Pusztai, Lajos

511 Background: Clinicopathological and molecular features, including estrogen receptor (ER) status and PAM50 subtypes, have shown an association with immunogenicity and tumor-infiltrating lymphocyte (TIL) levels in breast cancer (BC). To investigate the complexity of the immune response in HER2+ BC, we explored the association of T- and B-cell receptor (TCR and BCR) repertoires with clinicopathological characteristics, PAM50 subtypes and outcome in the NeoALTTO phase III trial. Methods: RNA sequencing (RNAseq) data from baseline tumor biopsies were available for 254 out of the 455 patients enrolled. TCR and BCR repertoires were extracted from RNAseq data using the MiXCR software. Repertoire and diversity measures (read counts, number of clones, evenness, Gini index, Shannon entropy, length of the complementarity-determining region 3 [CDR3], top and second top clone proportions) were estimated. PAM50 subtypes were computed from RNAseq data. Univariate and multivariate (adjusted for clinicopathological characteristics, TIL levels dichotomized using the median value of 12.5% and treatment arm) Cox proportional hazard models were used for survival analysis, while logistic regressions were used for pathological complete response (pCR), defined as ypT0/is. All results reported had a false discovery rate (FDR) <0.05. Results: Higher BCR read counts, number of clones and Gini index were significantly associated with ER-negative as well as grade 3 tumors. Among the PAM50 subtypes, HER2-enriched (HER2-E) showed significantly higher BCR read counts, number of clones and Gini index along with lower evenness compared to luminal A and B, as well as higher length of CDR3 than luminal A. Of note, basal-like showed similar BCR diversity measures to HER2-E. No significant differences were noted for TCR diversity measures. In multivariate analyses, neither TCR nor BCR features were associated with pCR, while BCR evenness (HR 1.5; 95%CI 1.1-2.1) and Gini index (HR 0.66; 95%CI 0.5-0.88) were associated with event-free survival. Conclusions: BCR repertoire measures suggest a clonal expansion in HER2-E and basal-like PAM50 subtypes. Furthermore, the implementation of BCR-derived biomarkers can help to identify patients with an improved clinical outcome after neoadjuvant anti-HER2 treatment. Our findings highlight the heterogeneity of the immune response within HER2+ BC and provide support for biomarker-driven treatment strategies including immunotherapy in this BC subtype. Further validation is required. Clinical trial information: NCT00553358 .

Abstract Background: The IMpassion130 study demonstrated prolonged overall survival when atezolizumab, a PD-L1 inhibitor, was added to nab-paclitaxel in PD-L1 positive patients with advanced triple negative breast cancer (TNBC). Approximately 40% of tumors were PD-L1 positive, utilizing a cutoff of ≥ 1% immune cell (IC) staining with the Ventana SP142 immunohistochemical (IHC) assay. The Food and Drug Administration (FDA) approved this assay as a companion test to determine patient eligibility for atezolizumab therapy. However, literature in lung cancer shows that pathologists have a high discordance in assessing PD-L1 on IC. The FDA companion test documentation for SP142 shows high inter-laboratory reproducibility with nearly 95% overall percent agreement (OPA) between 2 readers for 2 category scoring of IC (positive versus negative) in TNBC in a central laboratory. PD-L1 testing for breast cancer is now becoming widespread in pathology laboratories. The goal of this study was to assess concordance in PD-L1 scoring between 19 pathologists from 14 institutions examining the same 86 TNBC tissues stained with the SP142 and SP263 antibodies. We also present a new method to determine the minimum number for evaluators needed to estimate concordance between large numbers of readers as occurs in real life setting. Methods: Full tissue sections were stained exactly as prescribed on the label on the Ventana Benchmark with the SP142 and SP263 PD-L1 assays. Sixty-eight and 76 cases were evaluable respectively. Stained slides were scanned and digital files distributed to pathologists who independently scored cases as either negative (&lt; 1% IC staining) or positive (≥ 1% IC staining) and estimated the % of IC staining for positive cases. We applied a method that we call Observers Needed to Evaluate Subjective Tests (ONEST). For any combination of pathologists, we can quantify the degree of overall agreement using the proportion of tissue samples upon which all selected pathologists agreed, which can lead to a plot of non-increasing trajectory of agreement as the number of pathologists increases. We computed and plotted the empirical estimate of the overall agreement with the 95% confidence interval (CI) from 1000 randomly selected permutations of the pathologists. Results: PD-L1 was interpreted as positive with SP263 in an average of 78% of cases compared to 58% with the SP142 assay (p&lt;.0001). IC positive continuous scores ranged from 1-95% (mean=20%) and 1-90% (mean=10%) for SP263 and SP142. Complete 2 category (positive vs negative) scoring concordance across all observers was achieved in 38 cases (50%) with SP263 and 26 cases (38%) with SP142. The intraclass correlation coefficient (ICC) for 2 category scoring of SP263 and SP142 was 0.513 and 0.560 respectively. ONEST plots made for each assay for 19 pathologists showed a decrease in OPA as number of observers increased, reaching a low plateau of approximately 0.46 at 10 observers for SP263 and 0.42 at 8 observers for SP142. Conclusions: Utilizing the FDA approved SP142 assay, we found a higher prevalence of PD-L1 positive tumors than published in the IMpassion130 trial but lower prevalence than seen with the SP263 assay. The different proportion of positive cases seen with two different assays highlights the need to establish cutoffs for each assay to correspond with clinical benefit. The ICC of scoring immune cells with both PD-L1 assays showed poor reproducibility across multiple pathologists. The ONEST analysis finds a plateau with 10 pathologists, only reaching an OPA of 0.4 for immune cell assessment. This suggests that more than half of the pathologists in real world situations may mis-assign patient IC scores. This could lead to a high percentage of patients either receiving atezolizumab, when they are unlikely to benefit or not receiving atezolizumab when they may benefit. Citation Format: Emily Suzanne Reisenbichler, Gang Han, Vasiliki Pelekanou, Vesal Yaghoobi, Fahad S Ahmed, Andrew Bellizzi, Veerle Bossuyt, Jane Brock, Kimberly Cole, Oluwole Fadare, Omar Hameed, Krisztina Hanley, Beth T Harrison, M G Kuba, Amy Ly, Dylan Miller, Mirna Podoll, Anja C Roden, Mary A Sanders, Kamaljeet Singh, Shi Wei, Hannah Wen, Lajos Pusztai, David L Rimm. Prospective multi-institutional evaluation of pathologist assessment of PD-L1 assays 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 PD5-01.

Abstract Background: Achieving a pathologic complete response (pCR) has been shown on the patient level to predict excellent long-term event-free survival outcomes. Residual cancer burden (RCB) quantifies the extent of residual disease for patients who did not achieve pCR. A high proportion of metastatic events to the central nervous system (CNS), a known chemotherapy sanctuary site, was previously observed among the small number of relapses in patients achieving a pCR (Symmans et al 2017), raising the possibility that these CNS events may be independent of response in the breast. I-SPY2 is an adaptively randomized, phase II, platform trial that evaluates new drugs and combinations in the neoadjuvant setting for women with high-risk primary breast cancer. In this study, we evaluated the type and sites of recurrences by RCB classes in the I-SPY 2 TRIAL. Methods: I-SPY 2 patients enrolled prior to 11/2016 across 9 experimental and control arms, with available RCB and event-free survival (EFS) data were included in this analysis. The median follow-up is 3.8 years. We summarized the EFS event type, further sub-dividing the distant recurrence events by their site of relapse (CNS-only, CNS and other sites, Non-CNS). We estimated the overall and site-specific distant recurrence incidence in each RCB class at 3 years using a competing risk (Fine-Gray) model. In addition, we assessed the association between RCB and distant recurrence free survival including all distant recurrences (DRFS), as well as excluding the CNS-only recurrences (non-CNS DRFS) using a Cox model. Our statistics do not adjust for multiplicities beyond variables evaluated in this study. Results: Among 938 subjects, there were 180 EFS events, including 28 (16%) local recurrences (without distant recurrence and/or death) and 152 DRFS events. Among the DRFS events, 25 patients died without a distant recurrence. 127 experienced distant recurrences, including 22 (17.3%) with CNS-only, 16 (12.6%) with CNS and other sites, 87 (68.5%) with non-CNS distant recurrence; 2 (1.6%) patients had missing recurrence site information. Incidence of CNS-only recurrences are low and are similar across RCB classes (pCR/RCB-0 (n=338): 1%, RCB-I (n=129): 3%, RCB-II (n=328): 2%, RCB-III (n=143): 2% at 3 years). In contrast, the incidence of non-CNS recurrences increase with increasing RCB (RCB-0: 2%, RCB-I: 4%, RCB-II: 11%, RCB-III: 19% at 3 years). DRFS of RCB-I patients do not significantly differ from those achieving a pCR/RCB-0 (DRFS at 3 years: 92% vs. 95%, hazard ratio: 1.77 (0.87-3.63)); the small numerical difference is further reduced when the CNS-only recurrences are excluded (non-CNS DRFS at 3 years: 95% vs. 96%, hazard ratio: 1.48 (0.61-3.58)). CNS recurrences among DRFS events are proportionally higher within the pCR (5/16 (31%)) and RCB-I (5/12 (42%)) than in the RCB-II (8/57 (14%)) and RCB-III (4/42 (9%)) groups largely because of the relative low frequency of non-CNS recurrence events. Conclusions: In our high-risk I-SPY 2 cohort, CNS-only recurrences are uncommon but appear similar across RCB groups, independent of response, suggesting that the CNS is a treatment sanctuary site. In contrast, non-CNS recurrence rates increase as RCB increases. These findings, if confirmed, support the use of RCB to identify patients with excellent outcomes beyond those achieving a pCR; and suggest that inclusion of CNS only recurrences as an outcome event may impact the association between neoadjuvant therapy response and long-term outcome. Citation Format: Christina Yau, Angela DeMichele, W. Fraser Symmans, Lajos Pusztai, Douglas Yee, Amy S. Clark, Christos Hatzis, Jeffrey B. Matthews, Jodi Carter, Yunn-Yi Chen, Kimberly Cole, Laila Khazai, Molly Klein, Dina Kokh, Gregor Krings, Sunati Sahoo, Kathy S. Albain, A. Jo Chien, Kirsten K. Edmiston, Anthony D. Elias, Erin D. Ellis, David M. Euhus, Heather S. Han, Claudine Isaacs, Qamar J. Khan, Julie E. Lang, Janice Lu, Jane L. Meisel, Zaha Mitri, Rita Nanda, Donald W. Northfelt, Tara Sanft, Erica Stringer-Reasor, Rebecca K. Viscusi, Anne M. Wallace, Rachel Yung, Nola M. Hylton, Judy C. Boughey, Michelle E. Melisko, Jane Perlmutter, Hope S. Rugo, Richard Schwab, Laura J. van' t Veer, Donald A. Berry, Laura J. Esserman. Site of recurrence after neoadjuvant therapy: Clues to biology and impact on endpoints [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 P2-20-02.

Abstract Background: Recent studies have demonstrated independent validation of the prognostic relevance of residual cancer burden (RCB) after neoadjuvant chemotherapy. However, a pooled subject-level analysis of multiple cohorts is needed to determine estimates of long-term prognosis for each class of RCB in each phenotypic subtype of breast cancer (BC) to better inform on patient outcomes. Also, a pooled subject-level analysis allows more detailed analyses of generalizability of the prognostic meaning of RCB assessments in a broader experience of practice settings. Method: Subject-level RCB results, with relevant clinical and pathologic stage, tumor subtype and grade, demographic, treatment and follow-up data from 11 institutes/trials are being collected for combined analysis. The association between the continuous RCB index and event-free survival (EFS), and distant recurrence free survival (DRFS) were assessed using mixed effect Cox models with the incorporation of random RCB coefficients to account for between-study heterogeneity. We will also allow for differences in baseline hazard across biological BC subtypes and, if needed, across studies as well. In addition to this stratified mixed effect model, a multivariate analysis adjusting for age, T-category, nodal status and grade was performed within each subtype. In addition, mixed effect Cox models will be employed to evaluate association between RCB index with EFS and DRFS within each HR/HER2 subtype. Kaplan Meier estimates of EFS and DRFS at 5 and 10 years were computed for each RCB class within subtype. Results: We analyzed subject-level data from 9 institutes/trials representing 4077 patients currently available from an anticipated final total of 4,800 patients (to be presented at the meeting). There were 950 EFS and 876 DRFS events during follow up (median 65 months, IQR: 70 months). RCB index (continuous) was independently prognostic within each subtype: HR+/HER2- (EFS HR (per unit increase in RCB index) =1.64, 95%CI 1.48-1.82; DRFS HR=1.68, 1.51-1.87), HR+/HER2+ (EFS HR=1.80, 1.57-2.05; DRFS HR=1.93, 1.67-2.24), HR-/HER2+ (EFS HR=2.15, 1.76-2.62; DRFS HR=2.10, 1.77-2.50), and HR-/HER2- (EFS HR=2.05, 1.89-2.22; DRFS HR=2.16, 1.90-2.46); and remained prognostic in multivariate models adjusting for age, grade, and clinical T and N stage at diagnosis. Table 1 contains the response rate and estimated EFS at 5 years and 10 years for each RCB class within each HR/HER2 phenotype (DRFS results were similar). Conclusions: Long-term prognosis after pCR was similarly excellent in all phenotypic subtypes. RCB index and classification was independently and strongly prognostic in all subtypes, and generalizable to multiple practice settings. Prognostic differences by RCB class occurred within 5 years in HR- BC, but extended to 10 years in HR+ BC. RCB-I had slightly worse EFS than pCR in HR- BC and HR+/HER2+ BC (after 5 years), but the same EFS as pCR in HR+/HER2- BC. Complete analysis of all subjects, including neoadjuvant treatments, will be presented at the meeting. PhenotypeOutcomepCRRCB-IRCB-IIRCB-IIIHR+/HER2-Frequency (%)11%10%52%27%(N=1467)5 yr EFS (95% CI)91% (86-96)93% (89-98)82% (79-85)70% (65-75)10 yr EFS (95% CI)84% (75-93)88% (82-95)71% (67-75)52% (46-58)HR+/HER2+Frequency (%)38%18%35%9%(N=762)5 yr EFS (95% CI)94% (91-97)93% (88-98)78% (73-84)49% (37-65)10 yr EFS (95% CI)91% (86-96)79% (70-90)65% (59-73)42% (29-60)HR-/HER2+Frequency (%)66%11%18%5%(N=550)5 yr EFS (95% CI)93% (90-96)88% (79-97)60% (50-71)45% (30-69)10 yr EFS (95% CI)90% (86-94)84% (74-95)56% (46-68)45% (30-69)HR-/HER2-Frequency (%)41%13%33%13%(N=1293)5 yr EFS (95% CI)92% (90-94)85% (79-91)68% (63-72)28% (21-36)10 yr EFS (95% CI)87% (82-91)80% (72-88)63% (58-68)24% (18-33) Citation Format: Christina Yau, Marieke van der Noordaa, Jane Wei, Marie Osdoit, Fabien Reyal, Anne-Sophie Hamy, Marick Lae, Miguel Martin, Maria del Monte, I-SPY 2 TRIAL Consortium, Judy C Boughey, Rebekah Gould, Jelle Wesseling, Tessa Steenbruggen, Maartje van Seijen, Gabe Sonke, Stephen Edge, Stephen-John Sammut, Elena Provenzano, Jean Abraham, Peter Hall, Ashley Graham, Lorna Mackintosh, David Cameron, Alice Wang, Priyanka Sharma, Kimberly Cole, Lajos Pusztai, Mi-Ok Kim, Laura van ‘t Veer, Laura Esserman, W. Fraser Symmans. Residual cancer burden after neoadjuvant therapy and long-term survival outcomes in breast cancer: A multi-center pooled analysis [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 GS5-01.

2631 Background: Response to immune checkpoint inhibitors has been associated with immune activation and mutational load within a tumor. Previous results in other tumors have implicated MHC II protein tumor cell expression as a response predictor to immune checkpoint inhibitors. In the I-SPY 2 TRIAL, the anti-PD1 therapeutic antibody pembrolizumab (P) was available to HER2-negative subtypes and graduated in both the HR+/HER2- and TNBC signatures. Pre-specified biomarker analysis was performed to test tumor MHC II expression as a predictor of response to P in the I-SPY 2 TRIAL based on its central role in tumor antigen presentation. Methods: 156 patients (P: 67, controls: 89) had RPPA and pCR data. RPPA-based quantitative data for pan-MHC II protein isotypes HLA-DR/DP/DQ/DX and HLA-DR protein isotype was obtained from LCM-enriched tumor epithelium, and protein levels were assessed for association with pCR in the P and control arms separately using the Wilcoxon Rank Sum test (p < 0.05). Analysis was also performed in the HR+ and HR- subgroups. Markers were analyzed individually; p-values are descriptive and were not corrected for multiple comparisons. Results: Across all P- treated patients, the HLA class II molecules –DR and -DR/DP/DQ/DX had a positive association with response to P (p = 0.014 and p = 0.001). Expression of HLA-DR/DP/DQ/DX also had a positive association with response to P in HR+ tumors. Neither of these associations were seen in the control arm samples. Conclusions: The observation of elevation of MHC II protein expression in HER2- responding patients treated with P suggests that activation of antigen peptide exchange facilitated by these molecules in T and B cells may enhance response to P treatment.

Abstract Background: In women with breast cancer receiving neoadjuvant chemotherapy, residual cancer burden (RCB) predicts distant recurrence and survival. In those with high risk tumors, locoregional recurrence (LRR) remains a concern, and has been associated with type of local therapy received. We evaluated the impact of local therapy on LRR in the ISPY-2 TRIAL. Methods: Data were analyzed in Stata 14.2, using Chi2 test, log rank test, and a Cox proportional hazards model. RCB was considered a categorical variable (0/1 versus 2/3), as described in prior publications. Breast surgery categories were lumpectomy +/- radiotherapy, or mastectomy +/- radiotherapy. Axillary surgery was defined as sentinel lymph node (SLN) surgery (≤6 nodes removed) or axillary dissection (&gt;6 nodes). Results: Follow up data from the I-SPY2 TRIAL were available for 630 patients (median follow up 2.76 yrs, range 0.4-7.2). Type of local therapy was significantly associated with clinical stage at presentation, with stage III patients most frequently undergoing mastectomy + radiation (p&lt;0.001). Women with higher RCB were more likely to undergo mastectomy than those with lower RCB (61.3% vs 48.8% mastectomy rate, p=0.002), and more likely to receive adjuvant radiotherapy (62.0% vs 53.9%, p=0.048). There was no association between clinical stage, type of surgery, or radiotherapy and LRR (Table). Higher RCB was significantly associated with LRR, with 3 year locoregional recurrence free rate of 95.1% in RCB 0/1 versus 89.9% in RCB 2/3 (p=0.003). In a Cox model adjusting for clinical stage, tumor subtype, surgical therapy, RCB status, nodal radiation, and age, significant predictors for LRR were tumor subtype and RCB status. Hazard ratio (HR) for LRR in those with RCB 0/1 was 0.39 compared to those with RCB 2/3 (95% CI 0.17-0.87, p=0.021). There was no difference in LRR between breast conservation and mastectomy; within the breast conservation group, those who had lumpectomy alone had higher hazard of LRR compared to those having lumpectomy + radiation (HR 3.1, 95% CI 1.1-9.2, p=0.043). Conclusions: Extent of surgical therapy was not associated with local tumor control, regardless of advanced tumor stage at presentation. Rather, tumor biology and response to therapy were the best predictors of LRR. These data highlight the opportunity to minimize the morbidity of extensive surgical therapy for patients with excellent response to systemic therapy. LRR rates by clinical features and treatment status FrequencyLRR RateP valueClinical Stage 0.5I240 (47.5%)5.8% II185 (36.6%)8.7% III80 (15.8%)6.3% Tumor Subtype 0.014ER+PR+Her2-161 (26.4%)3.1% ER+PR-Her2-56 (9.2%)3.6% Her2+176 (28.9%)6.3% Triple negative216 (35.5%)11.1% Local therapy 0.169Lumpectomy85 (13.5%)11.8% Lumpectomy with radiation198 (31.4%)5.6% Mastectomy173 (27.5%)5.2% Mastectomy with radiation174 (27.6%)8.6% Axillary surgery 0.23None5 (0.8%)20% SLN329 (52.2%)5.8% ALND296 (47%)8.5% Axillary radiation 0.535Yes42 (6.7%)9.5% No588 (93.3%)7.0% Axillary management 0.2No surgery or radiation5 (0.8%)20.0% SLN312 (50%)5.3% SLN+Axillary radiation17 (2.7%)8.3% ALND271 (43%)10.3% ALND+Axillary radiation25 (4%)5.4% RCB 0.0020/1293 (50.1%)3.8% 2/3292 (49.9%)10.3% Citation Format: Silverstein J, Suleiman L, Yau C, Price ER, Singhrao R, Yee D, DeMichele A, Isaacs C, Albain KS, Chien AJ, Forero-Torres A, Wallace AM, Pusztai L, Ellis ED, Elias AD, Lang JE, Lu J, Han HS, Clark AS, Korde L, Nanda R, Northfelt DW, Khan QJ, Viscusi RK, Euhus DM, Edmiston KK, Chui SY, Kemmer K, Wood WC, Park JW, Liu MC, Olopade O, Leyland-Jones B, Tripathy D, Moulder SL, Rugo HS, Schwab R, Lo S, Helsten T, Beckwith H, I-SPY 2 TRIAL Consortium, Berry DA, Asare SM, Esserman LJ, Boughey JC, Mukhtar RA. The impact of local therapy on locoregional recurrence in women with high risk breast cancer in the neoadjuvant I-SPY2 TRIAL [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 P2-14-01.

Abstract Background: Patients achieving a pathologic complete response (pCR) following neoadjuvant therapy have significantly improved event-free survival relative to those who do not; and pCR is an FDA-accepted endpoint to support accelerated approval of novel agents/combinations in the neoadjuvant treatment of high risk early stage breast cancer. Previous studies have shown that recurrence risk increased with increasing burden of residual disease (as assessed by the RCB index). As well, these studies suggest that patients with minimum residual disease (RCB-I class) also have favorable outcomes (comparable to those achieving a pCR) within high risk tumor subtypes. In this study, we assess whether integrating RCB with MRI functional tumor volume (FTV), which in itself is prognostic, can improve prediction of distant recurrence free survival (DRFS); and identify a subset of patients with minimal residual disease with comparable DRFS as those who achieved a pCR. Imaging tools can then be used to identify the subset that will do well early and guide the timing of surgical therapy. Method: We performed a pooled analysis of 596 patients from the I-SPY2 TRIAL with RCB, pre-surgical MRI FTV data and known follow-up (median 2.5 years). We first assessed whether FTV predicts residual disease (pCR or pCR/RCB-I) using ROC analysis. We applied a power transformation to normalize the pre-surgical FTV distribution; and assessed its association with DRFS using a bi-variate Cox proportional hazard model adjusting for HR/HER2 subtype. We also fitted a bivariate Cox model of RCB index adjusting for subtype; and assessed whether adding pre-surgical FTV to this model further improves association with DRFS using a likelihood ratio (LR) test. For the Cox modeling, penalized splines approximation of the transformed FTV and RCB index with 2 degrees of freedom was used to allow for non-linear effects of FTV and RCB on DRFS. Result: Pre-surgical MRI FTV is significantly associated with DRFS (Wald p&lt;0.00001), and more effective at predicting pCR/RCB-I than predicting pCR alone (AUC: 0.72 vs. 0.65). Larger pre-surgical FTV remains associated with worse DRFS adjusting for subtype (Wald p &lt;0.00001). The RCB index is also significantly associated with DRFS adjusting for subtype (Wald p&lt;0.00001). Adding FTV to a model containing RCB and subtype further improves association with DRFS (LR p=0.0007). RCB-I patients have excellent DRFS (94% at 3 years compared to 95% in the pCR group). Efforts are underway to identify an optimal threshold for dichotomizing pre-surgical FTV and FTV change measures for use in combination with pCR/RCB-I class to generate integrated RCB (iRCB) groups as a composite predictor of DRFS. Conclusion: Pre-surgical MRI FTV is effective at predicting minimal residual disease (RCB0/I) in the I-SPY 2 TRIAL. Despite the association between FTV and RCB, FTV appears to provide independent added prognostic value (to RCB and subtype), suggesting that integrating MRI volume measures and RCB into a composite predictor may improve DRFS prediction. Citation Format: Hylton NM, Symmans WF, Yau C, Li W, Hatzis C, Isaacs C, Albain KS, Chen Y-Y, Krings G, Wei S, Harada S, Datnow B, Fadare O, Klein M, Pambuccian S, Chen B, Adamson K, Sams S, Mhawech-Fauceglia P, Magliocco A, Feldman M, Rendi M, Sattar H, Zeck J, Ocal I, Tawfik O, Grasso LeBeau L, Sahoo S, Vinh T, Yang S, Adams A, Chien AJ, Ferero-Torres A, Stringer-Reasor E, Wallace A, Boughey JC, Ellis ED, Elias AD, Lang JE, Lu J, Han HS, Clark AS, Korde L, Nanda R, Northfelt DW, Khan QJ, Viscusi RK, Euhus DM, Edmiston KK, Chui SY, Kemmer K, Wood WC, Park JW, Liu MC, Olopade O, Tripathy D, Moulder SL, Rugo HS, Schwab R, Lo S, Helsten T, Beckwith H, Haugen PK, van't Veer LJ, Perlmutter J, Melisko ME, Wilson A, Peterson G, Asare AL, Buxton MB, Paoloni M, Clennell JL, Hirst GL, Singhrao R, Steeg K, Matthews JB, Sanil A, Berry SM, Abe H, Wolverton D, Crane EP, Ward KA, Nelson M, Niell BL, Oh K, Brandt KR, Bang DH, Ojeda-Fournier H, Eghtedari M, Sheth PA, Bernreuter WK, Umphrey H, Rosen MA, Dogan B, Yang W, Joe B, I-SPY 2 TRIAL Consortium, Yee D, Pusztai L, DeMichele A, Asare SM, Berry DA, Esserman LJ. Refining neoadjuvant predictors of three year distant metastasis free survival: Integrating volume change as measured by MRI with residual cancer burden [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 P2-07-03.

Abstract Background LIV-1, a transmembrane protein and downstream target of STAT3, is highly expressed in breast cancer cells. It is associated with lymph node involvement and metastatic progression. SGN-LIV1A is an anti-LIV-1 antibody conjugated via a protease-cleavable linker to monomethyl auristatin E (MMAE). Upon binding to cell-surface LIV-1, SGN-LIV1A is internalized and releases MMAE, which disrupts microtubulin and induces apoptosis. Methods This ongoing, phase 1 study evaluates safety, tolerability, pharmacokinetics, and antitumor activity of SGN-LIV1A (q3wks IV) in women with LIV-1-positive, unresectable, locally advanced or metastatic breast cancer (LA/MBC) (NCT01969643). Patients (pts) with measurable disease and ≥2 prior cytotoxic regimens for LA/MBC are eligible. Pts with ≥ Grade 2 neuropathy are excluded. Response is assessed per RECIST v1.1; pts with stable disease (SD) or better can continue treatment until disease progression or intolerable toxicity. At completion of dose escalation in hormone receptor-positive/HER2-negative (HR+/HER2–) and triple-negative (TN) pts, expansion cohorts were opened to further evaluate safety and antitumor activity of monotherapy in TN pts. Tumor biopsies are evaluated for LIV-1 expression. Results To date, 69 pts (18 HR+/HER2–, 51 TN) have received a median of 3 cycles (range, 1–12) of SGN-LIV1A at doses of 0.5–2.8 mg/kg. Median age was 56 yrs. Pts had a median of 3 prior cytotoxic regimens for LA/MBC; 58 had visceral disease and 37 had bone metastases. No dose-limiting toxicities (DLTs) occurred in 19 DLT-evaluable pts; maximum tolerated dose was not exceeded at 2.8 mg/kg. Expansion cohorts of TN pts were opened at 2.0 and 2.5 mg/kg. Treatment-emergent adverse events (AEs) reported in ≥25% of pts were fatigue (59%), nausea (51%), peripheral neuropathy (44%), alopecia (36%), decreased appetite (33%), constipation (30%), abdominal pain, diarrhea, and neutropenia (25% each). Most AEs were Grade 1/2; AEs ≥ Grade 3 included neutropenia (25%) and anemia (15%). Febrile neutropenia occurred in 2 pts whose total dose exceeded 200 mg per cycle, including 1 treatment-related death due to sepsis. No other treatment-related deaths occurred on-study. Seven pts discontinued treatment due to AEs. In dose escalation, activity was observed in 17 efficacy evaluable (EE) HR+/HER2- pts, with a disease control rate (DCR= CR+PR+SD) of 59% (10 SD), including 1 pt with SD ≥24 wks. Among the 44 EE TN pts (dose escalation plus expansion cohorts), the objective response rate (ORR) was 32% (14 PR) with a confirmed PR rate of 21%, DCR was 64% (14 PR, 14 SD), and clinical benefit rate (CBR=CR+PR+SD ≥24 wks) was 36% (16 pts). For TN pts, median PFS was 11.3 wks (95% CI: 6.1, 17.1); 10 pts remain on treatment. Of 631 MBC tumor samples of all clinical subtypes evaluated for LIV-1, 91% were positive; 75% had moderate-to-high expression (H-score ≥100). Conclusions LIV-1 is expressed in almost all MBC tumors. SGN-LIV1A monotherapy was generally well tolerated and showed encouraging antitumor activity in heavily pretreated TN MBC, with a PR rate of 32%, confirmed PR rate of 21%, and CBR (≥24 wks) of 36%. Response duration data continue to evolve. Enrollment continues in the TN monotherapy expansion cohort. Citation Format: Modi S, Pusztai L, Forero A, Mita M, Miller KD, Weise A, Krop I, Burris III H, Kalinsky K, Tsai M, Liu MC, Hurvitz SA, Wilks S, Ademuyiwa F, Diab S, Han HS, Kato G, Nanda R, O'Shaughnessy J, Kostic A, Li M, Specht J. Phase 1 study of the antibody-drug conjugate SGN-LIV1A in patients with heavily pretreated triple-negative metastatic breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD3-14.