Lasofoxifene versus fulvestrant for ER+/HER2- metastatic breast cancer with an ESR1 mutation: results from the randomized, phase II ELAINE 1 trial

BACKGROUND

Acquired estrogen receptor alpha (ER/ESR1) mutations commonly cause endocrine resistance in ER+ metastatic breast cancer (mBC). Lasofoxifene, a novel selective ER modulator, stabilizes an antagonist conformation of wild-type and ESR1-mutated ER-ligand binding domains, and has antitumor activity in ESR1-mutated xenografts.

PATIENTS AND METHODS

In this open-label, randomized, phase II, multicenter, ELAINE 1 study (NCT03781063), we randomized women with ESR1-mutated, ER+/human epidermal growth factor receptor 2 negative (HER2-) mBC that had progressed on an aromatase inhibitor (AI) plus a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) to oral lasofoxifene 5 mg daily or IM fulvestrant 500 mg (days 1, 15, and 29, and then every 4 weeks) until disease progression/toxicity. The primary endpoint was progression-free survival (PFS); secondary endpoints were safety/tolerability.

RESULTS

A total of 103 patients received lasofoxifene (n = 52) or fulvestrant (n = 51). The most current efficacy analysis showed that lasofoxifene did not significantly prolong median PFS compared with fulvestrant: 24.2 weeks (∼5.6 months) versus 16.2 weeks (∼3.7 months; P = 0.138); hazard ratio 0.699 (95% confidence interval 0.434-1.125). However, PFS and other clinical endpoints numerically favored lasofoxifene: clinical benefit rate (36.5% versus 21.6%; P = 0.117), objective response rate [13.2% (including a complete response in one lasofoxifene-treated patient) versus 2.9%; P = 0.124], and 6-month (53.4% versus 37.9%) and 12-month (30.7% versus 14.1%) PFS rates. Most common treatment-emergent adverse events with lasofoxifene were nausea, fatigue, arthralgia, and hot flushes. One death occurred in the fulvestrant arm. Circulating tumor DNA ESR1 mutant allele fraction (MAF) decreased from baseline to week 8 in 82.9% of evaluable lasofoxifene-treated versus 61.5% of fulvestrant-treated patients.

CONCLUSIONS

Lasofoxifene demonstrated encouraging antitumor activity versus fulvestrant and was well tolerated in patients with ESR1-mutated, endocrine-resistant mBC following progression on AI plus CDK4/6i. Consistent with target engagement, lasofoxifene reduced ESR1 MAF, and to a greater extent than fulvestrant. Lasofoxifene may be a promising targeted treatment for patients with ESR1-mutated mBC and warrants further investigation.

U.S. prevalence of endocrine therapy-naïve locally advanced or metastatic breast cancer

Background

Variations in treatment choice, or late stage at first diagnosis, mean that, despite guideline recommendations, not all patients with hormone receptor (hr)-positive locally advanced or metastatic breast cancer (la/mbca) will have received endocrine therapy before disease progression. In the present study, we aimed to estimate the proportion of women with postmenopausal hr-positive la/mbca in the United States who are endocrine therapy-naïve.

Methods

Women in the Optum Electronic Health Record (ehr) database with a breast cancer (bca) diagnosis (January 2008-March 2015) were included. Patient and malignancy characteristics were identified using structured data fields and natural-language processing of free-text clinical notes. The proportion of women with postmenopausal hr-positive, human epidermal growth factor 2 (her2)-negative (or unknown) la/mbca who had not received prior endocrine therapy was determined. Results were extrapolated to the entire U.S. population using the U.S. National Cancer Institute's Surveillance, Epidemiology, and End Results database. Results are presented descriptively.

Results

In the ehr database, 11,831 women with bca had discernible information on postmenopausal status, hr status, and disease stage. Of those women, 1923 (16.3%) had postmenopausal hr-positive, her2-negative (or unknown) la/mbca, and 70.7% of those 1923 patients (n = 1360) had not received prior endocrine therapy, accounting for 11.5% of the overall population. Extrapolating those estimates nationally suggests an annual incidence of 14,784 cases, and a 5-year limited duration prevalence of 50,638 cases.

Conclusions

A substantial proportion of women with postmenopausal hr-positive la/mbca in the United States could be endocrine therapy-naïve.

Abstract P4-01-04: ESR1 mutation in cell free DNA (cfDNA) is associated with significantly increased circulating tumor cell (CTC)-clusters and progress in stage III/IV breast cancer after systemic treatments

Introduction: CTCs play a critical role in the process of tumor metastasis, and a portion of CTCs may form clusters that contain two or more CTCs bound together which were reported to have up to 50-fold of potential of forming distant metastasis in breast cancer (MBC) as compared to individual CTCs. However, molecular and genomic characterization of CTCs cluster remain largely unknown. Here we report a highly significant correlation between ESR1 mutation in cfDNA, CTCs count and CTC-cluster, which may help to understand MBC metastasis and predict treatment benefit, especially for metastatic or recurrent disease.

Methods: A total of 80 whole blood samples (7.5ml/each) were collected from 80 patients with stage III/IV BCa after informed consent under IRB-approved trial at the RHLCCC at Northwestern University before and after systemic therapies. Among these 80 patients, 41 patients received chemotherapy and 23 patients received endocrine therapy, among which 20 patients received combo treatments (16 plus Palpociclib, 1 plus Ribociclib, 2 plus Everolimus, and 1 plus trastuzumab). CTC enrichment and enumeration were performed in CELLTRACKS ANALYZERII® System (Menarini) by using CTC Kit Meanwhile, we detected the ESR1 hotspot mutations (Y537S and D538G) in plasma cfDNA from all 80 patients by Droplet digital PCR (ddPCR) assay using the QX200 ddPCR System (Bio-Rad). cfDNA was isolated from 2 mL of plasma using the QIAamp Circulating Nucleic Acid Kit (Qiagen) and the MAF was analyzed using QuantaSoft software (Bio-Rad).Database of CTCs and ESR1 mutation was linked with clinical database. Kruskal-Wallis test was used for statistics.

Results: Of the 80 samples analyzed, there were 57 samples without ESR1 mutations (Group 1), and 23 samples that had ESR1 mutations (8 Y537S mutations and 23 D538G mutations, Group 2). CTC positive (≥5) were detected in 13/57 samples (Group 1) and 15/23 samples, and the average amounts of CTCs were 21.77 CTCs/each sample and 59.86 CTCs/each sample in Group 1 and Group 2 respectively. There was a significant association between ESR1 mutations and high level of CTCs (P=0.000088). More important, CTC-clusters were found in 3 samples in Group 1 (5.26%) and in 5 samples in Group 2 (21.74%) respectively. There was a significant correlation between ESR1 mutations and CTC-clusters (P=0.026). Furthermore, there were 18/57 patients in group 1 and 5/23 in group 2 receiving chemotherapy. Moreover, 26/57 in group 1 and 15/23 in group 2 that received chemotherapy. Our results also confirmed that both endocrine therapy and chemotherapy benefited more patients without ESR1 mutations in compared with patients with ESR1 mutations (P<0.05).

Conclusion:We first elucidated the association between ESR1 mutations in ctDNA and CTC-cluster in MBC patients, and provides new insights on the molecular mechanisms associated with the metastasis process. In addition with the highly significant association between ctDNA ESR1 mutations and endocrine resistance we describe a new association allowing to expand the prognostic and predictive role of both tests enabling monitoring the metastatic prognosis and endocrine resistance for clinical decision-making.

Citation Format: Zhang Q, Gerratana L, Zhang Y, Flaum L, Shah A, Davis A, Behdad A, Gradishar W, Platanias L, Cristofanilli M. ESR1 mutation in cell free DNA (cfDNA) is associated with significantly increased circulating tumor cell (CTC)-clusters and progress in stage III/IV breast cancer after systemic treatments [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 P4-01-04.

Abstract P5-17-03: How is inflammatory breast cancer (IBC) different? Integration of clinico-pathological features and circulating tumor cells (CTCs)-based biomarkers for disease and prognostic assessment

Background: Since IBC is rare and burdened by a particularly unfavorable prognosis, biomarkers able to enhance diagnosis and risk assessment are of pivotal importance and a current unmet need. The aim of this study is to integrate standard clinico-pathological features with CTCs-based biomarkers for a more objective and detailed characterization of IBC.

Methods: This study analyzed retrospectively 251 Advanced Breast Cancer (BC) patients (pts) longitudinally characterized for CTCs and CTCs-based biomarkers at Thomas Jefferson University (Philadephia, PA) and Northwestern University (Chicago. IL). CTCs were enumerated through the CellSearch system (Menarini Silicon Biosystems), and characterized for HER2 expression using the CellSearch CXC Kit. Pts were defined as stage IV aggressive based on the previously reported ≥5 CTCs cut-off (Davis et al. 2018). Associations between clinical features, CTC-derived biomarkers and IBC were tested through uni and multivariate logistic regression. Survival was tested though log-rank test.

Results: Within the analyzed cases, 46% were diagnosed with IBC and among them, 38% was stage IV aggressive. CTC clusters (CTC_CL) were detectable in 12.5% of pts and HER2 positive CTCs (HER2_CTC) in 29.5%. Notably, IBC patients (pts) had a significantly lower CTC count with respect to non-IBC (median 2.5 vs 0 respectively for non-IBC and IBC; P=0.019). BC subtype (HER2 positive BC: OR 2.97; Triple negative BC: OR 2.13), liver and bone involvement (liver: OR 0.46; bone involvement: OR 0.31) were the only significant clinico-pathological features associated with IBC at univariate logistic regression. Interestingly, a marginal significance was observed for soft tissue involvement (OR 1.65, 95%CI 0.95 - 2.87, P=0.07). Stage IV aggressive and presence of HER2_CTC at baseline were moreover inversely associated with IBC. The multivariate model confirmed the significant association between IBC and HER2 positive BC subtype (OR 2.64, 95%CI 1.08 - 6.48, P=0.034), absence of bone involvement (OR 0.31, 95%CI 0.14 - 0.68, P=0.003) and absence of HER2_CTC (OR 0.38, 95%CI 0.15 - 0.98, P=0.045). The baseline detection of CTC_CL was a strong predictor of prognosis for OS in IBC pts (median OS (mOS) 7.6 months (mts) vs not reached (NR) respectively for detectable vs non-detectable CTC_CL; P<0.0001), while a trend was observed for HER2_CTC (mOS 9.9 mts vs NR respectively for detectable vs non-detectable HER2_CTC; P<0.082). Pts negative for CTC_CL at baseline had higher odds of developing CTC_CL in later time-points if stage IV aggressive (OR 12.27, 95%CI 2.10 - 71.57, P=0.005). Despite no baseline factors were significantly associated with the onset of HER2_CTC in later time-points, a trend (P=0.05) was observed for patients without lymph node involvement (OR: 5) and with bone involvement (OR: 4.3).

Conclusion: HER2_CTC and in particular CTC_CL are promising prognostic predictors in IBC. Stage IV aggressive IBC pts could benefit from a longitudinal CTCs assessment, being more prone to develop CTC_CL and therefore at higher risk of rapid disease progression. Probably due to the tropism for soft tissue, IBC is characterized by a lower number of HER2_CTC.

Citation Format: Gerratana L, Zhang Q, Wang C, Shah A, Davis AA, Ye Z, Zhang Y, Abu-Khalaf M, Flaum L, Strickland K, Rossi G, Behdad A, Gradishar W, Platanias L, Yang H, Cristofanilli M. How is inflammatory breast cancer (IBC) different? Integration of clinico-pathological features and circulating tumor cells (CTCs)-based biomarkers for disease and prognostic assessment [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 P5-17-03.

Abstract P3-01-08: HER2-negative metastatic breast cancer with HER2-positive circulating tumor cells (CTCs): A new CTC-defined HER2-positive subgroup

Introduction: CTCs can overexpress HER2 discordant from tumor HER2 expression. We aimed to describe characteristics of a CTC-defined group of pts with metastatic breast cancer (MBC) that is tumor HER2- and CTC HER2+ (HER2 tumor- CTC+).

Methods: We retrospectively analyzed data from pts treated at Northwestern University who had serial evaluation of CTCs and circulating tumor DNA (ctDNA). We included pts with pathologically confirmed HER2- MBC and HER2+ CTCs. CTCs were enumerated with the CellSearch immunomagnetic kit (Menarini Silicon Biosystems), HER2 expression on CTCs was determined using the CellSearch CXC Kit in 7.5 cc whole blood, and ctDNA was analyzed using the Guardant360 NGS assay (Guardant Health).

Results: Among 98 pts with HER2- MBC and CTC analysis, 46 (47%) had at least 1 HER2+ CTC. In this cohort the median age was 53. At initial BC diagnosis, 80% had early stage or locally advanced BC and 20% had de-novo metastatic disease. Baseline histology was 65% ductal, 20% lobular, 2% mixed ductal and lobular, and 13% unknown. Pathology of metastatic tumor was hormone receptor positive (HR+)/HER2- in 78% and triple negative in 22%. Detailed HER2 immunohistochemistry (IHC) and FISH results from metastases were available from 63% of pts of whom 72% had an IHC score of 0 or 1 and 28% had an IHC score of 2 with negative FISH testing. The median time from the most recent pathologic metastatic tumor assessment to the detection of a HER2+ CTC was 6.5 mo. Twenty-two pts had simultaneous (within 8 weeks) HER2- tumor confirmation and HER2+ CTC detection. The median lines of endocrine therapy (ET) for MBC prior to detection of HER2+ CTCs was 1 (range 0-5, 41% no ET, 17% 1 line, 41% >2 lines). Pts received a median of 2 (range 0-10) prior systemic therapies for MBC prior to detection of HER2+ CTCs, (20% 0 lines, 41% 1-3 lines, and 39% >4 lines). Among these 46 pts, CTCs were analyzed longitudinally in 104 samples, with HER2+ CTCs detected in 77 samples. Number of HER2+ CTCs at initial detection ranged from <5 in 24%, 5-50 in 43%, and >50 in 33%, with a median of 11.5 HER2+ CTCs. CTC clusters were noted in 37% of pts. At initial detection the proportion of CTCs that were HER2+ was 0-25% in 13% of pts, 26-50% in 46% of pts, and 51-100% in 41% of pts. Seven pts had ERBB2 aberrations in ctDNA. Of 12 pts with tumor sequencing, 2 had ERBB2 mutations, 1 had ERBB3 amplification, and 1 had overexpression of ERBB3 RNA. After detection of HER2+ CTCs, 18 pts received HER2 directed therapy (with chemotherapy in 13 pts, with endocrine therapy in 4 pts, and as monotherapy in 1 pt). Imaging demonstrated a partial response or stable disease in 9 pts (clinical benefit rate 50%), including in 1 pt with trastuzumab monotherapy, progressive disease in 8 pts, and not evaluated in 1 pt.

Conclusions: HER2+ CTCs are frequently detected simultaneously or soon after HER2- tumor assessment in MBC. Within this newly defined subgroup, the several responses seen with HER2 targeted therapy serve as a proof of concept that HER2 tumor- CTC+ patients can benefit from HER2 targeted therapy. Future studies are needed to determine a clinically relevant threshold for HER2+ CTCs to guide further study of HER2 therapy combinations in HER2 tumor- CTC+ pts.

Citation Format: Shah AN, Gerratana L, Zhang Q, Davis AA, Zhang Y, Flaum L, Behdad A, Platanias L, Gradishar WJ, Cristofanilli M. HER2-negative metastatic breast cancer with HER2-positive circulating tumor cells (CTCs): A new CTC-defined HER2-positive subgroup [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 P3-01-08.

Abstract P1-16-08: Response to subsequent therapy after dual immune checkpoint blockade in metastatic breast cancer

Introduction: While initial studies have found that combining chemotherapy with immune checkpoint blockade (ICB) can augment responses, additional toxicity has been observed. The optimal sequencing of chemotherapy and ICB has not yet been described. Sequential responses to chemotherapy after ICB have been reported in various tumor types; however, data is limited, and this has not been described in breast cancer to date.

Methods: We identified patients (pts) from a small pilot study in HER2-negative metastatic breast cancer (MBC) who received at least 1 cycle of durvalumab (PD-L1 inhibitor) and tremelimumab (CTLA-4 inhibitor). We excluded pts without follow up data or if they did not receive subsequent systemic therapy. Comparison of differences between subgroups was calculated by Fisher's exact test for categorical variables and Wilcoxon rank-sum test for continuous variables. Time to treatment failure (TTF) of subsequent therapy and overall survival (OS) were assessed by the Kaplan-Meier method and differences between breast cancer subtype were compared by log-rank tests.

Results: Twenty-three pts received at least 1 cycle of ICB of whom 14 pts were eligible for this analysis. Nine had estrogen receptor positive (ER+) BC and 5 had triple negative (TN) BC. There were no statistically significant differences between the ER+ and TN subgroups in age, race, ethnicity, ECOG performance status (PS) at end of ICB, or sites of metastatic disease except for more lymph node metastases in the TN cohort (p=0.003). Overall response rates to ICB in this cohort was higher in TN vs ER+ (40% vs 0%, p=0.11). Pts received a median of 4 lines of systemic therapy for MBC prior to ICB. Subsequent therapy after ICB was eribulin in 29%, carboplatin/gemcitabine in 21%, palbociclib + endocrine therapy (ET) in 14%, anthracycline in 14%, ixabepilone +/- capecitabine in 14%, and paclitaxel in 7%. Clinical response was seen in 8 pts (57%), of whom 5 had ER+ BC and 3 had TNBC. The median TTF of subsequent therapy was 3.0 mo (1.9, 5.5), which compared to a median TTF for therapy prior to ICB of 2.5 mo. The median OS was 12.3 mo (2.3-13.3). There were no significant differences between the ER+ and TN cohorts (log-rank test p=0.74 and 0.90 for TTF and OS, respectively. Subsequent therapy was discontinued due to progressive disease in 44%, decline in PS in 19%, liver failure in 6%, treatment related adverse event in 6%, and unknown cause in 13%. Two pts remain on subsequent therapy with palbociclib + ET beyond 6 mo without disease progression. There were no statistically significant differences between TTF >3 mo (n=5) and TTF <3 mo (n=9) subgroups. Pts with TTF >3 mo were numerically more likely to have a PS 0-1 (100 vs 78%), liver metastases (80 vs 56%), and ER+ BC (80 vs 56%). Pts with TTF <3 mo had more lymphopenia (66% vs 20%) and more lines of prior systemic therapy for MBC (median 6 vs 4).

Conclusions: While median duration of response on subsequent therapy was short, a subset of pts had significant clinical responses. These findings provide rationale for prospective validation as they provide strategies for sequencing ICB with standard therapies.

Citation Format: Shah AN, Yalamanchili A, Helenowski I, Bhole S, Woodman J, Gradishar WJ, Cristofanilli M, Santa-Maria CA. Response to subsequent therapy after dual immune checkpoint blockade in metastatic breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-16-08.

Abstract P4-01-18: Correlation between circulating tumor DNA (ctDNA) alterations and circulating tumor cells (CTC) uncovers new mechanisms of metastasis for patients with metastatic breast carcinoma (MBC)

Introduction:Novel molecular diagnostics including CTCs and ctDNA have been proved to predict disease metastasis and survival. However, the frequency of detection of actionable mutations using CTCs and ctDNA is variable based upon tumor related factors and diagnostic platform sensitivity. Herein, we evaluated a novel NGS technology in the ability of detecting driver and clonal genomic abnormalities in samples from MBC patients, and compared ctDNA alterations with CTCs and CTC-cluster. This study demonstrated several novel correlation between some specific ctDNA alterations and CTCs or CTCs related biomarkers, which opened new insight on mechanisms of metastasis for MBC.

Methods: This study included 52 samples from 26 patients with stage III/IV BCa treated at NMH (2016-2017) and who received standard systemic treatments based on disease subtypes. Whole blood samples (7.5ml/each) were used for CTC enrichment and enumeration in FDA approved CELLTRACKS ANALYZERII® System (Menarini). ctDNA from clinical plasma samples was analyzed by using PredicinePLUS, a NGS-based assay (Predicine Inc) with a 180-gene panel for genomic alterations mutations. Results of CTCs and ctDNA alterations were linked to clinical database. Matched pairs variations between CTCs and ctDNA alterations was compared by Wilcoxon signed-ranks test and Kruskal-Wallis test.

Results: Genomic Alterations (SNVs, Indels and copy number variations) were detected on 52 genes by PredicinePLUS assay. All samples (100%) demonstrated at least 1 somatic alterations. There were 75 mutations detected within 29 genes, and the variant frequency of mutated genes ranges from 0.11% to 68.56%. Increased CTCs were highly significantly correlated with genomic alterations in the genes (wild type vs alterations) including GATA3 (8vs 37), ESR1 ( 2.5 vs 41.3), CDH1 (3.5 vs 50.5) and CCND1 (4 vs 120) (P<0.01). Decreased CTCs were correlated with alterations of CDKN2A (20.5 vs 0) (P=0.025). CTC-cluster appear associated predominantly with alterations of CDH1 (P=0.0018), CCND1 (P=0.008) and BRCA1 (P=0.04). Furthermore, in HER positive CTCs group, ERBB2 mutations caused increased CTCs in compared with ERBB2 wild type (0 vs 5), when CCND1, CDKN2A, GATA3 and TP53 alterations were associated with increase of HER2 negative CTCs.

Conclusions: By using the novel diagnostic platform with the ability to identify ctDNA mutation and copy number variation, this study demonstrated several novel genes alterations which were highly correlated with CTCs, CTC-cluster and HER2. Some genes (CCND1 and CDH1) got involved into the changes on both CTCs and CTC-cluster, when some genes (CCND1, CDKN2A, ESR1 and GATA3) were related with change of CTCs and HER2 expression. Correlation of CTCs and ctDNA can be reliably and routinely used as non-invasive method for monitoring disease metastasis and predict the prognosis in MBC in clinic.

Citation Format: Davis A, Zhang Q, Gerratana L, Zhang Y, Flaum L, Shad A, Behdad A, Gradishar W, Platanias L, Cristofanilli M. Correlation between circulating tumor DNA (ctDNA) alterations and circulating tumor cells (CTC) uncovers new mechanisms of metastasis for patients with metastatic breast carcinoma (MBC) [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 P4-01-18.

Abstract P4-01-08: Characterization of circulating tumor free DNA (ctDNA) obtained from patients with metastatic breast carcinoma (MBC) undergoing systemic therapies using comprehensive genomic profiling

Introduction:Therapeutic benefit from individual treatments in patients with MBC is limited to small subsets of patients and of short duration due to tumor heterogeneity. Novel molecular diagnostics including ctDNA has been shown to predict response or resistance and survival. However, the frequency of detection of actionable mutations using ctDNA is variable based upon tumor related factors and diagnostic platform sensitivity (e.g. ddPCR or NGS). We evaluated a novel NGS technology in the ability of detecting driver and clonal genomic abnormalities in samples from MBC patients. Moreover, we wanted to compare the new technology to another state-of-the-art, commercially available diagnostic ctDNA testing with similar sensitivity to demonstrate both are able to detect genomic abnormalities in MBC.

Methods: This study included 30 samples from 15 patients with stage III/IV BCa treated at NMH (2016-2017) and who received standard systemic treatments based on disease subtypes longitudinally characterized for ctDNA before or 3 months after systemic therapies respectively. ctDNA from clinical plasma samples was first analyzed using PredicinePLUS, a NGS-based assay (Predicine Inc) with a 180-gene panel for genomic alterations mutations. The results were then independently analyzed with Guardant360TM (Guardant Health), a 73-gene panel. Matched pairs variations between Guardant360TM and Predicine was compared by Wilcoxon signed-ranks test. The prognostic impact of ctDNA was tested through Cox regression.

Results: Genomic Alterations (SNVs, Indels and copy number variations) were detected on 43 genes by PredicinePLUS assay. All samples (100%) demonstrated at least 1 somatic alterations. There were 75 mutations detected within 29 genes, and the variant frequency of mutated genes ranges from 0.11% to 68.56%. Median variant frequency was around 3.42%. Key cancer related genes including TP53, ESR1, PIK3CA, PTEN and BRCA1, are frequently mutated. Copy number variation were detected on 18 genes, among which 15 genes showed copy number gain, including MYC, PIK3CA, CCND1, and 3 genes (ATM, BRCA1 and CDKN2A) with copy number loss. There were no significant difference of % ctDNA (P=0.3967) and number of variations (P=0.5) between results of Predicine and Guardant360TM, neither to the comparison of main detected alterations (BRCA1, ESR1, MYC, PIK3CA and TP53) with Guardant360TM and Predicine (P=1). Furthermore, results from Predicine indicated that there is correlation with treatment response and benefit. A significant decrease on variations in %ctDNA levels (P=0.028) and variations in the number of genomic variants (P=0.028) after systemic therapies, was associated with longer overall survival.

Conclusions: Our study describes a novel diagnostic platform with the ability to identify ctDNA mutation and copy number variations in patients with MBC receiving systemic therapy. We also confirm that when comparing ctDNA using NGS platforms with similar sensitivity, the results are robust and reproducible which indicates that these technologies can be reliably and routinely used as non-invasive method for monitoring response to systemic therapies and predict the prognosis in MBC.

Citation Format: Zhang Q, Gerratana L, Zhang Y, Flaum L, Gradishar W, Platanias L, Cristofanilli M. Characterization of circulating tumor free DNA (ctDNA) obtained from patients with metastatic breast carcinoma (MBC) undergoing systemic therapies using comprehensive genomic profiling [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 P4-01-08.

Abstract P3-01-19: HER2-positive circulating tumor cells (CTCs) in advanced breast cancer (BC): A feature independent of BC subtype

Introduction: HER2 overexpression is observed on CTCs in advanced BC (ABC), but their significance is not known. We aimed to describe clinical, pathologic, and molecular associations with HER2 overexpression on CTCs in ABC patients (pts).

Methods: We conducted a retrospective analysis of data from ABC pts treated at Thomas Jefferson University and Northwestern University who had evaluation of CTCs and circulating tumor DNA (ctDNA). CTCs were enumerated with the CellSearch immunomagnetic kit (Menarini Silicon Biosystems), HER2 expression on CTCs was evaluated using the CellSearch CXC Kit, and ctDNA was analyzed using the Guardant360 NGS assay (Guardant Health). Associations with the presence of HER2+ CTCs were explored through univariate and multivariate logistic regression. Kruskal-Wallis testing evaluating HER2+ CTCs as a continuous variable was also conducted to confirm consistency of findings. Time to development of HER2+ CTCs was evaluated using Cox proportional hazards regression analysis.

Results: Baseline CTCs were evaluated in 209 pts (10% stage III, 90% stage IV) of whom 41% had no detectable CTCs, 23% had 1-4 CTCs, and 36% had >5 CTCs (stage IV aggressive). Twelve percent had CTC clusters. At least 1 HER2+ CTC was seen in 33% of pts at baseline draw. Of 39 patients with HER2+ BC, only 18% had HER2+ CTCs. Of patients with HER2+ CTCs, 55% had hormone receptor positive BC, 28% had triple negative BC, and 18% had HER2+ BC. On univariate logistic analysis, BC subtype or HER2 status was not associated with the presence of HER2+ CTCs. IBC pts represented 52% of pts and were less likely to have HER2+ CTCs (OR 0.40 95% CI 0.19-0.84). Bone metastases were associated with an increased likelihood of HER2+ CTCs (OR 2.46, 95% CI 1.12-5.38); however, other sites of metastases and number of metastatic sites were not correlated with HER2+ CTCs. Aggressive disease features including >5 CTCs and presence of CTC clusters were strongly associated with HER2+ CTCs (OR 15.72, 95% CI 6.89-35.8 and 8.97, 95% CI 3.23-24.89, respectively). Of 168 pts with ctDNA analysis, ERRB2 aberrations were seen in 22% of pts and were significantly associated with HER2+ CTCs (OR of 3.74, 95% CI 1.45-9.63). On multivariate analysis, the associations with >5 CTCs and ERBB2 alterations in ctDNA remained statistically significant. The associations of HER2+ CTCs with bone disease, >5 CTCs, CTC clusters, and ERBB2 alterations in ctDNA, and the inverse relationship with IBC were consistent when HER2+ CTCs were evaluated as a continuous variable with Kruskal-Wallis testing. Among pts without HER2+ CTCs at baseline, the time to detection of HER2+ CTCs correlated with the presence of bone metastases (HR 3.40, 95% CI 1.14-10.19), >5 CTCs (3.77, 95% CI 1.33-10.70), and visceral disease (HR 3.00, 95% CI 1.07-8.44).

Conclusions: HER2+ CTCs are common in ABC, independent of HER2 status of the tumor, and, in fact, common in the luminal BC. HER2+ CTCs were also strongly associated with CTC characteristics of aggressive disease with poor survival (CTCs clusters and >5 CTCs) and ERBB2 aberrations in ctDNA. Further studies will be investigating the role of HER2+ CTCs in endocrine resistance and the potential of anti-HER2 therapy in this unique CTC-defined setting.

Citation Format: Shah AN, Gerratana L, Davis AA, Zhang Q, Zhang Y, Rossi G, Wang C, Strickland K, Yang H, Flaum L, Abu-Khalaf M, Behdad A, Ye Z, Platanias L, Gradishar WJ, Cristofanilli M. HER2-positive circulating tumor cells (CTCs) in advanced breast cancer (BC): A feature independent of BC subtype [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 P3-01-19.

Abstract P3-01-10: Associations between plasma Interleukin 2 (IL-2) and HER2 expression in circulating tumor cell (CTC) and MYC alterations in circulation tumor DNA (ctDNA) open a new insight on immune microenvironment for patients with metastatic breast cancer (MBC)

Introduction: Overexpression of HER2 has been reported to be associated with metastasis and poor prognosis of patients with MBC. We reported in AACR 2018 that HER2 overexpression is associated with CTC-cluster. Preclinical data suggested that MYC and HER2 cooperate to drive stem cell phenotype and poor prognosis in MBC (Nair R). Furthermore, IL-2 upregulates the transcription of MYC (Grigorieva I) and gets involved into its alterations. We reasoned that further understanding of interactions of HER2 in CTC and MYC will be important to elucidate the mechanism of metastasis of MBC. Herein, we report a significant correlation between the plasma IL-2 level and HER2 expression in CTCs, and the IL-2 related MYC ctDNA alterations in MBC.

Methods: This study enrolled 43patients with stage III/IV BCa at the Northwestern Memorial Hospital (2016-2017) that had longitudinally detection of CTCs and ctDNA. Whole blood samples (7.5ml/each) were collected for CTCs enumeration by using CELLTRACKS ANALYZERII® System (Menarini) contains antibodies of anti-EpCAM for capturing CTCs, anti-CK-PE for epithelial cells, DAPI for nucleus, anti-CD45-APC for leukocytes and anti-HER-2/neu-FLU. The CTCs were classified based on phenotype as CK+, EpCAM+, DAPI+ and CD45-.Plasma ctDNA was analyzed using the Guardant360 TM NGS-based assay (Guardant Health), a 73 genes panel. ELISA for IL-2 was performed by using patients' plasma. Database of IL-2, HER2, CTCs and ctDNA was linked with clinical database and analyzed by Kruskal-Wallis test.

Results: CTCs ≥ 5 were found in 20 patients (46%). There were 15 patients that had HER2 negative CTCs (Group 1), and 5 patients had HER2 positive (Group 2) CTCs. The level of IL-2 was much higher in Group 1 (88.17pg) compared to Group 2 (66.81pg), indicating that patients with HER2 positive CTCs have significant lower IL-2 than patients with negative CTCs (P=0.02). Meanwhile, ctDNA MYC alterations were detected in 10 patients (including 1 L114R mutation, 7 CNV and 2 SNV) who have the average IL-2 level as 94.00pg. There were 11 patients without any alterations of MYC had average IL-2 level of 70.17pg, which indicated that patients with alterations in the ctDNA MYC have significant higher level of IL-2 in compared with patients without MYC alterations (P=0.02).

Conclusions: Findings of the correlation between overexpression of HER2 in CTCs and low IL-2 level indicated that low immunity may contribute to more aggressive MBC. And the higher level of IL-2 appear associated predominantly with MYC genomic alterations indicated that overexpression of MYC may also stimulate the immune response by upregulating IL-2 via a reverse feedback pathway. We postulated that increasing IL-2 suppresses the HER2 expression in CTC and breaks cooperation between HER2 and MYC. Although the interactions between them still unknown, our results suggest that IL-2 related immune microenvironment acts as a key player to suppress HER2- and MYC-mediated progress in MBC, including the formation of CTC-cluster. Monitoring and administration of IL-2 may benefit pretreated MBC patients and predict disease metastasis.

Citation Format: Zhang Q, Gerratana L, Zhang Y, Flaum L, Shah A, Davis A, Behdad A, Gradishar W, Platanias L, Cristofanilli M. Associations between plasma Interleukin 2 (IL-2) and HER2 expression in circulating tumor cell (CTC) and MYC alterations in circulation tumor DNA (ctDNA) open a new insight on immune microenvironment for patients with metastatic breast cancer (MBC) [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 P3-01-10.

Abstract P4-01-14: Association between interleukin 2 (IL-2) and circulating tumor DNA (ctDNA) is a novel biomarker for patients with metastatic breast cancer (BCa) after systemic therapies

Introduction: The detection and monitoring of ctDNA in metastatic breast cancer showed ability to predict treatment resistance and outcome. But the mechanisms has been a challenge to clinicians. Immune escape and immune tolerance has also been reported to cause BCa progress. Herein, we report a novel finding of the association between plasma IL-2 and the ctDNA in advanced BCa patients who received the systemic therapies, and it is potential utilization in clinic.

Methods: This study enrolled 43 patients with stage III/IV BCa at the Northwestern Memorial Hospital (2016-2017) that had longitudinally detection of ctDNA and circulating tumor cells (CTCs) before (baseline, BL) or 3 months after (first evaluation, FE) systemic therapies respectively. Duplicate whole blood samples (7.5ml/each) were collected in EDTA tubes from these patients. Plasma ctDNA was analyzed using the Guardant360 NGS-based assay (Guardant Health) and CTC enrichment and enumeration were performed in FDA approved semi-automated fluorescence CELLTRACKS ANALYZERII® System (Menarini Silicon Biosystems) by using CELLSEARCH® CXC Kit (Menarini). ELISA (Fisher) for IL-2 was performed by using patients' plasma. Database of IL-2, ctDNA and CTCs was generated and linked with clinical database. Kruskal-Wallis test was used for statistics. We previously reported cut-off of 5.7 was used to dichotomize the prognostic value of ctDNA percentage (%ctDNA) in 2018 ASCO. Matched pairs variations between IL2 levels at BL and at FE were tested through Wilcoxon signed-ranks test. Associations between %ctDNA and IL2 levels were explored through Kruskal-Wallis test. The prognostic impact of IL2 was tested through Cox regression.

Results: CTCs ≥ 5 were found in 23 patients at BL and 21 patients in FE respectively. There were 12 patients that had increase CTCs, and 31 patients with similar or less CTCs FE after systemic therapies. Decreased in CTCs was associated with increased IL-2 (P=0.004).The FE analysis showed that IL-2 dropped significantly in patients with CTC stably ≥5 (from 95.84pg to 79.46pg) after therapies (P<0.001). Furthermore, baselineIL-2 levels were significantly higher in patients with % ctDNA levels ≥5.7 (97.15pg) compared to patients with %ctDNA levels <5.7 (68.64pg) (P=0.0027). No other associations were highlighted in respect to age or number of ctDNA alterations. There was no significant variations between BL and FE levels of IL2 were observed according to BCa subtypes nor in respect to baseline %ctDNA ≥5.7 or CTCs ≥5. Compared with low level of BL IL-2 (<78.3pg) group, high level of BL IL-2 (≥78.3pg) had a significant negative impact on overall survival (OS) (P=0.037) in univariate analysis.

Conclusions: Our findings indicated that aggressive BCa with high level ctDNA mutation are associated with high level of IL-2 and immune response in patients with advanced disease. In addition we confirm a reverse correlation between change of IL-2 and change of CTCs potentially indication of immune escape. In summary, the study shows a dynamic relation between IL-2 level and tumor burden (ctDNA) and immune escape (CTCs) suggesting another potential biomarker to monitor interaction between tumor and immune environment.

Citation Format: Zhang Q, Gerratana L, Zhang Y, Flaum L, Shah A, Davis A, Behdad A, Gradishar W, Platanias L, Cristofanilli M. Association between interleukin 2 (IL-2) and circulating tumor DNA (ctDNA) is a novel biomarker for patients with metastatic breast cancer (BCa) after systemic therapies [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 P4-01-14.

Abstract P5-04-02: Progesterone receptor (PR) antagonism by telapristone acetate (TPA): A randomized, placebo-controlled phase IIB pre-surgical window trial in women with stage 0-II breast cancer

Background: In vitro and preclinical data indicate that TPA, a selective PR modulator, has activity against hormone-sensitive early breast cancer. We conducted a pre-surgical window trial of oral TPA in Stage 0-II breast cancer to assess the effect of TPA on suppression of cell proliferation (Ki67), and on differential gene expression in responsive and non-responsive tumors.

Methods: We enrolled 70 pre and postmenopausal women into a 1:1 randomized, double-blind, placebo-controlled trial of oral TPA 12mg (Repros Therapeutics Inc.) for 2-10 weeks. The primary endpoint was Ki67 labelling, comparing diagnostic core needle biopsy to post-therapy surgical specimens. Ki67 changes were quantitated by dual immunohistochemistry (Ki67/pan-cytokeratin) and image analysis (Aperio ImageScope and Definiens Tissue Studio®). RNA-sequencing (using RNA extracted from the paraffin blocks) was performed with Illumina TruSeq RNA Coding Access method. Differential gene expression pre-post therapy was assessed, followed by Gene Set Enrichment Analysis for pathway analysis. Ki67 changes from baseline were tested with Paired signed-rank test. For gene expression analysis, p values were calculated by Wald test and adjusted for multiple comparisons by Benjamini-Hochberg method (adjusted p <0.05 and 2-fold gene expression cut-off).

Results: Among 61 evaluable women, (29 placebo and 32 TPA) 97% of tumors were ER or PR positive and 91% were ER and PR positive (balanced across arms). A significant 6% decrease in mean %Ki67 was seen in the TPA arm (p= 0.003). When stratified by menopause, the significance held in premenopausal women (n= 22, p= 0.03) but not in postmenopausal women (n=10, p= 0.08). However, a Ki67 decrease (4%) was also observed in placebo group (p = 0.04); this was non-significant after pre- postmenopausal stratification. Overall, differential gene expression analysis showed no significant modulation of genes in either group. Using a pre-specified response parameter (50% relative reduction in Ki67), we identified 12/32 (38%) “responders” in the TPA, and 9/29 (31%) in the placebo arm. In sub-group analysis of these responders, we found 103 genes to be significantly modulated by treatment in the TPA “responders”, but saw no significant change in any gene expression in placebo “responders”. Gene set enrichment analysis for the 103 genes showed that TPA blocked the progression of cell cycle genes (PTTG1, PLK1, UBE2C, HIST1H3F, PSMD3, and etc.) and suppressed PGR and ERBB2 expression. In a pre-planned pooled analysis, these results will be combined with NCT02314156, reported in SABCS abstract 851790.

Conclusions: An anti-proliferative (Ki67) signal of TPA was observed in early stage breast cancer patients, but interpretation was limited by placebo group changes. The TPA group demonstrated differential suppression of proliferation-related genes among Ki67 responders, but the placebo group did not. Ongoing analysis will examine signatures related to stemness, metastasis, and immune suppression (potentially better endpoints in trials targeting P signaling). These analyses may help us select the right population and the right biomarkers for future trials.

Citation Format: Lee O, Sullivan ME, Xu Y, Shidfar A, Ivancic D, Zeng Z, Singhal H, Helenowski I, Jovanovic B, Hansen N, Bethke K, Gann P, Gradishar WJ, Clare SE, Khan SA. Progesterone receptor (PR) antagonism by telapristone acetate (TPA): A randomized, placebo-controlled phase IIB pre-surgical window trial in women with stage 0-II breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-04-02.

Abstract P5-17-02: Dissecting the biology of inflammatory breast cancer (BC) through cell free DNA and a circulating tumor cells (CTC)-derived signature

Background: The biological characteristics conferring Inflammatory BC's (IBC) distinctive and aggressive clinical features are currently not fully clarified. The aim of this study is to dissect IBC's biology through the integration of DNA and CTC-based circulating biomarkers.

Methods: This study retrospectively analyzed 251 Advanced BC (ABC) patients (pts) treated and longitudinally characterized for CTCs and circulating tumor DNA (ctDNA) at Thomas Jefferson University (Philadephia, PA) and Northwestern University (Chicago, IL). CTCs were enumerated through CellSearch (Menarini Silicon Biosystems), and characterized for HER2 expression using the CellSearch CXC Kit, while ctDNA was analyzed using the Guardant360 NGS assay (Guardant Health) and its percentage (%ctDNA) was classified based on the previously reported cut-off of 5.7% (Gerratana et al 2018). A subset of 117 pts was further characterized for circulating cell-free DNA (ccfDNA) through Qubit® dsDNA HS quantitation Assay (Thermo Fisher Scientific) and quantitative real-time PCR assay for ALU DNA repeats on chromosome 1.Associations between clinical characteristics, CTCs-derived biomarkers and IBC were explored through Fisher's exact test; survival was tested though Cox regression and log-rank test.

Results: Of the total 251 pts, 115 were diagnosed with IBC. Among the 117 patients characterized for ccfDNA, 70 had IBC. Median ccfDNA was 1.59 for IBC (IQR 1.02-3.19) and 2.37 for non-IBC (nIBC) (IQR 1.13-3.52), P=0.27. Consistent results were observed for %ctDNA levels (median value: 2 vs 1.6). The impact on OS of ccfDNA after log transformation was significant for the total population (HR 1.73 95%CI: 1.11-2.69) but not in IBC pts (HR 1.40 95%CI: 0.84-2.34). On the other hand, ctDNA high pts had a significantly worse OS (nIBC: HR 5.34 95%CI: 1.70-18.81 P=0.004; IBC: HR 4.05 95%CI: 1.91-8.58 P< 0.001). In the ctDNA high subgroup no differences in total number of CTCs were observed between IBC and nIBC, while significantly lower CTCs were observed in ctDNA low IBC pts (P=0.0097). The ctDNA low IBC subgroup had a higher incidence of HER2 positive BC (P=0.003) and a significantly lower incidence of CTCs clusters (P=0.006), HER2 positive CTCs (P=0.041). Notably, no associations were observed with stage at baseline, number of metastatic sites, liver, lung and visceral involvement. On the other hand, the ctDNA_high IBC subgroup was characterized by a lower incidence in liver, bone and visceral involvement (P=0.017, P=0.014 and P=0.03 respectively) and a marginally high incidence in soft tissue involvement (0.084). Moreover, IBC diagnosis conferred a significantly worse prognosis only in the ctDNA low subgroup (OS at 12 months nIBC: 100% vs IBC: 70%; P=0.049), while no differences were observed in the ctDNA_high subgroup (OS at 12 months nIBC: 29% vs IBC: 26%; P=0.767).

Conclusion: ctDNA is able to stratify BC according to aggressiveness independently from the sites and type of metastases, both in the IBC and nIBC subgroups. IBC has a distinctive CTCs/ctDNA-based signature, in particular ctDNAlow pts have a lower incidence of HER2 positive CTCs and CTC clusters. This signature is probably due to predominant lymphatic metastatic spread and aggressive phenotype.

Citation Format: Gerratana L, Zhang Q, Wang C, Shah A, Davis AA, Ye Z, Zhang Y, Abu-Khalaf M, Flaum L, Strickland K, Rossi G, Behdad A, Gradishar W, Platanias L, Yang H, Cristofanilli M. Dissecting the biology of inflammatory breast cancer (BC) through cell free DNA and a circulating tumor cells (CTC)-derived signature [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 P5-17-02.

Abstract PD4-05: Patterns of genomic alterations in ER-positive advanced breast cancer patients treated with CDK4/6 inhibitors

Background:Cyclin D kinase inhibitors (CDK-is) have shown clinical efficacy in estrogen receptor (ER)-positive metastatic breast cancer (MBC) when combined with aromatase inhibition or estrogen receptor (ER) antagonism. Despite the benefit of this approach, clinical resistance develops sometimes early in the treatment without any response to endocrine therapy (primary endocrine resistance) or after initial response (secondary resistance) in all patients in the metastatic setting and the molecular basis for this resistance are still largely unknown. We evaluated the pattern of genomic alterations in circulating cell-free tumor DNA (ctDNA) analysis of metastatic breast cancer patients with ER-positive tumors treated with palbociclib combined with either letrozole or fulvestrant and progressing during therapy.

Methods: We conducted a retrospective study of patients with ER-positive MBC who had longitudinal assessment of their disease by ctDNA analysis. The plasma-based assay was performed utilizing Guardant360 (Guardant Health, CA), a digital NGS technology to sequence a panel of > 50 cancer genes. After tabulating number of genomic alterations detected for every patient at baseline and after CDK-i therapy, analysis was performed to identify molecular profile changes in the entire population and in individuals with early progression of disease (<6 months).

Results: We analyzed data of 15 ER-positive MBC patients: 8 patients received fulvestrant/palbociclib and 7 received letrozol/palpociclib. The most common mutations before CDK-i therapy were: PIK3CA (16%), TP53 (16%), ESR1 (13%), KIT (9%), EGFR (3%), APC (3%), ERBB2 (3%), MYC (3%), PTEN (3%), RB1 (3%). After therapy with CDK-i the pattern of mutations showed stable and persistent incidence of PIK3CA, TP53 and ESR1. However, new mutations where identified: FGFR1 (6%), IDH (2%), BRCA1 (2%), BRCA2 (2%), CCNE (2%), CCND1 (2%), RAF (2%), AR (2%), ALK(2%). Also, the pattern of gene amplifications presented an increased rate of MYC and FGFR1 amp. Patients with progression of disease before 6 months of CDK-i therapy presented baseline higher number and variation of mutations compared to patients with disease controlled beyond 6 months of therapy.

Conclusion: Longitudinal assessment with ctDNA analysis suggest that a genomic alteration landscape consisting of persistent detection of driver and acquired mutations along with emergent new abnormalities in regulatory genes could potentially be related to primary or secondary resistance to CDK-Is in ER+ MBC patients. Future investigation of these alterations should be conducted.

Citation Format: Cruz MR, Limentani K, Taxter T, Santa-Maria CA, Behdad A, Gradishar WJ, Nagy RJ, Cristofanilli M. Patterns of genomic alterations in ER-positive advanced breast cancer patients treated with CDK4/6 inhibitors [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 PD4-05.

Abstract P2-02-21: The utility and correlation of circulating tumor cells (CTCs) and cell-free circulating tumor DNA (ctDNA) based on HER2 positivity

Background:

CTCs are well-established prognostic and predictive biomarkers for metastatic breast cancer (MBC) and other solid tumors. ctDNA is emerging as a quantitative blood-based biomarker for monitoring genomic alterations and disease progression. We evaluated the clinical utility and correlation of these liquid biopsy molecular tools in a cohort of MBC patients.

Methods:

CTC samples were obtained from an ongoing, prospective study of blood based prognostic biomarkers for breast cancer patients. At this time, 71 patients and 98 total samples have been collected. CTC enumeration was performed using the CellSearchTM platform (Menarini, IT). Within this cohort, MBC patients who had ctDNA testing were identified. ctDNA testing was performed using Guardant360TM (Guardant Health, CA), a digital next-generation sequencing technology. Two groups were analyzed: (1) HER2-negative patients with CTC ≥ 5 in 7.5 ml of blood (2) HER2-positive patients who had been treated with HER2 targeted therapy.

Results:

22 samples (N=16 patients) were found with CTC ≥ 5 (range 8-904) and concurrent ctDNA testing (median timeframe between collection 0 days, range 0-42 days). There was a significant association between number of CTCs and the total number of genomic alterations detected in ctDNA (paired two sample t-test, p=0.012). In addition, CTC enumeration was significantly correlated with somatic alteration burden of the dominant clone (paired two sample t-test, p=0.023). The most common alterations detected in the blood were TP53 (55% of patients, 18 total mutations), PIK3CA (41% of patients, 15 total mutations), and ESR1 (32% of patients, 14 total mutations). For patients with HER2 positivity receiving HER2-targeted therapies (N=16 samples from 11 patients), only 18.8% of samples had detectable CTCs (all less than 5) as compared to 75.0% of samples with detectable ctDNA alterations. In N=12 samples with detectable ctDNA mutations, mean number of genomic alterations was 4.4 with mean somatic mutation burden of 2.95%.

 CTCs detectedctDNA detectedCTC ≥ 5Mean number of ctDNA alterations+Mean somatic alteration burden+HER2- (only cases with CTC ≥ 5)100% (22/22)100% (22/22)100%6.716.1%HER2+ (all cases)18.8% (3/16)75.0% (12/16)0%4.42.95%+excludes ctDNA samples without detected genomic alterations

Conclusions:

In HER2-negative MBC patients, CTC enumeration was significantly correlated with the number of ctDNA genomic alterations and somatic alteration burden, indicating the potential for ctDNA as a prognostic, quantitative biomarker of tumor burden. In patients with HER2 positivity, ctDNA may be a more sensitive liquid biopsy tool given the rarity of detecting CTCs detection in this population using the CellSearchTM system. In HER2-positive patients, consideration of size-dependent selection of CTCs using filtration of cells that have undergone epithelial-mesenchymal transition may improve detection in this subgroup.

Citation Format: Davis AA, Zhang Y, Behdad A, Taxter T, Strickland K, Santa-Maria C, Flaum L, Cruz MR, Platanias LC, Gradishar WJ, Cristofanilli M. The utility and correlation of circulating tumor cells (CTCs) and cell-free circulating tumor DNA (ctDNA) based on HER2 positivity [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 P2-02-21.

Abstract OT1-03-06: Phase IB/II clinical trial to evaluate safety and efficacy of tucatinib in combination with palbociclib and letrozole in patients with hormone receptor positive and HER2-positive metastatic breast cancer

Breast cancers overexpressing HER2-oncogene and hormone receptors (HR) represent therapeutic challenge because of a bi-directional cross-talk between HR and HER2 pathways leading to tumor progression and drug resistance. There is a strong rationale for evaluation of novel targeted drug combinations in this breast cancer subtype.

We designed a phase IB /II clinical trial to test the combination of novel oral HER2 small molecule inhibitor tucatinib with CDK4/6 inhibitor palbociclib and aromatase inhibitor letrozole in patients with HR+/HER2+ metastatic breast cancer (NCT03054363). In addition to the rationale for the synergy of targeting HR, HER2 and CDK4/6 pathways simultaneously in this disease setting and its potential for anti-tumor efficacy, we propose this novel combination of three oral agents, if well tolerated, will be highly patient-centered as an effective non-chemotherapy based regimen for treatment of HR+/HER2+ breast cancer.

This multicenter clinical trial is conducted through the Academic Breast Cancer Consortium (ABRCC), with the University of Colorado Cancer Center as the lead site.

Target enrollment: 40 patients (20 patients in phase IB and 20 patients in phase II part).

Main inclusion criteria:

1. HR+/HER2+ locally advanced unresectable / metastatic breast cancer

2. Measurable or evaluable disease. Bone only disease is allowed.

3. Subjects without brain metastases are eligible; subjects with untreated asymptomatic CNS metastases not needing immediate local therapy, and subjects with stable brain metastases previously treated with radiation therapy or surgery are eligible

4. ECOG 0-1

5. Postmenopausal women, or premenopausal women on ovarian suppression

6. Prior treatments:

- At least two approved HER2-targeted agents (trastuzumab, pertuzumab, or TDM-1) at any time in the course of the disease

- At least 1 line of HER2-targeted therapy in the metastatic setting (with the exception of asymptomatic subjects with oligometastatic or bone / soft tissue only disease who, on investigator opinion, are appropriate for a front line single agent anti-endocrine therapy per NCCN guidelines)

- Up to 2 lines of prior endocrine therapy in the metastatic setting are allowed

7. Adequate organ and marrow function

Main exclusion criteria:

1. Previously treated progressing brain metastases

2. Brain metastases and contraindications to undergo contrast brain MRI

3. Toxicities of prior cancer therapies that have not resolved to grade 1 or less, except peripheral neuropathy, which must have resolved to grade 2 or less, and alopecia

4. Previous treatment with EGFR or HER2 tyrosine kinase inhibitors or CDK4/6 inhibitors

5. Systemic anti-cancer therapy or radiation within 2 weeks of the first dose of study drugs

6. Active bacterial, fungal or viral infections, hepatitis B, C, or HIV

7. Clinically significant cardio-vascular disease

Primary objectives:

- Phase IB: safety and tolerability of combination therapy

- Phase II: efficacy by PFS

Exploratory assessment of biomarkers of resistance and response will be performed in the blood and biopsy samples

Study contact: Elena Shagisultanova, MD, PhD, elena.shagisultanova@ucdenver.edu

Citation Format: Shagisultanova E, Diamond J, Stopeck A, Pusztai L, O'Regan R, Gradishar W, Brown-Glaberman U, Chalasani P, McSpadden T, Borakove M, Shedin T, Kabos P, Borges V. Phase IB/II clinical trial to evaluate safety and efficacy of tucatinib in combination with palbociclib and letrozole in patients with hormone receptor positive and HER2-positive metastatic 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 OT1-03-06.

Veliparib with temozolomide or carboplatin/paclitaxel versus placebo with carboplatin/paclitaxel in patients with BRCA1/2 locally recurrent/metastatic breast cancer: randomized phase II study

Background

Homologous recombination defects in BRCA1/2-mutated tumors result in sensitivity to poly(ADP-ribose) polymerase inhibitors, which interfere with DNA damage repair. Veliparib, a potent poly(ADP-ribose) polymerase inhibitor, enhanced the antitumor activity of platinum agents and temozolomide in early phase clinical trials. This phase II study examined the safety and efficacy of intermittent veliparib with carboplatin/paclitaxel (VCP) or temozolomide (VT) in patients with BRCA1/2-mutated breast cancer.

Patients and methods

Eligible patients ≥18 years with locally recurrent or metastatic breast cancer and a deleterious BRCA1/2 germline mutation were randomized 1 : 1 : 1 to VCP, VT, or placebo plus carboplatin/paclitaxel (PCP). Primary end point was progression-free survival (PFS); secondary end points included overall survival (OS) and overall response rate (ORR).

Results

Of 290 randomized patients, 284 were BRCA+, confirmed by central laboratory. For VCP versus PCP, median PFS was 14.1 and 12.3 months, respectively [hazard ratio (HR) 0.789; 95% CI 0.536-1.162; P = 0.227], interim median OS 28.3 and 25.9 months (HR 0.750; 95% CI 0.503-1.117; P = 0.156), and ORR 77.8% and 61.3% (P = 0.027). For VT (versus PCP), median PFS was 7.4 months (HR 1.858; 95% CI 1.278-2.702; P = 0.001), interim median OS 19.1 months (HR 1.483; 95% CI 1.032-2.131; P = 0.032), and ORR 28.6% (P < 0.001). Safety profile was comparable between carboplatin/paclitaxel arms. Adverse events (all grades) of neutropenia, anemia, alopecia, and neuropathy were less frequent with VT versus PCP.

Conclusion

Numerical but not statistically significant increases in both PFS and OS were observed in patients with BRCA1/2-mutated recurrent/metastatic breast cancer receiving VCP compared with PCP. The addition of veliparib to carboplatin/paclitaxel significantly improved ORR. There was no clinically meaningful increase in toxicity with VCP versus PCP. VT was inferior to PCP. An ongoing phase III trial is evaluating VCP versus PCP, with optional continuation single-agent therapy with veliparib/placebo if chemotherapy is discontinued without progression, in this patient population.

Clinical trial information

NCT01506609.

A pilot study of cabergoline for the treatment of metastatic breast cancer

PURPOSE

The prolactin (PRL) receptor is over-expressed in breast cancer, and pre-clinical data indicate that it contributes to breast oncogenesis. Cabergoline is a potent dopamine receptor agonist of D2 receptors and has a direct inhibitory effect on pituitary PRL secretion.

METHODS

A phase II study of cabergoline in patients with metastatic breast cancer was conducted. The primary end point of the study was to determine the clinical benefit rate (CBR) at 2 months. Eligible patients had tumors of any receptor status with no limit of prior lines of therapy. Measurable and unmeasurable diseases were allowed. Cabergoline 1 mg orally, twice weekly (1 cycle = 4 weeks) was given until disease progression or unacceptable toxicity. PRL receptor immunohistochemical staining was performed on available baseline tumor tissue; serial serum PRL levels were assessed.

RESULTS

Twenty women were enrolled; 18 were evaluable for CBR. Tumor receptor status was distributed as follows: HR-any/HER2+ 2(10%), HR+/HER2- 18 (90%). The CBR was 33% (6/18), median progression free survival was 1.8 months, and median overall survival was 10.4 months. Two patients experienced disease control for over 12 months. Most common treatment-related adverse events were nausea (30%), fatigue (25%), and elevation in alkaline phosphatase (15%). Nine patients had baseline tissue for analysis; there was no association between baseline tumor PRL receptor expression and clinical benefit (p = 0.24). Change in serum PRL level and response were not correlated after 2 months of treatment (p = 0.64).

CONCLUSION

Cabergoline was well tolerated, and while the ORR was low, a small subset of patients experienced extended disease control.

Meta-analysis of selected toxicity endpoints of CDK4/6 inhibitors: Palbociclib and ribociclib

PURPOSE

Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors such as palbociclib and ribociclib are associated with distinct adverse effects (AEs) compared to other targeted therapies. This meta-analysis of clinical trials summarizes these agents' toxicity profile.

METHODS

A librarian-guided literature search was conducted in March of 2017. The trials needed to have at least one of the study arms consisting of palbociclib or ribociclib monotherapy at currently FDA approved dose regimens. Heterogeneity across studies was analyzed using I² statistics. Data were analyzed using random effects meta-analysis for absolute risks.

RESULTS

Seven randomized trials and 1,332 patients were included in our meta-analysis. There was evidence of significant heterogeneity between studies for serious AEs but not for death. The pooled absolute risk (AR) for all-causality serious AEs and treatment-related death were 16% and 0%, respectively. Patients treated with CDK 4/6 inhibitors had an AR of grade 3/4 neutropenia of 61%; neutropenic fever and infections were rare (1% and 3%, respectively). Grade 3/4 nausea, vomiting, and rash were rare. There was no significant correlation between age of patients at study entry and the risk of grade 3/4 neutropenia.

CONCLUSION

Treatment with CDK 4/6 inhibitors is well tolerated and associated with a low risk of treatment-related deaths. There is an increased AR of grade 3/4 neutropenia but a low AR of associated infections.

Systematic analysis of early phase clinical studies for patients with breast cancer: Inclusion of patients with brain metastasis

PURPOSE

This systematic review aims to better define the limitations and patterns with which patients with MBC and CNS metastasis are enrolled into early phase developmental therapeutics trials.

METHODS

In June 2016, PubMed search was conducted using the following keywords: "Breast cancer". Drug-development phase 1, phase 2 or phase 1/2 trials for patients with MBC were included. Multiple-histology trials and trials without an efficacy endpoint were excluded.

RESULTS

In total, 1474 studies were included; Inclusion criteria for 423 (29%) allowed for CNS metastasis, 770 (52%) either excluded or did not document eligibility of patients with CNS disease. Trials accruing patients with HER2-positive MBC and including targeted therapies had higher odds of allowing for patients with CNS disease (adjusted OR 1.56, 95% CI 1.08-2.2.6; p=0.019 and 1.49, 95% 1.08-2.06; p=0.014, respectively). There were also higher odds of accrual of patients with CNS involvement into clinical trials over time (odds ratio=1.10, 95% CI 1.07-1.12; p<0.0001).

CONCLUSION

Most published early phase clinical trials either did not clearly document or did not allow for accrual of patients with CNS disease. Early phase trials with targeted agents or enrolling HER2+ MBC had higher odds of permitting CNS metastases.

Abstract PD1-02: Circulating tumor DNA (ctDNA): A real-time application of precision medicine to the management of metastatic breast cancer (MBC)

Background: Molecular diagnostic, in particular next-generation sequencing (NGS) technologies, improved the detection of actionable mutations (muts) in MBC at baseline and recurrence. We evaluated the ability of ctDNA to detect molecular abnormalities, monitor disease progression and predict outcome.

Methods: We conducted a retrospective study of 91 patients (pts) with locally advanced and MBC, who had longitudinal assessment of their disease by ctDNA analysis. The plasma-based assay was performed utilizing Guardant360 (Guardant Health, CA), a digital NGS technology to sequence a panel of &gt; 50 cancer genes. After tabulating number of muts and quantification of overall ctDNA detected for every patient at baseline, a receiver operating characteristic (ROC) analysis was performed to identify the best cut-offs that separated the pts who had a disease progression from those who hadn't, and the patients who died from those still alive. The overall survival (OS) analysis has been performed using Kaplan-Meier curves.

Results: 84 pts (92%) had stage IV cancer. 63% cases were ER+, 27% HER2+, 29% TNBC. 277 blood samples were collected and 84% had muts. 65% of the pts had serial samples. The average number of alterations detected in each sample was 3 (0-27) and the average ctDNA fraction detected was 4.5% (0-88.2%). The most common alterations were: TP53 (52%), PIK3CA (40%), ERBB2 (20%), NOTCH1 (15.5%), APC (14%), MET (13%). 16 pts (19%) were initiated on a targeted therapy based on ctDNA test results. At the time of analysis 36 pts (39.6%) were dead, 55 (60.4%) were currently alive. PFS was 5.2 months (ms) and OS was 21.5 ms. A statistically significant difference in PFS and OS by log rank test was found between % ctDNA at baseline &lt; 0.5 versus ≥ 0.5 (p = 0.003 and p = 0.012, respectively) and number of muts at baseline &lt; 2 versus ≥ 2 (p = 0.059 borderline and p = 0.0015). Moreover, a statistically significant association by Fisher's exact test was found between the number of alterations and the % ctDNA detected in the baseline sample (% of pts with muts ≥ 2 was 19% when % ctDNA &lt; 0.5%, versus 85% when % ctDNA ≥ 0.5%; p &lt; 0.0001).

PFS (ms) p = 0.059 (log rank test)Muts &lt; 2 (n = 32)Muts ≥ 2 (n = 58)658%40%1230%13%1821%6%24--PFS(ms) p = 0.003 (log rank test)% ctDNA &lt; 0.5(n = 27)% ctDNA ≥ 0.5(n = 60)665%39%1241%10%1823%6%24--

OS(ms) p = 0.002 (log rank test)Muts &lt; 2(n = 32)Muts ≥ 2(n = 57)697%66%1288%51%1888%42%24-29%OS(ms) p = 0.012 (log rank test)% ctDNA &lt; 0.5(n = 27)% ctDNA ≥ 0.5(n = 59)696%69%1290%55%1885%48%24-35%

Conclusions: ctDNA liquid biopsy provides a real-time, quantitative NGS-based assessment of MBC which is useful for treatment planning, disease monitoring and prognostic evaluation. Future prospective studies should consider the use of ctDNA for molecular and prognostic stratification.

Citation Format: Rossi G, Austin LK, Nagy RJ, Rademaker AW, Gradishar WJ, Santa-Maria CA, Curry-Edwards RL, Jain S, Flaum LE, Lima Barros Costa R, Zagonel V, Platanias LC, Giles FJ, Talasaz A, Cristofanilli M. Circulating tumor DNA (ctDNA): A real-time application of precision medicine to the management of metastatic breast cancer (MBC) [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 PD1-02.

Abstract OT1-02-07: SOPHIA: A phase 3, randomized study of margetuximab plus chemotherapy vs trastuzumab plus chemotherapy in the treatment of patients with HER2+ metastatic breast cancer

Background: Despite significant advances in targeted therapy, HER2+ metastatic breast cancer (MBC) remains incurable. Ideal treatment includes pertuzumab and trastuzumab in combination with a taxane in the first line setting, followed by ado-trastuzumab emtansine on progression. Optimal treatment regimens in the third and greater line of therapy are not defined, but continued anti-HER2 therapy is recommended. Margetuximab is a Fc-modified monoclonal antibody to HER2 that recognizes the same epitope on HER2 as does trastuzumab, with similar affinity. Margetuximab demonstrates increased affinity to the activating CD16A Fc-receptor found on NK cells and macrophages and decreased affinity to the inhibitory CD32B receptor compared to trastuzumab. In vitro studies showed enhanced antibody dependent cell-mediated cytotoxicity compared to trastuzumab. In a Phase 1 dose escalation and expansion trial, margetuximab showed single agent clinical activity against HER2+ tumors in patients previously treated with trastuzumab and other anti-HER2 agents. Methods: SOPHIA is a randomized, prospective study testing the hypothesis that margetuximab plus chemotherapy (CTX) is more effective than trastuzumab plus CTX in patients previously treated for HER2+ MBC. Sequential primary endpoints are centrally assessed progression free survival (PFS) and overall survival (OS). The study size of 530 patients is determined to have 80% power to detect a hazard ratio for OS of 0.75. Secondary endpoints are investigator assessed PFS and centrally assessed overall response rate. Eligibility includes prior treatment with trastuzumab, pertuzumab, and ado-trastuzumab emtansine; no more than 3 prior lines of therapy in the metastatic setting; prior demonstration of HER2+ status at a local reference laboratory; and absence of active brain metastases. Eligible patients are randomized 1:1 to receive CTX (physician's choice: capecitabine, eribulin, gemcitabine or vinorelbine) plus either margetuximab or trastuzumab until disease progression or toxicity. Antibody may be continued after stopping CTX in patients with responding or stable disease. Progress to date: The trial was initiated July 2015 and is ongoing in the US and Europe with planned expansion to Korea and Israel. ClinicalTrials.gov Identifier NCT02492711; Eudract 2015-000380-13.

Citation Format: Rugo HS, Pegram MD, Gradishar WJ, Cortes J, Curigliano G, Hong S, Wigginton JM, Lechleider RJ, Cardoso F. SOPHIA: A phase 3, randomized study of margetuximab plus chemotherapy vs trastuzumab plus chemotherapy in the treatment of patients with HER2+ metastatic breast cancer [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 OT1-02-07.

Abstract P1-05-06: Estrogen receptor 1 (ESR1) mutations in circulating tumor DNA (ctDNA): A guide to the management of advanced breast cancer (ABC)

Background: Estrogen receptor (ER)-α is expressed in about 70% of breast cancers and drugs that target the receptor function, selective estrogen receptor modulators (SERM) and aromatase inhibitors (AIs) represent the standard of care for patients (pts) with ER+ breast cancer. Nevertheless, prolonged exposure to endocrine therapy may result in acquired resistance and subsequent progression of disease. Recent evidence showed that activating mutations (muts) in the ligand-binding domain of ER-α occur in approximately 20% of pts exposed to endocrine therapies and those genomic abnormalities may represent the driver of endocrine resistance. In this context, ctDNA provides a non-invasive source for real-time next generation sequencing (NGS) studies, in order to understand the biology of ABC and guide and monitor treatment.

Methods: We conducted a retrospective review of 91 pts with ABC, including 57 pts with ER+ tumor, who had longitudinal assessment of their disease by ctDNA analysis. At the time of baseline sampling, 50/57 pts had stage IV cancer. The total number of blood samples collected was 184. 38 (67%) pts had serial samples. The average number of samples for each pt was 3 (range 1-7). The plasma-based assay was performed utilizing Guardant360 (Guardant Health, CA), a digital NGS technology to sequence a panel of &gt; 50 cancer genes.

Results: Among the ER+ subgroup (57 pts), we identified 11 pts (19%) harboring ESR1 muts in ctDNA. All 11 pts had metastatic disease: 2 (18%) had bone metastases, 2 (18%) had visceral metastases, 7 (64%) had both sites of disease. The median age was 55 years (range 33-73). 5 pts had inflammatory breast cancer. The most common ESR1 muts were: Y537S (6/11, 55%), D538G (4/11, 36%) and Y537N (3/11, 27%). 7 pts carried polyclonal muts. At the time of testing, 10 pts had already failed at least 1 line of endocrine therapy (average 2, range 1-5), including 6 pts that had received a fulvestrant-containing regimen, 8 pts ≥ 1 line of AIs. After the mut detection, 5 pt were on endocrine therapy and 4 pts were started on/continued chemotherapy. ESR1 muts disappeared in 2 pts (fulvestrant-palbociclib and chemotherapy respectively) who achieved stable disease as best response. Three pts continued to harbour muts and then progressed (one died). 2 pts had tissue NGS and ESR1 mut was not identified. Progression free survival and overall survival were 8 months (ms) and 21.5 ms in ESR1+ subpopulation versus 6.2 ms and 22.2 ms in the ESR1- pts (p = 0.78 and p = 0.97, respectively). At the time of analysis 5 pts were dead, 6 were currently alive.

  ESR1+ (n. pts) ESR1- (n. pts) Pts (total n.)1146 Previous chemotherapies11 (100%)31 (67%) Previous fulvestrant-containing regimens6 (54%)20 (43%) Previous AIs ± targeted therapy8 (73%)27 (59%)

Conclusions: We observed that ESR1 muts, a known driver of endocrine resistance, occurs at a high frequency in heavily pre-treated estrogen receptor positive ABC. Blood-based diagnostics can be used to identify ESR1 muts sometimes not detected by tissue-based sequencing of the metastatic lesions indicating tumor heterogeneity and allowing dynamic monitoring of ABC.

Citation Format: Rossi G, Lima Barros Costa R, Nagy RJ, Rademaker AW, Gradishar WJ, Santa-Maria CA, Curry-Edwards RL, Jain S, Flaum LE, Zagonel V, Platanias LC, Giles FJ, Talasaz A, Cristofanilli M. Estrogen receptor 1 (ESR1) mutations in circulating tumor DNA (ctDNA): A guide to the management of advanced breast cancer (ABC) [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 P1-05-06.

Abstract OT3-01-01: A phase II study of PD-L1 and CTLA-4 inhibition and immunopharmcogenomics in metastatic breast cancer

Background

A hallmark of cancer is its ability to evade the immune system, however, it can be harnessed to detect and destroy cancer cells through inhibition of immune checkpoints such as CTLA-4 and PD-L1. This strategy has complementary and non-redundant mechanisms resulting in immune activation and antitumor synergy; progression free survival benefit has already been demonstrated in melanoma. A critical barrier in developing immunotherapies, however, is the identification of predictive biomarkers of response to therapy. Immunopharmacogenomic biomarkers, such as mutational burden, neoantigen profiles, and T cell receptor sequencing will elucidate the molecular interface between cancer and immune system, and may predict those most likely to benefit.

Methods

A single arm Phase II study was designed to determine the efficacy of PD-L1 and CTLA-4 inhibition and effects on immunopharmacogenomic dynamics in patients with metastatic breast cancer. The primary endpoint of this proposal is to investigate the response rate of the PD-L1 inhibitor, durvalumab, and the CTLA-4 inhibitor, tremelimumab, in metastatic breast cancer; secondary endpoints will examine the T cell receptor repertoire clonality, tumor mutational burden and neoantigen profiles. A total of 30 patients will be enrolled and treated with durvalumab 1500mg IV and tremelimumab 75mg IV monthly for 4 doses, then durvalumab 750mg every 2 weeks for 18 doses to complete 1 year of therapy with the option to renew therapy for an additional year; biopsies and blood at baseline and 2 months will be collected to assess immunopharmacogenomic biomarkers. Patients are eligible if they have triple negative or ER-positive breast cancer and have progressed on at least one line of chemotherapy and standard endocrine therapy if applicable. This is the first study to investigate immunopharmacogenomic biomarkers of response to dual checkpoint blockade in patients with metastatic breast cancer.

Citation Format: Santa-Maria CA, Jain S, Flaum L, Park J-H, Kato T, Gross L, Uthe R, Tellez C, Stein R, Rademaker A, Gradishar WJ, Nakamura Y, Giles FJ, Cristofanilli M. A phase II study of PD-L1 and CTLA-4 inhibition and immunopharmcogenomics in metastatic breast cancer [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 OT3-01-01.

Abstract P6-11-03: A phase 2 open-label study of lucitanib in patients (pts) with FGF aberrant metastatic breast cancer (MBC)

BACKGROUND: Lucitanib is a potent, oral antiangiogenic tyrosine kinase inhibitor of Vascular Endothelial Growth Factor Receptors 1-3 (VEGFR1-3), Platelet-Derived Growth Factor Receptors alpha and beta (PDGFRα/β), and Fibroblast Growth Factor Receptors 1-3 (FGFR1-3). FGF aberrancies (amplification of FGFR1,or 11q[amplicon containing FGF ligands 3, 4, and 19]), are genomic alterations observed in over 20% of breast cancer pts and promote cancer proliferation and survival.

METHODS: MBC pts who had received at least 1 metastatic line of therapy were randomized 1:1 to 10 or 15 mg QD of lucitanib. Stratification was based on local assessment of FGF aberrancy; pts with both FGFR1 and 11q-amplified tumors were stratified as FGFR1 amplified. Central confirmation of FGFR1 or 11q amplification was done using Abbott FISH probes (FGFR1 or 11q copy number ≥ 6 and a ratio of FGFR1 or 11q to centromere ≥ 2). Investigator-assessed progression-free survival (PFS) was the primary endpoint. Secondary endpoints included objective response rate (ORR) per RECIST 1.1, disease control rate (DCR), duration of response (DR), and incidence of treatment-emergent adverse events (TEAE).

RESULTS: Enrollment completed in 3/2016; 178 pts that received at least 1 dose of lucitanib are included in this analysis (baseline characteristics in Table 1). Due to grade 3 hypertension in the 15 mg group (46% vs 37% in 10 mg group), enrollment to the 15 mg group was halted. Overall, most pts (97%) experienced at least 1 TEAE, with the most frequently (≥ 30%) occurring events being hypertension (73%), fatigue (48%), nausea (43%), hypothyroidism (40%), and headache (33%). Grade ≥ 3 TEAEs occurred in 66% of pts, with hypertension as the most frequent event (40%) followed by proteinuria and hyponatremia (both 6%). AEs were manageable with dose interruption or reduction, with approximately 8% of pts ending treatment due to an AE. Current median PFS is 3.5 mos (95% CI 2.8-4.6; range 0.62-12.95) and 2.6 mos (95% CI 1.8-2.9; range 0.82-18.87) respectively for the 10 mg and 15 mg treatment groups. No differences in clinical activity were observed by treatment group, FGF aberrancy, hormone receptor or HER2 status. Of the 168 evaluable pts, confirmed ORR was 3%; overall DCR was 27% (32% for pts in the 10 mg group compared to 20% for the 15 mg group); overall mean (standard deviation) DR of 3.3 (1.8) mos.

Baseline Characteristics 10 mg QD15 mg QD N=109N=69Age (years)Median5653Range27-8227-80SexFemale109 (100%)67 (97%)Male02 (3%)ECOG PSmissing5 (5%)2 (3%)051 (47%)30 (43%)153 (49%)37 (54%)Number of prior anticancer therapies in the metastatic setting&gt; 332 (29%)21 (30%)3-648 (44%)32 (46%)&gt; 629 (27%)16 (23%)Endocrine/HER2 statusmissing7 (6%)1 (1%)ER+ or PR+74 (68%)50 (73%)HER2+12 (11%)7 (10%)TNBC16 (15%)11 (16%)FGFR aberrancyFGFR1 amplified54 (49%)29 (42%)11q amplified31 (28%)24 (35%)FGFR1 and 11q amplified13 (12%)9 (13%)FGFR1 and 11q non-amplified11 (10%)7 (10%)

CONCLUSION: At 10 mg QD, lucitanib has modest activity with manageable toxicity in this heavily pretreated pt population. Future clinical development for lucitanib may focus on alternative biomarkers to identify sensitive tumors and rational combinations with other anti-cancer drugs.

Citation Format: Mayer IA, Arteaga CL, Nanda R, Miller KD, Jhaveri K, Brufsky AM, Rugo H, Yardley DA, Vahdat LT, Sadeghi S, Audeh MW, Rolfe L, Litten J, Knox A, Raponi M, Tankersley C, Isaacson J, Wride K, Morganstern DE, Vogel C, Connolly RM, Gradishar WJ, Patel R, Pusztai L, Abu-Khalaf M. A phase 2 open-label study of lucitanib in patients (pts) with FGF aberrant metastatic breast cancer (MBC) [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 P6-11-03.

Elevated incidence of fractures in women with invasive breast cancer

This study evaluates the incidence of bone fractures in women with BC.We found that women with invasive breast cancer are at an increased risk for bone fractures, with fractures most commonly occurring at lower extremity and vertebral sites. The risk is further increased in women undergoing cancer therapy.

INTRODUCTION

Bone loss and fractures in breast cancer have generally been attributed to aromatase inhibitor use. This study assessed the incidence of fractures after invasive breast cancer diagnosis and evaluated bone density and FRAX risk calculation at time of fracture occurrence.

METHODS

Retrospective cohort study of women with invasive breast cancer [June 2003-December 2011] who participated in an academic hospital based genetic biobank. Demographic and clinical characteristics were abstracted from the electronic medical record (EMR).

RESULTS

A total of 422 women with invasive breast cancer were assessed; 79 (28 %) sustained fractures during the observation period; fractures occurred at multiple skeletal sites in 27 cases (116 fractures). The incidence of fractures was 40 per 1000 person-years. Women who sustained fractures were mostly white and had a family history of osteoporosis (36.9 %, p = 0.03) or history of a prior fracture (6/79, p = 0.004). Fractures occurred 4.0 years (range 0-12 years) after cancer diagnosis. Fracture cases had femoral neck bone mineral density (BMD) of 0.72 + 0.12 g/cm(2), T-score of -1.2, that is, within the low bone mass range. Fractures most commonly occurred in lower extremities, vertebral, and wrist sites. Hip fractures accounted for 11 % of fractures, occurring at a median age of 61 years.

CONCLUSIONS

Fractures occur shortly after commencing cancer therapy. Rapid bone loss associated with cancer therapy may precipitate fractures. Fractures occur at relatively higher BMD in BC. Occurrence of fractures in invasive breast cancer raises the possibility of cancer-induced impairment in bone quality.

Emerging approaches for treating HER2-positive metastatic breast cancer beyond trastuzumab

Because metastatic breast cancer (MBC) is incurable in most cases, the goals of treatment are improvement in quality of life, management of symptoms, and prolonged survival. The human epidermal growth factor receptor 2 (HER2) is overexpressed in up to 30% of breast tumors, and before the development of HER-targeted therapy, HER2 positivity was predictive of poorer clinical outcomes. Trastuzumab and pertuzumab (anti-HER2 monoclonal antibodies), lapatinib (a small molecule inhibitor of HER2 and the epidermal growth factor receptor [EGFR]) are approved for treating HER2-positive MBC in the United States. Although trastuzumab plus chemotherapy is currently regarded as the first-line standard of care for HER2-positive MBC, it is not without shortcomings; these include its association with certain adverse events (e.g. cardiotoxic effect) and development of resistance. A number of investigational agents that target HER2 and other members of that receptor family are in clinical development for patients with HER2-positive MBC whose disease has progressed on trastuzumab. In addition, in an effort to overcome treatment resistance, clinical trials are evaluating combination therapy (investigational HER-targeted agents with trastuzumab or lapatinib). This review discusses recently completed and ongoing phase II and III clinical trials of investigational HER-targeted agents in the setting of trastuzumab-progressive, HER2-positive MBC.

Abstract P5-03-11: Possible role for cancer stem cells: results from a pilot neoadjuvant trial of HER-2 positive breast cancer patients treated with a combination of (Nab)-paclitaxel and lapatinib

Background: Lapatinib, a dual kinase inhibitor against both epidermal growth factor (EGFR) and human epidermal factor 2 (HER-2) and nanoparticle albumin bound (nab) paclitaxel was recently used by our group in a pilot study of early stage HER-2 positive breast cancer. We reported that the combination was well tolerated and showed good efficiency in this patient group. Cancer stem cells were recently identified in solid tumors including breast carcinomas. These tumor initiating stem cells are reported to be increased in HER-2 positive breast cancers. Lapatininb is postulated to reduce the percentage of breast cancer stem cells following HER-2 inhibition. This study aimed to investigate such an effect in this patient population of early stage HER-2 positive breast cancer cases uniquely treated by a combination of nab-paclitaxel and lapatininb.

Design: 30 patients with stage I-III HER-2 positive breast cancer were treated in a neoadjuvant setting with lapatinib 1,000mg/day and nab-paclitaxel 260 mg/m2 every 2 weeks for 4 cycles. The expression of the stem cell markers aldehyde dehydroganase (ALDH1) (BD), CD24 and CD44 (both Santa Cruz Biotechnology) was assessed immunohistochemically in breast cancer specimens prior to treatment and at the time of definitive surgery. Staining was considered negative if &lt; or = 1%, and positive if &gt;1%.

Results: Of the 30 patients, 28 underwent surgery and were evaluated for pathologic response. Complete pathologic response (pCR) was observed in 5/28 (17.9%) of the patients. Of the 17 patients for whom pre-treatment material was available 13 (76.5%) were positive for ALDH1 expression and 4 (23.5%) were negative. Of the 22 patients with material available for testing at the time of surgery, 5 showed pCR, 3 were negative and 14 (63.6%) were positive for ALDH-A1 expression. The CD44+/CD24- phenotype was variable and showed no difference between groups.

Conclusions: 1. Combination of lapatinib and nab-paclitaxel resulted in a complete pathologic response in almost 1/5 of the HER-2 positive early stage breast cancer patients. 2. Overall, there is a reduction in the number cancer stem cells following neoadjuvant treatment with lapatinib and nab-paclitaxel. Our results support the hypothesis that lapatinib may have an effect in manipulating the numbers of cancer stem cells in patients with HER-2 positive breast cancer. Additional studies are currently under way to further characterize these findings.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-03-11.

Abstract P2-14-01: Fulvestrant vs exemestane for treatment of metastatic breast cancer in patients with acquired resistance to non-steroidal aromatase inhibitors – a meta-analysis of EFECT and SoFEA (CRUKE/03/021 & CRUK/09/007)

Background: Optimal endocrine treatment (trt) for post-menopausal women with ER+ advanced breast cancer (ABC) progressing on or following a non-steroidal (NS) aromatase inhibitor (AI) is unclear. The EFECT study showed no difference in efficacy between the steroidal antiestrogen fulvestrant (F) & steroidal AI exemestane (E) in this setting (HR = 0.96, 95%CI: 0.82, 1.13; p = 0.65). Pre-clinical data suggest F may be more effective in a low estrogen environment. SoFEA investigated F combined with anastrozole (F+A) in patients (pts) with acquired resistance to previous AI compared with F alone & F alone vs. E. The combination of F+A was no better than F (HR = 1.00, 95%CI: 0.83, 1.21; p = 0.98) nor F alone better than E (HR = 0.95, 95%CI: 0.79, 1.14; p = 0.56); the lack of added benefit for F+A is consistent with previous 1st-line studies that have assessed this combination versus A alone (FACT & SWOG-S0226).

Methods: SoFEA is a multi-center partially blinded randomized phase III study postmenopausal women were allocated to F plus A (F+A n=243), F plus placebo (n = 231) or E (n = 249). Similarly, EFECT is a randomized, double-blind, placebo controlled, multi-center phase III trial of F (n = 351) versus E (n = 342) in postmenopausal women (see table). However, given the differences in prior endocrine therapy/responsiveness within SoFEA & EFECT populations, an individual pt meta-analysis combining data from SoFEA & EFECT will be conducted enabling exploration of putative effects within specific pt subgroups to establish evidence in support, or not, of a pt subgroup sensitive to F at the dose used in these trials. Subgroups to be analysed include receptor status, visceral involvement, AI sensitivity, age, NSAI setting & time on NSAI.

Results: 723 pts (480 in F & E) were enrolled from 82 UK & 4 South Korean centers (03/2004-04/2010) in SoFEA. 693 pts were enrolled from 138 centers worldwide (08/2003-11/2005) in EFECT. Trt was well tolerated in both trials; serious adverse events were rare. The meta-analysis will be conducted in July 2012 & results presented.

Conclusion: Combining individual pt data from SoFEA & EFECT via meta-analysis will provide definitive clinical information on pt's response to F at the dose used in these studies, in particular whether certain pts with acquired resistance to NSAI do experience benefit of use of this antiestrogen as opposed to E.

Abstract P5-17-01: Bevacizumab (B) in the adjuvant treatment of breast cancer - first toxicity results from Eastern Cooperative Oncology Group trial E5103

Background: A previous feasibility trial (E2104 – Ann Oncol 23(2):331–7,2012) suggested incorporation of B into anthracycline-containing adjuvant therapy was feasible but ongoing cardiac monitoring was required to define the true impact of B on cardiac function.

Methods: Patients (pts) were assigned 1:2:2 to one of three treatment arms. In addition to doxorubicin and cyclophosphamide followed by weekly paclitaxel, patients received either placebo (Arm A – AC&gt;T) or B during chemotherapy (Arm B - BAC&gt;BT), or B during chemotherapy followed by B monotherapy (15 mg/kg q3wk) for an additional 10 cycles (Arm C – BAC&gt;BT&gt;B). Randomization was stratified and B dose adjusted for choice of AC schedule (classical q3wk − 15 mg/kg; dose dense(dd) q2 wk − 10 mg/kg). When indicated, radiation and hormonal therapy were administered concurrently with B (for Arm C pts). The primary cardiac endpoint was the incidence of clinically apparent cardiac dysfunction (CHF)defined as symptomatic decline in left ventricular ejection fraction (LVEF) to below the lower limit of normal (LLN) or symptomatic diastolic dysfunction as assessed by independent review. Cumulative toxicity data as of Jan 23, 2012 are presented.

Results: From 11.07 to 2.11, 4994 pts were enrolled. Median age was 52; 80% received ddAC. Chemotherapy associated toxicities including myelosuppression (Grade 4 neutropenia 16/20/19%) and neuropathy (Grade ≥ 3 8/8/8%) were similar across all arms. Grade ≥ 3 hypertension/thrombosis/proteinuria/hemorrhage was reported by 7/3/&lt;1/&lt;1% of B-treated pts. 99 pts developed CHF, most commonly reported at the post-AC or post-T evaluation. After a median follow-up of 26 months, the cumulative incidence of clinical CHF at 15 months from randomization in Arm A/B/C was 1.0/1.7/2.9% respectively. Median age of CHF pts was 57; median baseline LVEF of CHF pts was 60.

Abstract OT1-1-04: ALTERNATIVE: safety and efficacy of lapatinib (L), trastuzumab (T), or both in combination with an aromatase inhibitor (AI) for the treatment of hormone receptor-positive (HR+), human epidermal growth factor receptor 2 positive (HER2+) metastatic breast cancer

Background: Overexpression of the human epidermal growth factor receptor 2 (HER2) gene in breast cancer is associated with an aggressive phenotype, poor prognosis, and resistance to endocrine therapies. Of HER2+ patients, ∼50% are also hormone receptor-positive (HR+). For patients who are both HER2+ and HR+, combining the AI letrozole with the dual tyrosine kinase inhibitor L has been shown to improve outcomes compared with letrozole alone. The combination of L and T, a humanized monoclonal antibody-targeting HER2, has been shown to improve outcomes compared with L alone.

Trial design: The ALTERNATIVE study is a Phase III, randomized, open-label, multicenter trial, which will examine the efficacy of L/T/AI in combination versus T/AI alone. Patients will be randomized to 1 of 3 treatment arms: L 1000 mg po QD plus T (loading dose of 8 mg/kg followed by maintenance with 6 mg/kg IV q3w plus an AI po QD); T plus an AI; or L 1500 mg po QD plus an AI. Choices of AI include letrozole, anastrozole, or exemestane.

Eligibility criteria: Postmenopausal female patients with HER2+/HR+ metastatic breast cancer (MBC) who have received neo/adjuvant T and endocrine therapy, are treatment naïve for MBC, and are not candidates for chemotherapy.

Specific aims: The primary efficacy endpoint is overall survival (OS), defined as the time from randomization until death due to any cause, for L/T/AI compared with T/AI alone. Secondary efficacy objectives include comparisons of OS between T/AI and L/AI as well as between T/L/AI and L/AI in addition to comparisons of progression-free survival, overall response rate, time to response, and duration of response. The safety objective is to evaluate the safety and tolerability for all 3 treatment groups.

A 4-year recruitment is anticipated. More than 200 centers across 37 countries are planned; approximately 110 centers are currently open for enrollment.

Statistical methods: The study is powered to detect a 42% reduction in risk of death (hazard ratio=0.70) in patients who receive L/T/AI (median 28.5 months) versus T/AI (median 20 months) using a 1-sided test for superiority with α=0.025. The required number of total events to achieve a power of 80% is 249. Secondary comparisons are not powered and will be based on the intent-to-treat population.

Present and target accrual: Twenty-six (26) of 525 patients have been randomized. Patients who have participated in previous neo-/adjuvant trials including a T regimen are eligible, provided they meet all other inclusion criteria.

The study is currently recruiting patients, with an anticipated target accrual of 525 patients by March 2016.

Clinical trial registry number: NCT01160211

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr OT1-1-04.

Taxanes for the treatment of metastatic breast cancer

Taxanes have remained a cornerstone of breast cancer treatment over the past three decades, improving the lives of patients with both early- and late-stage disease. The purpose of this review is to summarize the current role of taxanes, including an albumin-bound formulation that enhances delivery of paclitaxel to tumors, in the management of metastatic breast cancer (MBC). Since the introduction of Cremophor EL-paclitaxel to the clinic in the mid-1990s, a substantial amount of investigation has gone into subjects such as formulation, dose, schedule, and taxane resistance, allowing physicians greater flexibility in treating patients with MBC. This review will also examine how the shrinking pool of taxane-naive patients, a result of the expansion of taxanes into the neoadjuvant and adjuvant settings, will respond to taxane retreatment for metastatic disease. Taxane treatment seems likely to continue to play an important role in the treatment of MBC.

The sequential use of endocrine treatment for advanced breast cancer: where are we?

BACKGROUND

Hormone receptor-positive advanced breast cancer is an increasing health burden. Although endocrine therapies are recognised as the most beneficial treatments for patients with hormone receptor-positive advanced breast cancer, the optimal sequence of these agents is currently undetermined.

METHODS

We reviewed the available data on randomised controlled trials (RCTs) of endocrine therapies in this treatment setting with particular focus on RCTs reported over the last 15 years that were designed based on power calculations on primary end points.

RESULTS

In this paper, data are reviewed in postmenopausal patients for the use of tamoxifen, aromatase inhibitors and fulvestrant. We also consider the available data on endocrine crossover studies and endocrine therapy in combination with chemotherapy or growth factor therapies. Treatment options for premenopausal patients and those with estrogen receptor-/human epidermal growth factor receptor 2-positive tumours are also evaluated.

CONCLUSION

We present the level of evidence available for each endocrine agent based on its efficacy in advanced breast cancer and a diagram of possible treatment pathways.

OT3-01-09: Phase 3 Trial Comparing Capecitabine in Combination with SorafenIb or Placebo for Treatment of Locally Advanced or Metastatic HER2−Negative Breast Cancer (RESILIENCE)

Sorafenib (SOR) is an oral multikinase inhibitor with antiangiogenic and antiproliferative activity. SOR is currently indicated for renal cell and hepatocellular carcinoma, with indications in other tumor types being explored. In a double-blind, randomized phase 2b screening trial (SOLTI-0701) in patients with advanced HER2−negative breast cancer (BC), the addition of SOR to capecitabine (CAP) showed a statistically significant improvement in the primary endpoint of progression-free survival (PFS) compared with placebo (PL)+CAP (median 6.4 vs 4.1 mo; hazard ratio=0.58; 1-sided P=0.0006). The combination was tolerable. Grade 3/4 adverse events were comparable between treatment arms with the exception of grade 3 hand-foot skin reaction/syndrome (HFSR/HFS) (44% in SOR+CAP vs 14% in PL+CAP). The SOLTI-0701 results indicate a potential role for the oral combination of SOR+CAP in the treatment of BC and support a phase 3 trial.

Design: RESILIENCE is an ongoing multinational, double-blind, PL-controlled, randomized phase 3 trial designed to assess SOR+CAP as a first- or second-line therapy in advanced HER2−negative BC. Eligibility criteria include: ≥18 years of age; ≤1 prior chemotherapy regimen for advanced BC; and resistant to/failed taxane and anthracycline or no indication for further anthracycline treatment. Prior hormonal or radiation therapy is allowed, but prior use of VEGF inhibitors is not. Patients with significant cardiovascular disease or active brain metastases are not eligible. Patients are stratified by hormone receptor status, geographic region, and prior chemotherapy for advanced BC and randomized (1:1) to CAP (1000 mg/m2 po twice daily [BID], days 1–14 of a 21-day cycle) in combination with SOR (po BID, days 1–21, total dose 600 mg/day) or matching PL. CAP and SOR/PL doses can be escalated to 2500 mg/m2 per day and 800 mg/day, respectively, as tolerated. The protocol outlines strategies to manage toxicities with dose interruption and reduction. Dose re-escalation after reduction is allowed for SOR/PL (per protocol guidance) but not for capecitabine. Guidelines are provided for prophylactic and symptomatic treatment of HFSR/HFS. Radiographic assessment is every 6 wk for the first 36 wk, and every 9 wk thereafter. The primary endpoint is PFS. Assuming a 1-sided alpha of 0.005 and a power of 98.9%, the sample size is estimated at ∼519 patients, with primary analysis planned after 363 events. Secondary endpoints include overall survival, time to progression, overall response rate (RECIST 1.1 criteria), duration of response, and safety. In addition, patient reported outcomes will be assessed, and the trial will include an exploratory analysis of biomarkers. Enrollment began in Nov 2010. The trial is registered at ClinicalTrials.gov (NCT01234337).

Conclusions: RESILIENCE will provide definitive PFS data for SOR+CAP as a first- or second-line therapy in HER2−negative locally advanced or metastatic BC. The phase 3 design and improved dosing guidance since SOLTI-0701 will better characterize the benefit-to-risk profile of this regimen.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr OT3-01-09.

P5-19-03: Albumin-Bound Paclitaxel (ab-pac) Versus Docetaxel for First-Line Treatment of Metastatic Breast Cancer (MBC): Overall Survival and Safety Analysis of a Randomized Phase II Trial

Background

We previously reported the results of a phase II study evaluating the efficacy and safety of 3 different dosing regimens of ab-pac and docetaxel for the first-line treatment (Tx) of MBC (Gradishar et al. J Clin Oncol. 2009;27:3611–3619). Here, we report final overall survival (OS) and an analysis of safety and associated dose reductions (DRs).

Methods: Patients (pts; N = 300) with previously untreated MBC were randomized to 1 of 4 Tx arms (table). A step-down statistical approach was used for pairwise comparisons of Tx arms. The trial was powered for antitumor activity and safety.

Results: Tx arm C produced the longest OS (33.8 months) with an 11.6-month longer median OS vs arm B (HR 0.575; P = .008) and a 7.2-month longer median OS vs arm D (HR 0.688; P not statistically significant). OS data were consistent with previously reported investigator assessment of overall response rates and progression-free survival. Grade (gr) 4 neutropenia (np) was significantly less frequent in the ab-pac arms vs. the docetaxel arm (5-9% vs. 75%; P &lt; .001). Febrile np occurred in 1% of each ab-pac arm vs 8% in the docetaxel arm. Rates of gr 3 sensory neuropathy (SN) were 21%, 9%, 22% and 12%, respectively, in arms A-D (P = .083). No gr 4 SN occurred. Median time to improvement to ≤ gr 2 SN was 20–22 days in the ab-pac arms vs 41 days in the docetaxel arm. Gr 3 fatigue occurred in 5, 0, 4, and 19% of pts in arms A-D, respectively. In arm C, best response was observed at cycle 2, whereas DRs due to toxicity occurred later, at cycle 4 (table). The percentage of pts dose reduced due to ≥ 1 Tx-related toxicity were 18%, 17%, 47%, and 28% in arms A-D. The median cycles at which DRs occurred were 7, 5, 4, and 3, respectively. Np and SN were the most common toxicities leading to DRs.

P5-19-13: A Randomized Phase II Trial of First-Line Metastatic Breast Cancer (MBC) Patients: Sub-Set Analysis of Albumin-Bound Paclitaxel (ab-pac) Given Weekly at 150 mg/m2

Background

We previously reported the results of a phase II study evaluating the efficacy and safety of 3 different dosing regimens of ab-pac and docetaxel for the first-line treatment of MBC (Gradishar et al. J ClinOncol. 2009;27:3611). Here we report outcomes for a subset of patients (pts) during treatment with ab-pac at 150 mg/m2 weekly for the first 3 weeks of a 4-week schedule (qw 3/4).

Methods: Patients (N = 300) with previously untreated MBC were randomized to 1 of 4 treatment arms: arm A, ab-pac at 300 mg/m2 q3w; arm B, ab-pac at 100 mg/m2 qw 3/4; arm C, ab-pac at 150 mg/m2 qw 3/4; arm D, docetaxel at 100 mg/m2 q3w. A step-down statistical approach was used for pairwise comparisons of treatment groups. The trial was powered for antitumor activity and safety.

Results: Treatment arm C produced the longest overall survival (OS) (33.8 months) with an 11.6-month longer median OS vs arm B (22.2 months, HR 0.575; P = .008) and a 7.2-month longer median OS vs arm D (26.6 months, HR 0.688; P not statistically significant). Median OS in arm A was 27.7 months. These OS data were consistent with previously published overall response rates (ORR) and progression-free survival (PFS). Forty-seven percent of pts in arm C required dose reduction due to toxicity, including 27% due to neutropenia (np), 15% due to sensory neuropathy (SN), 3% due to allergy/immunology, 1% due to febrile np, and 1% due to ulceration of the skin. The median OS for the subset of pts requiring DRs in arm C was comparable to pts not dose reduced: 35.2 and 31.8, respectively. Pts who were dose reduced in arm C received a median of 2 additional cycles of treatment compared with those without DRs: 10 (range 2 — 27) vs 8 (range 1 — 27). Investigator assessed ORR and PFS were numerically higher in pts dose reduced vs those not reduced. Baseline characteristics were similar between pts requiring DRs vs not.

OT1-02-03: EGF114299: Safety and Efficacy of an Aromatase Inhibitor (AI) in Combination with Lapatinib (L), Trastuzumab (T) or Both for the Treatment of Hormone Receptor-Positive (HR+), HER2+ Metastatic Breast Cancer (MBC)

Background: Data from the L plus letrozole (EGF30008) and the Trastuzumab and Anastrozole Directed Against ER-Positive HER2−Positive Mammary Carcinoma (TaNDEM) studies demonstrated that HER2 targeted and endocrine therapy (ET) is a better strategy than ET alone. In EGF30008, progression-free survival (PFS) in the HER2+ population was statistically significantly longer in the letrozole plus L group compared with the letrozole plus placebo group. The HR was 0.71 (95% CI: 0.53−0.96; stratified log rank P=.019). Median PFS was 35.4 weeks in the letrozole plus L group compared with 13.0 weeks in the letrozole plus placebo group.

The present study (EGF114299) is a phase III, open-label, multicenter trial designed to evaluate benefit in overall survival (OS) provided by L/T/AI and L/AI, in pts with HR+/HER2+ MBC who have received neo-/adjuvant T and ET. It will also provide further data on dual HER2 suppression in an attempt to prevent acquired endocrine resistance.

Trial Design: Pts will be randomized to 1 of 3 treatment arms: L 1000 mg po QD plus T (loading dose of 8 mg/kg followed by maintenance with 6 mg/kg IV q3w plus an AI po QD); T plus an AI; or L 1500 mg po QD plus an AI). Choices of AI include letrozole, anastrozole, or exemestane.

Eligibility Criteria: HR+ (ER and/or PgR) and HER2+ Stage IV MBC pts are to be enrolled. Pts must have received neo-/adjuvant T and ET, and are treatment naive for MBC.

Specific Aims: The primary objective is to evaluate OS of L/T/AI as compared with T/AI. The secondary objectives are to assess: OS in T/AI vs L/AI and T/L/AI vs L/AI; PFS; overall response rate; clinical benefit rate; safety and tolerability; and QoL relative to baseline. A 4-year recruitment is anticipated. More than 200 centers across 25 countries are planned; approximately 50 centers are currently open for enrollment.

Statistical Methods: The study is powered to detect a 42% improvement in the risk of death (HR=0.70) in all pts receiving L/T/AI (median 28.5 months) compared with T/AI (median 20 months). The hypothesis will be tested using a 1-sided test for superiority with a=0.025 with a power of 80%.

Present and Target Accrual: One (1) of 525 pts has been randomized. The majority of eligible pts may reside in countries where T is commercially available and reimbursable, particularly North America and Western Europe. Patients who have participated in previous neo-/adjuvant trials including a T regimen are eligible, provided they meet all other inclusion criteria.

The study is currently recruiting pts, with an anticipated target accrual of 525 patients by March 2016.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr OT1-02-03.

A Phase I Trial of a Pegylated Liposomal Anthracycline (Doxil TM) and Lapatinib Combination in the Treatment of Metastatic Breast Cancer: Dose-Escalation Results of an Anthracycline and Lapatinib Combination Trial

Background: Liposomal formulations such as pegylated liposomal doxorubicin (PLD) were developed to improve the therapeutic index and overall benefit of the anthracyclines (A). Lapatinib (L) is a selective and highly competitive inhibitor of ErbB1 and ErbB2 tyrosine kinases. The combination of conventional doxorubicin and an ErbB2 targeting agent (trastuzumab) was effective but led to an unacceptable risk of cardiac toxicity. The combination of PLD and L however may be effective with less cardiac risk. Methods: This is an open-label, phase I, dose-escalation trial of PLD at 20, 30, 45 and 60 mg/m2 IV every 4 weeks (maximum of 8 doses) and L, 1500 mg po daily until progression in patients (pts) with metastatic breast cancer (MBC). EGFR and/or ErbB2 positivity was not required. Prior chemotherapy, endocrine therapy and trastuzumab were allowed however prior A use was limited to 240 mg/m2 of doxorubicin or 600 mg/m2 of epirubicin. Initially, prior EGFR targeting therapies were not allowed however the trial was subsequently amended to allow prior lapatinib. Concomitant CYP3A4 inducers/ inhibitors were not allowed. A left ventricular ejection fraction (LVEF) of ≥ 50% was required. The primary objective was to evaluate the safety, tolerability and feasibility of the combination of PLD and L, particularly with respect to cardiac safety. MUGAs were performed at entry and every 8 weeks thereafter. Results: 16 patients (PLD: 20 mg/m2 - 4 pts; 30 mg/m2 - 3 pts; 45 mg/m2 – 6 pts; 60 mg/m2- 3 pts) with a mean age of 53 yrs (range, 33-68) have been treated for a total of 30 treatment cycles. Dose-limiting toxicity (DLT) was not reached. One pt experienced an LVEF drop to &lt; 50% after 4 cycles however this was accompanied by a pericardial effusion felt to be secondary to progressive disease. Adverse events observed include: grade IV- mucus plugging and knee pain in 1 pt each; grade III- fatigue and hand-foot-syndrome (HFS) in 2 pts each and edema, diarrhea, dizziness, headache, stomatitis and skin toxicity in 1 pt each; grade I/II in ≥2 pts- anemia, leucopenia, fatigue, shortness of breath, pain, nausea, stomatitis, anorexia, diarrhea, increased alkaline phosphatase or transaminases, hypoalbuminemia and hyperglycemia. Preliminary response data in 11 evaluable pts reveals 1 PR, 3 SD, and 8 PD. Event-free and overall survival curves are as shown.Conclusions: In the first 16 pts treated, the combination of PLD and L has been well tolerated without treatment-related cardiac toxicity. One pt experienced an LVEF drop to &lt; 50%, however this was felt likely to be disease-related. DLT was not reached however grade 3 HFS occurred in 2 out of 3 pts in the 60 mg/m2 cohort. A pharmacokinetic interaction cohort at the 45 mg/m2 dose is planned.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3096.

Dasatinib Plus Capecitabine for Advanced Breast Cancer: Safety and Efficacy Data from Phase 1 Study CA180-004

Background: SRC is a potential therapeutic target in breast cancer and has a central role in hormone therapy resistance and in osteoclast activity. Dasatinib is a potent SRC inhibitor that inhibits breast cancer cell proliferation and migration in vitro, including synergy with 5FU in some cell lines, and inhibits osteoclast activity in clinical trials. CA180-004 is a phase 1 study designed to identify dose-limiting toxicities (DLT) and recommended phase 2 doses of dasatinib plus capecitabine in women with advanced breast cancer (ABC). Safety and efficacy data are now reported with additional follow-up.Methods: Cohorts of pts with ABC were treated at four dose levels (DL) with capecitabine (mg/m2 twice daily [BID] on D1-14 of 21-day cycles) and dasatinib (mg daily): DL1: capecitabine 825 + dasatinib 50 BID; DL2: capecitabine 825 + dasatinib 70 BID; DL3: capecitabine 1000 + dasatinib 70 BID; DL3a: capecitabine 1000 + dasatinib 100 once daily (QD). All pts had performance status 0-1, prior taxane and/or anthracycline and ≤2 prior chemotherapy-containing regimens for advanced disease. Disease assessments were performed every 6 weeks. DL3a was expanded for further safety and efficacy estimate using best objective response and progression-free survival (PFS) rates.Results: To date, 47 pts with ABC have been treated, 31 in escalation phase plus 16 in expansion (5 too early). Median age was 52 years (range 35-77). Tumor subtypes: 14% were Her2-amplified, 57% ER+ or PR+, 29% triple-negative. Safety was previously reported (ASCO 2009) for escalation phase; no MTD was defined based on DLTs. Of 20 evaluable pts in DL3a, 2 DLTs have been observed: 1 pneumonia, pain and pleural effusion plus 1 diarrhea, neutropenia, vomiting, mucositis and anemia. The most common drug-related adverse events (AEs, any grade) were headache, fatigue/asthenia, nausea/vomiting, diarrhea, hand-foot syndrome (HFS) and pleural effusion. The most common grade 3/4 AEs were fatigue/asthenia, HFS, vomiting and diarrhea. To date, 19 have remained on treatment ≥4 months, including 3 for &gt;1 year. Median duration of treatment (n=42) was 13 weeks; 23 pts have discontinued for progression and 7 for toxicity. Of 38 pts with on-study assessment, 6 had confirmed partial response (treatment durations 17+, 23, 25, 36+, 71, 73 wks), 6 had unconfirmed partial or clinical response (5, 11, 13, 18, 23+, 24 wks), and 9 had prolonged stable disease (16+, 17, 23+, 24+, 25+, 29, 39+, 48+, 63+ wks). Updated efficacy data, including PFS by hormone receptor status, will be presented.Conclusions: Dasatinib and capecitabine combination treatment was well tolerated and encouraging efficacy was observed. Further assessment of this combination is warranted.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3092.

Nab-paclitaxel weekly or q3w compared to docetaxel q3w as first-line therapy in patients with metastatic breast cancer: An economic analysis of a prospective randomized trial

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Background: In patients with MBC, the current practice is first-line chemotherapy often with a taxane such as docetaxel. However, docetaxel is associated with dose-limiting toxicities. A nanoparticle albumin-bound (nab) formulation of paclitaxel was recently developed to overcome the safety drawbacks of docetaxel and to provide additional efficacy. A randomized phase II trial comparing nab-paclitaxel 100 or 150 mg/m2 weekly 3 out of 4 and nab-paclitaxel 300 mg/m2 q3w to docetaxel 100 mg/m2 q3w reported improved progression-free survival and reduced toxicity with the former regimens (Gradishar, 2008). To measure the economic value of the nab-paclitaxel regimens, an economic analysis from the perspective of the United Kingdom (UK) was conducted. Methods: The current study extracted data captured during the randomized trial. Resource utilization data contained within the database were converted into UK cost estimates. This consisted of costs for chemotherapy, drug delivery, patient monitoring, supportive care drugs, and hospitalization due to toxicity. Multivariate regression analysis was then conducted to compare the total cost of therapy between the four regimens. Results: Growth factor use, hospital days for side effects management, and toxicity-induced protocol discontinuations were higher in the docetaxel group. When all of the cost components were combined for the entire population (n = 300), patients in the nab-paclitaxel 100 mg/m2 weekly and 300 mg/m2 q3w groups had comparable costs to the docetaxel control (£15,396 vs. £15,809 vs. £12,923; p = NS). The nab-paclitaxel 150 mg/m2 weekly arm had significantly higher overall costs of £27,222 but was associated with a significant improvement in progression-free survival relative to docetaxel. As alternatives to docetaxel, the incremental cost per progression-free year gained with nab-paclitaxel 100, 150 mg/m2 weekly and 300 mg/m2 q3w were £5,600, £31,800, and £9,900 respectively. Conclusions: Given its more favorable safety profile, superior efficacy, and reasonable economic impact, nab-paclitaxel (weekly or q3w) can be a preferred option over docetaxel as first-line chemotherapy in MBC.

[Table: see text]

Dasatinib plus capecitabine (Cap) for progressive advanced breast cancer (ABC): Phase I study CA180004

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Background: SRC family kinases (SFK) mediate numerous signal-transduction pathways relevant to breast cancer as well as osteoclast function. Dasatinib, a potent oral inhibitor of SFK and other kinases has preclinical activity in breast models and in vitro synergy with Cap in some breast cancer cell lines (KPL-4 and HCC-70). A phase I trial of dasatinib plus Cap was conducted to define dose-limiting toxicities (DLT), maximum tolerated (MTD), and recommended phase II (RP2D) doses. Methods: Sequential cohorts of pts with ABC were treated with Cap twice daily (BID) on days 1–14 and dasatinib daily in 21-day cycles using dose levels (DL) for Cap (mg/m2) and dasatinib (mg): DL1: Cap 825 + dasatinib 50 BID; DL2: Cap 825 + dasatinib 70 BID; DL3: Cap 1000 + dasatinib 70 BID; DL3a: Cap 1000 + dasatinib 100 once daily (QD). All pts had ECOG performance status 0–1, had prior anthracycline and/or taxane, and received ≤2 regimens in advanced setting. MTD was based on DLT in first cycle and RP2D also based on tolerability of additional cycles. Results: 31 pts with ABC, median age 53 years (range 36–78) were treated. Number of pts treated/evaluable for DLT/reported DLT (event) were DL1: 7/6/1 (headache, grade 3); DL2: 9/7/0; DL3: 6/6/1 (diarrhea, grade 3), and DL3a: 9/9/1 (pneumonia, grade 3). Most frequent AEs related to either drug and occurring at any time on study (n pts) were nausea (12), vomiting (7), diarrhea (6), abdominal pain (2), fatigue (8), headache (7), musculoskeletal pain (1), and pleural effusion (4); hand-foot syndrome (5) was as expected for Cap alone. 11 patients experienced a Grade 3–4 non-hematologic AE at some point during the study. Laboratory abnormalities were uncommon. To date, 20 pts have continued treatment for ≥6 weeks and 9 pts for ≥12 weeks. Number of pts who (at any time) reduced dasatinib/reduced Cap/discontinued for toxicity were DL1: 2/2/1; DL2 2/2/3; DL3: 2/1/2; DL3a: 0/1/1. Updated safety and efficacy data will be presented. Conclusions: Dasatinib + Cap was tolerated without unexpected combined-treatment toxicity; few pts required dose reduction in later cycles. The recommended phase II dose, Cap 1000 plus dasatinib 100 QD, is well tolerated and will be studied for efficacy in an expanded patient cohort.

[Table: see text]