Abstract P1-09-05: Radiosensitization of androgen receptor (AR)-positive triple-negative breast cancer (TNBC) cells using seviteronel (INO-464), a selective CYP17 lyase and AR inhibitor

Background: Increased rates of locoregional recurrence (LR) have been observed in TNBC despite chemotherapy and radiation (RT). A novel radiosensitizer screen nominated the AR as a promising target for treatment of radioresistant breast cancer, including TNBC. We assessed the activity of seviteronel (Sevi), a selective CYP17 lyase and AR inhibitor in Phase 2 clinical development for advanced breast and prostate cancer, as a potential radiosensitizer in AR+ TNBC model.

Methods: Clonogenic survival assays were used to determine the intrinsic RT sensitivity of 21 breast cancer cell (BCC) lines. IC50 values were determined for 130 clinically available compounds and correlation coefficients were calculated using IC50 values and SF-2Gy. Gene expression was measured using RNA Seq or qRT-PCR and protein expression was measured using RPPA arrays. AR function was assessed using functional inhibition with Sevi in MDA-MB-453, ACC-422, ACC-460, SUM-185 (all four AR+ TNBC), MDA-MB-231 (AR- TNBC), and T47D (AR- ER+) BCC lines. Double-stranded DNA (dsDNA) break repair was assessed with γH2AX foci counting. In vivo tumor growth was measured with varying control and treatment groups (16-20 tumors/group). Kaplan-Meier analysis was performed to estimate local control. A Cox proportional hazards model and multi-variate analysis (MVA) were used to determine variables associated with LRF survival.

Results: Our novel radiosensitizer screen identified the activity of anti-androgen therapy as a potentially effective strategy for radiosensitization in RT-resistant BCC lines (R2 =0.46, p-value < 0.01) (Speers et al, J Clin Oncol 35, 2017 (suppl; abstr e12102). Heterogeneity in AR expression was identified in human BCC lines and TNBC samples from patients (N=2098). There was a strong correlation between AR RNA expression and protein expression across all BC intrinsic subtypes. AR inhibition using Sevi induced radiation sensitivity in vitro with an enhancement ratio (ER) of 1.24-1.69 in four different AR+ TNBC lines. No such radiosensitization was seen in AR(-) TNBC or ER+, AR(-) BCC lines. Radiosensitization was at least partially dependent on impaired dsDNA break repair with significant delays in dsDNA break repair at 16 and 24 hours in all AR+ TNBC lines examined (p-value < 0.01). AR inhibition with Sevi significantly radiosensitized AR+ TNBC xenografts in mouse models and markedly delayed tumor-volume tripling time (TTT) and tumor growth (MDA-MB-453: median TTT 16.1 days for RT alone vs. not reached after 45 days for Sevi+RT, p-value <0.001). Similar delays were seen in tumor growth, weight, and tumor doubling. Clinically, TNBC patients whose tumors had higher than median expression of AR had higher rates of LR after RT (HR for LR ˜3, p-value <0.01, 2 independent datasets). In MVA, high AR expression was the variable most significantly associated with worse LR survival after RT in TNBC patients, outperforming all other variables (HR of 3.42; p-value < 0.01).

Conclusions: Our results implicate the AR as a mediator of radioresistance in breast cancer and support the rationale for developing Sevi as a novel radiosensitizing agent in AR+ TNBC.

Citation Format: Speers CW, Chandler B, Olsen E, Wilder-Romans K, Moubadder L, Nyati S, Rae J, Hayes DF, Spratt DE, Wahl DR, Eisner J, Feng FY, Pierce LJ. Radiosensitization of androgen receptor (AR)-positive triple-negative breast cancer (TNBC) cells using seviteronel (INO-464), a selective CYP17 lyase and AR inhibitor [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-09-05.

Neoadjuvant systemic therapy in breast cancer: use and trends in radiotherapy practice

BACKGROUND

The use of neoadjuvant systemic therapy (nast) in the treatment of breast cancer is increasing, and the role of adjuvant radiation therapy (rt) in that setting is uncertain. We sought to review and report the use of nast, its trends over time, and its relationship with the prescribing patterns of locoregional rt in a provincial cancer system.

METHODS

Patients with stages i-iii breast cancer diagnosed during 2007-2012 were identified using a provincial database. Patient, tumour, and treatment characteristics were extracted. Multivariable logistic regression analyses were used to assess associations with the use of nast. Kaplan-Meier and Cox regression were used for survival analyses.

RESULTS

Of the 11,658 patients who met the inclusion criteria, 602 (5%) had received nast. Use of nast was more frequent in stage iii patients (53%) than in stages i and ii patients (2%). In clinically lymph-node positive patients, a pathology assessment was made approximately 50% of the time. Higher clinical tumour stage and increasing clinical nodal stage predicted for increasing use of nast and of nodal rt after nast, but pathologic nodal status after nast was not associated with use of nodal rt. A statistically significant survival difference was observed between patients in the nast and no-nast groups, but that significance disappeared in a multivariable Cox regression analysis.

CONCLUSIONS

This population-based study demonstrated 5% use of nast for breast cancer. Most patients received nodal rt after nast, and nodal rt was not associated with pathologic stage after nast. Findings likely reflect the realities of clinical practice and show that reliance on clinical nodal staging results in outcomes similar to those reported in the literature.

The heart of the matter: cardiac assessment in professional footballers

AIM

Sudden cardiac death is the leading medical cause of death during exercise.1 Our objective was to retrospectively analyse the routine cardiac assessment of professional footballers to aid physician management and improve player safety.

METHODS

Footballers from five professional clubs between March 2012 and October 2014 were included (n=265). All were performed in line with the recommendations of the Football Association Cardiology Committee, incorporating clinical examination, 12-lead ECG, echocardiography and health questionnaire.2 Data was retrospectively collected, inspected and analysed using Excel spreadsheets. Findings were classified as 'normal' or 'not normal', and not normal assessments were further broken down into 'clear-cut pathology' (pathology with widely accepted guidance on management) or 'grey screen'.

RESULTS

Footballers were aged 13 to 37 years, with 69% aged over 18 and 31% under. The majority of the review population was White European (66%). Of the review population 11% had 'not normal' assessments, of these assessments 83% were considered grey screens (by Consultant Cardiologist) requiring further investigation or surveillance. Overall clear-cut pathology was identified in 2%.

CONCLUSIONS

A high proportion of the players (9%) had grey screens. The majority of these were due to ECG or structural abnormalities, which are clinically challenging to differentiate from physiological adaptation of the athletic heart and potentially fatal conditions. The extent to which these findings put the athlete at risk of a life threatening cardiac event is un-?quantified. Team physician's need to be aware of managing the on-going risk with these patients and ensure suitable ?follow up and assessment on a regular basis to mitigate this.

Abstract P1-10-02: A signature predictive of early vs. late recurrence after radiation treatment (RT) for breast cancer that may inform the biology of early, aggressive recurrences

Purpose: Unmet clinical needs in breast cancer (BC) management include the identification of patients (pts) at high risk to fail locally despite standard local therapy including RT and understanding the biology of these recurrences. We previously reported1 a RT response signature and here extend those studies to identify a signature predictive of timing of recurrence after completion of RT (before or after 3 years).

Methods: Two independent patient cohorts (treated with BCS) from non-randomized clinical trials were used for training and validation. The training cohort included 119 pts with in-breast tumor recurrence and the validation cohort had 25 pts with recurrences. Initial feature selection used Spearman's rank correlation correlating gene expression (14,806 genes) to recurrence time. Genes with sig. correlation (FDR <0.1) and large expression range (fold change >2) were used to train an elastic net penalized Poisson regression model. This model was locked and then applied to the validation dataset. Cox regression was used for both univariate and multivariable analyses (UVA and MVA). To identify biological-related concepts, Spearman's corr. coefficients of recurrence time to gene expression within the training cohort were used to generate a pre-ranked list upon which GSEA pathway analysis was performed.

Results: Spearman's correlation identified 485 genes whose expression was significantly associated with recurrence time (early vs. late). Feature reduction further refined the gene list to 41 genes, which were retained within the signature and locked for further validation. In the training dataset the Spearman's correlation of the continuous score to recurrence time was 0.852 with a P-value of 1.3x10-34 and an AUC of 0.92. Application of this early vs late signature to an independent BC validation set accurately identifies pts with early vs. late recurrences (Spearman's corr.=0.537, p-value<0.007, AUC=0.74, sensitivity=0.71, specificity=0.73, PPV=0.77, NPV=0.67). In UVA and MVA the early vs. late recurrence signature remained the most significant factor associated with recurrence time. Although independent of intrinsic subtype, GSEA analysis of the 41 genes retained within the signature identifies proliferation and EGFR concepts associated with early recurrences and luminal and ER-signaling pathways associated with late recurrences. Knockdown of genes associated with the early and late recurrences is currently underway to assess phenotypic changes (proliferation and clonogenic survival as a measure of early and durable RT response) associated with the early and late recurrence-associated genes.

Conclusion: In this study we derive a BC-specific RT signature predictive of early vs. late recurrence with biologic relevance and validate this signature for prediction of timing of recurrence in an independent clinical dataset. By identifying pts with tumors likely to recur sooner vs. later this signature has the potential to allow for a furthered understanding of the biology underlying early and late recurrences and has a potential to personalize RT, particularly in patients for whom treatment intensification is needed.

1. Clin Cancer Res. 2015 Aug 15;21(16):3667-77.

Citation Format: Speers C, Chang L, Santola A, Liu M, Zhao SG, Chandler B, Olsen E, Bartelink H, Feng FY, Pierce LJ. A signature predictive of early vs. late recurrence after radiation treatment (RT) for breast cancer that may inform the biology of early, aggressive recurrences [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 P1-10-02.

Abstract P5-16-17: Population based long term outcomes of pathologic complete response after neoadjuvant chemotherapy in stage I-III breast cancer: The British Columbia experience

Background:

Neoadjuvant chemotherapy is a treatment option for breast cancer patients (pts) with locally advanced disease and for pts with operable breast cancer who desire breast conservation. Neoadjuvant therapy also allows for early evaluation of the effectiveness of systemic therapy. Pathologic complete response (pCR) has been shown in clinical trials to be associated with improved survival. The objective of this study was to determine if the outcomes demonstrated in clinical trials can be applied in the population based setting by comparing the outcomes of breast cancer pts who achieved pCR (no invasive disease in breast and nodes) vs. those that did not achieve a pCR.

Methods:

This is a retrospective cohort study of stage I-III invasive breast cancer pts treated with neoadjuvant chemotherapy from 2005 to 2010 in British Columbia. Cases were identified from the Breast Cancer Outcomes Unit database. Data was collected on demographics, tumor pathology, and type of treatment (chemotherapy, endocrine therapy, trastuzumab) and linked to standard clinical outcomes.

Results:

267 pts who met inclusion criteria were identified, of whom 5% had stage I, 33% Stage II and 59% Stage III breast cancer. Median follow up was 7.4 years. Overall 74 pts (28%) demonstrated a pCR and 193 pts did not. pCR pts had better 5-yr overall survival (OS) vs. non-pCR pts: 88% vs. 73% (HR 0.43, 95% CI 0.23-0.82, p=0.01). 5-yr disease free survival (DFS) was 84% in pCR pts vs. 70% in non-pCR pts (HR 0.45, 95% CI 0.24-0.83, p=0.01). Similarly, 5-yr breast cancer specific survival (BCSS) and distant disease free survival (DDFS) were significantly better in favor of the pCR cohort: HR 0.39 (95% CI 0.18-0.82, p=0.01) and HR 0.45 (95% CI 0.24-0.83, p=0.02) respectively. pCR pts were more likely to be HER2-positive and/or ER negative.

Conclusions:

Our population based results showed that early stage breast cancer pts who achieved pCR after neoadjuvant chemotherapy had better outcomes on all survival parameters compared to pts who did not achieve a pCR. This finding is consistent with results from neoadjuvant clinical trials and the FDA meta-analysis. These 'real world' results demonstrate that pCR can be used as a surrogate endpoint for survival outcomes even among non-trial pts.

Citation Format: Sun J, Gondara L, Diocee R, Speers C, Lohrisch C, Chia S. Population based long term outcomes of pathologic complete response after neoadjuvant chemotherapy in stage I-III breast cancer: The British Columbia experience [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 P5-16-17.

Abstract P6-12-05: Targeting estrogen receptor mutations for treatment of endocrine therapy resistance in breast cancer

This abstract was withdrawn by the authors.

Abstract P5-12-10: Comparison of the efficacy of tamoxifen and aromatase inhibitors on survival in adjuvant menopausal breast cancer

Background

Meta-analyses of postmenopausal endocrine therapy and recent studies in premenopausal women suggest that aromatase inhibitors (AI) may be superior to tamoxifen (T) in preventing recurrence in early hormone receptor positive (HR+) breast cancer (BC), although there are recent concerns about the impact on overall survival (OS). The BC Cancer Agency adopted ASCO guidelines of an AI as part of adjuvant therapy for menopausal HR+ BC in 2003. Using our population based data, we sought to compare the 10 year survival outcomes for patients starting either T or AI following surgery for HR+BC.

Methods

Histopathologic and demographic data were collected for all menopausal patients referred to the BC Cancer Agency with a T1-2, node negative, HR+, HER2 negative BC diagnosed between 01/2003 and 12/2009. Patients with prior or synchronous contralateral BC were excluded. Data was cross-referenced to the provincial pharmacy database, which tracks hormone therapy. Significant factors affecting survival were identified using Cox proportional hazard model for OS and Fine and Gray's (FG) model for BC specific and Cardiac Specific Survival (CSS) with causes other than event of interest defined as competing.

Results

We identified a cohort of 3421 cases with median follow up of 7.8 years (y) for T and 7.4 y for AI. Median age was 65y in both groups, and 8.5% received chemotherapy. 47.8% of tumors were T1c and 22.2% were T2; 15.8 % were grade 3. 10 year OS was 84.4% (95% Confidence Intervals [CI] 82.4%, 86.2%) and 82.7% (95% CI 79.4%, 85.6%) for T and AI cohorts, respectively, (p= 0.02). BCSS did not differ between the groups (p=0.54). We categorized causes of death in each cohort as from BC (20.4% T, 20.6% AI), other cancers (25.4% T, 22.1% AI), cardiovascular-related (CVS) (25.8% T, 34.6% AI), thromboembolic (0.3% T, 0.7% AI %) and other (25.4%T, 19.1 % AI). Table 1 shows Univariate (U), multivariable (M), hazard ratios (Hz) and 95% CI.

Table 1 OSBCSSCSS UM (KM)UM ( FG)UM  Hz Hz HzTumour Size, continuous<0.0001<0.0001<0.0001<0.0001<0.00010.0280  1.282 (1.142,1.438) 1.882 (0.631,2.090) 1.272 (1.026, 1.577)Age at dx,continuous<0.0001<0.00010.00190.2637<0.0001<0.0001  1.094 (1.080,1.108) 1.016 (0.988,1.044) 1.152 (1.122,1.183)Grade , 3 vs 1<0.00010.0557<0.00010.00180.29930.8719  1.341 (0.993,1.811) 2.973 (1.501,5.889) 1.051 (0.576,1.915)LVI, Yes vs No0.00040.0465<0.00010.00010.24870.0671  1.357 (1.005,1.833) 2.732 (1.637,4.558) 0.474, (0.213,1.054)Chemo use, Yes or No0.0990.21220.05350.50290.02050.8710  0.748 (0.474,1.180) 1.284 (0.618,2.670) 1.128 (0.264,4.824)AI vs T0.020.29270.59250.25540.00410.0123  1.124 (1.142,1.438) 0.742 (0.443,1.241) 1.658 (1.116,2.463)

Conclusion

While trials show that AIs improve relapse free survival after menopausal HR+BC, their impact on BCSS has been minimal. By contrast they may contribute to CVS deaths, as suggested by our data. We plan to explore this observation further by examining baseline cardiac risk factors within our T and AI cohorts, and by exploring OS, BCSS, and CSS among patients switching to AI after starting T, to identify the optimal adjuvant hormone therapy strategy for menopausal women with HR+ early BC.

Citation Format: Chay WY, Speers C, Gondara L, Tyldesley S, Ellard SL, Lohrisch CA, Gelmon KA. Comparison of the efficacy of tamoxifen and aromatase inhibitors on survival in adjuvant menopausal 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 P5-12-10.

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.

Population-based analysis of the impact and generalizability of the NSABP-B24 study on endocrine therapy for patients with ductal carcinoma in situ of the breast

BACKGROUND

In 1999, the National Surgical Adjuvant Breast and Bowel Project (NSABP)-B24 trial demonstrated that tamoxifen reduced relapse risk in women with ductal carcinoma in situ (DCIS) treated with breast-conserving surgery (BCS) and radiotherapy (RT). In 2002, Allred's subgroup analysis showed that tamoxifen mainly benefitted estrogen receptor (ER)-positive disease. This study evaluates the impact and generalizability of these trial findings at the population level.

PATIENTS AND METHODS

From 1989 to 2009, 2061 women with DCIS underwent BCS + RT in British Columbia. The following cohorts were analyzed: (1) pre-NSABP-B24 era (1989-1998, N = 417); (2) post-NSABP-B24 era (2000-2009, N = 1548). Cohort 2 was further divided into pre- and post-Allred eras.

RESULTS

Endocrine therapy (ET) was used in 404/2061 (20%) patients. Median age of patients treated with compared with without ET, was 53 versus 57 years, (P < 0.0005). One of 417 (0.2%) versus 399/1548 (26%) patients took ET before versus after NSABP-B24. Among the post-Allred era cohort treated with ET (N = 227), tumors were ER-positive in 65%, ER-negative in 1%, and ER-unknown in 33%; whereas of those treated without ET (N = 801), ER was positive in 43%, negative in 15%, and unknown in 42% (P < 0.0005). On multivariable analysis of the post-NSABP-B24 era, ET was associated with improved event-free survival (EFS) (hazard ratio 0.6; P = 0.02); 5-year EFS were 96.9% with ET versus 94.5% without ET.

CONCLUSIONS

ET use in DCIS patients treated with BCS + RT increased significantly after the NSABP-B24 study. ER+ disease and younger age were associated with increased ET use. ET was associated with improved EFS, confirming the generalizability of trial data at a population level.