Unselected Triple-negative Breast Cancer Research Articles

Abstract PS16-01: Comparison of an Atezolizumab monotherapy window followed by Atezolizumab and chemotherapy vs. Atezolizumab and chemotherapy alone in triple negative breast cancer (TNBC) – final analysis of the neoadjuvant neoMono trial

Abstract Background: Improvement of systemic therapy of TNBC still is a medical need. Exploratory data from the neoadjuvant GeparNuevo trial suggested a benefit from an immune checkpoint inhibitor (ICI) monotherapy window in TNBC. The neoMono trial prospectively analyzed whether the addition of a preceding Atezolizumab monotherapy window prior to Atezolizumab and chemotherapy (CTX) improves pCR rates among patients (pts) with early TNBC. In an interim analysis after 100 pCR events, patients with unselected TNBC did not show a significant benefit from an Atezolizumab monotherapy window, while an exploratory analysis suggested a highly clinically relevant benefit among pts with PD-L1 positive TNBC. Here we present the final primary endpoint analysis. Methods: NeoMono is a phase 2 randomized multicenter trial that was planned to recruit a maximum of 458 female and male pts with primary TNBC (defined as ER/PR < 10% and HER2 negative) with tumor stages cT1c – cT4d (cN0 and cN+). As the protocol mandated termination of trial recruitment based on the results of the interim analysis, the final ITT population was limited to 359 pts. PD-L1 status had to be identifiable by central pathology by means of the VENTANA PD-L1 (SP142) assay and was defined by PD-L1 expression on immune cells (IC). Neoadjuvant treatment in both study arms consisted of Atezolizumab 1200 mg every 3 weeks in addition to neoadjuvant CTX (12 x Carboplatin/Paclitaxel q1w followed by 4x Epirubicin/Cyclophosphamide q3w). Combination therapy in arm A was preceded by an Atezolizumab monotherapy window of 840 mg once two weeks prior to initiation of combination therapy, while patients in arm B received no immune monotherapy window. Study goals are to compare the efficacy of neoadjuvant CTX + Atezolizumab with versus without a two-week atezolizumab monotherapy window preceding CTX + ICI (primary endpoint: pCR) and to identify biomarkers for response and resistance through analysis of sequential tissue and liquid biopsies. The neoMono statistical design uses Bayesian posterior probabilities (uniform prior distribution) and logistic regression to analyze the primary endpoint. Results: 180 pts in arm A and 179 in arm B from 34 study sites were included in the final primary endpoint analysis. Demographics and baseline characteristics as well as drug exposure were well-balanced in both arms. Posterior mean pCR rates in the ITT population in study arms A and B were 65.7% (95% high posterior density interval (HPDI): 58.5%, 72.5%) and 69% (62.2%, 75.9%), respectively. In an exploratory analysis stratified by PD-L1 IC status (negative: < 1% versus positive: ≥ 1%), pCR rates in arm A were 91.5% in the PD-L1 IC-positive group and 56.1% in the PD-L1 IC-negative group, the corresponding pCR rates in arm B were 82.2% and 64.5%, respectively. In a multivariate analysis of the ITT population including tumor size, nodal status, tumor grade, age and PD-L1 status, the odds ratio for achieving a pCR was 4.77 (p < 0.001) for PD-L1-positive and 2.36 (p=0.023) for grade 3 tumors. In an exploratory analysis including HER2 status, odds for achieving a pCR were significantly higher for patients with HER2-negative (IHC 0) vs. HER2-low tumors (OR 1.73, p=0.036). No new safety signals were observed. Conclusion: The final primary endpoint analysis of the neoMono trial demonstrated the highest pCR rates ever reported in a phase II/III trial in TNBC. While a significant impact of an ICI monotherapy window on the pCR rate after combination of CTX + ICI in an unselected ITT population could not be demonstrated, neoMono indicates for the first time in a randomized prospective setting that patients with immune active TNBC might derive particular benefit from a preceding ICI monotherapy window. The results of the neoMono trial are mainly justifying the conduction of a confirmative trial in immune active TNBC. However, our results underscore the potential role of pre-therapeutic ICI monotherapy window as part of future therapeutic concepts in TNBC. Citation Format: Hans-Christian Kolberg, Johannes Schumacher, Ramona Erber, Michael Braun, Peter A. Fasching, Eva-Maria Grischke, Christian Schem, Michael P. Lux, Mustafa Deryal, Oliver Hoffmann, Bernhard Heinrich, Georg Kunz, Kristina Lübbe, Petra Krabisch, Arndt Hartmann, Philip Raeth, Sabine Kasimir-Bauer, Cornelia Kolberg-Liedtke. Comparison of an Atezolizumab monotherapy window followed by Atezolizumab and chemotherapy vs. Atezolizumab and chemotherapy alone in triple negative breast cancer (TNBC) – final analysis of the neoadjuvant neoMono trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS16-01.

A randomized phase II clinical trial of talazoparib maintenance therapy in patients with triple-negative breast cancer who showed platinum-sensitivity on first- or second-line platinum-based chemotherapy: KCSG BR21-10.

TPS1132 Background: A potent PARP inhibitor, talazoparib, demonstrated superior clinical activity compared to standard chemotherapy in germline BRCA1/2-mutant advanced breast cancer patients. However, the role of talazoparib treatment in BRCA1/2 wild-type triple-negative breast cancer (TNBC) patients remains undefined, although high incidence of homologous recombination deficiency (HRD) is one of the major characteristics of the TNBC. Previous studies indicated clinical responsiveness to platinum agents is a useful surrogate for HRD that may predict favorable PARP inhibitor response. Here, we present a phase II study to test talazoparib maintenance therapy in germline BRCA1/2 mutation unselected advanced TNBC patients after platinum-based chemotherapy. Methods: The KCSG BR21-10 study (NCT04755868) is a randomized double-blind placebo-controlled phase II clinical trial of talazoparib maintenance therapy in metastatic TNBC patients whose tumor showed platinum-sensitivity to first- or second-line platinum-based chemotherapy. The criteria for platinum-sensitivity were set as follows: remaining complete response (CR), partial response (PR), or stable disease (SD) after 6 to 9 tri-weekly doses or 18 to 27 weekly doses of platinum-based chemotherapy. The eligible TNBC patients are enrolled to the trial after completion of platinum-based therapy and 1:1 randomized to receive talazoparib (once daily 1.0 mg) or placebo maintenance therapy. The patient with any germline BRCA1/2 mutation status is eligible, and randomization stratification factors include line of platinum-based chemotherapy, response to platinum-based chemotherapy, and germline BRCA1/2 mutation status. The talazoparib/placebo maintenance treatment is initiated within 8 weeks after the last platinum chemotherapy. At the time of progression of disease, unblinding can be performed and patients in placebo arm may be eligible for crossover to talazoparib single treatment. The primary endpoint is progression-free survival (PFS) after randomization by RECIST 1.1, and the key secondary endpoints are overall survival, PFS2, objective response rate, adverse events by CTCAE 5.0 criteria, and quality of life. We also planned exploratory study to find predictive biomarker by tumor tissue and blood analysis. The median PFS from the randomization is expected to be 3 months in the placebo maintenance arm and we expect that talazoparib maintenance will improve PFS with hazard ratio of 0.65. It is predicted that a total of 206 patients (103 patients in each arm) are required with the α of 0.05 and power of 0.8 (1-β) by two-sided test, considering monthly 3% dropout rate. Currently, 23 of planned 206 patients have been enrolled. Clinical trial information: NCT04755868 .

Abstract P5-03-01: Long-term oncologic outcome of unselected triple-negative breast cancer patients according to BRCA1/2 mutations: a comprehensive single institution study

Abstract Background Triple-negative breast cancer (TNBC) is known to have a higher risk of early recurrence and relatively low risk of late recurrence compared to luminal type breast cancer. Among all subtypes of breast cancer, TNBC is more likely to have BRCA1/2 germline mutation which showed prevalence rate from about 10% to 20% in previous reports. To date, there are only few studies about the effect of BRCA1/2 mutations on the long-term oncologic prognosis in TNBC patients. We analyzed long-term oncologic outcome in unselected TNBC patients according to BRCA1/2 mutations in a comprehensive single institution. Methods Among 11,994 patients who underwent primary breast cancer surgery at Samsung Medical Center (SMC) between June 2008 and January 2016, 1,628 (13.6%) were TNBC patients. Of those, patients with inadequate and unavailable samples at SMC biobank and patients with follow-up duration less than 12 months and who had distant metastasis at presentation were excluded from the study, and 953 patients were enrolled. A retrospective study was conducted and BRCA1/2 genetic testing was done with SMC biobank samples through Next Generation Sequencing (NGS). Results Among 953 unselected TNBC patients, 122 patients (12.8%) had BRCA1/2 mutations: 91 (9.5%) were in BRCA1, and 32 (3.4%) were in BRCA2. One patient had both BRCA1/2 mutations. BRCA1/2 carriers were more likely to have personal history of ovarian cancer (9.0% vs. 0.5%, p < 0.0001), family history of breast cancer and/or ovarian cancer (40.2% vs. 9.4%, p < 0.0001), bilateral breast cancer (4.9% vs. 1.2%, p = 0.0105), and higher nuclear grade (86.0% vs. 74.0%, p = 0.0250). The median follow-up duration was 80.9 months. There were no significant differences in disease-free survival (DFS), distant metastasis-free survival (DMFS), overall survival (OS), and breast cancer-specific survival (BCSS) (p = 0.375, 0.268, 0.413, and 0.133, respectively) between BRCA1/2 carriers and non-carriers. However, BRCA1/2 carriers showed significantly worse contralateral breast cancer (CBC)-free survival than non-carriers (p < 0.0001). Sixty and 120-months cumulative recurrence rate were 18.5% and 31.2% for BRCA1/2 carriers versus 19.3% and 22.7% for non-carriers (p = 0.834 and 0.136, respectively). However, cumulative recurrence rate at 150 months showed absolute but not statistically significant difference between BRCA1/2 carriers and non-carriers (36.2% versus 23.5%, p = 0.080). Cumulative CBC recurrence rate on 60, 120- and 150-months estimates were 6.7%, 18.7% and 25.5% for BRCA1/2 carriers versus 1.1%, 2.7% and 5.2% for non-carriers which showed statistically meaningful difference (p = 0.025, 0.006 and 0.018, respectively). Sixty months, 120- and 150-months cumulative expire rate were 11.2%, 15.6% and 27.7% for BRCA1/2 carriers versus 14.3%, 20.7% and 20.7% for non-carriers (p = 0.319, 0.202 and 0.549, respectively). Discussion In this unselected cohort of patients with TNBC, we found 12.8% (122 patients among 953) prevalence of BRCA1/2 mutations. The median follow-up duration was 80.9 months. There was no significant difference in DFS, DMFS, OS and BCSS by BRCA1/2 mutation status in long-term follow up. However, BRCA1/2 carriers showed significantly worse CBC recurrence rate at 60, 120- and 150- months. And also, BRCA1/2 carriers had 12.7% higher risk of recurrence than non-carriers at 150 months, which was not statistically meaningful but showed absolute difference. Among patients with CBC recurrence, 41.3% (12 patients among 29) were BRCA1 carriers, over 85% had TNBC type of recurred CBC and approximately 80% underwent chemotherapy. In conclusion, we demonstrated that CBC recurrence risk is relatively high in TNBC patients with BRCA1 mutation and showed high chance to receive chemotherapy. Therefore, long-term follow up and appropriate genetic counseling, risk assessment should be done properly for BRCA1/2 mutation carriers in TNBC patients. Citation Format: Soo Yeon Chung, Jai Min Ryu, You Jin Jung, Yeon Jin Kim, Hye Jin Kim, Seok Jin Nam, Seok Won Kim, Jonghan Yu, Byung Joo Chae, Jeong Eon Lee, Se Kyung Lee, Sung-Won Kim, Eun Young Kim. Long-term oncologic outcome of unselected triple-negative breast cancer patients according to BRCA1/2 mutations: a comprehensive single institution study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-03-01.

Antibody-drug conjugates targeting TROP-2: Clinical development in metastatic breast cancer

Antibody drug conjugates (ADCs) combine the potent cytotoxicity of chemotherapy with the antigen -specific targeted approach of antibodies into one single molecule. Trophoblast cell surface antigen 2 (TROP-2) is a transmembrane glycoprotein involved in calcium signal transduction and is expressed in multiple tumor types. TROP-2 expression is higher in HER2-negative breast tumors (HR+/HR-) and is associated with worse survival. Sacituzumab govitecan (SG) is a first-in-class TROP-2-directed ADC with an anti-TROP-2 antibody conjugated to SN-38, a topoisomerase inhibitor via a hydrolysable linker. This hydrolysable linker permits intracellular and extracellular release of the membrane permeable payload enabling the “bystander effect” contributing to the efficacy of this agent. There was significant improvement in progression free survival (PFS) and overall survival (OS) with SG versus chemotherapy in pretreated metastatic triple negative breast cancer (TNBC), resulting in regulatory approval. Common adverse events (AE) reported were neutropenia and diarrhea. SG also demonstrated clinical activity versus chemotherapy in a phase III trial of HR+/HER2-metastatic breast cancer (MBC) and is under evaluation in first-line metastatic and early stage TNBC as well. Datopotamab deruxtecan (Dato-DXd) is a TROP-2 ADC that differs from SG in that it has a cleavable tetrapeptide linker and a more potent topoisomerase inhibitor payload. This construct is highly stable in circulation with a longer half-life than SG, and undergoes cleavage in presence of intracellular lysosomal proteases. Dato-DXd demonstrated preliminary efficacy in unselected metastatic TNBC, with common AEs of low-grade nausea and stomatitis. Dato-DXd is being investigated in phase III studies in metastatic TNBC and HR+/HER2- MBC. These novel TROP-2 ADCs have the potential to deliver enhanced efficacy with reduced toxicity in MBC and possibly in early stage breast cancer (EBC).

136MO Differential benefit of low-dose cyclophosphamide and methotrexate maintenance chemotherapy among TNBC subtypes in the context of the IBCSG 22-00 study

Triple-negative breast cancer (TNBC) is a heterogeneous disease with at least five molecular subtypes characterized by distinct gene expression, genomic and tumor microenvironment (TME) profiles. The phase III adjuvant IBCSG 22-00 trial evaluating low-dose cyclophosphamide and methotrexate (CM) chemotherapy did not show a clinical benefit in unselected TNBC patients. Here, we aimed to explore whether specific TNBC molecular subtypes and TME features could predict benefit to low-dose CM maintenance chemotherapy in the IBCSG 22-00 study.

Anlotinib plus tislelizumab combined with chemotherapy as neoadjuvant treatment in triple-negative breast cancer: A prospective, single-arm, open-label phase II study.

TPS618 Background: Neoadjuvant anti-PD-(L)1 therapy confers an improvement in pathological complete response (pCR) rate in unselected triple-negative breast cancer (TNBC). Combination of antiangiogenic agent plus immune checkpoint inhibitor and chemotherapy therapy for advanced TNBC is reported as a promising anti-tumor strategy presented in the FUTURE-C-PLUS study. Tislelizumab is a humanized immunoglobulin G4 anti-PD-1 monoclonal antibody engineered to minimize binding to FcγR on macrophages. Anlotinib is a novel multi-target tyrosine kinase inhibitor that effectively inhibit VEGFR, FGFR, c-KIT, c-MET and RET. Previous studies have proven the efficacy of both anlotinib monotherapy and combination with immune checkpoint inhibitor in advanced breast cancer. This phase II study aims to evaluate the efficacy and safety of anlotinib plus tislelizumab combined with chemotherapy as neoadjuvant treatment in TNBC. Methods: This is a prospective, single-arm, open-label, phase II trial. Eligible patients (pts) were women, aged 18-75 years, ECOG status 0-1, previously untreated invasive TNBC with histologically confirmed (cT1N1-2M0 or cT2-4N0-2M0). 32 pts will be enrolled and received 5 cycles of anlotinib (8 mg qd, d1-14; 21 days per cycle) with 6 cycles of tislelizumab (200 mg, once every 3 weeks) plus nab-paclitaxel (260 mg/m2, once every 3 weeks) and anthracycline (epirubicin 75 mg/m2 or doxorubicin 60 mg/m2), followed by surgery. The primary endpoint is pathological complete response rate (pCR, ypT0/Tis ypN0) and the secondary endpoints include invasive disease-free survival (iDFS), event-free survival (EFS), overall survival (OS), and safety. A sample size of 32 patients was estimated to provide a 80% power to detect a difference of 25% in pCR at a significance level of α = 0.05. The study was initiated in August 2021. Clinical trial information: NCT04914390.

Abstract P4-07-16: Correlation of Trop-2 expression with clinicopathological characteristics and outcome in triple-negative breast cancer (TNBC)

Abstract Purpose Trophoblast cell-surface antigen-2 (Trop-2) is a transmembrane calcium signal transducer highly expressed in multiple solid tumors including breast cancer. Trop-2 overexpression has been associated with poor survival, but limited data exist about the association between Trop-2 expression, clinicopathological characteristics and outcome in patients with TNBC. Given the approval of sacituzumab govitecan in unselected TNBC and its evaluation in other breast cancer settings, Trop-2 emerges as an important target for antibody-drug conjugates. Methods We included 470 patients with TNBC, treated with upfront surgery or upfront chemotherapy at the University Hospitals Leuven from 2000-2017. Trop-2 expression was determined with IHC (ab227689, Abcam) on whole slide tumor sections from resection specimens (upfront surgery group) or core needle-biopsy (upfront chemotherapy group) and assessed as continuous (H-score 0-300) and categorical (high 200-300, medium 100-200 and low <100) variables. Stromal tumor infiltrating lymphocytes (sTIL; low, intermediate and high), mitotic score and androgen receptor (AR) expression (10%-cutoff) were scored. We assessed associations between Trop-2 expression and age, BMI (lean 18-25 (low), overweight 25-30 and obese ≥30 (high)), tumor grade and size, histological subtype, lymphovascular invasion (LVI), presence of DCIS, nodal status, sTILs, AR, standardized mitotic index and outcome (distant recurrence-free survival (DRFI), invasive disease-free survival (IDFS) and breast cancer-specific survival (BCSS)). Associations between continuous variables were assessed by the Spearman correlation coefficient (ρ). Cox proportional hazards models were used to assess the association between Trop-2 expression of tumor characteristics and outcome. Results are presented as hazard ratios (HR) with incremental increase of continuous Trop-2. Results The median age at diagnosis was 51y (range 22-85y) and the median follow-up 9.6y. For the group with upfront surgery (N=406), AR was positive in 21.5% of cases. Low, medium and high Trop-2 expression was seen in 55.7%, 23.6% and 20.7%. Higher Trop-2 expression was correlated with higher age at diagnosis (ρ=0.13, p=0.009). LVI was more frequent in Trop-2-high (39%) compared to Trop-2-medium (19%) or -low (20%) (p=0.004). Patients in Trop-2-high subgroup had more nodal involvement (45%) compared to Trop-2-medium (29%) (p=0.03). There was no correlation between Trop-2 expression with sTILs, BMI, AR or outcome. However, we found significantly improved DRFI and BCSS with increasing Trop-2 expression for the BMI-low subgroup (HR=0.95 [95%C.I. 0.89;0.99], p=0.02 and HR=0.95 [95%C.I. 0.89;0.99], p=0.04). For the group with upfront chemotherapy (N=64), AR was positive in 28.1% of cases. Low, medium and high Trop-2 expression was seen in 45.3%, 53.1% and 1.6% of cases. No difference was seen for Trop-2 expression in patients with pathological complete response (N=22) and residual disease (N=42) (median 100 vs 100 H-score, p=0.96). Higher Trop-2 expression was seen in lean compared to obese patients (100 vs 50, p=0.03). Conclusion In patients with TNBC treated with upfront surgery, higher Trop-2 expression was correlated with older age, more LVI and nodal involvement. There was overall no correlation between Trop-2 expression with sTILs, AR or outcome. Limited numbers of events warrant caution in interpretation. Citation Format: Hava Izci, Kevin Punie, Lise Waumans, Annouschka Laenen, Hans Wildiers, Freija Verdoodt, Christine Desmedt, Jan Ardui, Ann Smeets, Sileny Han, Ines Nevelsteen, Patrick Neven, Giuseppe Floris. Correlation of Trop-2 expression with clinicopathological characteristics and outcome in triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-07-16.

The Clinical Value of Chemotherapy Combined With Capecitabine in Triple-Negative Breast Cancer-A Meta-Analysis.

Purpose: Triple-negative breast cancer (TNBC) is the most dangerous subtype of breast cancer with high rates of metastasis and recurrence. The efficacy of capecitabine in chemotherapy for TNBC is still controversial. This study evaluated the efficacy and safety of capecitabine combining with standard, adjuvant or neoadjuvant chemotherapy for TNBC. Methods: We systematically searched clinical studies through PubMed, Cochrane library, Embase, Wanfang Database, China Academic Journals (CNKI), and American Society of Clinical Oncology’s (ASCO) annual conference report. Studies were assessed for design and quality by the Cochrane risk of bias tool. A meta-analysis was performed using Review Manager to quantify the effect of capecitabine combined with standard, adjuvant or neoadjuvant chemotherapy on the disease-free survival (DFS) rate and overall survival (OS) rate of TNBC patients. Furthermore, safety analysis was performed to evaluate the adverse events. Results: Twelve randomized controlled clinical trials involving totally 4854 TNBC patients were included, of which 2,214 patients received chemotherapy as control group, and 2,278 patients received capecitabine combining with chemotherapy. The results indicated that capecitabine could significantly improve the DFS [hazard ratio (HR) 0.80, 95% confidence interval (CI) 0.71–0.90, P = 0.0003] and OS (HR 0.83, 95% CI 0.74–0.93, P = 0.001). In subgroup analysis, the combination of capecitabine and cyclophosphamide exhibited a significant benefit in all outcomes (DFS HR 0.75, 95% CI 0.63–0.90, P = 0.002; OS HR 0.65, 95% CI 0.52–0.80, p < 0.0001). Additionally, defferent dose of capecitabine subgroup showed same significant effect on the results. Safety analysis showed that the addition of capecitabine was associated with a much higher risk of hand-foot syndrome, diarrhea and mucositis or stomatitis. Conclusion: The results showed that adjuvant capecitabine could bring significant benefits on DFS and OS to unselected TNBC patients, the combination of capecitabine and cyclophosphamide could improve the survival rate of patients, although the addition of capecitabine could bring significant side effects such as hand foot syndrome (HFS) and diarrhea.

Germline and tumor BRCA1/2 pathogenic variants in Chinese triple-negative breast carcinomas.

BRCA1/2 screening for all triple-negative breast cancer (TNBC) patients younger than 60years may still be an economic burden in China. Further evidences that include incidence and outcome of BRCA1/2 pathogenic variants (PV) screened based on younger age or family history (FH) are worth discussing for improving the cost-effectiveness of BRCA1/2 testing in Chinese TNBC. We aimed to investigate the prevalence of germline and tumor BRCA1/2 PV based on age screening in Chinese TNBC patients. Paired blood and tumor DNA from 124 unselected Chinese TNBC patients with less than or equal to 55years were collected and analyzed for BRCA1/2 PV. Clinicopathological characteristics including age at diagnosis, FH and follow-up data were collected for further analysis. The entire frequency of germline and tumor BRCA1/2 PV was 21.0 and 25%, respectively. Among them, 20 (16.1%) germline and 5 (4.0%) somatic BRCA1/2 single-nucleotide variant/insertion/deletions were found by NGS testing, 6 (4.8%) BRCA1 large genomic rearrangements were detected in blood DNA by MPLA. There was significant correlation between FH of HBOC and germline BRCA1/2 PVs among these patients. Patients with tumor BRCA1/2 PVs had significant improvements than non-carriers in PFS (p = 0.047). No significant impacts were found between various mutation status in OS outcomes. No significant differences were found between BRCA1 or BRCA2 and non-carriers in PFS or OS. There is a high incidence of germline and tumor BRCA1/2 PVs in Chinese TNBC patients with less than or equal to 55years old. Tumor BRCA1/2 PV carriers showed an improved survival outcome. Our results suggest that BRCA1/2 PVs testing addressed within each specific clinical scenario could be more cost-effective for patients.

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

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

Olaparib monotherapy as primary treatment in unselected triple negative breast cancer

The antitumor efficacy of PARP inhibitors (PARPi) for breast cancer patients harboring germline BRCA1/2 (gBRCA1/2) mutations is well established. While PARPi monotherapy was ineffective in patients with metastatic triple negative breast cancer (TNBC) wild type for BRCA1/2, we hypothesized that PARPi may be effective in primary TNBCs without previous chemotherapy exposure. In the phase II PETREMAC trial, patients with primary TNBC >2 cm received olaparib for up to 10 weeks before chemotherapy. Tumor biopsies collected before and after olaparib underwent targeted DNA sequencing (360 genes) and BRCA1 methylation analyses. In addition, BRCAness (multiplex ligation-dependent probe amplification), PAM50 gene expression, RAD51 foci, tumor-infiltrating lymphocytes (TILs) and PD-L1 analyses were performed on pretreatment samples. The median pretreatment tumor diameter was 60 mm (range 25-112 mm). Eighteen out of 32 patients obtained an objective response (OR) to olaparib (56.3%). Somatic or germline mutations affecting homologous recombination (HR) were observed in 10/18 responders [OR 55.6%, 95% confidence interval (CI) 33.7-75.4] contrasting 1/14 non-responders (OR 7.1%; CI 1.3-31.5, P= 0.008). Among tumors without HR mutations, 6/8 responders versus 3/13 non-responders revealed BRCA1 hypermethylation (P= 0.03). Thus, 16/18 responders (88.9%, CI 67.2-96.9), in contrast to 4/14 non-responders (28.6%, CI 11.7-54.7, P= 0.0008), carried HR mutations and/or BRCA1 methylation. Excluding one gPALB2 and four gBRCA1/2 mutation carriers, 12/14 responders (85.7%, CI 60.1-96.0) versus 3/13 non-responders (23.1%, CI 8.2-50.3, P= 0.002) carried somatic HR mutations and/or BRCA1 methylation. In contrast to BRCAness signature or basal-like subtype, low RAD51 scores, high TIL or high PD-L1 expression all correlated to olaparib response. Olaparib yielded a high clinical response rate in treatment-naïve TNBCs revealing HR deficiency, beyond germline HR mutations. ClinicalTrials.gov identifier: NCT02624973.

Why pathologists and oncologists should know about tumour-infiltrating lymphocytes (TILs) in triple-negative breast cancer: an Australian experience of 139 cases

The presence of increased tumour infiltrating lymphocytes (TILs) is established as a positive prognostic factor in triple-negative breast cancer (TNBC). The majority of studies have examined the role of TILs in predicting response to chemotherapy, but their role as a general prognostic marker in TNBC is unclear. Moreover, there is a lack of consensus in the literature regarding a suitable cut-off point by which to stratify patients into prognostic groups. Therefore, we sought to confirm the prognostic value of TILs in an independent cohort of unselected TNBCs, and to determine an appropriate cut-off point by which to stratify TIL scores into prognostically significant categories. We used the International TILs Working Group (ITWG) methodology to assess the density of stromal TILs in our cohort of 139 TNBC patients undergoing curative resection at our institution. The percentage TILs scores were categorised first into three groups: low (0-10%), intermediate (15-50%), and high (55-100%). A second binary variable was also created by separating cases into low TILs (≤50%) and high TILs (>50%) groups. Using the three-tiered system, mean disease-free survival was 156, 99 and 94 months for the high, intermediate and low TILs groups, respectively (p=0.030). However, no statistically significant improvement was observed for overall survival. Using the two-tiered system, statistically significant improvements in both overall survival (p=0.030) and disease-free survival (p=0.010) were observed. This survival benefit remained statistically significant in multivariate analyses (p=0.010, p=0.014). We conclude that TILs scored using the ITWG system and dichotomised at a cut-off score of 50%, are a powerful predictor of all-cause and disease-free survival in TNBC regardless of chemotherapy treatment.

Abstract P3-06-12: Autophagy-mediated survival mechanism to c-Src inhibitor therapy in triple negative breast cancer

Abstract c-Src (Src) is a proto-oncogene involved in signaling that culminates in the control of multiple biological functions. Src is also one of the most frequently upregulated pathways in triple negative breast cancer (TNBC). Dysregulation of Src has been detected in TNBC and is strongly associated with tumor metastasis and poor prognosis. However, even after promising preclinical studies, Src inhibitors did not show major clinical advantage in unselected TNBC populations. We have previously published that metastatic TNBC has high energy-dependency to mitochondrial fatty acid beta-oxidation (FAO) and FAO activates Src by inducing autophosphorylation at Y419. However, our recent analysis suggests that as observed with the Src inhibitors, TNBC tumors treated with FAO inhibitors also develop drug-resistance and exhibit continuous tumor growth. Evaluation of their drug resistance mechanism revealed that while short-term inhibition of FAO or Src induces autophagic and apoptotic cell deaths, long-term inhibition results in autophagy-mediated drug resistance and survival. Further analyses suggest that FAO/Src inhibitors promote interferon regulatory factor 1 (IRF1) expression and activate mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway via the induction of cellular reactive oxygen species (ROS) in TNBC. Activated MEK/ERK then suppresses IRF1 expression and induces survival pathways for drug resistance and tumor survival. Validation of in vitro findings using in vivo TNBC models confirmed that combination of FAO/Src inhibitors with MEK/ERK inhibitor or ROS scavenger provide significant benefit to overcome the therapeutic resistance of TNBC. These findings open-up new therapeutic opportunities to manage TNBC patients with currently non-targetable metastatic tumors. Citation Format: Kwanghwa Jung, Junhyoung Park, Tirupataiah Sirupangi, Dongya Jia, Nishant Gandhi, Shivanand Pudakalakatti, Jessica Elswood, Weston Porter, Nagireddy Putluri, Xiang H.-F Zhang, Xi Chen, Pratip K. Bhattacharya, Chad J. Creighton, Michael T. Lewis, Jeffrey M. Rosen, Lee-Jun C. Wong, Gokul M. Das, C. Kent Osborne, Mothaffar F Rimawi, Benny Abraham Kaipparettu. Autophagy-mediated survival mechanism to c-Src inhibitor therapy in triple negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-06-12.

Abstract P2-02-14: Metabolic regulation and drug resistance in c-Src activated triple negative breast cancer

Abstract c-Src (Src) is a proto-oncogene involved in signaling that culminates in the control of multiple biological functions. Src is also one of the most frequently upregulated pathways in triple negative breast cancer (TNBC). Dysregulation of Src has been detected in TNBC and is strongly associated with tumor metastasis and poor prognosis. However, even after promising preclinical studies, Src inhibitors did not show major clinical advantage in unselected TNBC populations. We have previously published that metastatic TNBC has high energy-dependency to mitochondrial fatty acid beta-oxidation (FAO) and FAO activates Src by inducing autophosphorylation at Y419. However, our recent analysis suggests that as observed with the Src inhibitors, TNBC tumors treated with FAO inhibitors also develop drug-resistance and continue tumor growth. Evaluation of their drug resistance mechanism revealed that while short-term inhibition of FAO or Src induces autophagic and apoptotic cell deaths, long-term inhibition results in autophagy-mediated drug resistance and survival. Further analyses suggest that FAO and Src inhibitors activate mitogen-activated protein (MAP) kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway via the induction of cellular reactive oxygen species (ROS) in TNBC. Activated MEK/ERK then induces survival pathways for drug resistance and tumor survival. Validation of in vitro findings using in vivo TNBC models confirmed that combination of FAO/Src inhibitors with MEK/ERK inhibitors can provide significant benefit to overcome the therapeutic resistance of TNBC. These findings open-up new therapeutic opportunities to manage TNBC patients with currently non-targetable metastatic tumors. Citation Format: Jung KH, Park JH, Sirupangi T, Jia D, Gandhi N, Pudakalakatti S, Elswood J, Porter W, Putluri N, Zhang XH-F, Chen X, Bhattacharya PK, Creighton CJ, Lewis MT, Rosen JM, Wong L-JC, Das GM, Osborne CK, Rimawi MF, Kaipparettu BA. Metabolic regulation and drug resistance in c-Src activated triple negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-02-14.

Abstract OT3-03-02: A phase 2, open-label, single-arm, multi-center study of talazoparib for neoadjuvant treatment of germline BRCA1/2 mutation patients with early-stage triple-negative breast cancer (TNBC)

Abstract Background: Approximately 15% of all breast cancers are triple negative and deleterious BRCA1/2 mutations are found in ˜11% of unselected TNBC. In the phase 3 EMBRACA trial (NCT01945775), the poly (ADP-ribose) polymerase (PARP) inhibitor talazoparib was superior to chemotherapy in prolonging progression-free survival in BRCA1/2 mutation patients with advanced breast cancer. A recent pilot study (NCT02282345) of 20 patients, explored the feasibility of neoadjuvant talazoparib in BRCA1/2 mutation patients; pathologic complete response (pCR) was reported at 53% with 6 months of single agent talazoparib. Trial Design: This phase 2, single-arm, open-label, multi-center study has a Simon 2-stage design. Eligible pts have stage I-III invasive TNBC (ER and PR &amp;lt;10%), with germline BRCA1/2 mutations who are suitable for neoadjuvant therapy. Pts will receive talazoparib 1 mg daily for 24 weeks, followed by breast surgery, which should occur within 4 to 6 weeks of the last dose. Ultrasound will be performed serially to assess tumor response. The primary objective is to evaluate pCR after 24 weeks of neoadjuvant talazoparib. pCR (ypT0/is ypN0) will be assessed by independent central review. Safety will also be assessed. Pts will be followed for at least 5 years to assess long term outcomes (event-free and overall survival). After surgery, any further adjuvant therapy will be given at the discretion of the treating physician. Pt reported outcomes will be assessed electronically including the global health status/quality of life, functions, and symptoms using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaires C30 and BR23. Plasma pharmacokinetic (PK) samples for determination of talazoparib concentrations will be collected at defined timepoints to describe the steady-state PK of talazoparib. Exploratory biomarker research will also take place. Approximately 122 men and women will be enrolled in the study, of which 112 evaluable pts are planned. With 112 evaluable pts and one interim futility look, the null hypothesis that the true pCR rate is 35% will be tested against a 1-sided alternative. This design yields a 1-sided type 1 error rate of 2.5% and power of 90% when the true pCR rate is 50%. An interim analysis will be performed to evaluate the efficacy of talazoparib after 28 evaluable pts undergo talazoparib treatment for 24 weeks, followed by surgery, and are assessed for pCR by central review. This trial is currently recruiting and is registered at clinicaltrials.gov (NCT03499353). Funding: This study is sponsored by Pfizer, Inc. Citation Format: Litton J, Symmans F, Gogineni K, Saltzman M, Telli ML, Usha L, Chakrabarti J, Tudor IC, Quek RG, Czibere A. A phase 2, open-label, single-arm, multi-center study of talazoparib for neoadjuvant treatment of germline BRCA1/2 mutation patients with early-stage triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT3-03-02.

Prevalence and oncologic outcomes of BRCA 1/2 mutations in unselected triple-negative breast cancer patients in Korea.

Triple-negative breast cancer (TNBC) accounts for 10-20% of all diagnosed BCs and it is enriched in BRCA1 mutation. Guidelines for Western countries suggest that BRCA 1/2 genetic testing should be done for patients with TNBC diagnosed less than 60 years, but there is lack of evidence supporting genetic testing in Asian populations. We determined the prevalence of germline BRCA 1/2 mutations among unselected Korean patients with TNBC and analyzed oncologic outcomes. From among 1628 women with TNBC who underwent surgery at Samsung Medical Center (SMC) between Jul 2008 and Jan 2016, 999 samples were available in the SMC biobank for testing germline BRCA 1/2 mutations using next-generation DNA sequencing. Overall, 131 Korean patients (13.1%) had BRCA 1/2 mutations: 97 (9.7%) were in BRCA 1, and 35 (3.5%) were in BRCA 2. One patient had both BRCA 1 and BRCA 2 mutations. Overall, 68 distinct pathologic or likely pathogenic variants (43 BRCA1 and 25 BRCA2) were found. Among those diagnosed at ≤ 60 years, the prevalence of BRCA 1/2 mutation was 14.5%. The mean age of diagnosis of BRCA1/2 mutation carriers was significantly younger than that of non-carriers (45.6 vs. 50.1 years, p < 0.0001). The median follow-up duration was 53.6months. There were no significant differences in disease-free survival, overall survival, or breast cancer-specific survival (p = 0.799, 0.092, and 0.124, respectively) between BRCA 1/2 carriers and non-carriers, although BRCA 1/2 carriers showed significantly worse contralateral breast cancer-free survival (p < 0.0001) than non-carriers. In unselected TNBC patients, we found BRCA 1/2 mutations in 13.1% of overall patients and 14.5% of patients ≤ 60years. We suggest that Korean women with TNBC diagnosed at ≤ 60years should be tested for BRCA1/2 mutation.

Abstract A04: Dasatinib shows different cytotoxicity in triple-negative breast cancer cell lines

Abstract Background: Triple-negative breast cancer (TNBC) is defined by the lack of significant expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2). Thus, TNBC is resistant to existing molecular targeted drugs such as trastuzumab or tamoxifen, and has a worse prognosis than non-TNBC. In addition, recent studies suggest that TNBC may represent a heterogeneous group of tumors with regards to gene expression, prognosis, and chemotherapy response. Although various molecular targeted drugs for TNBC have been attempted in clinical trials, almost all were negative outcomes because TNBC patients have a heterogeneous behavior. Therefore, in order to establish an efficient therapy, it is important to investigate the difference in response to molecular targeted drugs. From this viewpoint, we focused on dasatinib (Bcl-Abl/Src kinase inhibitor, approved in chronic myeloid leukemia) for the reason that it has been shown to be effective in some patients, even though it failed in clinical trials of unselected TNBC patients in the past. Here, to elucidate the mechanism of different response in dasatinib treatment on TNBC, we attempted to analyze the effects of dasatinib on cytotoxicity in some kinds of TNBC cell lines and to analyze the expression of targeted protein (Src) expression as a first step for elucidating the molecular mechanism of some kinds of TNBC cell lines. Methods: In this study, we used four TNBC cell lines such as HCC1806, HCC1395, MDA-MB-453, and MDA-MB-436, and one non-TNBC cell line, MCF-7. These cells were treated with a range of concentrations of dasatinib (0.001, 0.01, 0.1, 1, 10, or 100 μM) for 72 h. After treatment, cytotoxicity was evaluated by WST-8 assay and molecular expression was examined by Western blotting. Results and Discussion: WST-8 assay revealed that dasatinib showed high cytotoxicity in MCF7, HCC1395, and HCC1806 (IC50 were 0.162, 0.490, and 0.110 μM, respectively). Compared to these three cell lines, dasatinib showed low cytotoxicity in MDA-MB-453 and MDA-MB-436 (IC50 were 6.93 and 7.59 μM, respectively). Then, to investigate the mechanism that the dasatinib showed the different cytotoxicity among these cell lines, the expression of Src, target of dasatinib was examined. The higher expression of Src was observed in three cell lines, indicating relatively high cytotoxicity for dasatinib than the others. Although expression of Src was not observed in MDA-MB-453, that in MDA-MB-436 was the same extent as MCF7 despite low cytotoxicity for dasatinib. Thus, we evaluated the protein activity downstream of the Src pathway. Regarding the three cell lines in which dasatinib showed relatively high cytotoxicity, the phosphorylation of Akt after dasatinib treatment was degraded. However, there was no significant change of Akt activity in the two cell lines that showed relatively low cytotoxicity on dasatinib treatment. Now, in order to elucidate the molecular mechanism of dasatinib resistance observed in MDA-MB-436, we focus on autophagy that has reported to be suppressed by Src. In this regard, we indicated that the expression of LC3-II, known as a marker for autophagy, was higher in MDA-MB-436 than that of other cells in this study. Therefore, we are trying to clarify the relationship between Src and LC3-II. Conclusions: Each TNBC cell line shows the different response to dasatinib and the different Src expression, suggesting that the efficacy of dasatinib could not be dependent on the expression of Src. Thus, to clarify the mechanism of differences of cytotoxicity caused from a variety of TNBC cell lines, it is necessary to analyze more protein expressions upstream or downstream of the Src pathway. Citation Format: Yuya Haga, Kazuma Higashisaka, Lili Yang, Naoki Sekine, Kazuya Nagano, Yasuo Tsutsumi. Dasatinib shows different cytotoxicity in triple-negative breast cancer cell lines [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr A04.

Abstract 1331: Inhibition of mitochondrial reprogramming regulated c-Src in triple-negative breast cancer activates autophagy-mediated survival mechanism

Abstract c-Src is a proto-oncogene involved in signaling that culminates in the control of multiple biological functions. Src is also one of the most frequently upregulated pathways in triple negative breast cancer (TNBC). Dysregulation of Src has been detected in TNBC and is strongly associated with tumor metastasis and poor prognosis. However, even after promising preclinical studies, Src inhibitors did not show major clinical advantage in unselected TNBC populations. Thus, understanding the mechanism of drug resistance to Src inhibition has major clinical significance in TNBC patients. The full activation of Src signature depends on the autophosphorylation at Y419 that allows the substrate to gain access. We have previously published that metastatic TNBC has high energy-dependency to mitochondrial fatty acid beta-oxidation (FAO) and FAO activate Src by inducing autophosphorylation at Y419. However, our recent analysis suggests that as observed with the Src inhibitors, treatment with FAO inhibitors only attenuate the TNBC tumor growth, but do not result in complete regression. Evaluation of their drug resistance mechanism revealed that while short-term inhibition of FAO or Src induces autophagic and apoptotic cell deaths, long-term inhibition results in autophagy-mediated drug resistance and survival. Studies using p53 knocked out TNBC cells confirmed that the autophagy-mediated resistance to Src inhibition is independent of their p53 status. Further analyses suggest that FAO and Src inhibitors increase the phosphorylation of ERK1/2 in TNBC. Treatment with MAPK/ERK inhibitors abolished the FAO or Src inhibitor-mediated autophagy activation. Validation of in vitro findings using in vivo TNBC patient-derived xenograft (PDX) models confirmed that Src inhibition enhances ERK1/2 activity and induces autophagy in TNBC. Overall, our results suggest that long-term FAO or Src inhibition results in ERK-mediated autophagy activation and therapeutic resistance in TNBC. This finding will have major therapeutic impact in the management of currently non-targetable aggressive TNBC. Citation Format: Kwang Hwa Jung, Jun Hyoung Park, Tirupataiah Sirupangi, Dongya Jia, Shivanand Pudakalakatti, Nishant Gandhi, Jessica Elswood, Vasanta Putluri, Chad J. Creighton, Weston Porter, Michael T. Lewis, Xi Chen, Nagireddy Putluri, Pratip K. Bhattacharya, Lee-Jun C. Wong, Gokul M. Das, Benny A. Kaipparettu. Inhibition of mitochondrial reprogramming regulated c-Src in triple-negative breast cancer activates autophagy-mediated survival mechanism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1331.

Platinum-based neoadjuvant chemotherapy (NACT) in triple-negative breast cancer (TNBC): A systematic review and meta-analysis of randomized controlled trials (RCTs).

595Background: The role of platinum-based NACT in TNBC is highly controversial and its use is not endorsed by current guidelines in unselected TNBC patients. Our meta-analysis aimed to better evalu...

Abstract 1221: Triple-negative breast cancer (TNBC) phosphoproteomics

Abstract Background: We hypothesized that the biphasic relapse pattern of TNBC could be explained by a limited number of activation patterns of signaling nodes. In addition, we sought to determine whether the hyperactive signaling nodes, distinguishing the cases with favorable vs adverse outcome, could be potential targets. Methods: Training set of 34 frozen tumor samples divided in two sets, (A) 13 patients, relapsed in &amp;lt;4 years; (B) 21 patients relapse-free &amp;gt;12 years, (mimicking the percentage and relapse patterns of unselected TNBC, but paired for T, N, G and Ki67). TNBC cell lines: 7 indolent (no metastases in 60 weeks) and 3 aggressive, develop metastases and kill recipient mice in &amp;lt;4 months. Shotgun phosphoproteomics and TiO2-IMAC phosphopeptide enrichment coupled with mass spectrometry runs in a Orbitrap Elite Mass Spectrometer was performed. Spectra were processed with MaxQuant software. Differentially expressed phosphopeptides were obtained by applying linear models R limma package. Differential kinase activation driving the profiles segregating cured vs. relapsing cases was done using linear sequence motif analysis. The hyperactivated kinases were validated in an independent set of 113 consecutive TNBC cases with 12+ years of follow-up spotted in TMAs by using an in-house algorithm for immunohistochemistry coupled with computer-aided quantitation using an Ariol scanning, we took the kinases in the upper quartile (high activity). Survival analysis was performed with KM curves and log rank test; and Cox proportionate hazards model was used for multivariate models. Results: 11405 phosphopeptides were identified and quantified in the training set. Supervised clustering of relapsed vs. cured cases showed that 161 and 541 peptides were significantly up-regulated in the A and B groups, respectively (FDR&amp;lt;0.15). After kinase-to-kinase co-linearity was ruled-out , gathering the high activity (upper quartile) of six kinases (a combined variable, herein Var1) showed statistically significant association with relapse, being these: PRKCE, pERK, c-KIT, CDK6, pP70S6K and pPNKP. Cox proportional hazards model of any of the six probes high (var1) vs rest: 9.9 vs. not reached years (P&amp;lt;0.001). Patients that had any of the 6 kinases high have 47% of chance to relapse (only 2 out of 42 relapsed patients have 0/6 active kinases) vs patients with Var1 negative, 7% of chance (29 patients out of 72 have 0/6 active kinases) we also observed constants patterns of activations in the different sets expressions of kinases. We considered the kinases at Var1 as a potentially targets and we developed a pharmacological in vitro assay, testing pairs inhibitors on 10 TNBC cell lines; 99.3% of the combinations were supra-additive. Conclusion: High throughput p-proteomics allows a parsimonious segregation of early TNBC cases, easily detecting the cases with long-term cure vs the remaining while identifying potential therapeutic solutions for the patients falling in the adverse prognostic subgroups. Citation Format: Sara Fernandez Gaitero, Ivana Zagorac, Jose Francisco Lopez-Acosta, Gonzalo Gomez-Lopez, David González Pisano, Javier Muñoz Peralta, Luis Manso, Soledad Alonso, Renske Penning, Maarten Altelaar, Albert JR Heck, Miguel Quintela-Fandino. Triple-negative breast cancer (TNBC) phosphoproteomics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1221. doi:10.1158/1538-7445.AM2017-1221