Abstract P4-03-15: Targeting Src kinase blocks development of afatinib resistance in HER2-positive breast cancer

Background: Afatinib is an irreversible pan-HER inhibitor approved for non-small cell lung cancer. We have previously shown that afatinib inhibits growth of HER2-positive breast cancer cells and enhances response to trastuzumab. However, we have also shown that long-term exposure to tyrosine kinase inhibitors leads to the development of acquired resistance. To determine if acquired afatinib resistance develops in HER2-positive breast cancer cells, we exposed a HER2-positive breast cancer cell line to afatinib for 6 months and investigated alterations in the cells following long-term exposure.

Methods: SKBR3 cells were treated with 150 nM afatinib twice-weekly for 6 months. Growth response to drug inhibitors was assessed by acid phosphatase assay. Drug sensitivity was examined in four HER2-positive cell lines (SKBR3, EFM192A, BT474 and HCC1954) and three acquired trastuzumab resistant cell lines (SKBR3-T, BT474-T and EFM192A-T). Reverse phase protein array (RPPA) was used to determine alterations in key signaling pathways. Src, p-Src, EGFR, p-EGFR, ERK1/2, p-ERK 1/2 levels were examined by Western blotting. To examine the prevention of the development of afatinib resistance, cells were treated twice weekly with afatinib, dasatinib, or the combination and stained with crystal violet when confluent.

Results: Following 6 months of afatinib treatment, the SKBR3-A cells were more resistant to afatinib compared to parental cells (IC50 SKBR3-A 284 ± 28.2 nM vs SKBR3-Par 10.9 ± 3.4 nM). Furthermore, the resistant cells were cross-resistant to lapatinib, neratinib and trastuzumab. RPPA interrogation of the SKBR3-A cells showed alterations in several pathways, including significantly increased levels of p-Src (Y416). SKBR3-A cells were more sensitive to Src inhibition with dasatinib compared to SKBR3-Par cells and the combination of afatinib and dasatinib was highly synergistic in SKBR3-A cells (CI value = 0.09 ± 0.06). The combination of afatinib and dasatinib was also synergistic in the trastuzumab resistant SKBR3-T cells (Table). Afatinib and dasatinib inhibited EGFR and Src activation and ERK 1/2 signalling in SKBR3-A cells.

Short-term resistance assays showed that the addition of dasatinib to afatinib blocks the emergence of resistant cells in three of four HER2 positive cell lines tested and two of the three acquired trastuzumab resistant cell lines tetsed.

Conclusion: HER2-positive breast cancer cells that are highly sensitive to afatinib can develop acquired resistance to afatinib within six months. Src is a potential target to prevent the development of afatinib resistance and thus combined treatment with afatinib and dasatinib may be beneficial in patients with HER2-positive breast cancer.

Percentage growth in HER2-positive cells treated with afatinib and/or dasatinib for 5 days. 20 nM Afatinib40 nM Dasatinib20 nM Afatinib + 40 nM DasatinibSKBR325.2 ± 6.1109.9 ± 6.222.6 ± 6.2SKBR3-A62.1 ± 0.787.3 ± 11.036.3 ± 0.3*SKBR3-T42.6 ± 4.9107.4 ± 9.729.3 ± 3.5*BT47418.2 ± 3.079.5 ± 5.213.3 ± 1.1BT474-T6.9 ± 2.795.3 ± 2.06.2 ± 2.3EFM192A39.1 ± 4.7105.7 ± 3.135.3 ± 2.7EFM192A-T30.4 ± 5.299.8 ± 2.528.5 ± 4.4HCC195461.8 ± 8.180.5 ± 8.219.4 ± 3.6** indicates enhanced anti-proliferative response for the combination compared to the single agents.

Citation Format: Conlon N, Canonici A, Morgan C, Cremona M, Hennessey BT, Eustace A, O'Brien N, Slamon D, Crown J, O'Donovan N. Targeting Src kinase blocks development of afatinib resistance in HER2-positive 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 P4-03-15.

Abstract P2-05-02: Functional genomic screening identifies ubiquitin-specific protease 11 (USP11) as a novel regulator of ER-alpha transcription in breast cancer

Approximately 70% of breast cancers overexpress the estrogen receptor α (ERα) and depend on this key transcriptional regulator for growth and differentiation. The discovery of novel mechanisms controlling ERα function represent major advances in our understanding of breast cancer progression and potentially offer attractive new therapeutic opportunities. Here, we investigated the role of deubiquitinating enzymes (DUBs), which act to remove ubiquitin moieties from proteins, in regulating transcriptional activity of ERα in breast cancer.

To identify DUBs involved in the regulation of ERα transcriptional activity, we performed an RNAi loss-of-function screen using a library of shRNA vectors targeting all human DUB genes. The DUB library consisted of pools of four non-overlapping shRNAs targeting all 108 known or putative DUBs (432 shRNAs in total). We found that suppression of a number of DUBs markedly repressed or enhanced the activity of an estrogen-response-element (ERE) luciferase reporter following estradiol (E2) stimulation. Of particular interest, suppression of the BRCA2-associated DUB, USP11, was found to down-regulate ERα transcriptional activity.

Subsequent validation using two individual siRNAs targeted to USP11 revealed a notable reduction in expression of endogenous ERα target genes in the ZR-75-1 cell line, as quantified using qRT-PCR. Further validation was carried out in a HEK293T USP11 knockout cell line, where reduced activity of an ERE-luciferase reporter was detected when compared to wild-type cells. This phenotype was rescued with a USP11 overexpression vector, both in the presence and absence of E2. Furthermore, USP11 expression was found to be upregulated in the estrogen-independent cell line LCC1 when compared to their parental MCF7 cells. Knockdown of USP11 in LCC1 cells resulted in decreased mRNA expression of a panel of ERα target genes, while RNA-seq revealed a downregulation of several putative ERα target genes and a downregulation of many cell cycle-associated proteins.

To support the prognostic relevance of USP11, immunohistochemical staining of a breast cancer tissue microarray (103 ER+ patients available for final analysis) was performed. Kaplan-Meier analysis of this cohort revealed a highly significant association between high USP11 expression and poor overall (p=0.030) and breast cancer-specific survival (p=0.041). In silico analysis of publically available breast cancer gene expression datasets further supported an association between high USP11 mRNA levels and poor prognosis. We observed a significant correlation between high expression of USP11 mRNA in ER-positive patients and poor distant metastasis-free survival (HR 2, CI 1.37-2.91, p=0.00023). This correlation was also significant in ER-positive patients who had received tamoxifen only (HR 2.9, CI 1.63-5.15, p=0.00015).

These results suggest a role for USP11 in driving cellular growth and identify USP11 as novel therapeutic target in breast cancer.

Citation Format: Dwane L, Das S, Moran B, O'Connor AE, Mulrane L, Dirac AM, Jirstrom K, Crown JP, Bernards R, Gallagher WM, Ní Chonghaile T, O'Connor DP. Functional genomic screening identifies ubiquitin-specific protease 11 (USP11) as a novel regulator of ER-alpha transcription in 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 P2-05-02.

Abstract P6-08-17: Pregnancy associated breast cancer: Evaluating maternal outcomes. A multicentre study

Background

Pregnancy associated breast cancer (PABC) is defined as breast cancer (BC) diagnosed during the gestational period (GP) or in the first year postpartum (PP). Despite its infrequent occurrence, the incidence of PABC appears to be rising due to the increasing propensity for women to delay childbirth. We have established the first combined prospective and retrospective registry study of PABC in Ireland to examine specific clinicopathological characteristics, treatments and maternal outcomes. We present the retrospective findings to date.

Methods

We performed a retrospective multicentre observational study of patients (pts) with PABC treated in the eight Irish cancer centres from August 2001 to March 2017. Data extracted included information on pt demographics, tumour biology, staging, treatment administered and maternal outcomes. Standard biostatistical methods were used for analysis.

Results

111 PABC patients were identified. Sixty pts (54%) were diagnosed during the GP and 51 (46%) within 1 year PP. Median age at diagnosis was 36 years (yrs). Table 1 illustrates baseline characteristics. Two thirds of pts were node positive and a similar proportion had grade 3 pathology. Seventy pts (63%) were estrogen receptor (ER) positive, 36 (32%) HER2 positive, 25 (22%) triple negative. Twenty-two pts (20%) were metastatic at presentation. Seven pts (6%) had a known BRCA 1/2 mutation. The median OS (overall survival) and DFS (disease free survival) for the entire cohort was 107.4 and 94.2 months respectively (resp). There was no survival difference between those diagnosed during the GP versus PP. 5 yr DFS and OS was 68.6% and 69.2% resp. This compares unfavourably to results reported by the National Cancer Registry of Ireland in a similar age-matched BC population between 2000-2012 where the 5 yr OS was 86.5%. Variables in our study associated with poorer outcomes included younger age, tumour size, node positivity and lack of estrogen expression.

Baseline characteristics PABC patients (n=11) %(n)Diagnosed in GP (n=60) %(n)Diagnosed 1yr PP (n=51) %(n)p valueDemographic    Age at diagnosis3636(25-49)36(21-44)0.31Stage    I-II54(60)55(33)53(27)0.85III23(26)23(14)23(12)1IV20(22)18(11)22(11)0.81Unknown3(3)3(2)2(1)1Pathology    Grade 366(74)70(42)63(32)0.43Node positive66(73)68(41)63(32)0.55ER+/HER2-41(45)38(23)43(22)0.69ER+/HER2+23(25)28(17)16(8)0.17ER-/HER2+14(16)17(10)12(6)0.59Triple negative22(25)17(10)29(15)0.11Surgery    Breast conservation23(26)25(15)21(11)0.82Mastectomy56(63)57(34)59(30)0.84Adjuavnt/Neoadjuvant treatment    Chemotherapy73(81)77(46)69(35)0.39Anthracycline68(55)78(36)54(19)0.03Taxane89(72)93(43)83(29)0.16Anti HER2 agent21(23)18(11)24(12)0.63Endocrine therapy64(52)63(29)66(23)0.84Radiotherapy79(64)74(34)86(30)0.85Relapse in Stage I-III    Local relapse15(13)12(6)18(7)0.55Distant relapse24(21)22(11)25(10)0.80

Conclusions

PABC patients may have a poorer outcome. Our study reported higher rates of triple negative and HER2 positive breast cancer which are associated with more aggressive biology. Prospective evaluation of clinicopathological features, pharmacokinetics of treatments selected and maternal and fetal outcomes is imperative in this distinct pt group.

Citation Format: Prior L, Teo M, Greally M, Ward C, O'Leary C, Aslam R, Darwish W, Ahmed N, Watson G, Kelly D, Kiely L, Hassan A, Gleeson J, Featherstone H, Lim M, Murray H, Gallagher D, Westrup J, Hennessy B, Leonard G, Grogan L, Breathnach O, Horgan A, Coate L, O'Mahony D, Coate L, O'Reilly S, Gupta R, Keane M, Duffy K, O'Connor M, Kennedy J, McCaffrey J, Higgins M, Kelly C, Carney D, Gullo G, Crown J, Walshe J. Pregnancy associated breast cancer: Evaluating maternal outcomes. A multicentre study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-08-17.

Abstract OT3-06-05: A phase Ib/II trial of coPANlisib in combination with tratuzumab in pretreated recurrent or metastatic HER2-positive breast cancer “PantHER”

Background

The phosphoinositide 3 kinase (PI3K) pathway is important in the oncogenic function of HER2. Aberrent activation of PI3K is implicated in resistance to trastuzumab and other HER2-targeted therapies and is frequent, with up to 22% of HER2 positive breast cancer having a PIK3CA mutation. Copanlisib is a pan-class 1 PI3K inhibitor that shows particular activity against PI3Kα, the isoform encoded by the PIK3CA gene. Copanlisib has been shown to re-sensitise trastuzumab resistant cell lines to trastuzumab with synergism seen in some cell lines between copanlisib and HER2 targeted therapy.

Trial design

The study is a phase Ib/II open label, single arm adaptive, multi-centre trial of copanlisib in combination with trastuzumab. Eligible patients are treated with a dose escalation schedule of copanlisib IV on Days 1, 8 and 15 of a 28 day cycle with trastuzumab 2 mg/kg weekly (loading dose of 4 mg/kg in cycle 1). The phase II dose will be based on the maximum tolerated dose (MTD) established in Phase Ib. Patients are treated until radiologic or symptomatic progression, unacceptable toxicity, consent withdrawal or physician's decision.

Eligibility criteria

Eligible patients must have recurrent incurable or metastatic HER2-positive breast cancer that has progressed on at least one prior line of trastuzumab or T-DM1-based treatment regimen in this setting. Patients with treated and controlled brain metastases are eligible. Participants must have adequate organ function and ECOG PS ≤ 2. Patients recruited for the Phase II part of the study must have a PIK3CA mutation. Patients with uncontrolled arterial hypertension, uncontrolled diabetes or recent clinically serious infections are excluded.

Specific aims

The primary end point for the phase Ib part of this study is to determine the MTD for the combination. For the phase II study is anti-tumour efficacy, measured by Clinical Benefit Rate (CBR).

Secondary end points are evaluation of safety and tolerability, progression-free survival, time to treatment failure, duration of response and overall survival. Incorporated translational endpoints include examination of molecular tumor adaptation in tissue and blood. Given the role of PI3K in cellular glucose metabolism, an additional exploratory objective is to determine if quantitive reduction in metabolic signal on Positron Emission Tomography-Computed Tomography (PET-CT) is predictive of benefit from therapy.

Statistical methods

To establish the MTD, we use a modified 3+3 design where 3 additional patients will be accrued even if the first 3 patients accrued experience no dose limiting toxicities (DLT) in sequential cohorts for a planned 12 patients. To determine the CBR, a one sample exact binomial test with a one sided significance level of 5%, 19 evaluable patients will provide >80% power to detect a difference between the null hypothesis proportion of 30% for CBR versus the alternative hypothesis proportion of 65%.

Present accrual and target accrual

There are 9 patients recruited so far to the phase Ib part of this study. Target accrual is 12 and for phase II is 19 patients.

Contact information for people with a specific interest in the trial

Prof Bryan Hennessy, Beaumont Hospital, Dublin Ireland

Funded by Bayer

Citation Format: Keegan NM, Walshe J, Gullo G, Kennedy J, Bulger K, Kelly CM, Crown J, Toomey S, Egan K, Kerr J, Given M, Hernando A, Teiserskiene A, Grogan L, Breathnach O, Morris PG, Keane M, Hennessy BT. A phase Ib/II trial of coPANlisib in combination with tratuzumab in pretreated recurrent or metastatic HER2-positive breast cancer “PantHER” [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 OT3-06-05.

Abstract P4-21-27: Plasma chemokine profile of HER2+ breast cancer (BC) patients treated with docetaxel (D) and carboplatin (C) in combination with trastuzumab (T) and/or lapatinib (L) in the neo-adjuvant setting

Background: Chemokines (chemotactic cytokines) are key regulators of the immune response, attracting immune cells to sites of inflammation, activating adhesion molecules, promoting extravasation and influencing T-cell subset polarization. Recent clinical data has shown a strong correlation between tumor infiltrating lymphocytes (TILs) and response to T therapy in HER2+ BC while the combination of chemotherapy, T and L has proven superior to chemotherapy and T alone in the neo-adjuvant setting (NeoALTTO). This preliminary study examines the levels of 40 circulating chemokines in 32 HER2+ BC patient plasma samples from ICORG 10-05 (neo-adjuvant DCT, DCL or DCTL) to investigate differences in chemokine profiles between treatment arms and patient's response to treatment.

Methods: Pre-treatment blood samples were collected before commencement of chemotherapy; post-treatment samples were collected two weeks prior to surgery. All patients received G-CSF concurrent with treatment. A panel of 40 chemokines and chemokine-associated cytokines were assessed by Luminex xMAP multiplex assay. Matched patient samples were run in single replicates and analysed together (n=32) or by comparing DCT (n=12) and DCTL (n=14) treatment arms (using a paired Mann-Whitney test and adjusting for multiple testing using Bonferroni correction). DCL (n=6) was omitted from the arm comparison due to low numbers. In addition, principle components analysis (PCA) was used to explore any trends within the data based on patient response (pathological complete response (pCR, n=15), partial response (PR, n=12), and non-response (NR, n=4)). 12 non-age matched healthy volunteer controls were also included in the PCA.

Results: PCA shows a clear separation between pre- and post-treatment samples. 30 of the 40 chemokines examined were significantly differentially expressed (adjusted p-value of <0.05) post-treatment across all treatment arms. When comparing DCT and DCTL, nine chemokines were significantly altered post-therapy in both arms with two chemokines, CCL24 (p=0.039) and IL-16 (p=0.039), increased in DCT only and ten chemokines, CCL11 (p=0.009), CX3CL1 (p=0.004), CXCL1 (p=0.009), CCL1 (p=0.024), IL-2 (p=0.043), IL-6 (p=0.034), IL-8 (p=0.004), CXCL11 (p=0.004), CXCL16 (p=0.004) and TNF-alpha (p=0.004) altered in DCTL only. PCA identified no trend between pre- and post-treatment chemokine levels and response.

Conclusions: DCT and DCTL produce statistically different alterations in the plasma chemokine profiles of HER2+ BC patients. Pre- or post-treatment levels of the chemokines examined are not collectively predictive of patient response to treatment. Further work is required to elucidate the relevance of DCT- and DCTL-specific chemokine alterations to response.

Citation Format: Collins DM, Madden SF, Gaynor N, Gallagher WM, O'Donovan N, Crown J. Plasma chemokine profile of HER2+ breast cancer (BC) patients treated with docetaxel (D) and carboplatin (C) in combination with trastuzumab (T) and/or lapatinib (L) in the neo-adjuvant setting [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 P4-21-27.

Abstract P5-14-12: Long-term outcome of HER2-normal early stage breast cancer (ESBC) patients (Pts) treated with docetaxel-cyclophosphamide (TC) chemotherapy (CTx): Mature results of a single-institution experience

BACKGROUND

Anthracycline(A)-containing regimens (AReg) became an established standard (neo)adj CTx for ESBC following fairly consistent demonstration of a modest superiority over older anti-metabolite/alkylating CTx. However, substantial translational data and a recently presented pooled analysis [Blum, 2016] suggest that this superiority could be largely driven by greater benefits in specific ESBC subgroups, i.e. HER2-altered BrCa (due to co-amplification of topoisomerase 2 and HER2), and triple-negative BrCa (TNBC). A are cardiotoxic (including late onset of cardiomyopathic congestive heart failure) and potentially leukaemogenic. In late 2006, following the results of the first USONC randomized clinical trial that showed superior outcomes of the non-AReg TC (docetaxel/cyclo­phosphamide) over AC, we established a routine, uniform policy of TC for all Pts receiving (neo)adj CTx for HER2-normal ESBC. We report the mature follow up of this single-institution unselected experience.

METHODS

We performed a retrospective outcome analysis of all Pts who received at least 1 cycle of (neo)adj TC (docetaxel 75 mg/m2 + cyclophosphamide 600 mg/m2 IV every 3 weeks) at our Department for HER2-normal ESBC and with at least 5 years of follow up (FU). Pts were identified by systematic analysis of the dataset of the Oncology Pharmacy Unit. Information on tumour characteristics [e.g. axillary lymph nodes (N) metastases, hormonal receptors (HR) and HER2 status] and Pts FU were retrieved and collected into an ad hoc designed database. Pts with node-positive (N+) ESBC received TC×6 cycles, and Pts with high-risk node-negative (N−) [e.g. primary tumour (T) >2 cm, or HRneg, or T >3 cm] ESBC received TC×4 cycles. Pts received adjuvant hormone therapy and radiotherapy as per standard of care. From 2008 on, many lower risk HR+/N− Pts were not given CTx due to OncotypeDx availability.

RESULTS

Between September 2006 and December 2015, 810 female HER2-normal ESBC Pts were treated with (neo)adj TC. In the final outcome analysis we included 464 Pts treated before June 2011 thus having a minimum FU of 5 years. Pts characteristics are: median age 53 yrs (range 30-77), N− 246 (53%), N+ 218 (47%), hormone receptors positive (HR+) 391 (84%), TNBC 73 (16%). The database was locked as of June 1st 2016. Median FU from first cycle of TC is 7.5 yrs (range 5.3-10). 63 BrCa-specific relapse events (defined as time to local, regional or distant recurrence, invasive contralateral breast cancer, excluding non-breast second primaries) have been observed, accounting for an overall Relapse-Free Survival (RFS) rate of 86.4%. 42 deaths have occurred, 36 (86%) due to BrCa, accounting for an Overall Survival (OS) rate of 91%. RFS and OS rates for the different Pts subgroups are reported in Table 1

Table 1 - Outcome parameters RFS (%)OS (%)All Pts8691HR+/N-9396HR+/N+8190TN/N-9191TN/N+5858

CONCLUSIONS

These mature data with long FU suggest that the outcome for a large cohort of unselected Pts with HER2-normal HR+ ESBC (regardless of nodal status) and for TN/N− ESBrCa treated with nonAReg TC is excellent. However, N+TN ESBrCa in this setting remains a significant clinical challenge.

Citation Format: Losurdo A, Gullo G, Buckley C, Lowry C, Ballot J, Silva N, Hammond L, Crown J. Long-term outcome of HER2-normal early stage breast cancer (ESBC) patients (Pts) treated with docetaxel-cyclophosphamide (TC) chemotherapy (CTx): Mature results of a single-institution 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 P5-14-12.

Abstract P1-05-18: Genomic copy number alterations (CNA) associated with pCR in HER2-positive (HER2+) early-stage breast cancer (BrCa) patients receiving neoadjuvant trastuzumab (T)

Introduction: Genetic alterations such as amplifications and deletions frequently contribute to tumorigenesis. These alterations can change gene expression which alters the normal cell growth and survival regulatory mechanisms. Characterisation of DNA copy number alterations (CNA) is important to understand cancer progression and response to therapy. The aim of this study is to determine patterns of CNAs in HER2+ early-stage BrCa patients achieving pathological complete response (pCR) to neoadjuvant T therapy.

Methods: Retrospective analysis of our database of 95 HER2+ BrCa (stages I-III) who received T neoadjuvantly revealed 46 % (44/95) achieved pCR compared with 53 % (51/95) who did not respond (NR). DNA from pre-treatment tumour biopsy specimens from neoadjuvant T therapy patients was extracted, and array-based comparative genomic hybridization (aCGH, n = 8; 6 pCR:2 NR) was used to identify CNAs, which correlated with pCR. Pathway analysis was then used to identify functionally relevant genes in aberrant regions.

Results: aCGH analysis of DNA from pCR and NR identified distinct patterns of CNAs. HER2 amplicon was confirmed by IHC and aCGH in all samples. Although there was no significant difference in the average CNAs between groups (20±17 vs 17±2), there was greater variation in the range of CNAs in pCR (8-56 CNA) compared to NR (15-19 CNA). More gains and amplifications were observed in pCR patients with more deletions in the NR group. The most common chromosomal amplification region included chr8q12.1-q24 with 87.5% of all cases displaying gains. Of the 6 patients who achieved pCR, 50% displayed a deletion in chr9 spanning p24.3-p21.3, consistent with a deletion of tumour suppressor CDKN2A. No aberrations in chr9 were observed in NR cohort. The deleted genomic region contained 65 common protein-coding genes, with the interferon biological pathway as the most significant (p=1.03E-36).

Conclusions: Distinct genomic CNAs were observed between patients achieving pCR compared to NR. However, of the 8 pts characterised here, none have relapsed. Follow-up data revealed a relapse rate of 6.8 % (3/44) vs 11.8 % (6/51) in the pCR and NR groups, respectively. To further elucidate the immunological response, we will present CNA data patterns on relapse and response and compare the impact of CNAs, immune-related proteins and pCR as surrogate predictors for outcome.

Citation Format: Walsh N, Gullo G, Maguire A, O'Donovan N, Quinn C, Crown J. Genomic copy number alterations (CNA) associated with pCR in HER2-positive (HER2+) early-stage breast cancer (BrCa) patients receiving neoadjuvant trastuzumab (T) [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 P1-05-18.

Mutant p53: a novel target for the treatment of patients with triple-negative breast cancer?

The identification and validation of a targeted therapy for patients with triple-negative breast cancer (TNBC) is currently one of the most urgent needs in breast cancer therapeutics. One of the key reasons for the failure to develop a new therapy for this subgroup of breast cancer patients has been the difficulty in identifying a highly prevalent, targetable molecular alteration in these tumors. Recently however, the p53 gene was found to be mutated in approximately 80% of basal/TNBC, raising the possibility that targeting the mutant p53 protein product might be a new approach for the treatment of this form of breast cancer. In this study, we investigated the anti-cancer activity of PRIMA-1 and PRIMA-1^MET (APR-246), two compounds which were previously reported to reactivate mutant p53 and convert it to a form with wild-type (WT) properties. Using a panel of 18 breast cancer cell lines and 2 immortalized breast cell lines, inhibition of proliferation by PRIMA-1 and PRIMA-1^MET was found to be cell-line dependent, but independent of cell line molecular subtype. Although response was independent of molecular subtype, p53 mutated cell lines were significantly more sensitive to PRIMA-1^MET than p53 WT cells (p = 0.029). Furthermore, response (measured as IC₅₀ value) correlated significantly with p53 protein level as measured by ELISA (p = 0.0089, r=-0.57, n = 19). In addition to inhibiting cell proliferation, PRIMA-1^MET induced apoptosis and inhibited migration in a p53 mutant-dependent manner. Based on our data, we conclude that targeting mutant p53 with PRIMA-1^MET is a potential new approach for treating p53-mutated breast cancer, including the subgroup with triple-negative (TN) disease.

Impact of palbociclib plus letrozole on pain severity and pain interference with daily activities in patients with estrogen receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer as first-line treatment

Background Palbociclib is a recently approved drug for use in combination with letrozole as initial endocrine-based therapy for the treatment of postmenopausal women with advanced estrogen receptor-positive/human epidermal growth factor receptor 2-negative (ER+/HER2-) breast cancer. This report assesses the impact of palbociclib in combination with letrozole versus letrozole alone on patient-reported outcomes of pain. Methods Palbociclib was evaluated in an open-label, randomized, phase II study (PALOMA-1/TRIO-18) among postmenopausal women with advanced ER+/HER2- breast cancer who had not received prior systemic treatment for their advanced disease. Patients received continuous oral letrozole 2.5 mg daily alone or the same letrozole dose and schedule plus oral palbociclib 125 mg, given once daily for 3 weeks followed by 1 week off over repeated 28-day cycles. The primary study endpoint was investigator-assessed progression-free survival in the intent-to-treat population, and these results have recently been published (Finn et al., Lancet Oncol 2015;16:25-35). One of the key secondary endpoints was the evaluation of pain, as measured using the Brief Pain Inventory (BPI) patient-reported outcome tool. The BPI was administered at baseline and on day 1 of every cycle thereafter until disease progression and/or treatment discontinuation. Clinical trial registration This study is registered with ClinicalTrials.gov (NCT00721409). Results There were no statistically significant differences in Pain Severity or Pain Interference scores of the BPI between the two treatment groups for the overall population or among those with any bone disease at baseline. A limitation of the study is that results were not adjusted for the concomitant use of opioids or other medications used to control pain. Conclusions The addition of palbociclib to letrozole was associated with increased efficacy without negatively impacting pain severity or pain interference with daily activities.

Long-term outcomes after adjuvant treatment of sequential versus combination docetaxel with doxorubicin and cyclophosphamide in node-positive breast cancer: BCIRG-005 randomized trial

BACKGROUND

The optimal regimen for adjuvant breast cancer chemotherapy is undefined. We compared sequential to concurrent combination of doxorubicin and cyclophosphamide with docetaxel chemotherapy in women with node-positive non-metastatic breast cancer. We report the final, 10-year analysis of disease-free survival (DFS), overall survival (OS), and long-term safety.

PATIENTS AND METHODS

A total of 3298 women with HER2 nonamplified breast cancer were randomized to doxorubicin and cyclophosphamide every 3 weeks for four cycles followed by docetaxel (AC → T) every 3 weeks for four cycles or docetaxel, doxorubicin, and cyclophosphamide (TAC) every 3 weeks for six cycles. The patients received standard radiotherapy and endocrine therapy and were followed up for 10 years with annual clinical evaluation and mammography.

RESULTS

The 10-year DFS rates were 66.5% in the AC → T arm and 66.3% in the TAC arm (P = 0.749). OS was 79.9% in the AC → T arm and 78.9% in the TAC arm (P = 0.506). TAC was associated with higher rates of febrile neutropenia, although G-CSF primary prophylaxis greatly reduced this risk. AC → T was associated with a higher rate of myalgia, hand-foot syndrome, fluid retention, and sensory neuropathy.

CONCLUSION

This 10-year analysis of the BCIRG-005 trial confirmed that the efficacy of TAC was not superior to AC → T in women with node-positive early breast cancer. The toxicity profiles differ between arms and were consistent with previous reports. The TAC regimen with G-CSF support provides shorter adjuvant treatment duration with less toxicity.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT00312208.

Abstract P1-13-07: Superiority of tandem high-dose chemotherapy (HDC) versus conventionally dosed chemotherapy (CDC) in patients with metastatic breast cancer (MBC): Long term follow-up of IBDIS: A prospective random assignment trial (PRT)

Background

The partial chemo-sensitivity of MBC, together with pre-clinical models, provided a rationale for studies of extreme dose-escalation with autologous haematopoietic progenitor support (ASCT). Early studies of HDC as salvage following failure of CDC produced high rates of temporary response. Subsequent single arm studies in pts who were preselected for responsiveness to CDC yielded 10-20% durable remissions suggesting that HDC might cure some MBC pts. The likelihood of selection bias mandated randomised trials of this CDC induction-HDC consolidation approach. We hypothesised that an alternative strategy-accelerated multi-cycle HDC- might provide an optimal HDC strategy (Crown J, Norton L, Ann Oncol 1996).

Methods

In IBDIS, pts received a brief phase of CDC induction (doxorubicin/docetaxel-"AT"), followed by tandem cycles of HDC, or, further CDC (AT followed by CMF), as initial CRx for MBC. Hormone receptor-positive patients received endocrine therapy post-chemotherapy, and pts with localized metastases received consolidative radiotherapy.

Results: Accrual failed in the aftermath of the disclosure of research fraud involving a South African HDC study, and the reporting of negative PRCTs at ASCO 1999. Only 110 of a planned 264 patients were enrolled, but it was decided to maintain follow-up, which is now 15 years. HDC and CDC groups were well-balanced for prior adjuvant (25 v 25), prior anthracycline (8 v 10), positive receptor status (32 v 31). There were 8 treatment-related deaths (6-HDC, 2 CDC). Complete and overall response rates (CR/OR) were significantly superior for HDC v CDC (CR-29% v 6%, OR-71% v 44%). Event-free-survival at median 5 yrs were HDC 6 (11%) versus CDC 0 (p=.027). At fifteen years three HDC pts remain alive and free from relapse. All CDC are deceased. The hazard ratio for PFS is currently 0.59 (0.39-0.88) favouring HDC p=.009. The HR for overall survival is 0.72 (0.48-1.08)p=.11

Discussion:

Despite accrual failure, IBDIS was and remains a positive study for its primary endpoint of PFS. The 100% relapse and death rate for CDC on our study is typical of the published literature. Data from IBDIS are included in the Cochrane meta-analysis of HDC which showed an advantage for PFS. The contention that HDC produced superior activity to CDC appears to have been correct, however the magnitude of the benefit is smaller than was hoped by investigators in the field.

While our data support the hypothesis that there is a dose response relationship in the chemotherapy of MBC, the small benefit and high toxicity of HDC, preclude it being recommended as a standard treatment for any pts with MBC.

Citation Format: Crown J. Superiority of tandem high-dose chemotherapy (HDC) versus conventionally dosed chemotherapy (CDC) in patients with metastatic breast cancer (MBC): Long term follow-up of IBDIS: A prospective random assignment trial (PRT). [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 P1-13-07.

Abstract P4-14-15: Pre-treatment stromal tumour-infiltrating lymphocytes (S-TILs) are correlated with complete response (CR) to chemotherapy (Chemo) plus trastuzumab (T) in HER2-positive (H+) metastatic breast cancer (MBC)

Background. We have previously reported that ChemoT produces durable (>5 years) CR in a minority of pts with H+MBC, prompting a search for predictive markers. Extensive lymphocytic infiltration of cancers is correlated with high levels of immune gene signatures. International consensus guidelines on TILs define "lymphocyte-predominant BC" at a threshold of S-TILs of 50-60% versus tumour cells. High levels of S-TILs has been correlated with improved outcome in HER2+ early stage BC pts treated with ChemoT. We investigated the degree of S-TIL infiltration in metastatic biopsies from pts with HER2+MBC prior to ChemoT, and attempted to determine whether S-TILs predicted CR in HER2+MBC.

Methods. We searched a database of all pts with HER2+ MBC treated at our institution with anti-HER2 therapy over 15yrs to identify pts who achieved CR according to RECIST 1.0 criteria, which lasted for at least 6 months. We matched them with an equal number of pts from the database who were treated during the same period, but who had progressive (POD) or stable disease (SD) as best response to T. Pts must have at least one pre-treatment tumour sample available for S-TILs assessment, and adequate clinical and follow-up information. S-TILs (mononuclear cells including lymphocytes and plasma cells) contained within the boundaries of invasive tumour were identified on a representative haematoxylin and eosin stained slide and scored as a percentage of the stromal area alone, according to the International TILs Working Group 2014 methodology [Salgado R, 2015]. S-TILs were assessed specifically for this study by a senior pathologist who scored the samples and who was blinded to pts response and clinical details.

Results. Out of 246 MBC pts registered in the HER2+ database we identified 31 CR pts with at least one available pre-treatment metastatic sample. A cohort of 31 matching POD-SD pts was randomly obtained from the same database. In 8 cases (7 CR / 1 POD-SD) S-TILs could not be assessed due to inadequate material, or for other technical reasons. The final study sample is 54 pts (24 CR / 30 POD-SD). Pts characteristics are as follows: median age (range): CR 55 (29-78) / POD-SD 56 (26-89), hormone receptor (HR) pos: CR 12 (50%) / POD-SD 18 (60%), De Novo MBC at diagnosis: CR 13 (54%) / POD-SD 8 (27%) [p<0.05]. All pts received chemotherapy with T (+ lapatinib in 3 pts as part of a clinical trial), and continued on T until POD. Pre-treatment S-TILs >50% were statistically significantly more frequent in CR (50% of pts) than POD/SD (20%) [chi-square p=0.02]. No statistically significant difference in the HR status was observed between the two groups (CR vs POD-SD) or between the high and low S-TILs pts.

Conclusions. S-TILs >50% in the pre-treatment tumour biopsy of HER2+MBC were significantly correlated with subsequent CR to ChemoT, supporting the hypothesis that the immunological effects of T may play a role in determining response. Speculatively, S-TILs might identify pts with a higher likelihood of benefit from T. Further study of the potential role of S-TILs as predictors of T benefit are required.

Citation Format: Gullo G, Quinn C, Zacchia A, Fennelly D, Defrein A, Ballot J, Zanoni D, Walshe J, Maltese M, McDermott E, Crown J. Pre-treatment stromal tumour-infiltrating lymphocytes (S-TILs) are correlated with complete response (CR) to chemotherapy (Chemo) plus trastuzumab (T) in HER2-positive (H+) 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 P4-14-15.

Abstract P4-13-02: Treatment patterns of post-disease progression in the PALOMA-1/TRIO-18 trial

Background

Palbociclib (P) is an oral CDK4/6 inhibitor. In PALOMA-1/TRIO-18, a randomized phase 2 trial, addition of P to letrozole (L) significantly prolonged progression-free survival (PFS) (20 mo with P+L vs 10 mo with L alone; HR = 0.488, P=0.0004; Finn et al, Lancet Oncol, 2015) in postmenopausal women with estrogen-receptor-positive (ER+), HER2-negative advanced breast cancer (ABC) in the first-line setting. At the time of final PFS analysis, overall survival (OS) was immature.

Objectives

It is clinically important to understand whether patients (pts) benefit from standard of care endocrine therapy (ET) after they progressed on P+L as first-line treatment for ABC. We report patterns of post-progression treatment in the next line of therapy immediately following participation in the PALOMA-1 trial.

Methods

Postmenopausal women with ER+ and HER2- ABC who had not received any treatment for their advanced disease were randomized to receive P+L (N = 84) or L alone (N = 81) in the first-line setting. The primary endpoint was investigator-assessed PFS. Tumor assessment was performed every 8 weeks. Post-progression treatment data was captured and analyzed.

Results

As of the data cut-off (Nov 29, 2013), 40 progression events had occurred in the P+L arm and 59 in the L alone arm. 50% of pts in the P+L arm vs. 64% in the L alone arm received ET after progression on study treatment. 60% of pts in the P+L arm vs. 66% in the L alone arm received chemotherapy (CT) after progression on study treatment. The time to 1st subsequent ET/ CT after progression on study treatment, duration of 1st subsequent ET/CT, and choice of 1st subsequent ET/ CT are shown in Table 1.

Table 1 P + LL N=84N=81Patients (pts) with Disease Progression, NN (%)a40 (47.6)59 (72.8)Pts who received subsequent Endocrine Therapy (ET) after progression on study treatment, n(%)b20 (50.0)*38 (64.4)*Time from randomization to 1st subsequent ET (days), median (range)465.5 (239-1100)368.5 (65-1102)Duration of 1st subsequent ET (days), median (range)**153 (24-592)151 (16-1135)Choice of 1st subsequent ET, n(%)bFulvestrant9 (22.5)15 (25.4)Exemestane6 (15.0)9 (15.3)Medroxyprogesterone4 (10.0)1 (1.7)Letrozole1 (2.5)5 (8.5)Tamoxifen08 (13.6)Pts who received subsequent Chemotherapy (CT) after progression on study treatment, n(%)b24 (60.0)*39 (66.1)*Time from randomization to 1st subsequent CT (days), median (range)388.5 (69-918)281 (46-1013)Duration of 1st subsequent CT (days), median (range)**92 (1-457)120 (1-1143)Choice of 1st subsequent CT, n(%)bCapecitabine1 (2.5)10 (17.0)Mitoxantrone13 (32.5)1 (1.7)Paclitaxel013 (22.0)Other10 (25)15 (25.4)apercentages are based on N as denominator; bpercentages based on NN as denominator; *some patients had both ET and CT after progression; **calculated as treatment stop date minus treatment start date +1; if treatment was ongoing at time of data cut-off, stop date was imputed as Nov 29, 2013.

Conclusions

P+L delayed the time to ET/CT as compared to L alone. Pts benefited from standard of care ET/CT after they progressed on P+L as first-line treatment for ABC as demonstrated by the length of time on subsequent therapies; no difference was observed from the L alone arm.

Clinical Trial Information: NCT00721409

Funding Source: Pfizer.

Citation Format: Finn RS, Crown JP, Ettl J, Pinter T, Thummala A, Shparyk Y, Patel R, Randolph S, Kim S, Huang X, Nadanaciva S, Huang Bartlett C, Slamon DJ. Treatment patterns of post-disease progression in the PALOMA-1/TRIO-18 trial. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-13-02.