) and CSF (n=13) using validated liquid chromatography-mass spectrometry methods. Results: Tucatinib and ONT-993 plasma concentrations were consistent with previous studies and exhibited high interindividual variability. Tucatinib and ONT-993 were detectable in the CSF within 2 hours post tucatinib administration; concentrations ranged from 0.57 to 25 ng/mL for tucatinib (IC50 for tucatinib against HER2 is 3.3 ng/mL) and 0.28 to 4.7 ng/mL for ONT-993. Tucatinib concentrations in the CSF per timepoint were in a similar range to unbound plasma (plasmaub) tucatinib. CSF to plasmaub ratios were generally consistent over time; the steady-state (cycle 2) median tucatinib CSF to plasmaub ratio was 0.83 (0.19 to 2.1). ONT-993 CSF to plasmaub ratios were similar to tucatinib CSF to plasmaub ratios. Conclusions: In patients with LM from HER2+MBC who were treated with tucatinib, trastuzumab, and capecitabine, tucatinib and ONT-993 were detectable in the CSF of all patients at median levels similar to plasmaub tucatinib. This is the first documented evidence of tucatinib distributing into the CSF in patients with HER2+MBC. Efficacy and safety of tucatinib, trastuzumab, and capecitabine in patients with HER2+ LM will be reported upon completion of TBCRC 049 accrual. Clinical trial information: NCT03501979 .

The impact of gut microbial composition on response to neoadjuvant chemotherapy (NACT) in early-stage triple negative breast cancer (TNBC)

590

Background: The impact of gut microbiome on tumor biology, progression and response to immunotherapy has been shown across cancer types. However, there is little known about the impact of gut microbial composition on response to chemotherapy. We have previously shown that the gut microbiome remains unaltered during NACT in a cohort of 32 patients. Here we investigate the association between gut microbiome and response to NACT in a larger cohort of early-stage TNBC. Methods: Longitudinal fecal samples were collected from 85 patients with newly-diagnosed, early-stage TNBC patients enrolled in the ARTEMIS trial (NCT02276443). Patients all received standard NACT with adriamycin/cyclophosphamide (AC); volumetric change was assessed using ultrasound and patients with < 70% volumetric reduction (VR) after 4 cycles of AC were recommended to receive targeted therapy in addition to standard NACT to improve response rates. We performed 16S sequencing on bacterial genomic DNA extracted from 85 pre-AC fecal samples using the 2x250 bp paired-end read protocol. Quality-filtered sequences were clustered into Operational Taxonomic Units and classified using Mothur method with the Silva database version 138. For differential taxa-based univariate analysis, abundant microbiome taxa at species, genus, family, class, and order levels were analyzed using DESeq2 after logit transformation. Alpha-diversity indices within group categories were calculated using phyloseq. Microbial alpha diversity (within-sample diversity) was measured by Simpson's reciprocal index. β-diversity was measured using weighted UniFrac distances between the groups. The association between microbiota abundance and pathologic complete response (pCR) or residual disease (RD) was assessed using DESeq2 analysis. Results: Pre-AC fecal samples from 85 patients were available for analysis. Amongst them, there were 46 patients with pCR and 39 patients with RD. There was no significant difference in alpha diversity (p = 0.8) or beta-diversity (p = 0.7) between the pCR and RD groups. However, relative to patients with RD, the gut microbiome in patients with pCR was enriched for the Bifidobacterium longum species (p = 0.03). The gut microbiome in patients with RD was enriched for Lachnospiraceae (p = 0.03) at the genus level and the Bacteroides thetaiotaomicron species (p = 0.02). Conclusions: We have demonstrated significant differences in the gut microbial composition in patients with pCR as compared to patients with RD. Further investigation in larger studies is needed to support therapeutic exploration of gut microbiome modulation in TNBC patients receiving chemotherapy such as probiotic supplementation or fecal microbiota transplant.

Neoadjuvant atezolizumab (atezo) and nab-paclitaxel (nab-p) in patients (pts) with triple-negative breast cancer (TNBC) with suboptimal clinical response to doxorubicin and cyclophosphamide (AC)

592

Background: Neoadjuvant anti-PD-(L)1 therapy confers an improvement in pathological complete response (pCR) rate in unselected TNBC. However, given the potential for long-term morbidity from immune related adverse events (irAE), it is important to optimize the risk-benefit ratio for the use of these novel agents in the curative neoadjuvant setting. Suboptimal clinical response to neoadjuvant therapy (NAT) by sonography is associated with low rates of pCR rate (2-5%, GeparTrio and Aberdeen trials). Here, we report the results of a single arm phase II study of atezo and nab-p as the second phase of NAT in pts with TNBC with suboptimal clinical response to AC (NCT02530489). Methods: Pts with stage I-III TNBC showing suboptimal response to 4 cycles of doxorubicin and cyclophosphamide (AC), defined as disease progression or a <80% reduction in tumor volume by sonography, were eligible. Pts received atezo (1200mg IV, Q3 weeks x 4), and nab-p (100mg/m2 IV, Q1 week, x 12) as the second phase of NAT before undergoing surgery followed by adjuvant atezo (1200mg IV, Q3 weeks, x 4 cycles). This single arm, two-stage Gehan-type study was designed to detect an improvement in pCR from 5% to 20% in order to deem the regimen worthy of further study in a large, randomized, phase II/III trial; success was defined as pCR in 8 out of 37 pts enrolled. In a subset of pts, sufficient baseline tumor tissue was available for stromal TIL assessment (n=29). Results: 34 pts were enrolled from 2/2016-12/2020. Among the 33 pts who have completed NAT, the pCR rate was 30% (10/33, 95% CI: 16-49%) and the pCR/RCB-I rate was 42% (14/33, 95% CI: 25-61%). Clinicopathological characteristics are described in the table below. Treatment-related adverse events (all grades) occurring in ≥ 20% of pts include fatigue (73%), anemia (55%), peripheral sensory neuropathy (55%), neutropenia (48%), rash (42%), ALT elevation (39%), AST elevation (33%), nausea (30%), anorexia (24%), diarrhea (21%), myalgia (21%). Discontinuation of atezo due to irAEs occurred in 4 pts (12%, nephritis [n=2]; adrenal insufficiency [n=1]; hepatitis [n=1]); 2 of these pts had pCR. Conclusions: This study met its primary endpoint, demonstrating a promising signal of activity in this high risk pt population (pCR=30% vs 5% in historical controls). The 12% discontinuation rate due to irAEs confirms that further evaluation of a strategy administering immunotherapy only to pts with high risk disease not responding to AC warrants further investigation. Exploratory genomic and immunological correlative studies are ongoing. Clinical trial information: NCT02530489. [Table: see text]

Prognostic impact of high stromal tumor-infiltrating lymphocytes (sTIL) in the absence of pathologic complete response (pCR) to neoadjuvant therapy (NAT) in early stage triple negative breast cancer (TNBC)

583

Background: Pathologic complete response is an excellent surrogate for disease-free survival (DFS) and overall survival (OS) in TNBC. High sTIL is associated with improved pCR rates in TNBC. Recent data suggest that high sTIL is also associated with improved outcomes in patients who received no chemotherapy for early stage TNBC (Park, Annals of Oncology, 2019). Thus, we hypothesized that high sTIL may have prognostic impact in patients who do not achieve pCR to NAT. Methods: Pretreatment core biopsies from 182 patients with early-stage TNBC enrolled on the ARTEMIS trial (NCT02276443) were evaluated for sTIL by H&E. Patients were stratified according to sTIL (low < 30%, and high > 30%) and pCR (patients with pCR vs. no pCR). The primary outcome measure was DFS, defined from the date of diagnosis to the first local recurrence, distant metastases or death. Cox proportional hazards regression model was used. During follow-up 33 events for DFS were observed. Results: Among subjects who achieve pCR, DFS was excellent regardless of sTIL status and significantly better than those without pCR (p < 0.05). However, patients with high sTIL and no pCR demonstrated significantly worse DFS compared to all subjects having pCR (HR 0.18, 95% CI 0.04-0.76, p = 0.02). Additionally, we did not find a significant difference between high and low sTIL patients who did not achieve pCR. Conclusions: In early TNBC receiving NAT, for patients failing to achieve pCR, high sTIL was not associated with improved DFS; outcomes were comparable to those with low sTIL without pCR. Thus, high sTIL at baseline does not appear to confer an intrinsic prognostic benefit in the absence of pCR.

Tucatinib versus placebo added to trastuzumab and capecitabine for patients with previously treated HER2+ metastatic breast cancer with brain metastases (HER2CLIMB)

1005

Background: Tucatinib (TUC) is an investigational, highly selective HER2 kinase inhibitor. HER2CLIMB (NCT02614794) showed clinically meaningful and statistically significant improvements in overall survival (OS) and progression free survival (PFS) in all pts, prolongation of PFS in pts with brain metastases (BM), and objective response rate (ORR) when TUC was added to trastuzumab (T) and capecitabine (C). Primary methods and outcomes have been reported previously (Murthy NEJM 2019). We report the results of exploratory efficacy analyses in pts with BM. Methods: All pts with HER2+ metastatic breast cancer (MBC) enrolled in HER2CLIMB had a baseline brain MRI. Pts with BM were eligible and classified as untreated, treated stable, or treated and progressing. Pts were randomized 2:1 to receive TUC or placebo, in combination with T and C. Efficacy analyses in pts with BM at baseline were performed by applying RECIST 1.1 to the brain based on investigator evaluation. CNS-PFS (progression in the brain or death) and OS were evaluated in BM pts overall. Intracranial (IC) confirmed ORR (ORR-IC) and IC duration of response (DOR-IC) were evaluated in BM pts with measurable IC disease. After isolated brain progression, pts could continue study therapy after local treatment until second progression, and time from randomization to second progression or death was evaluated. Results: Overall, 291 pts (48%) had BM at baseline: 198 (48%) in the TUC arm and 93 (46%) in the control arm. There was a 68% reduction in risk of CNS-PFS in the TUC arm (HR: 0.32; 95% CI: 0.22, 0.48; P < 0.0001). Median CNS-PFS was 9.9 mo in the TUC arm vs 4.2 mo in the control arm. Risk of death overall was reduced by 42% in the TUC arm (OS HR: 0.58; 95% CI: 0.40, 0.85; P = 0.005). Median OS was 18.1 mo vs 12.0 mo. ORR-IC was higher in the TUC arm (47.3%; 95% CI: 33.7, 61.2) vs the control arm (20.0%; 95% CI: 5.7, 43.7). Median DOR-IC was 6.8 mo (95% CI: 5.5, 16.4) vs 3.0 mo (95% CI: 3.0, 10.3). In pts with isolated brain progression who continued study therapy after local treatment (n = 30), risk of second progression or death was reduced by 67% (HR: 0.33; 95% CI: 0.11, 1.02), and median PFS from randomization was 15.9 mo vs 9.7 mo, favoring the TUC arm. Conclusions: In pts with heavily previously treated HER2+ MBC with BM, TUC in combination with T and C doubled the ORR-IC, reduced risk of IC progression or death by two thirds and reduced risk of death by nearly half. If approved, TUC in combination with T and C has the potential to become a new standard of care in pts with HER2+ MBC with and without BM. Clinical trial information: NCT02614794 .

Statistical modeling of a novel clinical trial design using neoadjuvant therapy (NAT) to personalize therapy in patients (pts) with triple-negative breast cancer (TNBC)

595

Background: 40-50% of pts with TNBC develop pathologic complete response (pCR) with adriamycin/cyclophosphamide (AC)àtaxane (T) NAT; thus, most pts treated in randomized trials (RCTs) adding experimental drugs (ED) to standard NAT do not benefit from trial participation. A personalized trial design that enriches for non-pCR to standard NAT would diminish toxicity from ED in pts who do not need them and enrich ED in high-risk pts that are most likely to benefit. Methods: ARTEMIS (NCT02276443) is a non-randomized trial to study personalization of NAT in TNBC. Tumor biopsies were performed pre-NAT and volumetric change by ultrasound (VCU) after 4 cycles of AC (or upon clinical progression) assessed response. Pts with sensitive TNBC (VCU >=70% after AC) had T as the second phase of NAT. Pts with <70% VCU were offered phase II trials. pCR was assessed at surgical resection. 273 pts had available pCR status and 222 had complete data to generate a model predictive of response using multivariate logistic regression with common clinical factors. Data was randomly divided into training (n=111) and validation (n=111) sets. Results: 85 pts (38%) had pCR and VCU after AC x 4 was the strongest predictor of pCR. Other factors significant on multivariate analysis and included in the model were T stage (T1-4), stromal TIL, Ki67 and PD-L1. When applied to the validation data set, the accuracy of this model for predicting pCR was 76.6%, sensitivity 78.6% and specificity 75.4%. The PPV was 66.0% and the NPV was 85.2% with a ROC curve AUC of 82.4%. Using these data, ED exposure (table) was estimated for the ARTEMIS study design vs a 1:1 or a 2:1 RCT design (with an estimated pCR in control arm=40%), with a demonstrated benefit for personalization. Conclusions: This modeling indicates that personalization of NAT trials has the potential to enrich ED exposure for non-responsive disease as well as diminish ED exposure in pts likely to achieve pCR with standard NAT. Improved prediction of pCR would further enhance personalized trial design. Clinical trial information: NCT02276443 . [Table: see text]

Comprehensive profiling of androgen receptor-positive (AR+) triple-negative breast cancer (TNBC) patients (pts) treated with standard neoadjuvant therapy (NAT) +/- enzalutamide

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Background: The luminal androgen receptor (LAR) subtype of TNBC has a low pathologic complete response (pCR) rate after NAT. We determined the pCR rate of the enzalutamide and paclitaxel (ZT) regimen for pts with anthracycline-insensitive AR+ TNBC (NCT02689427), and related biomarkers. Methods: ARTEMIS (NCT02276443) is a non-randomized trial to determine if NAT can be used to personalized therapy. Pts received 4 cycles of doxorubicin-based NAT (AC). Pts with insensitive disease by imaging were offered clinical trials as the second phase of NAT based upon molecular profiling of pre-treatment biopsies. Immunohistochemistry (IHC) of AR+≥10% was the threshold for selecting ZT (enzalutamide 160 or 120 mg PO qD + paclitaxel 80 mg/m2 qW for 12 cycles). pCR was determined by surgery after NAT. Trial had two-stage Phase II design, and we report the completed first stage. We evaluated the concordance between Vanderbilt LAR subtype by molecular profiling (microarray and RNAseq) and IHC %AR+ cells. Frequency of PI3K pathway alterations within the LAR subtype was assessed. Results: 267 pts had tumors profiled by IHC, 220 by microarray, 187 by RNAseq and 197 by whole exome sequencing. 96 pts had post-AC RNAseq. LAR scores from both RNAseq and microarray profiling (n = 139) were highly concordant (R = 0.89, P < 0.001) and identified ~10% of TNBCs tested as LAR. The %AR+ cells from IHC correlated with LAR subtype scores according to RNAseq (R = 0.6, P < 0.001), with a cut-point of ≥30% AR+ having the best concordance with LAR subtype. Unlike other subtypes, by serial profiling, LAR TNBCs did not change subtype signatures after exposure to AC. LAR TNBCs had low rates of pCR (23%) and high rates of PI3K pathway activating aberrations (85%); however PI3K aberrations did not correlate with pCR. Seventeen patients with AC-insensitive TNBC received ZT. Five of 15 patients (33.3%) had responses (pCR or RCB-I). Toxicities are Grade (Gr) 4 syncope (n = 1), Gr3 abnormal liver function (n = 2), Gr3 neutropenia (n = 4). IHC & LAR subtype scores did not statistically associate with response to ZT (P = 0.8, P = 0.9). However, all responders to ZT had an upregulated androgen response pathway (ssGSEA Z > 1) as measured by transcriptomic analysis in pre-treatment biopsies analysis (P = 0.05, ppv = 0.56, npv = 1). Conclusions: The LAR TNBC subtype has a low pCR rate to NAT. Among pts with AC-insensitive TNBC, baseline upregulated androgen response pathway and LAR subtype may benefit from the ZT regimen, potentially by PI3K targeting. Clinical trial information: NCT02689427 .

Evaluation of predictive biomarkers for AR therapy and to identify the LAR subtype of TNBC

595

Background: Androgen-receptor-like (LAR) triple-negative breast cancer (TNBC) is a subtype identified using Vanderbilt’s molecular signature. LAR subtype has the lowest pCR rate for NACT among all TNBC subtypes (10% vs. 28% for TNBC in general). We launched a clinical trial to determine the effectiveness of enzalutamide and paclitaxel (ZT) in improving this poor chemo. response in the neoadjuvant setting for pts with anthracycline-refractory, androgen receptor (AR)+ TNBC (NCT02689427). However, we do not yet have a robust predictive biomarker to detect an activated AR pathway and have not seen a robust correlation between molecular LAR subtype and AR IHC staining intensity. Methods: Molecular profiling and immunohistochemical analysis of key biomarkers (LAR, Ki67, and vimentin) was performed for all pts enrolled in A Randomized triple negative breast cancer enrolling Trial to Confirm Molecular Profiling Improves Survival (ARTEMIS; NCT02276443). Patients receive 4 cycles of AC, followed by an experimental arm or standard taxane, tailored using nuclear IHC staining. IHC staining of ≥30% AR+ was used as a threshold for selection for enzalutamide combination arm. We evaluated the concordance between LAR-subtype using molecular profiling vs % AR+ cells via IHC. Results: As part of the clinical trial, tumors with ≥30% AR+ cells were classified as LAR. In addition, we used RNA profiling to assign Vanderbilt subtype scores, resulting in classification of 15 tumors as LAR+. We observed a significant correlation (r=0.75) between LAR score and %AR+ cells, with 13 of 15 LAR tumors having ≥30% AR+ cells. Among patients with high % of AR+ tumor cells, 11 received enzalutamide, with 43% (3/7) having responses (pCR or RCB-I). Conclusions: Comparison on numerical scores for Vanderbilt subtype and IHC scores suggests ≥30% AR+ IHC staining as the threshold (ppv=0.65, npv=0.98, Table) to identify the molecular LAR subtype. We observed a trend where response rate was higher in patients with ≥ AR+ IHC scores treated with enzalutamide; however, these results need confirmation in a larger cohort of patients. Clinical trial information: NCT02689427, NCT02276443. [Table: see text]

Beyond TILs: Predictors of pathologic complete response (pCR) in triple-negative breast cancer (TNBC) patients with moderate tumor-infiltrating lymphocytes (TIL) receiving neoadjuvant therapy

572

Background: Increased TIL in TNBC is associated with higher rates of pCR. High TIL is also associated with improved disease free survival and overall survival. The aim of this study is to identify data cut-points of pre-treatment low, moderate and high TIL count based on pCR and to identify clinical and pathological predictors of pCR in patients with moderate TIL. Methods: We evaluated the relationship between pCR and TIL in 180 patients with stage I-III TNBC enrolled in the ARTEMIS trial (NCT02276443). Recursive portioning was used to identify cut-points. Clinical and pathological variables such as age at diagnosis, stage, race, histology as well as Ki-67, vimentin, and androgen receptor (AR) by immunohistochemistry, were evaluated in pts with moderate TIL. A multivariable logistic regression model identified variables independently, significantly associated with pCR. Results: Four TIL groups were identified with pCR rates of 23%, 31%, 48% and 78% respectively (p < 0.0001) (Table A). In the two combined moderate TIL groups, 90 (97%) pts were evaluable for the multivariate model. Stage I-II disease, high Ki-67 and low AR were associated with increased probability of pCR (Table B). The multivariable logistic regression model area under the ROC curve was 0.78 (95% CI=0.68-0.88; p<0.0001). A model of computed risk score [ Stage I-II (score 2)+Ki-67≥ 50% (score 1)+AR<10% (score 1)] predicted a probability of 67% for pCR when all three variables were favorable (Table). Conclusions: Four TIL groups were identified. In pts with moderate TIL levels, early stage disease, high Ki-67 and low AR were associated with increased probability of pCR with neoadjuvant therapy. [Table: see text]

Immunologic responses in triple-negative breast cancer patients in a randomized phase IIb trial of nelipepimut-S plus trastuzumab versus trastuzumab alone to prevent recurrence

556

Background: Breast cancer (BC) patients (pts) expressing low levels of HER2 by (immunohistochemistry (IHC) 1-2+) are not eligible for trastuzumab (Tz). However, in a randomized phase 2b trial, triple negative BC (TNBC) pts demonstrated a significantly better DFS with nelipepimut-S (NPS) + Tz vs Tz alone. Here, we assess the ex vivo and in vivo immune responses (IR) in both arms. Methods: Disease-free pts (n = 275) with HER2 IHC 1-2+, non-amplified BC who were node positive and/or had TNBC were randomized 1:1 to granulocyte-macrophage-colony stimulating factor (GM-CSF) or NPS+GM-CSF. ±NPS was given every 3 weeks x 6 followed by 4 boosters every 6 months (mo). All pts received Tz concurrently for 1 year per label regimen and were followed for recurrence. IR were evaluated ex vivo by clonal expansion of NPS-specific cytotoxic T lymphocytes (CTL) by dextramer-staining/flow cytometry at time points over 3 years. In vivo IR were assessed by delayed type hypersensitivity (DTH) reactions periodically. Results: The trial enrolled 97 TNBC pts; 60 had 4 timepoints available for analysis (37 NPS + Tz pts; 23 Tz pts). The NPS+Tz group exhibited increases in CTL frequencies vs baseline: 208%, 303%, 379% at 18, 24 and 30 mo, respectively. NPS+Tz pts’ mean CTL frequencies increased from 0.029 ±0.001% at baseline to 0.112±0.026% at 30 mo (p = 0.01) compared to Tz pts who were 0.027 ±0.001% at baseline and 0.057 ±0.016% at 30 mo (p = 0.71). Only 4 NPS+Tz pts recurred as compared to 13 in the Tz arm. While limited by low numbers, recurrent NPS + Tz pt did not mount an IR by ex vivo assessment (range: 0.0 - 0.026%) or by DTH (all measurements: 0 mm), while non-recurrent pts mounted both clonal CTL expansion (range: 0.000- 0.33%) and enhanced DTH (range: 0.0- 80.5mm). Conclusions: NPS+Tz combination is more efficacious in generating time-dependent antigen (NPS)-specific CTL by both ex vivo and in vivo measures vs Tz. Based on these preliminary data, it appears that both ex vivo and in vivo IR to NPS were attenuated in pts with TNBC recurrence. Further analysis of read-outs from these assays to validate the relationship of IRs to clinical effect seen with NPS+Tz in TNBC pts is underway. Clinical trial information: NCT02297698.

Final analysis of nelipepimut-S plus GM-CSF with trastuzumab versus trastuzumab alone to prevent recurrences in high-risk, HER2 low-expressing breast cancer: A prospective, randomized, blinded, multicenter phase IIb trial

1

Background: Preclinical data shows synergism between trastuzumab (Tz) and HER2-targeted vaccines. We evaluated adjvuant nelipepimut-S (NPS) + GM-CSF with Tz compared to Tz with GM-CSF alone in HER2 low-expressing (LE) breast cancer (BC) patients (pts) to prevent recurrences. After a planned interim analysis showed benefit in triple negative BC (TNBC) pts, the decision was made to close the trial with guidance from the independent DSMB. Here, we report the final analysis of the trial with 7 months (mo) of added follow-up (f/u). Methods: The phase 2b trial enrolled clinically disease-free BC pts after standard therapy. Pts were HLA-A2, A3, A24, and/or A26+, had HER2-LE (IHC 1-2+, FISH non-amplified) BC and were node positive and/or TNBC. Pts were randomized to placebo with GM-CSF(control group, CG) or NPS with GM-CSF (vaccine group, VG), while all received Tz Q3wk for 1 year. GM-CSF or NPS + GM-CSF were given q3wks x 6 starting with the 3rd Tz dose, and boosters every 6 months x 4. Safety was assessed and pts were followed clinically for recurrences. The primary outcome was DFS at 24 mo. Results: 589 pts were screened at 26 sites. 275 pts were enrolled and randomized (VG:136, CG:139). There were no clinicopathologic differences between groups. Concurrent Tz and NPS was safe with no added overall or cardiac toxicity compared to CG and no grade 4/5 toxicities. In the ITT analysis (median f/u 25.7 mo), the estimated DFS was favorable but did not reach significance in the VG compared with the CG (HR 0.62, 95% CI: 0.31-1.25, p = 0.18). In the TNBC pts, the VG had statistically improved DFS compared to the CG (HR 0.26, 95% CI: 0.08-0.81, p = 0.013). Conclusions: The combination of NPS with Tz is safe with no added toxicity compared to Tz alone, even after prolonged exposure (25.7 mo). In this final analysis, there was a trend towards benefit in the ITT population that improved since the interim analysis with added f/u. The significant benefit seen at interim in the TNBC pts continued to strengthen in the VG group. These findings could position the NPS + Tz combination as an adjuvant therapy for early-stage TNBC and warrant further study. Clinical trial information: NCT01570036.

Abstract P3-10-23: Changes in the expression of HER2 and other genes in HER2-positive metastatic breast cancer induced by treatment with ado-trastuzumab emtansine and/or pertuzumab/trastuzumab

Background: Although tremendous progress has been achieved with targeted therapy for HER2-positive (HER2+) metastatic breast cancer, most advanced tumors eventually develop resistance. Improving our understanding of mechanisms of resistance to anti-HER2 therapy is needed to develop new therapeutic approaches. The purpose of this study was to identify the mechanisms of resistance to treatment with ado-trastuzumab emtansine (T-DM1) and/or taxane/pertuzumab/trastuzumab (TPH).

Methods: In our preclinical analysis, HER2+ cell lines resistant to treatment with T-DM1 (n=5), and pertuzumab/trastuzumab (n=3) were generated. HER2 expression in the original and resistant cell lines was compared using Western blot, and HER2 gene amplification was compared in them using fluorescence in situ hybridization (FISH) and a Droplet Digital Polymerase Chain Reaction HER2 copy-number-validation assay. In our clinical analysis, nine patients with HER2+ metastatic breast cancer who had progressed on T-DM1 and/or TPH were enrolled. Patients underwent biopsies following treatment with T-DM1 and/or TPH. Targeted next-generation sequencing was performed using the FoundationOne® assay (Foundation Medicine, Inc.) to identify gene alterations. Also, the HER2 expression before and after the therapy was compared using immunohistochemistry and/or FISH.

Results: In preclinical analysis, HER2 expression/amplification by Western blot and gene copy-number analysis was significantly decreased in T-DM1–resistant cell lines (four of five cell lines; P &lt; 0.01) but not in pertuzumab/trastuzumab-resistant cell lines (none of three cell lines). In clinical analysis, the patients' median age was 54 years (range, 45-77 years), and five patients (56%) were ER+. Five patients (56%) received first-line anti-HER2 therapy, and four patients (44%) received two lines of anti-HER2 therapy prior to enrollment. We observed loss of HER2 expression in four of nine patients (44%) after undergoing anti-HER2 therapy. After receiving TPH, one of eight patients (13%) lost HER2 positivity according to FISH. In contrast, after T-DM1, three of four tested patients (75%) lost HER2 amplification by FISH. As for next-generation sequencing, we analyzed seven samples: three after treatment with TPH and four after treatment with T-DM1. In four of these samples (57%), we observed loss of HER2 amplification: one after treatment with TPH and three after treatment with T-DM1. TP53 mutations were seen in all patients. Additionally, we observed TOP2A and MCL1 amplification in two patients with ERBB2 amplificationand AKT1 amplification in one patient with ERBB2 amplification loss.

Conclusions: We show for the first time that T-DM1–resistant breast cancer cells lose HER2 expression and amplification. Additionally, we observed loss of HER2 expression in patient samples following treatment with HER2 targeted therapy. Further study of resistant tumor samples is required to understand the impact of HER2 loss on outcomes. For the time being, repeating biopsy analysis of a metastatic site after treatment with T-DM1 to determine the HER2 expression status is reasonable, and it may increase the efficacy of future anti-HER2 therapy.

Citation Format: Kida K, Lee J, Liu H, Lim B, Murthy RK, Sahin AA, Tripathy D, Ueno NT. Changes in the expression of HER2 and other genes in HER2-positive metastatic breast cancer induced by treatment with ado-trastuzumab emtansine and/or pertuzumab/trastuzumab [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 P3-10-23.

Abstract OT2-07-08: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Paplomata E, Borges V, Loi S, Abramson V, Hamilton E, Hurvitz S, Lin N, Walker L, Murthy RK. Withdrawn [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 OT2-07-08.

Abstract P2-09-01: Subgroups analysis of a multicenter, prospective, randomized, blinded phase 2b trial of trastuzumab + nelipeptimut-S (NeuVax) vs trastuzumab for prevention of recurrence in breast cancer patients

Background:HER2 low-expressing (LE) (IHC 1-2+, FISH non-amplified) breast cancer (BC) patients (pts) have not benefited from HER2-directed therapy despite HER2 antigen availability. Triple negative BC (TNBC), in particular, is immunogenic and in need of additional therapeutic options. We have previously shown the HER2-derived nelipeptimut-S (E75) + GM-CSF (NeuVax) to be synergistic with trastuzumab (Tz) in pre-clinical and pilot clinical studies. In a planned interim analysis of a multi-center, prospective, randomized, single-blinded, placebo-controlled phase 2b trial of Tz + NeuVax vs Tz to reduce recurrence in HER2 LE, node-positive (NP) and/or triple negative BC (TNBC) pts, we previously reported that the NeuVax + Tz was safe without added cardiac toxicity and demonstrated a significant reduction of recurrences in TNBC pts. This analysis examines additional subsets in this trial.

Methods:HER2 LE, NP and/or TNBC pts who were clinically disease-free after standard therapy were randomized to receive Tz+NeuVax (vaccine group; VG) or Tz+GM-CSF (control group; CG). All pts received 1 yr of Tz per label. NeuVax or GM-CSF was given every 3 weeks x 6 starting with the 3rdTz dose, and then boosted every 6 months x 4. This pre-specified interim analysis was triggered 6 months after last enrollment. The primary endpoint is intention-to-treat 24 month disease-free survival (DFS) evaluated by log rank.

Results: Of 275 pts randomized in the study (VG n=136, CG n=139), 98 had TNBC (VG=53, CG=45). In the interim analysis, estimated disease-free survival (DFS) was assessed with a median follow up of 18.8 months. No significant clinicopathologic differences were seen between treatment groups. In the TNBC group, estimated DFS was higher overall in VG vs CG (91.9% v 69.9%, p=0.023; hazard ratio [HR] 0.29, 95% confidence interval [CI] 0.09-0.90). On TNBC subgroup analysis, estimated DFS was higher in VG vs CG among pts who received neoadjuvant chemotherapy (VG n=35, CG n=31; HR 0.26, CI 0.07-0.93; p=0.03), HER2 IHC 1+ BC (VG n=34, CG n=28; HR 0.20, CI 0.04-0.96; p=0.03), pts who were AJCC 7thedition stage I/II (VG n=37, CG n=27; HR incalculable, no recurrences in the VG, p=0.008), and pts 351yr of age (VG n=32 & CG n = 26; HR 0.26 CI 0.07,0.94; p=0.009). HRs did not appreciably vary based on the histologic grade or presence of lymphovascular invasion.

Conclusion:Examining the subgroups from the pre-specified interim analysis demonstrates a highly significant clinical benefit in TNBC pts overall. Within the TNBC cohort, specific benefit was seen in pts who received chemotherapy neoadjuvantly, expressed lower HER2, were earlier stage, and were older in age. These factors may help enrich the TNBC population targeted in a definitive Phase 3 study in TNBC patients with residual disease after neoadjuvant chemotherapy.

Citation Format: Clifton GT, Kemp Bohan PM, Hale DF, Myers JW, Brown TA, Holmes JP, Vreeland TJ, Litton JK, Murthy RK, Mittendorf EA, Peoples GE. Subgroups analysis of a multicenter, prospective, randomized, blinded phase 2b trial of trastuzumab + nelipeptimut-S (NeuVax) vs trastuzumab for prevention of recurrence in breast cancer patients [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 P2-09-01.

Abstract P6-17-04: 3-year relapse-free survival of stage II-III HER2-neu positive breast cancer treated with pertuzumab and trastuzumab-containing neoadjuvant therapy compared to trastuzumab-containing therapy

Background: Pertuzumab (P) in combination with trastuzumab (H) based chemotherapy is FDA-approved as a standard neoadjuvant treatment for patients with clinical stage II-III HER2-positive (HER2+) breast cancer (BC). The goal of this study was to evaluate the pathologic complete response (pCR) rate for neoadjuvant HP-containing regimens compared to H-containing regimens and report the 3-year relapse-free survival (RFS) for patients who had a pCR compared to those with residual disease (RD).

Methods: All patients with stage II-III non-inflammatory HER2+ BC who received neoadjuvant H-containing or HP-containing therapy and underwent definitive breast and axillary surgery were identified from 2005 to 2016 through an institutional database. Medical records were examined for patient demographics, breast cancer stage, pathology results, surgical outcomes, and treatment details. pCR was defined as ypT0/is, ypN0. RFS was defined as the interval from surgery to date of last followup or death from any cause. Descriptive statistics, Cox proportional hazards, and Kaplan-Meier estimates were used for statistical analysis.

Results: Patient characteristics and results by pCR or RD status are shown in the table below. The median age was 51 (22-84) years for the HP group and 50 (21-87) years for the H group. The median follow-up time was 1.9 (0-4.2) years for the HP group and 5.3 (0.1-12) years for the H group. For the HP group, the 3-year RFS was 98% (95% CI: 95, 100) for the pCR group and 90% (95% CI: 83, 97) for the RD group; HR 0.17 (0.04, 0.82), p=0.012. For the H group, the 3-year RFS was 91% (95% CI: 88,94) for the pCR group and 75% (95% CI: 71-79) for the RD group; HR 0.31 (0.22, 0.44), p&lt;0.0001. Among the 520 patients who achieved pCR and the 502 patients who had RD, the effect of HP vs. H was statistically significant (pCR: HR 0.24 (0.06, 1.00); p=0.015) (no pCR: HR 0.46 (0.22, 0.94); p=0.017).

Conclusion: Patients who achieve pCR have an improved 3-year RFS compared to patients who have RD. Treatment with HP-containing neoadjuvant regimens is associated with a high 3-year RFS.

VariableHP (n=215)H (n=807)  pCR n=121RD n=94pCR n=399RD n= 408Age at Diagnosis&lt;5043%46%46%51% ≥5057%54%54%49%Menopausal StatusPremenopausal46%50%53%57% Postmenopausal54%50%47%43%Clinical Stage at DiagnosisIIA40%29%34%29% IIB29%31%23%28% IIIA14%15%17%16% IIIB0%5%5%9% IIIC17%20%21%18%Clinical Nodal StatusNode (+)63%76%69%73% Node (-)37%24%31%27%Nuclear Grade1II25%32%22%28% III75%65%78%72%HR statusHR(+)52%74%52%67% HR(-)48%26%48%33%Adjuvant therapyTrastuzumab88%80%100%100% Trastuzumab and Pertuzumab3%5%0%0% Unknown9%15%20%0%11 patient in the HP pCR group had nuclear grade 1; 2 patients in the HP RD group had nuclear grade 1 tumors 2 2 patients received adjuvant TDM-1 on the NSABP B50 protocol

Citation Format: Murthy RK, Raghavendra AS, Hess KR, Barcenas CH, Lim B, Moulder SL, Giordano SH, Mittendorf EA, Thompson A, Ueno NT, Valero V, Litton JK, Tripathy D, Chavez-Macgregor M. 3-year relapse-free survival of stage II-III HER2-neu positive breast cancer treated with pertuzumab and trastuzumab-containing neoadjuvant therapy compared to trastuzumab-containing therapy [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 P6-17-04.

Abstract P6-03-05: Risk of needle-track seeding with serial ultrasound guided biopsies in triple negative breast cancer

Background: Image-guided percutaneous needle biopsy of the breast is a common procedure. In breast cancer patients (pts) undergoing core biopsies and surgical resection on the same day, the rate of tumor cell displacement along the needle track has been reported to be up to 50%. However, the clinical significance of this finding in triple negative breast cancer (TNBC) patients (pts) undergoing serial biopsies while receiving neoadjuvant chemotherapy (NACT) is unknown. Here we report the incidence of needle-track seeding (NTS) in a cohort of TNBC pts enrolled on a molecular triaging protocol involving serial biopsies of the index breast lesion.

Methods: We reviewed the clinical records of 144 consecutive TNBC pts enrolled on a molecular triaging protocol at MD Anderson Cancer Center. Per protocol, all pts underwent a pre-treatment research biopsy and were initiated on anthracycline based NACT (AC). Pts with inadequate response to front-line NACT were encouraged to undergo additional biopsies of the index breast lesion prior to switching therapies. Serial breast ultrasound (US) was performed to monitor therapeutic response and incidental evidence of needle-track seeding noted on US was documented.

Results: Clinicopathological characteristics of the pts are summarized in Table 1. 89% (128/144) of pts had a diagnostic breast biopsy done at another center prior to presenting at MDACC. To date, we have performed 209 US guided biopsies of index breast lesions in 144 pts. 92% (193/209) of these biopsies were done mainly for research purposes. 1.4% (2/144) of pts were found to have evidence of NTS on follow up US. The first pt had a T1N0 (1.9cm), grade 3, invasive ductal carcinoma (IDC) at diagnosis. She underwent a diagnostic biopsy followed by a research biopsy before initiating AC. She was found to have NTS as well as progression of disease (PD) on follow up US after 2 cycles of AC. The second pt had a T2N0 (3cm), grade 3 IDC at diagnosis. She underwent a diagnostic biopsy at another center, followed by a research biopsy before initiating AC. Like the first pt, she was found to have NTS and PD on follow up US after 2 cycles of AC. Both pts are currently on neoadjuvant clinical trials of novel agents.

Conclusion: The rate of NTS detected on US in TNBC pts undergoing serial biopsies of index breast lesions while receiving NACT is low and further studies are needed to determine the impact of serial biopsies on long term outcomes in TNBC.

Table 1: Patient CharacteristicsCharacteristicN=144Age - Median (years, interquartile range)55 (46-62)Tumor Size Mean (cm, standard deviation)3.4 (2.2)T1 – n(%)35 (24)T2 – n(%)89 (62)T3 – n(%)19 (13)T4 – n(%)1 (1)Clinical Nodal Status Negative – n(%)74 (51)Positive – n(%)70 (49)Grade 1 – n(%)1 (1)2 – n(%)17 (12)3 – n(%)124 (86)Unknown – n(%)2 (1)Histologic Subtype Invasive ductal carcinoma – n(%)121 (84)Invasive lobular carcinoma – n(%)2 (1)Mixed ductal and lobular carcinoma – n(%)3 (2)Metaplastic carcinoma – n(%)13 (9)Not specified – n(%)5 (3)Laterality Right – n(%)72 (50)Left – n(%)72 (50)

Citation Format: Yam C, Santiago L, Candelaria RP, Adrada BE, Rauch GM, Hess KR, Litton JK, Piwnica-Worms H, Mittendorf EA, Ueno NT, Lim B, Murthy RK, Damodaran S, Helgason T, Huo L, Thompson AM, Gilcrease MZ, Symmans WF, Moulder SL, Yang W. Risk of needle-track seeding with serial ultrasound guided biopsies in triple negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-03-05.

Abstract P1-07-22: Androgen receptor positivity is associated with nodal disease in triple negative breast cancer

Background: Gene expression profiling (GEP) has identified several molecularly distinct subtypes of triple negative breast cancer (TNBC). Currently, GEP-based molecular diagnostics are not routinely used in clinical decision making due to the lack of proven benefit, costs involved and long turnaround time. However, two molecularly distinct subtypes of TNBC, the luminal androgen receptor (AR) and mesenchymal subtypes, have surrogate CLIA-certified immunohistochemical (IHC) markers, AR and vimentin (VM), respectively, which have the potential for application in the clinic. Here we report the rates of AR and VM positivity and their association with clinicopathological characteristics in a cohort of TNBC pts receiving NACT.

Methods: As part of an ongoing molecular triaging protocol, 144 pts with stage I-III TNBC underwent a pretreatment biopsy for molecular characterization (MC) prior to initiating neoadjuvant chemotherapy (NACT). IHC for AR and VM were performed using commercially available antibodies. AR+ and VM+ were defined as ≥10% and ≥50% staining, respectively. Pts were randomized 2:1 to know (intervention arm, n=93) and not know (control arm, n=51) the MC results. The charts of pts randomized to the intervention arm were reviewed. Categorical variables were analyzed using Fisher's exact test. Ordinal and continuous variables were analyzed using the Wilcoxon rank-sum test and Student's t test as appropriate.

Results: 31% (29/93) and 16% (15/93) of pts were AR+ and VM+, respectively. Only 4% (4/93) of pts were both AR+ and VM+. Clinicopathological characteristics are summarized in Table 1. AR+ pts were more likely to have clinically node positive disease as compared to AR- pts (66% vs 34%, p=0.007). There were no significant differences in clinical tumor size or grade between AR+ and AR- pts. VM+ and VM- pts had similar clinicopathological characteristics.

Conclusion: Pts with AR+ TNBC were more likely to have node positive disease. The impact of AR+ on long term outcomes should be investigated in prospective studies.

Table 1: Association between patient characteristics and AR/VM status AR  VM   AR+ (n=29)AR- (n=64)p-valueVM+ (n=15)VM- (n=78)p-valueAge - Median (years, interquartile range)58 (48-65)52 (46-61)0.05855 (48-64)56 (47-62)0.88Clinical Tumor Size      Mean (cm, standard deviation)3.5 (1.8)3.0 (1.8)0.2872.7 (1.7)3.3 (1.9)0.31T1 – n(%)5 (17)21 (33)0.2307 (47)19 (24)0.098T2 – n(%)21 (72)36 (56) 7 (47)50 (64) T3 – n(%)3 (10)7 (11) 1 (7)9 (12) Clinical Nodal Status      Negative – n(%)10 (34)42 (66)0.0078 (53)44 (56)1.00Positive – n(%)19 (66)22 (34) 7 (47)34 (44) Grade      2 – n(%)6 (21)5 (8)0.0763 (20)8 (10)0.293 – n(%)23 (79)59 (92) 12 (80)70 (90) 

Citation Format: Yam C, Huo L, Hess KR, Litton JK, Yang W, Piwnica-Worms H, Mittendorf EA, Ueno NT, Lim B, Murthy RK, Damodaran S, Helgason T, Thompson AM, Santiago L, Candelaria RP, Rauch GM, Adrada BE, Symmans WF, Gilcrease MZ, Moulder SL. Androgen receptor positivity is associated with nodal disease in triple negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-07-22.

Abstract P6-03-04: Central nervous system miliary metastasis in breast cancer patients

Background: Little is known regarding central nervous system (CNS) miliary metastasis (MiM), which was first described as “carcinomatous encephalitis” by Madow and Alpers in 1951. The majority of reported cases arise from primary lung and gastrointestinal adenocarcinomas, with occasional melanoma primaries and one reported case in breast cancer. Moreover, clinicopathologic correlates, disease outcomes and prognostic factors in these patients are poorly understood. Although identified most frequently on neuroimaging, radiographic criteria to objectively diagnose MiM do not exist. In this analysis of patients with brain metastasis from primary breast cancer, we propose objective, stringent radiographic criteria for CNS MiM diagnosis and identify clinicopathologic factors contributing to disease outcomes.

Methods: Using a prospectively maintained electronic database, 1,002 female patients diagnosed with brain metastasis from primary breast cancer between 2000 and 2015 were identified. Only patients with neuroimaging available for direct review (CT or MRI) were included. Our radiographic criteria for MiM diagnosis were: 1) ≥20 metastatic lesions per image slice on ≥2 noncontiguous image slices by MRI, or 2) ≥10 lesions per image slice on ≥2 noncontiguous image slices by CT, and 3) MiM lesions were required to be present bilaterally and in both the supra- and infratentorial compartments. These criteria were established upon direct review of all neuroimaging by a neuroradiologist. Number and anatomic distribution of metastatic lesions were the patterns best observed to identify cases of CNS MiM on case review; lesion size was not a reliable pattern for MiM identification. Log rank tests were used for statistical analyses.

Results: Using stringent criteria, 486 patients were included in this analysis. Twenty patients with MiM were identified (4.1%). Ten patients were diagnosed with MiM at initial brain metastasis presentation; 10 developed MiM after known brain metastasis. Biomarker based subtype distribution was as follows: HR-/HER2- (TNBC) (n=8), HR+/HER2+ (n=3), HR+/HER2- (n=4), HR-/HER2+ (n=4), unknown (n=1).

Table 1: Disease Outcomes Based on Biomarker SubtypeBiomarker SubtypeMedian Time to MiM (months) (p=0.104)Median Survival after MiM (months) (p=0.008)TNBC (n=8)32.3 (12.1-132.5)1.8 (0.5-4.0)HR+/HER2+ (n=3)44.2 (33.2-71.5)10.8 (10.2-13.3)HR+/HER2- (n=4)110.2 (23.0-156.0)4.8 (0.8-9.8)HR-/HER2+ (n=4)27.1 (3.7-39.4)4.0 (1.8-5.0)All* (n=20)37.4 (3.7-156.0)3.7 (0.4-12.3)Key: BM: Brain metastasis; * Includes 1 patient with unknown subtype.

Conclusions: Reports of MiM consist overwhelmingly of lung and gastrointestinal adenocarcinoma primaries. This retrospective, observational study is the first to establish that CNS MiM occurs in breast cancer with an incidence of roughly 4%. Review of an additional 1,600 patient charts is underway, but this preliminary study is the first to identify clinicopathologic correlates and determine disease outcomes in patients with MiM; it is also the first to propose stringent radiographic criteria for the diagnosis of CNS MiM, and further updated data will be presented at the meeting.

Citation Format: Bashour SI, Ibrahim NK, Schomer DF, Colen RR, Sawaya R, Suki D, Rao G, Murthy RK, Moulder SL, Abugabal Y, Hess KR, Fuller GN. Central nervous system miliary metastasis in breast cancer patients [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-03-04.

A feasibility study of neoadjuvant talazoparib for operable breast cancer patients with a germline BRCA mutation demonstrates marked activity

This study was undertaken to determine the feasibility of enrolling breast cancer patients on a single-agent-targeted therapy trial before neoadjuvant chemotherapy. Specifically, we evaluated talazoparib in patients harboring a deleterious BRCA mutation (BRCA+). Patients with a germline BRCA mutation and ≥1 cm, HER2-negative primary tumors were eligible. Study participants underwent a pretreatment biopsy, 2 months of talazoparib, off-study core biopsy, anthracycline, and taxane-based chemotherapy ± carboplatin, followed by surgery. Volumetric changes in tumor size were determined by ultrasound at 1 and 2 months of therapy. Success was defined as 20 patients accrued within 2 years and <33% experienced a grade 4 toxicity. The study was stopped early after 13 patients (BRCA1 + n = 10; BRCA2 + n = 3) were accrued within 8 months with no grade 4 toxicities and only one patient requiring dose reduction due to grade 3 neutropenia. The median age was 40 years (range 25–55) and clinical stage included I (n = 2), II (n = 9), and III (n = 2). Most tumors (n = 9) were hormone receptor-negative, and one of these was metaplastic. Decreases in tumor volume occurred in all patients following 2 months of talazoparib; the median was 88% (range 30–98%). Common toxicities were neutropenia, anemia, thrombocytopenia, nausea, dizziness, and fatigue. Single-agent-targeted therapy trials are feasible in BRCA+ patients. Given the rapid rate of accrual, profound response and favorable toxicity profile, the feasibility study was modified into a phase II study to determine pathologic complete response rates after 4–6 months of single-agent talazoparib.

An investigational PARP inhibitor seems safe and possibly effective when given ahead of surgery to women with BRCA-mutated breast cancer. Jennifer Litton and colleagues from the University of Texas MD Anderson Cancer Center in Houston, USA, conducted a small feasibility study to see if patients with stage I-III breast cancer and inherited mutations in BRCA1 or BRCA2 would put off their standard course of chemotherapy ahead of surgery to first receive two months of talazoparib, an experimental inhibitor of poly ADP ribose polymerase (PARP), an enzyme involved in DNA damage repair. The trial was a resounding success. In fact, owing to rapid patient enrollment, decreases in tumor volume among all 13 participants and few signs of serious side effects, the researchers amended the study protocol to give talazoparib for longer and test for therapeutic efficacy.

A randomized, double-blinded, controlled study of tucatinib (ONT-380) vs. placebo in combination with capecitabine (C) and trastuzumab (Tz) in patients with pretreated HER2+ unresectable locally advanced or metastatic breast carcinoma (mBC) (HER2CLIMB)

TPS1107

Background: Tucatinib (ONT-380) is a highly selective small molecule inhibitor of HER2 kinase with nanomolar potency. Unlike dual HER2/EGFR agents, it does not inhibit EGFR at clinically relevant concentrations, decreasing the potential for EGFR-related toxicities (severe skin rash and diarrhea). In preclinical studies, tucatinib demonstrated synergistic activity with Tz, and was active in HER2+ models of brain metastases (mets). In a Phase 1b study, tucatinib was combined with C and Tz in pts with HER2+ MBC previously treated with trastuzumab emtansine (T-DM1) and Tz. Objective responses were seen, including in pts with brain mets. The combination was well tolerated, with low rates of Gr 3 diarrhea at the recommended dose (300 mg PO BID, equivalent to the single agent MTD). Based on these data, tucatinib is now being evaluated in a study in combination with C and Tz (HER2CLIMB). Methods: The primary study objective is to assess the effect of tucatinib vs. placebo given with C + Tz on progression-free survival (PFS) based on independent central review. Additional objectives include PFS in patients with brain mets, overall survival, ORR, duration of response, clinical benefit rate, and safety. The study population includes adult patients with progressive HER2+ locally advanced or MBC who have had prior treatment with a taxane, Tz, pertuzumab and T-DM1. Patients with brain mets, including untreated or progressive brain mets, may be enrolled. 480 patients will be enrolled in North America, Europe, Israel, and Australia. Patients are receiving C (1000 mg/mg2 PO BID for 14 days of a 21-day cycle) and Tz (6 mg/kg IV once every 21 days), and are being randomized in a 2:1 ratio to tucatinib 300 mg PO BID or placebo. Patients with isolated CNS progression may continue on study treatment after undergoing local CNS therapy. An independent Data Monitoring Committee is monitoring patient safety. Clinical trial information: NCT02614794.

Long-term survival of de novo stage IV human epidermal growth factor receptor 2 (HER2)-positive breast cancers treated with HER2 targeted therapy

1021

Background: An increasing number of metastatic HER2 positive cancers represent de novo stage IV disease as fewer early stage patients relapse. We hypothesize that a subset of these has long progression free survival (PFS) after initial combined modality HER2-targeted therapies. Methods: 483 patients with de novo stage IV HER2 positive breast cancer diagnosed between 1998-2015 were identified through the medical records at Yale and MD Anderson Cancer Centers, respectively. Treatment, clinical variables and survival were extracted and compared between those who achieved “no evidence of disease” (NED) status with initial therapy and those who did not. Results: All patients received trastuzumab and 94 (20%) also received pertuzumab as first line therapy.The median OS was 5.5 years (95% Cl: 4.8-6.2); OS rates at 5 and 10 years were 54% (95% CI: 48%-60.4%) and 18% (95% Cl: 11.4%-28.3%), respectively and PFS were 41% (95% CI: 35%-48%) and 41% (95% CI: 35%-48%). Sixty-three patients (13.0%; 95% CI: 10.2% -16.4%) achieved NED. The PFS and OS at 5 and 10 years were the same 100% and 98% (95% CI: 94.6%-100%), respectively. For patients with no-NED (n = 420), the median OS was 4.7 years (95% Cl: 4.2-5.3), the PFS and OS rates at 5 and 10 years were 12% (95% CI: 4.5%-30.4%) and 0% and 45% (95% CI: 38.4%-52.0%) and 4% (95% CI: 1.3%-13.2%), respectively. NED patients had significantly longer progression free survival (log-rank test p≤0.001) and overall survival (log-rank test p≤0.001), more frequently had single organ site metastasis (76% vs 57%, p = 0.005), and more frequently had surgery for primary tumor (59% vs. 25%, p ≤0.001) than no-NED patients, but there was no significant difference in age, grade, race, year of diagnosis, ER status, treatment distribution, or radiation between the groups. Conclusions: About 13% of de novo, stage IV, HER-2 positive MBC patients achieved NED with HER-2 targeted therapies, all of these patients were progression free at 5 years and overall survival at 10-years was 98% compared to 4% among those with no-NED in our data sets. These results suggest that aggressive multimodality therapy of newly diagnosed stage IV HER2 positive cancers to render them NED may be warranted.

A randomized, triple negative breast cancer enrolling trial to confirm molecular profiling improves survival (ARTEMIS)

TPS590

Background: Following neoadjuvant chemotherapy (NACT), patients (pts) with triple negative breast cancer (TNBC) achieving pathologic complete response/residual cancer burden-0 (pCR/RCB-0) or minimal residual disease (RCB-I) have an improved relapse free survival when compared to pts with more extensive residual disease (RCB-II/III) (Symmans et al, JCO 2017). Pts with chemo-resistant TNBC have a poor prognosis as there are currently no FDA-approved targeted agents available for TNBC. We previously reported the ability of a novel gene expression signature (GES) to predict sensitivity to NACT (Hatzis et al, JAMA 2011). Here we seek to prospectively validate the use of this GES in combination with imaging to predict response to NACT and establish the clinical impact of selecting pts predicted to have non-responsive disease (NRD) for enrollment in clinical trials of targeted therapy. Methods: All pts will undergo a biopsy of the primary tumor for molecular characterization (MC) and will be randomized 2:1 to know their MC results (intervention arm) or not (control arm). A maximum of 360 pts will be enrolled and randomized using a group sequential design with one-sided O’Brien-Fleming boundaries, with two equally spaced binding interim tests for futility and superiority and one final test, having an overall Type I error of 0.05 and power of 0.80 to detect an improvement in pCR/RCB-I from 50% to 64%. Secondary endpoints include rates of clinical trial enrollment, disease free survival and integrated biomarker analyses. All pts will receive 4 cycles of anthracycline-based NACT with imaging done every 2 cycles to assess response. After completion or progression on anthracycline-based NACT, pts predicted to have NRD based on MC/imaging (intervention arm) or imaging alone (control arm) will be offered enrollment on a clinical trial. Pts are eligible if they have stage I-III TNBC with a primary tumor that is ≥1.5cm. Pts with contraindications to anthracyclines and/or taxanes are excluded. Enrollment began in November 2015. 105 pts have been enrolled to date with 71 and 34 pts randomized to the intervention and control arms, respectively. Clinical trial information: NCT02276443.

TBCRC 036: Window of opportunity clinical trial reveals adaptive kinome reprogramming in single and combination HER2-targeting in breast cancer (BrCa)

1027

Background: HER2 targeting is challenging due to heterogeneity in response and resistance. Adaptive kinome reprogramming (AKRP) is a resistance mechanism to kinase-targeted therapy (Rx) in TNBC ( Cancer Discovery2017). We studied AKRP in HER2+ BrCa by comparing transcriptome and kinome profiles before and after Rx with FDA-approved anti-HER2 drugs and combinations: trastuzumab (T), pertuzumab (P), T+P, or T+ lapatinib (T+L). Profiling was by RNA sequencing (RNAseq) and multiplexed inhibitor beads coupled with mass spectrometry (MIB/MS). MIB affinity-purification selectively enriches the functional kinome ( > 250 kinases per sample) for identification/quantification by MS. Methods: Eligible patients (pts) had biopsy then randomization to: T (8 mg/kg iv), P (840 mg iv), T+P (same doses), or T+L (8mg/kg iv x1, 1000 mg po/d) 7 days before breast surgery. RNAseq and MIB/MS on paired pre- and post-Rx samples were analyzed using DESeq2 (comparison of mean difference in log2fold change (post/pre)) and MaxQuant (kinome response profiling) software. Results: Of 23 evaluable pts, we obtained informative paired RNAseq data in 13 (5 T, 3 P, 3 T+P, 2 T+L), and identified distinct expression responses (padj≤0.05) between Rx arms, such as FGFR4 increase in P vs T or T+P. All samples had HER2 enrichment by RNAseq. Kinome response profiling from 11 pts (3 T, 3 P, 4 T+P, 2 T+L) revealed consistent increases in MIB binding (abundance a/o activity) of several tyrosine kinases regardless of Rx, including immune-related kinases SYK, IRAK4, FGR, and FES. Other kinases, such as p90Rsk and GSK3B, exhibited increased binding in response to T and T+P, but not P alone. While not quantifiable in every sample due to detection limits, HER2 inhibition was observed by loss of MIB binding in select post-Rx versus pre-Rx comparisons. Conclusions: HER2 inhibition upregulates and activates specific receptor tyrosine kinases in tumor cells as well as alterations that may reflect changes in the immune compartment. HER2+ BrCa exhibit plasticity, characterized by distinct expression and kinome profile changes within 1 week of initiating Rx, and reprogramming in both immune responses and BrCa cells. Clinical trial information: NCT01875666.

A feasibility study of neoadjuvant talazoparib for early-stage breast cancer patients with a germline BRCA pathogenic variant: NCT02282345

TPS595

Background: Poly-(adenosine diphosphate [ADP]-ribose) polymerase (PARP) is a family of enzymes responsible for DNA repair via base excision repair as well as maintenance of genetic stability. BRCA mutation carriers appear to have significant sensitivity to PARP inhibitors, not only from synthetic lethality but also potentially PARP trapping in the metastatic setting. A 2-month window study of talazoparib was reported at ESMO in 2016. In 13 patients treated, the median % tumor shrinkage by ultrasound was 88% (range 30-98%) and the study was halted early to allow for this expansion of neoadjuvant talzoparib as the only treatment prior to surgery to evaluate pathologic response. Primary Objective: Evaluate the rate of pathologic complete response (pCR)/RCB-0 + residual cancer burden (RCB)-I responses in patients with early stage breast cancer and a known BRCA pathogenic variant. Methods: 20 patients with stage I-III breast cancer and a known BRCA mutation will be accrued on this IRB-approved study. Patients will receive 4-6 months of neoadjuvant talazoparib and then proceed to surgery. Radiation, chemotherapy and endocrine therapy will be given when appropriate in teh adjuvant setting. Brief Eligibility Criteria: Patients with an identified BRCA pathogenic variant and diagnosed with a stage I-III breast cancer at least 1 cm in size are eligible. Tumors can have any ER or PR status but HER2 over-expressed cancers were excluded. Prior systemic or radiation therapy for previous breast cancer is excluded, but prior surgical treatment for contralateral DCIS is allowed. Correlative Science: Blood and biopsies prior to initiation of therapy will be collected to evaluate biomarkers of therapy efficacy as well as to initiate patient derived xenograft (PDX) models. Other studies will include: immunohistochemistry, targeted or whole exome sequencing for BRCA pathway mutations and other somatic and germline alterations; RNA sequencing; immune response; transcriptional profiles to assess TNBC subtype, reverse phase protein array (RPPA); generation of PDX models and mammosphere cultures. Clinical trial information: NCT02282345.

Effect of neoadjuvant pertuzumab-containing regimens on pathologic complete response rates in stage II-III HER2-neu positive breast cancer: A retrospective, single institutional experience

580

Background: Pertuzumab (P) in combination with trastuzumab (H) based chemotherapy is currently FDA- approved as a standard neoadjuvant treatment for patients with clinical stage II-III HER2-positive (HER2+) breast cancer (BC). The chemotherapy backbone of HER2-targeted therapy varies and may include taxane (T) and/or anthracycline (A), or carboplatin (C). The goal of this study was to retrospectively evaluate the pathologic complete response (pCR) rate for HP-containing regimens compared to H containing regimens for stage II-III HER2+ BC. Methods: We identified all patients (n = 1150) with stage II-III HER2+ BC who received neoadjuvant HER2-targeted therapy from 2005 to 2016 through an institutional database. All patients underwent primary breast and lymph node surgery. pCR was defined as ypT0/is, ypN0. Univariate/multivariate logistic regression and chi-squared test for comparing proportions was used for the statistical analysis. Results: pCR was significantly higher for the HP group (n = 200) compared to the H group (n = 950): 44% vs. 41%, odds ratio = 1.8 (95% CI = 1.3, 2.5; P = 0.0002). Even with adjustment for all clinically significant factors (age, stage, tumor grade, hormone receptor (HR) status, A or C exposure), the improvement was statistically significant (adjusted OR = 2.1 (95% CI = 1.5, 2.9; P < 0.0001). The pCR rate by stage and HR status for the HP group is 62% vs. 55% (stage II vs. III) and 71% vs. 51% (HR- vs. HR+). The effect of P was not modified by HR status (HR-, OR = 2.3; HR+, OR = 1.7, P = 0.39) or by A (A-yes, OR = 1.8; A-no, OR = 2.6) (P = 0.28 for interaction) or C (C-yes, OR 2.6; C-no, OR = 1.8) (P = 0.30 for interaction). P was significantly more likely to be given to patients without A (36% vs. 10%, P < 0.0001) and more likely to be given to patients with C (30% vs. 14%, P < 0.001). In both groups, significant predictors of pCR were found to be stage, HR status, and C exposure. Conclusions: Pertuzumab containing regimens yield higher pCR rates compared to non-Pertuzumab containing regimens in stage II- III HER-2 positive breast cancer. The effect of Pertuzumab is not modified by anthracycline or carboplatin use.

Proof-of concept phase I study of everolimus, letrozole and trastuzumab in hormone receptor-positive, HER2-positive/amplified or mutant metastatic breast cancer or other solid tumors: Evaluating synergy and overcoming resistance

2583

Background: Preclinical models suggested synergistic antineoplastic activity of anti-estrogen therapy with HER2 and mTOR inhibitors. Methods: We designed a 3+3 dose escalation phase I study of the aromatase inhibitor letrozole 2.5mg PO daily, mTOR inhibitor everolimus 2.5-10mg PO daily and HER2 antibody trastuzumab 4-8mg loading dose followed by 2-4mg maintenance dose IV on day 1 of 21-day cycle in patients with hormone-receptor positive, HER2-positive/amplified or mutant advanced cancers (confirmed by immunohistochemistry and/or FISH and/or next-generation sequencing). The primary objectives were to determine maximum tolerated dose (MTD), dose limiting toxicities (DLT), overall safety and response. Results: A total of 18 patients (men, 1; women, 17; HER2 amplification, 14; HER2 mutation, 4; breast cancer, 15; ovarian cancer, 1; cervical cancer, 1; gastroesophageal junction cancer, 1), median age 56 years, median of 6 prior therapies (including letrozole [9] or other aromatase inhibitor [8]; everolimus [3]; trastuzumab [14] or other HER2 targeted therapy [1]) were enrolled in the planned 6 dose levels. The MTD has not been reached and grade 3 (G3) mucositis at the dose level 4 was the only DLT. Other G3 or G4 drug-related toxicities included G4 hyperglycemia in 1 patient, G3 hyperglycemia in 3 patients, G3 thrombocytopenia in 1 patient, G3 anemia in 1 patient and G3 headache in 1 patient. Of 18 patients, 3 (17%) had a partial response (all with heavily-pretreated breast cancer with HER2 amplification [2] or HER2A775_G776insYVMA mutation [1]), 11 (61%) stable disease (SD) including 7 (39%) patients with SD > 6 months (all with heavily-pretreated breast cancer), 3 (17%) progressed and 1 had pending evaluation. The median change in size of target lesions per RECIST 1.1. was -11% (-68% to +47%). Median progression-free survival was 9 months (95% CI 5.8-12.2). Conclusions: The combination of letrozole, everolimus and trastuzumab is well tolerated with encouraging activity in heavily-pretreated patients with HER2-amplified or mutant advanced breast cancer. Clinical trial information: NCT02152943.

Abstract P6-09-35: Proposal for a new breast cancer staging classification: Incorporating clinical and biologic factors

Background: The current breast cancer staging system, based on anatomy, does not always reflect the variable clinical course outcomes seen in the clinic. Other important and known determinants of prognosis and survival in breast cancer are age, grade, and receptor subtypes. In this analysis, we sought to demonstrate that these additional factors were important determinants of breast cancer specific and overall survival with an intention to propose a new staging classification. Methods: Through a prospectively maintained electronic database at the University of Texas MD Anderson Cancer Center, we identified patients with newly diagnosed invasive breast cancer, stage I-IV, who received surgery as an initial treatment from 1997 to 2014. Data points for the earliest invasive breast cancer event were recorded: age, pathologic stage (7th edition AJCC), grade, ER status, PR status, HER2-neu status, adjuvant treatment history, and outcomes (breast cancer-specific survival [BCSS] and overall survival [OS]). Cox proportional hazards model was used for the statistical analysis. Results: Of 22,131 patients, 99% were women in the following age groups (median age at surgery, 53 years [range, 16-98 years]): age &lt; 40 (13%), 40-69 (76%), &gt;70 (11%). Pathologic stages were: I: 50%, II: 39%, III: 9% and IV: 2%; 768 (3.5%) patients had bilateral breast cancer. Biological subtypes were as follows: Triple-negative (TN): 6%, Hormone receptor-positive/HER2-negative (HR+/HER2-): 70%, HER2-positive (HER2+): 24% (HR+, 9%; HR- 15%). Median follow-up was 7.9 years (95% CI, 7.8-8.0). In multivariate Cox regression modeling, age, grade, and clinical biomarker-based subtypes were significantly associated with breast cancer specific survival (BCSS).

Table 1. Breast cancer specific-survival: Multivariate modelCovariateLevelHR95% CI (p value)Overall p valueAge at DiagnosisLess than 401.521.37-1.68 (&lt;.0001) 40-69Reference&lt;.0001 70-791.050.89-1.24 (0.55) Over 801.150.79-1.66 (0.47)Pathologic StageIAReference&lt;.0001 IIB0.880.58-1.32 (0.54) IIA2.201.96-2.46 (&lt;.0001) IIB3.453.06-3.89 (&lt;.0001) IIIA4.293.70-4.96 (&lt;.0001) IIIB3.432.45-4.79 (&lt;.0001) IIIC6.585.52-7.84 (&lt;.0001) IV15.1212.72-17.96 (&lt;.0001)Biologic SubtypeHR+, HER2-Reference&lt;.0001 HR+, HER2+*0.580.46-0.73 (&lt;.0001) HR-, HER2+*1.100.90-1.35 (0.35) TN**2.001.82-2.21 (&lt;.0001)Nuclear GradeIReference&lt;.0001 II1.731.34-2.23 (&lt;.0001) III3.292.55-4.24 (&lt;.0001)*All patients were treated with trastuzumab in the adjuvant setting **Considering TN as the reference (HR (95% CI): HR+/HER2- (0.50 (0.45-0.55)), HR+/HER2+ (0.29 (0.23-0.37)), HR-/HER2+ (0.55(0.45-0.68). Abbreviations - BCSS: HR: hazard ratio, CI: confidence interval, HR+: hormone receptor positive, HR-: hormone receptor negative, HER2+: Her2-neu positive, HER2-: HER2-neu negative, TN: triple negative, Reference: 1.00

Conclusion: More individualized prediction of outcomes for breast cancer is possible by considering clinical and biologic characteristics in addition to anatomic stage. We intend to integrate pathologic stage, age, and biologic factors into a novel prognostic model to propose a new staging classification for breast cancer.

Citation Format: Murthy RK, Song J, Raghavendra AS, Li Y, Hsu L, Barcenas CH, Tripathy D, Berry D, Hortobagyi GN. Proposal for a new breast cancer staging classification: Incorporating clinical and biologic factors [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 P6-09-35.

Clinicopathological and surgical factors associated with long-term survival in patients with HER2-positive metastatic breast cancer

Trastuzumab-based treatment has dramatically improved the outcomes of HER2-positive (HER2+) metastatic breast cancer (MBC) patients, with some patients achieving prolonged survival times. In this study, we aim to identify factors that are associated with long-term survival. Patients with HER2+ MBC treated with anti-HER2 target therapy were identified. Patients were grouped according to overall survival (OS) and categorized as long-term survivors (LTS, OS ≥ 5 years), or non-long-term survivors (non-LTS, OS < 5 years). Descriptive statistics and multivariable logistic regression modeling were used. A sensitivity analysis was carried out, including only patients diagnosed before 2007; therefore, 5 years of potential follow-up was possible. 1063 patients with HER2+ MBC diagnosed between 1994 and 2012 and treated with anti-HER2 therapy were identified. Among them, 154 (14.5 %) patients were categorized as LTS (median OS 92.2 months). Among LTS, 63.4 % were HR-positive and 32 % had de novo stage IV disease. Hormone receptor positivity (OR) 1.69; 95 % CI 1.17-2.44), resection of metastases (OR 2.38; 95 % CI 1.53-3.69), and primary breast surgery in patients with de novo stage IV (OR 2.88; 95 % CI 1.47-5.66) were associated with improved long-term survival. Greater number of metastatic sites (≥3 vs. 1, OR 0.41; 95 % CI 0.23-0.72) and visceral metastases (OR 0.61; 95 % CI 0.4-0.91) were associated with poor survival. Hormone receptor positivity, low burden of disease, metastasis to soft and bone tissues, and surgical management with resection of the metastatic site and the primary tumor were associated with long-term survival in patients with MBC who received anti-HER2 treatment.

Abstract OT2-03-03: Women's triple-negative, first-line treatment: Improving outcomes in triple-negative breast cancer using molecular triaging and diagnostic imaging to guide neoadjuvant therapy

BACKGROUND:

In triple negative breast cancer (TNBC), pathologic compete response/residual cancer burden-0 (pCR/RCB-0) or minimal residual disease (RCB-I) following neoadjuvant chemotherapy (NACT) is associated with a good prognosis. This is in contrast to extensive residual disease (RCB-II-III) which carries approximately a 50% chance of recurrence. These patients have a particularly poor prognosis as there are currently no targeted agents to salvage chemoresistant disease. It is important to predict pCR in order to direct responsive disease toward standard NACT and non-responsive disease (NRD) to therapy on clinical trials.

TRIAL DESIGN:

The use of genomic signatures (JAMA, 2011; 305:1873-81) and imaging to predict response to NACT will be validated, and the clinical impact of selecting patients with predicted NRD for targeted therapy on clinical trial will be determined. Patients will undergo primary tumor biopsy for molecular profiling and will be randomized 2:1 to know the results versus not (control). Following that, all patients will receive 4 cycles of anthracycline-based NACT, with imaging used for response assessment. Patients with molecular/imaging criteria for NRD will be offered enrollment on a clinical trial based upon molecular profiling or based upon physician/patient choice (control).

INCLUSION CRITERIA:

Tumor size ≥1.5 cm diameter; TNBC by standard assays; ≥18 years of age; LVEF ≥50%; adequate organ and bone marrow function

EXCLUSION CRITERIA:

Stage IV disease; invasive cancer within 5 years; excisional biopsy of the primary tumor; features that limit response assessment by imaging; unfit for taxane and/or antracycline regimens; prior anthracycline therapy; ≥grade II neuropathy; Zubrod performance status of ≥2; history of serious cardiac events

PRIMARY AIM:

- Prospectively determine the impact of a molecular diagnostic/imaging platform in patients with localized invasive TNBC

SECONDARY AIMS:

- Compare rates of clinical trial enrollment

- Evaluate disease free survival in the experimental arms compared to control standard NACT

- Perform integrated biomarker analyses and identify therapeutic targets for resistant disease

STATISTICAL METHODS:

A maximum of 360 patients will be randomized (2:1)using a group sequential design with one-sided O'Brien-Fleming boundaries, with two equally spaced binding interim tests for futility and superiority and one final test, having an overall Type I error .05 and power .80 to detect an improvement in pCR/RCB-I from 50% to 64%.

Citation Format: Mitri ZI, Ueno NT, Yang W, Valero V, Litton JK, Murthy RK, Ibrahim NK, Arun BK, Mittendorf EA, Hunt KK, Meric-Bernstam F, Thompson A, Piwnica-Worms H, Tripathy D, Symmans F, Moulder-Thompson S. Women's triple-negative, first-line treatment: Improving outcomes in triple-negative breast cancer using molecular triaging and diagnostic imaging to guide neoadjuvant therapy. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT2-03-03.

Abstract P3-14-02: Targeting the PI3K/AKT/mTOR pathway for the treatment of mesenchymal triple-negative breast cancer (TNBC): Evidence of efficacy and proof of concept from a phase I trial with dose expansion of mTOR inhibition in combination with liposomal doxorubicin and bevacizumab

Background: Approximately 30% of TNBCs are characterized by microarray as claudin-low, mesenchymal or mesenchymal stem cell-like and, unlike basal TNBCs, these tumors frequently harbor aberrations in the PI3K/AKT/mTOR axis, raising the possibility of targeting this axis to enhance chemotherapy response. Assays to clinically identify mesenchymal TNBCs are under development, but published results confirm that up to 30% are metaplastic breast cancers (MpBCs), a chemo-refractory group of tumors that contain a mixture of epithelial and mesenchymal components, making them identifiable by microscopy. As such, MpBCs serve as surrogates of response for potential regimens to treat mesenchymal TNBC.

Methods: Patients (pts) with advanced TNBC (N=64) were treated with liposomal doxorubicin (D), bevacizumab (A) and the mTOR inhibitors temsirolimus (T) or everolimus (E). D and A were administered IV on day 1 with T (IV on days 1, 8 and 15) or E (continuous daily oral administration) using 21 day cycles. Response was assessed every 6 weeks using RECIST. When available, archived tissue was evaluated for aberrations in the PI3K pathway using standard assays.

Results: Fifty-two MpBC pts were treated with DAT (N=39) or DAE (N=13). Median age was 58 (range 37-79); median # of prior regimens for metastatic disease was 1 (range 0-5). The objective response rate (ORR) was 21% [complete response (CR)=4 (8%); partial response (PR)=7 (13%)] and 10 (19%) pts had stable disease (SD)≥6 months for a clinical benefit rate (CBR) of 40%. Tissue was available for testing in 43 pts and 32 (74%) had a PI3K pathway activating aberration (Table 1).

Response According to PI3K Pathway AberrationPI3K Pathway AberrationN (%)CRPRSD≥6monthsCBRORRAny PI3K Pathway Aberration*32 (74)46444%31%PIK3CA Mutation19 (59)23447%26%p.H1047R12 (38)21350%25%p.E545K6 (19)02150%33%p.G1007R1 (3)010100%100%p.E545A1 (3)0000%0%p.H1047Y1 (3)0000%0%p.K111E1 (3)0000%0%p.E542K1 (3)0000%0%PIK3CA Amplification1 (3)010100%100%PTEN Mutation5 (16)0000%0%PTEN Loss5 (16)02040%40%AKT1 p.E17K Mutation2 (6)0000%0%AKT2 Amplification1 (3)100100%100%PIK3R1 Mutation2 (6)01050%50%NF2 Mutation1 (3)100100%100%No PI3K Pathway Aberration11 (26)00545%0%*Some tumors had &gt;1 aberration detected

PI3K pathway activation was associated with a significant improvement in ORR (31 vs 0%; P=0.043) but not CBR (44 vs 45%; P=1.000) or progression-free survival (median 5.1 vs 2.9 months; P=0.352). A pt with 5 year+ durable CR (on maintenance everolimus) had a mutation in NF2. To emphasize the importance of pt selection, it is notable that 12 pts with non-metaplastic TNBC were also treated with DAT, and only 1 pt had a response (CR/PR=1; SD≥6 months=0), for a CBR that was significantly worse than pts with MpBC (8 vs 40%; P=0.045).

Conclusions: Using MpBC as a surrogate of response, DAT/DAE has significantly better activity in mesenchymal compared to non-selected TNBC. Response is enhanced in pts with PI3K pathway activation. DAT/DAE should be tested in non-metaplastic, mesenchymal TNBC once a diagnostic assay is available.

Citation Format: Basho RK, Gilcrease M, Murthy RK, Helgason T, Booser DJ, Karp DD, Meric-Bernstam F, Wheler JJ, Valero V, Albarracin C, Litton J, Chavez-MacGregor M, Ibrahim NK, Murray JL, Koenig KB, Hong D, Subbiah V, Kurzrock R, Janku F, Moulder S. Targeting the PI3K/AKT/mTOR pathway for the treatment of mesenchymal triple-negative breast cancer (TNBC): Evidence of efficacy and proof of concept from a phase I trial with dose expansion of mTOR inhibition in combination with liposomal doxorubicin and bevacizumab. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-14-02.

Abstract P4-14-22: A single-center, open-label phase 1b study of entinostat, and lapatinib alone, and in combination with and trastuzumab in patients with HER2+ metastatic breast cancer after progression on trastuzumab

Background: Our in vitro and in vivo preclinical data showed that entinostat enhances the efficacy of lapatinib in HER2 positive (HER2+) breast cancer cells via FOXO3-mediated Bim1 expression, which resulted in enhanced apoptosis in HER2 targeted therapy (lapatinib and trastuzumab)-resistant breast cancer (IBC and non-IBC) cells [Lee et al.]. Based on these findings, we conducted a phase 1b trial of entinostat to determine the maximal tolerated dose (MTD) in combination with lapatinib alone and in combination with lapatinib and trastuzumab for metastatic HER2+ breast cancer patients (pts), who progressed on trastuzumab.

Method: This was a single-center, open-label phase 1b study to evaluate the dose limiting toxicity (DLT) and determine MTD. 3+3 dose escalation schedule was used for Cohorts 1 and 2. Pts received lapatinib and entinostat (Cohort 1) or entinostat, lapatinib, and trastuzumab (Cohort 2). Initial dose of lapatinib 1250mg in Cohort 1 and 1000mg for Cohort 2 to match standard dose in combination with trastuzumab dose. In Cohort 1, entinostat was given PO on day 1 and 15 every 28 days cycle at dose levels 10 mg (level 0), 12 mg (level 1), or 15 mg (level 2). The dose levels for Cohort 2 were 12 mg (co-level 0) or 15 mg (co-level 1) on day 1 and 15 every 28 days cycle. While lapatinib and entinostat were given 28 days cycle due to entinostat dosing, the dosing of trastuzumab followed approved schedule every 21 days starting at 8mg/kg loading followed by 6mg/kg q 3 wks in Cohort 2 and 3. After the MTD of entinostat in cohort 2 was determined at 12mg, an expansion cohort of 10 pts (cohort 3) was conducted.

Results: Median age was 52 (26-69 yrs). Median number of prior trastuzumab-based regimens was 2 (1-6), 8 pts had lapatinib containing treatment prior to the trial, including 5 pts who had clinical benefit. 16 had ER+ and 13 ER negative, and 9 had IBC. Clinical efficacy and toxicity of treatment is summarized in table 1. Out of 14 pts who had clinical benefit (CR, PR, SD), 6 had IBC. Three pts are still on therapy (1CR, 1PR, 1SD).

Table 1. Clinical Efficacy, Toxicity of combination Receptor StatusResponseGrade 3 toxicityGrade 4 toxicityCohort 1HER2+/ER- (N=8) HER2+/ER+ (N=7)CR (N=1; 8M), SD (N=4;1,2,4M)Lapatinib dose reduction: 3 pts Rash (2) Abdominal pain + dyspnea (1)Entinostat dose reduction: 2pts Neutropenia (1 at 12mg, 1 at 15mg)Cohort 2/3HER2+/ER- (N=8) HER2+/ER+ (N=6)CR (N=2; 3,6M), PR (N=2;4,5M) SD (N=5;1,2,4,6M)Lapatinib dose reduction: 2 pts Diarrhea (N=1 at 12mg N=1 at 10mg) Entinostat dose reduction: 5 pts Neutropenia (N=2 at 12 mg) Leukopenia (N=1 at 12mg) Anemia (N=1 at 12mg)Entinostat dose reduction: 2pts Hypokalemia (N=1 at 12mg) Thrombocytopenia (N=1 at 15mg)CR: complete response, PR: partial response, SD: stable disease, N=number of pts, M=months

Conclusion: MTD was reached at 12mg q 2wkly entinostat, lapatinib 1000 mg daily and trastuzumab 8 mg/kg followed by 6mg/kg q 3 wks. This combination was safe and had promising clinical efficacy in patients with trastuzumab-resistant metastatic HER2+ breast cancer including IBC, warranting further study.

Citation Format: Lim B, Jackson S, Alvarez RH, Ibrahim NK, Willey JS, Murthy RK, Booser DJ, Giordano SH, Barcenas CH, Brewster A, Walters RS, Brown PH, Tripathy D, Valero V, Ueno NT. A single-center, open-label phase 1b study of entinostat, and lapatinib alone, and in combination with and trastuzumab in patients with HER2+ metastatic breast cancer after progression on trastuzumab. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-14-22.

Effect of a new model for multidisciplinary breast cancer care on clinical metrics leading to efficiency and timeliness of access

107

Background: The multidisciplinary approach to breast cancer care provides a coordinated mechanism for evaluating and treating new patients. Improving the structure of clinic models may further enhance the delivery of cancer care. Methods: In May 2013, multi-team (MT) clinics were introduced in the breast center at the University of Texas MD Anderson Cancer Center. Local patients with newly diagnosed breast cancer were scheduled to be seen in a MT clinic with testing coordinated for the same day. Patient cases were first reviewed and examined concurrently by physicians from each discipline (surgical, medical, radiation), followed by sequential visits with each clinician for a more detailed discussion. The goal of this program was to determine whether a highly integrated multidisciplinary clinic model would improve the efficient delivery of cancer treatment. Results: From 5/2013 – 5/2014, 211 newly diagnosed and untreated breast cancer patients were seen in the MT clinic. Clinical metrics were reviewed retrospectively and compared to newly diagnosed and untreated patients who entered the clinic using the standard model (non-MT patients) (n=1944). Please see Table for details of the data. Conclusions: Multi-team clinics improved clinical metrics leading to efficiency and timeliness of access. The model enriched for a population of patients who were more likely to receive treatment within the breast center, utilize institutional resources, and enroll into clinical trials. [Table: see text]

Abstract P3-11-02: Women with pregnancy-associated early breast cancer achieve improved emotional well-being as a result of their cancer experience

Background: Pregnancy-associated early breast cancer (PAEBC) has increased in incidence as more women pursue childbearing at an older age. The objective of this study was to measure the impact of diagnosis and treatment on emotional health and evaluate the positive emotional outcomes in a group of women with PAEBC. Methods: Between 1989 and 2010, 81 patients were treated for PAEBC with 5-flurouracil, doxorubicin and cyclophosphamide (FAC) chemotherapy. Patients completed the Impact of Events Scale-Revised (IES-R), which is a questionnaire that measures subjective distress caused by traumatic events and the Post-traumatic Growth Inventory (PGI), which measures positive outcomes after a traumatic event. Results: Of the 81 women, 53% (43/81) completed the IES-R and 44% (36/81) also completed the PGI. The time since diagnosis ranged from 6 months to greater than 5 years. The median age of the participants was 33 years (range 26-43 years). Of the 43 patients who completed the IES-R, 91% (39/43) did not use avoidance as a primary coping strategy; they felt well equipped to deal with feelings about their diagnosis and treatment. Of patients who inadvertently thought about their diagnosis, 70% (30/43) noted that they avoided becoming upset by their thoughts. Less than 10% (9/43) of patients surveyed felt apathetic towards their diagnosis and subsequent treatment. In terms of positive outcomes, 94% (33/36) felt they were enabled to depend on others in times of crises and felt a greater appreciation for people and their kindness following their diagnosis of PAEBC. Eighty-six percent (31/36) had changed their priorities about what is important in life, felt more compassionate towards others, and felt a greater appreciation for the value of their own life. In addition, 86% (30/36) of patients indicated that they had discovered their inner strength and felt more inclined to change things in their life. Finally, 75% of patients surveyed felt they had developed a stronger religious faith because of their experience and had a better understanding of spiritual matters. The majority of patients reported improvement in interpersonal skills – placing more effort into their relationships and sharing a greater sense of closeness with others. Conclusions: Although women who experience PAEBC are thought to be at high risk for experiencing psychosocial distress, these findings suggest that most do not suffer negative emotional consequences; in fact, these data suggest that they often achieve improved emotional well-being as a result of their cancer experience. It is possible that these women have better emotional outcomes because they have successfully carried a pregnancy while facing a life-threatening illness. Comparisons to other premenopausal breast cancer survivors will be crucial in interpreting these findings.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-11-02.

Impact of adjuvant trastuzumab on outcomes of HER2-positive breast cancer patients treated with HER2-targeted therapy in the metastatic setting

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Background: Trastuzumab (T) was approved for the adjuvant treatment of women with early-stage, HER-2 overexpressing (HER2+) breast cancer in 2006. There are limited data outlining the outcomes of patients with HER2+ breast cancer who receive adjuvant T-based therapy and then receive T and/or lapatinib in the metastatic setting. Methods: We identified 540 patients with HER2+ breast cancer treated with T or lapatinib as part of their first-line treatment for metastatic disease from 01/1997 to 11/2011. HER-2 positivity was assessed by immunohistochemistry (score, 3+) or fluorescence in situ hybridization (HER2/CEP17 ratio ≥ 2). We excluded 17 patients from this analysis because they were either lost to follow-up or received less than 2 cycles of therapy at the institution. Statistical analyses were performed using the chi-square test to compare proportions between groups and the Cox proportional hazards regression analysis to compare survival times and estimate the corresponding hazard ratio with 95% confidence interval. Results: Of the 523 patients eligible for analysis, 76 patients had received T in the adjuvant setting and 447 had not. In the group who did not receive adjuvant T, 48% (213/447) of patients achieved a complete or partial response (CR/PR), whereas only 13% (14/76) achieved a CR/PR in the adjuvant T group (P<.0001). After adjustment for age, disease-free interval, post-menopausal status, stage at presentation, ER/PR status, and nuclear grade, the odds ratio was 0.27 (CI 0.13 - 0.56, p = 0.0004). Overall survival from first evidence of metastasis was significantly longer in the group who did not receive adjuvant T (39 months vs. 24 months, HR = 1.8, 95% CI 1.3-2.4). For OS, the adjusted hazard ratio was 1.5 (CI 1.04 - 2.1, p = 0.029). Age, DFI and stage were also significant predictors of OS. Conclusions: Patients with HER2+ metastatic breast cancer who were T naive, had a higher response rate (CR/PR) to front line HER2 targeted therapy and a longer OS compared to patients with metastatic HER2+ breast cancer who received T in the adjuvant setting. These findings highlight the importance of recognizing a pre-treated population and calls for further research in this area.

Sequential spectral domain OCT documentation of retinal changes after branch retinal artery occlusion

Branch retinal artery occlusions (BRAO) are characterized histopathologically by inner retinal edema initially and atrophy in the presence of persistent ischemia. The duration of ischemia leading to irreversible atrophic retinal changes is not clear. Spectral-domain optical coherence tomography (SD-OCT) provides non-invasive detailed in-vivo histological changes in the retina. In this case report, we show sequential in vivo pathological changes seen in the inner retinal layers, in spite of clinical improvement, following the migration of an intraretinal embolus on the optic nerve head, which had previously resulted in symptomatic BRAO.

Mechanism of extracellular release of human neutrophil calprotectin complex

Calprotectin is an abundant cytosolic protein complex of human neutrophils with in vitro extracellular antimicrobial activity. Studies suggest that calprotectin may be actively secreted from intact HL-60 cells and that it can be translocated to polymorphonuclear neutrophil (PMN) cell membranes. To examine whether calprotectin is secreted extracellularly, we incubated soluble and particulate stimuli, including live and heat-inactivated Candida albicans, with whole blood and measured calprotectin levels in the plasma. We compared the release of calprotectin to that of lactoferrin, a protein known to be secreted by PMNs. Extracellular lactoferrin was detected after incubation with any of the particulate stimuli. In contrast, a significant increase in extracellular calprotectin was found only after incubation with live C. albicans. Specifically, the increase in extracellular calprotectin correlated directly with a proportional decrease in PMN viability. Our results indicate that human PMN calprotectin is not secreted extracellularly except as a result of cell disruption or death.