Abstract S4-05: Interrogating the landscape of long noncoding RNAs in breast cancer to identify predictors of tamoxifen resistance

Background: We previously performed an informatics-based analysis on RNA sequencing libraries from 7,256 tumor and normal tissue specimens to delineate the landscape of long noncoding RNAs (lncRNAs) in the human transcriptome. This analysis identified 58,648 lncRNAs, including over 45,000 novel transcripts (Iyer MK et al, Nature Genetics, 2015). We now interrogate this lncRNA compendium to identify top candidate estrogen receptor (ER)-associated lncRNAs in breast cancer and characterize their association with disease progression.

Methods: To prioritize differentially expressed lncRNAs in cancer vs normal tissue, and in ER+ vs ER- disease, we performed Sample Set Enrichment Analysis (SSEA) on >1000 RNA Seq libraries, from breast cancer and normal tissue samples from The Cancer Genome Atlas project. The effect of the top prioritized lncRNA on cancer phenotypes was studied via in vitro proliferation, colony formation, invasion and tamoxifen resistance assays in MCF7 and T47D cells, and via in vivo mouse xenograft studies and chick chorioallantoic membrane (CAM) assays. To study the mechanism by which this lncRNA promotes tumor progression, we identified its top protein interactors and subdomains responsible for function, and then studied the effects of disrupting function of this lncRNA on cancer phenotypes. Finally, in a "guilt-by-association" study, we developed a signature of 150 protein coding genes most strongly associated with our lncRNA of interest, and investigated the association of this signature with clinical outcomes using Oncomine analyses.

Results: SSEA analysis on over 1000 TCGA samples nominated Breast Cancer Associated Transcript (BRCAT 431) as the top overexpressed ER-regulated lncRNA in breast cancer. In vitro experiments demonstrate that siRNA-mediated knockdown of BRCAT431 resulted in significantly decreased proliferation, colony formation, and invasion (by >50% in most assays). Tamoxifen resistance was associated with significantly increased BRCAT431 levels in both MCF7 and T47D cells, and knockdown of BRCAT431 reversed tamoxifen resistance. In vivo xenograft and CAM studies demonstrate that knockdown of BRCAT431 also significantly decreased xenograft growth and tumor invasion by >50%. RNA pulldown followed by mass spectrometry identified the RNA binding protein hnRNPL as a key protein interacting with BRCAT431. Deletion studies identified a 27 base region of BRCAT431 necessary for its interaction with hnRNPL, and loss of this region abrogated BRCAT431- induced invasion. Finally, guilt-by-association studies demonstrate a strong association between BRCAT431 overexpression and tumor grade, recurrence, and metastases.

Conclusion: In this study, we develop the largest reported compendia of breast cancer lncRNAs. We prioritize BRCAT431 as the top lncRNA upregulated in ER-positive breast cancers, and demonstrate that it confers aggressive oncogenic phenotypes in vitro and in vivo. We identify a novel mechanism by which this lncRNA functions. Our results suggest that by promoting tamoxifen resistance, BRCAT431 increases the clinical risk of recurrence and metastases in breast cancer. Overall, this study supports the rationale for investigating lncRNAs as novel biomarkers and therapeutic targets in breast cancer.

Citation Format: Feng FY, Niknafs Y, Han S, Ma T, Speers C, Malik R, Evans J, Zhang C, Pierce LJ, Hayes DF, Rae JM, Chinnaiyan AM. Interrogating the landscape of long noncoding RNAs in breast cancer to identify predictors of tamoxifen resistance. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr S4-05.

Abstract P2-02-19: Somatic genetic profiling of circulating tumor cells (CTC) in metastatic breast cancer (MBC) patients

Introduction: Somatic mutations, including those in TP53, PIK3CA, and estrogen receptor alpha (ESR1), are key to the biology of cancer and response to therapy. Recently, somatic cancer-associated mutations have been identified in circulating cell free plasma tumor DNA (ptDNA). Less is known about the mutation profile of DNA extracted from CTC (CTC-DNA). Since CTC-DNA provides mutational information of single cells, we hypothesize CTC-DNA will complement ptDNA to give greater insight into tumor heterogeneity.

Methods: Patients with ER positive MBC who were enrolled in the Mi CTC-ONCOSEQ, a companion trial to Mi-ONCOSEQ (the Michigan Oncology Sequencing Program), and who had ≥5CTC/7.5 ml whole blood were included. CTC were enriched from white blood cells (WBC) with CellSearch© (CXC kit). CTC and WBC were then purified using DEPArrayTM. DNA from individual CTC and WBC was isolated and subjected to whole genomic amplification (Ampli 1TM WGA). Genetic analysis was performed on individual CTC, pooled CTC and pooled WBC DNA by multiplexed PCR based targeted next generation sequencing (NGS) using the Oncomine Comprehensive Panel (targeting ∼130 onco- and tumor suppressor genes) and the Ion Torrent Proton. All patients had exome sequencing performed on research biopsies of metastases using an Illumina HiSeq 2500 platform.

Results: This pilot study was conducted using high quality DNA from two patients assessed to date. Both patients had lobular carcinoma and as expected harbored somatic, deleterious CDH1 (E-cadherin) mutations (frameshift and non-sense) in both research biopsy and CTC-DNA. These data supported our approach. Patient #1 was TP53 wild type in her research biopsy, but multiple CTC harbored somatic TP53 frame-shift mutations (Table). Patient #2 harbored an ESR1 Y537S mutation in her research biopsy. However, only 4 of 7 CTC also harbored this somatic, heterozygous mutation.

Prioritized mutations in CTCPt#Cell Type (CTC vs WBC), numberGeneMutationVariant fraction (expected 1=homozygous; 0.5=heterozygous)Found in research biopsy?1CTC_A2CDH1p.I584fs1YES CTC_A4  1  CTC_A7  0.54  CTC_pool*  0.74  WBC_pool  0  CTC_A2TP53p.152_156del1NO CTC_A4  1  CTC_A7  0.51  CTC_pool*  0.88  WBC_pool  0 2CTC_A9ESR1p.Y537S0.52YES CTC_D1  0.34  CTC_D2  0.46  CTC_D6  0.65  CTC_pool*  0.35  WBC_pool  0  CTC_A12  0  CTC_D3  0  CTC_D7  0  CTC_A12CDH1p.Q641X1YES CTC_A9  1  CTC_D1  1  CTC_D3  1  CTC_D6  1  CTC_pool*  1  WBC_pool  0 * pool of all CTC

Conclusions: We demonstrate the ability to purify CTC, isolate, and amplify DNA of suitable quality for genetic analysis using a comprehensive targeted sequencing panel. Both known and novel alterations were identified in comparison to research biopsy specimens. This approach allows single cell analysis demonstrating heterogeneity of mutational status in different single cells. Studies of CTC-ESR1 and other genetic abnormalities in patients with known tissue mutations who participated in Mi CTC-ONCOSEQ are now underway.

Citation Format: Paoletti C, Cani AK, Aung K, Darga EP, Cannell EM, Hovelson DH, Yazdani M, Blevins AR, Tokudome N, Larios JM, Thomas DG, Brown ME, Gersch C, Schott AF, Robinson DR, Chinnaiyan AM, Bischoff F, Hayes DF, Rae JM, Tomlins SA. Somatic genetic profiling of circulating tumor cells (CTC) in metastatic breast cancer (MBC) patients. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-02-19.

Abstract P3-05-01: Molecular analysis of cancer tissue, circulating tumor cells (CTC) and cell-free plasma tumor DNA (ptDNA) suggests variable mechanisms of resistance to endocrine therapy (ET) in estrogen receptor (ER) positive metastatic breast cancer (MBC)

Introduction: Fifty percent of ER positive MBC patients do not benefit from ET. Potential mechanisms of resistance to ET in this patient population include absence of ER expression by deletion or suppression, alteration in ER signaling pathway genes, or upregulation of multiple growth factor receptor pathways. We hypothesized that genotyping and phenotyping of CTC combined with genomic analysis of ptDNA will provide important insights into the multiple mechanisms of ET resistance and that a set of blood tests might serve as a "liquid biopsy" abrogating the need for tissue specimens.

Methods: Twenty-four patients providing informed consent were enrolled into the Mi CTC-ONCOSEQ study, a companion trial to Mi-ONCOSEQ (the Michigan Oncology Sequencing Program). Seven of these patients (5 with ER immunohistochemistry (IHC) positive and 2 with ER negative cancers) who had available archived primary and metastatic cancer tissue, a research metastatic biopsy for genomic analysis, and who had ≥5CTC/7.5 ml whole blood (WB) characterized for ER protein (CTC-ER) are the focus of this report. All the patients were ET refractory. None of them was progressing on fulvestrant at the time of study entry. CTC enumeration and phenotyping was performed with CellSearch©. Circulating ptDNA was analyzed by droplet digital polymerase chain reaction (ddPCR). ER status from archived tissue was obtained from chart review. ER mRNA expression was determined in the research biopsy of metastatic tissue by using quantitative RNA sequencing. Mutational status of ER gene, ESR1, was determined by Next-gen Sequencing using the Illumina HiSeq 2500 platform.

Results: The 2 control patients with triple negative breast cancer had negative CTC-ER. Discordance between CTC-ER and tissue ER by IHC was observed (Table). Two of the 5 ER positive patients retained CTC-ER positivity (39% and 19% of the CTC). One of them (#7) harbored an ESR1 mutation in the research biopsy tissue and in ptDNA, whereas the other (#14) had wild type (WT) ESR1. CTC-ER protein levels in patients #12, 17 and 24 were negative. All had WT ESR1 in the research biopsy tissue. Of note, patient #12 had WT ESR1 in the research biopsy, but an ESR1 mutation was detected in her ptDNA.

Pt#CTC-ER Tissue-ER  ESR1 status in research biopsyESR1 status in ptDNA N[deg]CTC/7.5ml WB% CTC-ER +Primary by IHCMet by IHCMet research biopsy by mRNA  71839%+++Y537SY537S141619%+NA+WTWT12130%+++WTD538G17160%++weakly+WTWT242750%+weakly+weakly+WTWT

Conclusions: These exploratory data suggest heterogeneous mechanisms of resistance to ET in patients with previously determined ER-positive MBC, including ESR1 mutations in ER positive cases (seen in 2 patients) and loss of ER expression (seen in CTC of 3 patients). In contrast, other cancers continue to express WT ESR1, and therefore must have developed alternative mechanisms of resistance. At least 2 of these mechanisms can be detected and monitored with complementary circulating assays: CTC and ptDNA. Further investigations are needed to understand the heterogeneous mechanisms of resistance to ET.

Citation Format: Paoletti C, Aung K, Cannell EM, Darga EP, Chu D, Kidwell KM, Thomas DG, Tokudome N, Brown ME, McNutt LM, Gersch C, Schott AF, Park BH, Robinson DR, Chinnaiyan AM, Rae JM, Hayes DF. Molecular analysis of cancer tissue, circulating tumor cells (CTC) and cell-free plasma tumor DNA (ptDNA) suggests variable mechanisms of resistance to endocrine therapy (ET) in estrogen receptor (ER) positive metastatic breast cancer (MBC). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-05-01.

Abstract P3-07-64: Association between gene variants in SULT1A1 and UGT1A4 and disease outcomes in patients enrolled in SWOG S0226 and treated with anastrozole alone or in combination with fulvestrant for metastatic breast cancer

Background: Anastrozole (A) blocks estrogen production by inhibiting the activity of CYP19 aromatase. Fulvestrant (F) blocks estrogen receptor (ER) signaling by competitive binding, leading to ER degradation by ubiquitination. SWOG S0226 ("Phase III Randomized Trial of Anastrozole versus Anastrozole and Fulvestrant (250mg LD) as First Line Therapy for Post Menopausal Women with Metastatic Breast Cancer," ClinicalTrials.gov Identifier:NCT00075764) demonstrated that combination of A+F is superior to A alone as first-line therapy for patients with ER positive metastatic breast cancer (Mehta et al, NEJM, 2012). Our functional preclinical studies have shown that single nucleotide polymorphisms (SNPs) in SULT1A1 and UGT1A4, drug conjugation enzymes that inactivate A and F, result in decreased enzyme activity toward these drugs (Edavana et al, DMD, 2013; Edavana et al Pharmgenomics Pers Med 2013). We therefore hypothesized that these SNPs will be associated with disease outcomes in S0226 patients due to altered drug levels.

Methods: Germline DNA was available for 295 (43.5%) patients enrolled in S0226 overall (157 on A and 138 on A+F). SNPs in SULT1A1 and UGT1A4 were determined either by direct sequencing or allele-specific PCR (TaqMan) assays.

Results: There was no difference in progression-free survival (PFS) or overall survival (OS) comparing patients with or without available germline DNA (p = 0.86 and 0.36, respectively). The SULT1A1 G902A allele (rs6839), which confers decreased mRNA and enzymatic activity, was associated with improved PFS (GG/GA vs. AA; HR 0.74, 95% CI 0.56-0.98, p=0.033) and OS (HR 0.70, 95% 0.50-0.98, p=0.039). In exploratory subset analyses of PFS, the SULT1A1 G902A association was similar across both treatment arms (A HR=0.75; 95% CI 0.51-1.10; A+F HR=0.73; 95% CI 0.48-1.11). For OS there was some evidence of a difference by treatment (A HR=0.60; 95% CI 0.38-0.96; A+F HR=0.82; 95% CI 0.50-1.32), though no significant interaction was evident (p=0.30).

The UGT1A4 G-163A promoter variant, which leads to decreased protein expression, was not associated with PFS (AA/AG vs. GG HR 0.88, 95% CI 0.68-1.14, p=0.33); however, this variant was associated with OS (HR 0.71, 95% CI 0.52-0.96, p=0.027). In subset analyses with OS, the difference was marginally stronger in the A arm (HR 0.63, 95% CI 0.42-0.97, p=0.035) compared to the A+F arm (HR 0.77, 95% CI 0.49-1.21, p=0.25), though the interaction was not significant (p=0.40).

Conclusion: SULT1A1 and UGT1A4 gene variants resulting in decreased enzyme activity were associated with better PFS, OS or both in patients enrolled in SWOG S0226. Planned validation studies correlating these SNPs with drug levels and disease outcomes in additional patient cohorts will establish their clinical utility in identifying patients who benefit from A and F alone or in combination.

Funding: Supported by NIH/NCI CA118981; NIH/NCI/NCTN grants CA180888, CA180819, and CA180863; and in part by AstraZeneca.

Citation Format: Kadlubar SA, Barlow WE, Mehta RS, Daniels JR, Albain KS, Vandengerg TA, Dakhil SR, Tirumali NR, Lew DL, Gralow JR, Livingston RB, Hortobagiyi GN, Hayes DF, Rae JM. Association between gene variants in SULT1A1 and UGT1A4 and disease outcomes in patients enrolled in SWOG S0226 and treated with anastrozole alone or in combination with fulvestrant for metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-07-64.

Abstract P1-04-01: Significance of circulating tumor cells in metastatic triple negative breast cancer: Results of an open label, randomized, phase II trial of nanoparticle albumin-bound paclitaxel with or without the anti-death receptor 5 tigatuzumab (TBCRC 019)

Background: Circulating Tumor cells (CTCs) are prognostic at baseline and first follow-up in patients with metastatic breast cancer (MBC). Using the most commonly used assay (CellSearch®), we have previously reported the ability to detect apoptotic vs. non-apoptotic CTCs in patients with MBC. However, there has been concern regarding the performance of the CellSearch® assay in patients with triple negative (TN) MBC. We hypothesized that CellSearch® is an effective assay in patients with TN MBC, and that CTC-apoptosis might further separate prognosis. Therefore, we studied CTCs in patients with TN MBC who participated in a prospective randomized phase II trial testing for activity of tigatuzumab (TIG) in combination with nanoparticle albumin-bound paclitaxel (nab-PAC) conducted by the Translational Breast Cancer Research Consortium (overall results reported by Forero A., et al, ASCO 2013).

Methods: Whole blood (WB) was drawn into a CellSave tube at baseline, day 15, and day 29 and CTC counts were determined using the CXC CellSearch® kit. Apoptosis was characterized by staining with a monoclonal antibody that detects a neo-epitope on fragmented cytokeratin (M-30) and independently by visual inspection (nucleic condensation and/or fragmentation, as well as granular cytokeratin). Association between levels of CTCs and CTC-apoptosis with the overall response rate (ORR) and progression free survival (PFS) at baseline, day 15, and day 29 was assessed using logistic regression, Kaplan Meier curves, and Cox proportional hazards modeling.

Results: Of the 60 patients entered into the trial, 52 were evaluable for CTCs. Of these, 19/52 (36.5%), 14/52 (26.9%), and 13/49 (26.5%) had elevated CTCs (≥5CTC/7.5 ml WB) at baseline, day 15, and day 29, respectively. Patients with elevated CTCs at each time point had worse PFS than patients with low or no CTCs. Hazard rates (HR) at baseline, day 15, and day 29 were 2.38 (95% CI: 1.27-4.45, p = 0.007), 2.87 (95% CI: 1.46-5.66, p = 0.002), and 3.40 (95% CI: 1.68-6.89, p = 0.001), respectively. The odds of overall response for those who had elevated CTCs compared to those who did not at baseline, day 15, and day 29, were 0.25 (95% CI: 0.073-0.81, p = 0.024), 0.18 (95% CI: 0.04-0.67, p = 0.014), and 0.06 (95% CI: 0.01-0.28, p = 0.001), respectively. There was no apparent prognostic effect comparing the degree of CTC-apoptosis vs. non-apoptosis.

Conclusions: Similar to observations in other intrinsic subgroups, CTCs were detected in a large fraction of TN MBC patients at baseline using CellSearch® assay, and reductions in CTC levels reflected response. In these homogenously prospectively enrolled TN MBC patients, regardless of treatment, CTCs are prognostic at baseline, day 15, and day 29. It does not appear that analysis of CTC-apoptosis is prognostic.

Supported by Susan G. Komen for the Cure, Veridex, LLC, Fashion Footwear Charitable Foundation of New York/QVC Presents Shoes on Sale™ (DFH), Associazione Sandro Pitigliani and by a studentship from FIRC (CP), Triple Negative Breast Cancer Foundation, The AVON Foundation, and The Breast Cancer Research Foundation.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-04-01.

Abstract S3-02: Associations between baseline patient-reported symptoms and discontinuation of adjuvant aromatase inhibitor (AI) therapy

Background: Non-adherence and non-persistence with AI therapy are common and have been associated with increased mortality. A major reason for premature discontinuation of therapy is toxicity of AI therapy. We performed an exploratory analysis to investigate associations between patient-reported symptoms at the time of AI initiation and discontinuation of AI therapy due to toxicity.

Methods: 503 postmenopausal women with early stage ER positive breast cancer were enrolled into a randomized open label clinical trial of exemestane versus letrozole for 2 years. Questionnaires about sleep quality (PSQI), mood disorders (CESD), and general symptoms (NSABP symptom questionnaire) were completed prior to AI initiation. For each item on the symptom questionnaire, responses were dichotomized as not at all vs any. To analyze total number of symptoms the following 4 symptoms were included: PSQI>5, CESD≥16, any degree of joint pain, and any degree of difficulty concentrating. Subjects were evaluated 1, 3, 6, 12, and 24 months after AI initiation. Reasons for treatment discontinuation were prospectively recorded. The primary endpoint of this exploratory analysis was treatment discontinuation due to toxicity ≤12 months following AI initiation. Linear and logistic regression analyses were performed to analyze associations between clinical factors and baseline symptoms and treatment discontinuation by 12 months.

Results: One hundred forty-two subjects (28.8%) discontinued therapy because of toxicity by or at 12 months. On univariate analysis, poor sleep quality (PSQI>5), depression (CESD≥16), forgetfulness, and total number of symptoms were statistically significantly associated with treatment discontinuation. On multivariable logistic regression, treatment discontinuation due to toxicity was statistically significantly associated with AI medication, and there was a trend towards an association with both younger age and increasing total number of symptoms present at baseline.

Univariate and multivariate analysis of baseline predictors of AI treatment discontinuation   Univariate analysisMultivariate analysisSymptom/characteristic% subjectsOR (95% CI)P valueOR (95% CI)P valueAge (yrs) mean 58.0 (9.0)0.98 (0.96-1.00)0.060.98 (0.95-1.00)0.076Drug (vs letrozole) 49.5%1.47 (0.99-2.18)0.0541.57 (1.04-2.38)0.033Estradiol (BL, pg/ml) mean 10.6 (37.2)1.01 (0.997-1.02)0.151.01 (1.00-1.02)0.091Prior taxane (vs no) 32.7%1.23 (0.82-1.85)0.331.14 (0.73-1.78)0.57Total # symptoms1 vs 028.2%1.56 (0.89-2.73)0.0241.27 (0.70-2.31)0.092 2 vs 021.5%1.52 (0.84-2.77) 1.54 (0.83-2.88)  ≥3 vs 023.7%2.41 (1.37-4.23) 2.10 (1.15-3.84) Depression 15.2%1.03 (1.01-1.06)0.012  Forgetfulness (vs none) 45.5%1.64 (1.11-2.43)0.014  Difficulty concentrating (vs none) 23.7%1.35 (0.86-2.11)0.19  Joint pain (vs none) 57.6%1.42 (0.95-2.12)0.09  Poor sleep quality (vs good) 47.4%1.84 (1.23-2.75)0.003  Vaginal dryness (vs none) 31.5%1.37 (0.91-2.08)0.14  CI: confidence interval; OR: odds ratio

Conclusions: Patient-reported symptoms present prior to initiation of AI therapy may predispose patients to early discontinuation of treatment. Pre-emptive management of these symptoms, rather than treatment of AI toxicity after its development, may improve adherence to and persistence with therapy.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr S3-02.

Abstract P1-08-11: Association of variants in candidate genes on lipid profiles in women with early breast cancer on adjuvant aromatase inhibitor therapy

Background

Aromatase inhibitors (AI) can exert unfavorable effects on lipid profiles, but previous studies have reported inconsistent results. Given the intricate biological relationship between estrogen and lipid profiles, these mixed results may be explained in part by variation in genes encoding proteins involved in the drug's target and in estrogen metabolism and signaling. The purpose of this study was to investigate associations of single-nucleotide polymorphisms (SNP) in candidate genes with AI-mediated changes in lipid profiles.

Methods

We completed a prospective multicenter randomized observational open-label study to test the association of SNPs in candidate genes on biomarkers of estrogenic and anti-estrogenic activity in post-menopausal women with early breast cancer who were recommended adjuvant AI therapy. Eligible women were randomly assigned to exemestane or letrozole, and were followed for 2 years. We genotyped 137 SNPs from germ line DNA in the following candidate genes: ARVCF, COMT, CYP19A1, ESR1, ESR2, PGR, EP300, EZH2, NCOA1-3, NCOR1-2, NRIP, and PELP1. Lipid profiles including total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triglycerides (TG) were measured at baseline and 3 months after initiating AI. We conducted genetic association data analysis and multivariate linear regressions to analyze the genetic effects using dominant, recessive, and additive models. Multivariate analysis included age, body mass index, prior hormone replacement therapy, and prior tamoxifen. To adjust for multiple comparisons, only SNPs with a p<0.0003 were considered significant.

Results

We enrolled 502 women in to the study, but for this analysis we excluded women who did not have genetic data (n = 33), had incomplete data (n = 23), discontinued or crossed over AI therapy (n = 48), women not fasting at both time points (n = 89), or those on lipid-lowering medications (n = 162). A total of 200 women were evaluable (letrozole 107, exemestane 93). Lipid profiles in all patients (n = 200) at baseline and 3 months after initiating AI, respectively, were as follows: TC 204.9 and 203.3 (unchanged, p = 0.43); HDL 61.3 and 56.8 (decreased, p = 6.3E-10); LDL 122.2 and 124.6 (unchanged, p = 0.22); and TG 107.1 and 103.6 (unchanged, p = 0.26). Genetic association and multivariate analysis revealed that SNPs in ESR1 and NCOR1 are significantly associated with additional changes in lipid parameters as summarized in Table 1.

Table 1.Significant findings of multivariate linear regressions analyzing genetic associations between candidate gene SNPs and lipid profiles of AI-treated women.CohortNumberSNP (gene)Minor Allele FrequencyLipid ParameterModel UsedMean Absolute Change (mg/dL)P-valueAll patients184rs9340958 (ESR1)0.07TCRecessive-2.250.0003Letrozole96rs9340958 (ESR1)0.07TCRecessive5.280.00009 101rs3020368 (ESR1)0.09TCRecessive6.350.00007Exemestane93rs3798758 (ESR1)0.03HDLDominant, additive-7.970.00001 88rs926848 (ESR1)0.03HDLDominant, additive-7.970.00002 93rs61753150 (NCOR1)0.01TGDominant, additive-11.630.00003

Conclusions

Variants in genes involved in estrogen metabolism and signaling are associated with changes in lipid profiles in AI-treated women and should be validated in other studies.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-08-11.

Abstract PD6-4: Heterogeneity of expression of estrogen receptor by circulating tumor cells suggests diverse mechanisms of resistance to fulvestrant in metastatic breast cancer patients

Introduction: Fulvestrant is a selective estrogen receptor down-regulator (SERD). Recent studies have shown that the efficacy of fulvestrant is dose-related. However, at the higher dose (500 mg/month) most cancers develop resistance and progress. We previously reported expression of several markers, including estrogen receptor (ER) and BCL-2, on breast cancer circulating tumor cells (CTC) using CellSearch®. We now report pilot data showing inter-patient heterogeneity of these markers on CTC in patients with known ER positive breast cancer whose disease is progressing on fulvestrant.

Methods: We conducted a pilot trial to determine the analytical validity of measuring expression of markers of endocrine sensitivity (ER, BCL-2) or resistance (HER-2, Ki-67) with fluorescent-labeled antibodies using the CellSearch® system. Patients with ER positive metastatic breast cancer (MBC) whose disease was progressing on any type of therapy were eligible after signed informed consent. This report is limited to the subjects who were progressing on fulvestrant. Whole blood (WB) was characterized for CTC counts and each of the four molecular markers using the CXC CellSearch® kit.

Results: Of 50 enrolled patients, seven were progressing on fulvestrant. Two patients had no detectable CTC, while five patients had an average of ≥5 CTC/7.5 mL WB. Results are shown in a table below:

   CTC-ERCTC-BCL-2Patient #Fulvestrant dose (mg/month)Days since last doseN CTC/7.5 mL of WB% of CTC-ER+N CTC/7.5 mL of WB% of CTC-BCL-2+295002880%110%4550028170%170%2250341010%714%850031812%1735%172507728%367%

These exploratory data suggest widely different mechanisms of resistance to fulvestrant in different patients with ER positive MBC. In two of the patients (29, 45) treated with 500 mg/month, both CTC-ER and CTC-BCL-2 expression were absent, suggesting no signaling through the ER pathway. We hypothesize either that fulvestrant was actively down-regulating ER, but the cancers had adopted other growth and survival pathways, or that ER negative, hormone-independent clones had evolved. In the other three cases, ER was clearly present with evidence of signaling, based on BCL-2 expression. Two of these patients (2, 17) were on the lower dose of fulvestrant, now considered to be less effective. However, the third (8) was on the higher dose and yet still had evidence of ER signaling. This observation suggests that some patients may benefit from even higher doses of SERD therapy.

Conclusions: These pilot results suggest heterogeneous biological or pharmacological mechanisms of resistance to SERD therapy. These data suggest that CTC-ER and CTC-BCL-2 expression could serve as pharmacodynamic monitoring tools for dose escalation of fulvestrant or other SERDs. Further molecular analysis might provide biological bases for resistance to fulvestrant.

Supported by Veridex, LLC, Fashion Footwear Charitable Foundation of New York/QVC Presents Shoes on Sale™ (DFH), Associazione Sandro Pitigliani and by a studentship from FIRC (CP).

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD6-4.

Circulating tumour cells: insights into tumour heterogeneity

Tumour heterogeneity is a major barrier to cure breast cancer. It can exist between patients with different intrinsic subtypes of breast cancer or within an individual patient with breast cancer. In the latter case, heterogeneity has been observed between different metastatic sites, between metastatic sites and the original primary tumour, and even within a single tumour at either a metastatic or a primary site. Tumour heterogeneity is a function of two separate, although linked, processes. First, genetic instability is a hallmark of malignancy, and results in 'fixed' genetic changes that are almost certainly carried forward through progression of the cancer over time, with increasingly complex additional genetic changes in new metastases as they arise. The second type of heterogeneity is due to differential but 'plastic' expression of various genes important in the biology and response to various therapies. Together, these processes result in highly variable cancers with differential response, and resistance, to both targeted (e.g. endocrine or anti-human epithelial growth receptor type 2 (HER2) agents) and nontargeted therapies (e.g. chemotherapy). Ideally, tumour heterogeneity would be monitored over time, especially in relation to therapeutic strategies. However, biopsies of metastases require invasive and costly procedures, and biopsies of multiple metastases, or serially over time, are impractical. Circulating tumour cells (CTCs) represent a potential surrogate for tissue-based cancer and therefore might provide the opportunity to monitor serial changes in tumour biology. Recent advances have enabled accurate and reliable quantification and molecular characterization of CTCs with regard to a number of important biomarkers including oestrogen receptor alpha and HER2. Preliminary data have demonstrated that expression of these markers between CTCs in individual patients with metastatic breast cancer reflects the heterogeneity of the underlying tumours. Future studies are designed to determine the clinical utility of these novel technologies in either research or routine clinical settings.

Predictors of recovery of ovarian function during aromatase inhibitor therapy

BACKGROUND

Aromatase inhibitors (AIs) may cause a rise in estrogen levels due to ovarian function recovery in women with clinical chemotherapy-induced ovarian failure (CIOF). We carried out a prospective registry trial to identify predictors of ovarian function recovery during AI therapy.

PATIENTS AND METHODS

Women with hormone receptor (HR)-positive breast cancer who remained amenorrheic and had hormonal levels consistent with ovarian failure after adjuvant chemotherapy were enrolled in a multi-institutional clinical trial of anastrozole. Subjects underwent frequent assessment using an ultrasensitive estradiol assay. Multivariable analysis was used to evaluate clinical and biochemical predictors of ovarian function recovery within 48 weeks.

RESULTS

Recovery of ovarian function during AI therapy was observed in 13 of 45 (28.9%) assessable subjects after a median 2.1 months (range 0.6-11.9). Median age at chemotherapy initiation was statistically significantly different between those who regained ovarian function (43 years, range 40-51) and those who remained postmenopausal (49 years, range 44-52; P < 0.0001).

CONCLUSIONS

A significant proportion of women with CIOF recover ovarian function during AI therapy, including a woman over age 50 at initiation of chemotherapy. Tamoxifen remains the standard of care for women with CIOF. If an AI is used, patients should be monitored frequently with high-quality estradiol assays. CLINICALTRIALS.GOV: NCT00555477.

Abstract S6-3: Neurocognitive impact in adjuvant chemotherapy for breast cancer linked to fatigue: A Prospective functional MRI study

Background: Our previous research showed evidence of compromised cognitive function prior to adjuvant chemotherapy for breast cancer, with fatigue as a contributory factor. Fatigue is a common symptom reported by women treated for breast cancer, yet its association with neurocognitive function has not been systematically examined. In this prospective study, we examined possible alterations in neurocognitive responses, namely, working memory, from pre- to post- adjuvant treatment during functional magnetic resonance imaging (fMRI) and further investigated whether early fatigue might be linked to cognitive alterations over time.

Methods: Women treated with either adjuvant chemotherapy (anthracyline-based combination regimen, n=29) or radiotherapy (n = 37) for localized breast cancer (Stages 0-IIIa) and age-matched healthy controls (n = 32) were enrolled. Participants performed a verbal working memory task (VWMT) with varying levels of demand for cognitive control during fMRI scanning and provided self-reports of fatigue (FACT-F) at two time points coincident with pre- and one-month post chemotherapy assessments. Imaging data were analyzed with general linear models using SPM5; comparative statistics were used to determine group differences, and correlational analyses addressed relationships of fatigue and neurocognitive measures.

Findings: The chemotherapy group reported significantly greater severity of fatigue (p &lt; .05) and performed less accurately on the VWMT both pre- and one-month post-treatment than the other groups. Greater fatigue was correlated with poorer performance on the VWMT at both time points across groups, with stronger correlation post-treatment (r = −.22, p = .03). A 2 time-point (pre- vs. post-treatment) × 2 group (chemotherapy vs. controls) × 2 demand-level contrasts (high minus low vs. medium minus low) analytic model showed a significant group × time interaction (p &lt; .05), mainly due to lower pre-treatment activation in an area of the prefrontal cortex supporting working memory, the anatomical left inferior frontal gyrus (LiFG), at higher task demand in the chemotherapy group. The radiotherapy group scored between the other two groups with intermediate activation of those contrasts. Of interest, lower pre-treatment activation in the LiFG in the high-low demand contrast predicted severity of fatigue across all participants at the post-treatment assessment (r = −.27, p &lt; .01), linking early compromise in neurocognitive performance with greater fatigue over time.

Discussion: Neurocognitive alterations during a working memory task and greater fatigue were evident before any adjuvant chemotherapy for breast cancer. Notably, functional alterations in working memory processes were evident with fMRI before adjuvant chemotherapy and predicted severity of post-treatment fatigue. Importantly, across all participants, greater fatigue over time was correlated with reduced cognitive performance. Taken together, these findings indicate that pre-treatment neurocognitive compromise and fatigue are key contributors to the cognitive impact often attributed solely to chemotherapy. Early therapeutic interventions targeting fatigue may improve cognitive function and reduce the distress of “chemo brain” throughout the course of adjuvant treatment.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr S6-3.

A SNP in steroid receptor coactivator-1 disrupts a GSK3β phosphorylation site and is associated with altered tamoxifen response in bone

The coregulator steroid receptor coactivator (SRC)-1 increases transcriptional activity of the estrogen receptor (ER) in a number of tissues including bone. Mice deficient in SRC-1 are osteopenic and display skeletal resistance to estrogen treatment. SRC-1 is also known to modulate effects of selective ER modulators like tamoxifen. We hypothesized that single nucleotide polymorphisms (SNP) in SRC-1 may impact estrogen and/or tamoxifen action. Because the only nonsynonymous SNP in SRC-1 (rs1804645; P1272S) is located in an activation domain, it was examined for effects on estrogen and tamoxifen action. SRC-1 P1272S showed a decreased ability to coactivate ER compared with wild-type SRC-1 in multiple cell lines. Paradoxically, SRC-1 P1272S had an increased protein half-life. The Pro to Ser change disrupts a putative glycogen synthase 3 (GSK3)β phosphorylation site that was confirmed by in vitro kinase assays. Finally, knockdown of GSK3β increased SRC-1 protein levels, mimicking the loss of phosphorylation at P1272S. These findings are similar to the GSK3β-mediated phospho-ubiquitin clock previously described for the related coregulator SRC-3. To assess the potential clinical significance of this SNP, we examined whether there was an association between SRC-1 P1272S and selective ER modulators response in bone. SRC-1 P1272S was associated with a decrease in hip and lumbar bone mineral density in women receiving tamoxifen treatment, supporting our in vitro findings for decreased ER coactivation. In summary, we have identified a functional genetic variant of SRC-1 with decreased activity, resulting, at least in part, from the loss of a GSK3β phosphorylation site, which was also associated with decreased bone mineral density in tamoxifen-treated women.

PD04-01: Predictors of Recovery of Ovarian Function during Aromatase Inhibitor (AI) Therapy

Background: AIs may cause a paradoxical rise in estrogen levels due to re-activation of ovarian function in women with chemotherapy-induced ovarian failure (CIOF). Therefore, identification of residual ovarian estradiol production is critical if such women are treated with adjuvant AI therapy rather than tamoxifen. We performed a prospective registry trial to identify predictors of recovery of ovarian function during AI therapy.

Methods: Women with hormone receptor (HR) positive breast cancer who were pre- or peri-menopausal at diagnosis and who remained amenorrheic for ≥8 weeks after cyclophosphamide-containing adjuvant chemotherapy were enrolled in a multi-institutional, open-label clinical trial of anastrozole (1 mg/day). Following confirmation that serum estradiol (E2) levels were &lt;20 pg/ml using an ultrasensitive E2 assay (Quest Diagnostics), subjects initiated anastrozole. Serum E2 was assessed biweekly for 12 wks, then less frequently, for 72 wks. Multivariable logistic regression was used to evaluate clinical predictors (age at AI initiation OR chemotherapy, menopausal status at chemotherapy, body mass index (BMI), baseline E2) of recovery of ovarian function defined as elevated serum E2 levels or return of menses.

Results: Sixty-nine women were enrolled; current status is given in Table 1.

P4-07-16: Development of Circulating Tumor Cell-Endocrine Therapy Index in Metastatic Breast Cancer Patients

Introduction: Only ∼ 50% of patients (pts) with estrogen receptor (ER) positive metastatic breast cancer (MBC) benefit from endocrine therapy (ET). Currently only clinical judgment can be used to identify pts with endocrine-refractory MBC, who are better palliated with chemotherapy. Circulating Tumor Cells (CTC) are reliably enumerated using an automated immunomagnetic system (CellSearch®; Veridex LLC). High CTC levels predict rapid progression in pts with MBC. We have developed a multi-parameter assay, the CTC-Endocrine Therapy Index (CTC-ETI) using CellSearch® that may identify pts with ER positive MBC who are unlikely to benefit from ET and may be better served with chemotherapy. CTC-ETI scores are assigned based on CTC levels coupled with the relative percent and degree of marker positivity on the CTC. We report preliminary results from a pilot single institutional study.

Methods: CellSearch® has 4 fluorescence channels. Three distinguish CTC from WBC (DAPI, anti-cytokeratin, anti-CD45). The 4th “empty” channel was used to measure ER, BCL-2, HER-2, and Ki-67 expression with fluorescent-labeled antibodies. These 4 markers reflect sensitivity (ER, BCL-2) or resistance (HER-2, Ki-67) to ET. Forty ml of blood was drawn into 4 CellSave® tubes from pts with progressive MBC. Whole blood from 4 tubes was pooled and divided into 4 different 7.5 ml aliquots of blood, which were processed and characterized for CTC counts and each of the four molecular markers using the CXC CellSearch® kit.

Results: 21 pts have been accrued to the feasibility study. One patient was ineligible. Five of 20 pts had low CTC counts (&lt;5 CTC/7.5ml whole blood), and are expected to have a relatively favorable prognosis. CTC-ETI was successfully determined in 10 pts (50%): 2 pts had low, while 3 had intermediate, and 5 had high CTC-ETI. Technical difficulties precluded accurate CTC-ETI in the remaining 5 patients. Of note, expression of the biomarkers among CTC in single patients was heterogeneous, suggesting that future iterations of the CTC-ETI will have to consider expression variability. Further exploratory results regarding associations between CTC-ETI and outcomes will be presented.

Conclusions: ER, BCL-2, HER-2, and Ki-67 can be accurately determined on CTC using the 4th channel in the CellSearch® system to calculate CTC-ETI. We predict that lower CTC-ETI scores (low or no CTC, or CTC with high CTC ER and BCL-2 and low CTC HER-2 and Ki-67) could be associated with favorable response to ET. Successful completion of the feasibility study will lead to a prospective trial to determine if high CTC-ETI at baseline predicts resistance and rapid progression on ET in women starting a new endocrine therapy for MBC.

Supported by Veridex, LLC, Fashion Footwear Charitable Foundation of New York/QVC Presents Shoes on Sale ™ (DFH), Associazione Sandro Pitigliani and by a studentship from FIRC (CP).

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-07-16.

Plasma letrozole concentrations in postmenopausal women with breast cancer are associated with CYP2A6 genetic variants, body mass index, and age

The associations between plasma letrozole concentrations and CYP2A6 and CYP3A5 genetic variants were tested in the Exemestane and Letrozole Pharmacogenomics (ELPH) trial. ELPH is a multicenter, open-label prospective clinical trial in women randomly assigned (n≈250 in each arm) to receive 2 years of treatment with either oral letrozole (2.5 mg/day) or oral exemestane (25 mg/day). CYP2A6 and CYP3A showed effects on letrozole metabolism in vitro. DNA samples were genotyped for variants in the CYP2A6 and CYP3A5 genes. Plasma letrozole concentrations showed high interpatient variability (>10-fold) and were associated significantly with CYP2A6 genotypes (P<0.0001), body mass index (BMI) (P<0.0001), and age (P=0.0035). However, CYP3A5 genotypes showed no association with plasma letrozole concentrations. These data suggest that CYP2A6 is the principal clearance mechanism for letrozole in vivo. CYP2A6 metabolic status, along with BMI and age, may serve as a biomarker of the efficacy of letrozole treatment or a predictor of adverse effects.

Abstract P3-02-06: Correlation of BCL-2 and Apoptosis on Circulating Tumor Cells and Breast Cancer Tissue

Background: Circulating Tumor Cell (CTC) levels are prognostic markers in metastatic breast cancer (MBC). Further phenotypic characterization of CTC may provide an opportunity for non-invasive evaluation of predictive and prognostic markers. Apoptosis is a common form of chemotherapy-induced cell death. Monoclonal antibody (MAb) M30 recognizes a neo-epitope on fragmented cytokeratin and is a marker of apoptosis. BCL-2 is an anti-apoptotic marker and may predict for resistance to anti-neoplastic therapy. We have previously reported the results of a pilot clinical trial to estimate M30 and BCL-2 expression in CTC from patients with MBC. The current study was performed to correlate the expression of both BCL-2 and M30 in CTC with breast cancer tissue samples. Methods: Of the 85 patients in the original pilot study, 52 (61%) had evaluable tissue available (39 primary and 12 metastatic lesions; one unknown) and were included in this analysis. CTC were collected at baseline and were isolated, enumerated, and phenotypically characterized for M30 and BCL-2 using the CellSearch® System. CTC phenotype is reported as percentage of cells with positive staining. Tissue Microarrays (TMA) were constructed and immunohistochemically stained for M30 (anti-Cytodeath™ M30, Roche) and Bcl-2 (M-0887, DAKO) and scored using the Allred method.

Results: Tissue staining for M30 and Bcl-2 were inversely correlated. Of the 52 patients with TMA available for investigation, 22 (42%) had &gt; 5 CTC/7.5 ml whole blood. A positive, but non-significant, correlation was observed between increasing numbers of CTC levels and tissue BCL-2 Allred Score (Spearman r=0.36; p=0.1310). M30 staining was detected in ≥10% of CTC in 20 of the 22 (91%) patients with elevated CTC, while BCL-2 staining was detected in ≥10% of CTC in 19 of the 22 (86%) patients. Little if any correlation was observed between CTC M30 and tissue M30 expression, however CTC BCL-2 was positively correlated with tissue Bcl-2 expression (Spearman r=0.47; p=0.0440). Conclusions: BCL-2 and M30 can be characterized in both CTC and breast cancer tissue. The likelihood of having elevated CTC may be associated with higher BCL-2 expression, and CTC BCL-2 was associated with tissue BCL-2 expression. Although the clinical implications of these findings are unknown, they offer the opportunity for future trials to investigate whether CTC BCL-2 and M30 might be useful to identify patients with cancers that are resistant to standard therapies. Furthermore, CTC BCL-2 and M30 might be monitored in clinical trials of novel, apoptosis-inducing therapeutic agents.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-02-06.

Abstract P2-14-09: Prospective Evaluation of Change in 2-Point Discrimination of Index Finger as a Potential Early Predictive Marker for Carpal Tunnel Syndrome among Women Receiving Adjuvant Aromatase Inhibitor Therapy for Postmenospausal Breast Cancer in the Exemestane and Letrozole Pharmacogenomics (ELPh) Trial

Introduction: Third generation aromatase inhibitors (AIs) represent an integral part of hormonal therapy in postmenopausal women with hormone receptor (HR)-positive breast cancer. AIs are associated with musculoskeletal symptoms in up to 50% of women. Post-hoc analyses of adjuvant AI trials (ATAC and IES) have suggested that AIs might be associated with carpal tunnel syndrome (CTS), a pressure-induced neuropathy disorder caused by compression on the median nerve. The clinical diagnosis of CTS is made with typical symptoms of pain, weakness, and paresthesias in affected arm. A variety of tests, including change in 2-point discrimination (2PD) can be used to aid in diagnosis. However, the actual incidence of CTS and clinical utility of diagnostic tests such as 2PD have not been prospectively examined among women receiving AIs. Methods: Postmenopausal women with stage 0-III HR-positive breast cancer, who had completed local therapy and, if indicated, adjuvant chemotherapy, and who were enrolled in the multi-center Exemestane and Letrozole Pharmacogenetics (ELPh) trial underwent prospective evaluation of 2PD with the Disc-criminator™ (sliding aesthesiometer) at baseline, and 3 months, following initiation of the AI. The end of the Disc-criminator™ was applied at the two points at same time to the skin on the volar tip pulp of the index fingers, and the threshold value (in mm) was determined as the shortest distance between the two points a woman was able to differentiate. The exercise was repeated thrice at each point. Abnormal 2PD thresholds were defined using standard criteria (outside 95 percentile for age). The differences in mean 2PD from baseline to 3 months were analyzed using a multivariate mixed effects model where the correlations from repeated measures were accounted for by assuming an unstructured covariance structure. A p value &lt; 0.05 was considered statistically significant.

Results: A total of 104 women underwent baseline 2PD testing. The mean age was 59 years, 55.8% had stage I disease, and 42.3% received adjuvant chemotherapy. We observed abnormal 2PD thresholds in 1.9% and 3.5% of women at baseline and 3 months respectively. There was a significant worsening in the adjusted mean 2PD from baseline (3.4 mm) to 3 months (4 mm, p=0.01). The increase in mean 2PD following 3 months of AI therapy was higher among women with age &gt; 55 (p=0.02), BMI &gt; 25 (p=0.002), African Americans (p=0.02), and those who received adjuvant chemotherapy (p=0.05), as compared to their counterparts. Conclusion: Adjuvant AI therapy was associated with a significant worsening of 2PD at 3 months, particularly among older women, overweight women, and those receiving adjuvant chemotherapy. Correlation with CTS symptoms and need for surgical release will be presented at the meeting. Our results suggest that 2PD is a non-invasive method that may potentially allow for early detection of CTS. If confirmed, change in 2PD could serve as an objective early predictor for subsequent CTS in postmenopausal women with breast cancer initiating AI therapy.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-14-09.

Abstract P6-15-03: Phase Ib Trial of the Gamma Secretase Inhibitor (GSI), MK-0752 Followed by Docetaxel in Locally Advanced or Metastatic Breast Cancer

Background: The cancer stem cell hypothesis asserts that there is a small population of cells within a tumor that has the ability to self renew and differentiate, and that these cells drive tumor growth and metastasis but are resistant to conventional cytotoxic chemotherapy. Pathways involved in stem cell growth and differentiation are viable targets for new anticancer therapies. One such pathway, Notch, is inhibited by GSIs which prevent translocation of Notch intracellular domain to the nucleus. Inhibition of GS concurrent with chemotherapy might improve disease control by targeting both stem cells and differentiated cells within the tumor. This Phase Ib clinical trial was designed to determine the MTD of the GSI, MK-0752, in combination with docetaxel, and to evaluate an effect on stem cell markers in serial tumor biopsies.

Methods: Eligible subjects had metastatic breast cancer or locally advanced breast cancer that did not respond to anthracycline therapy. Patients with disease that progressed on a taxane, or who had received a taxane within 6 months were excluded. MK-0752 was administered orally on days 1-3 of each 21-day cycle of therapy, in escalating doses. Dose levels (mg/day) 1=300; 2=450; 3=600; and 4=800. Docetaxel 80 mg/m2 IV was administered day 8, with pegfilgrastim day 9 each cycle. Treatment was continued until disease progression, unacceptable toxicity, or symptomatic deterioration. The trial was monitored using the Time to Event Continual Reassessment Method, targeting a 20% toxicity rate. Tumor biopsies were performed at baseline, after 1 cycle, and at treatment completion in a subset of patients.

Results: 30 patients were enrolled between Mar 2008 and Jan 2010. Dose limiting toxicities of the combination included diarrhea, hand-foot syndrome, and LFT elevation. 20/30 patients experienced Grade 1 or 2

fatigue. The final estimates and confidence intervals for the probability of dose limiting toxicity at each dose level are summarized in the table:

Probability = probability of dose-limiting toxicity 20 enrolled patients had measurable disease by RECIST criteria. Of these, 9 had PR, 8 SD, and 3 PD, for an estimated RR of 45% to the combination. 2 patients have been maintained on therapy in excess of 22 cycles. Conclusions: Dose level 3 was identified for further study in a Phase II randomized trial. Efficacy of docetaxel was not inhibited by MK-0752, as a 45% RR in patients with measurable disease was observed. There is intriguing long term disease stabilization in 2 patients. Evidence of an effect of the combination on the stem cell population was apparent on serial biopsies as presented at SABCS Dec 2009 (Abstract # 48); additional biopsy data will be presented.