Preoperative immune checkpoint inhibition and cryoablation in early-stage breast cancer

Local cryoablation can engender systemic immune activation/anticancer responses in tumors otherwise resistant to immune checkpoint blockade (ICB). We evaluated the safety/tolerability of preoperative cryoablation plus ipilimumab and nivolumab in 5 early-stage/resectable breast cancers. The primary endpoint was met when all 5 patients underwent standard-of-care primary breast surgery undelayedly. Three patients developed transient hyperthyroidism; one developed grade 4 liver toxicity (resolved with supportive management). We compared this strategy with cryoablation and/or ipilimumab. Dual ICB plus cryoablation induced higher expression of T cell activation markers and serum Th1 cytokines and reduced immunosuppressive serum CD4+PD-1hi T cells, improving effector-to-suppressor T cell ratio. After dual ICB and before cryoablation, T cell receptor sequencing of 4 patients showed increased T cell clonality. In this small subset of patients, we provide preliminary evidence that preoperative cryoablation plus ipilimumab and nivolumab is feasible, inducing systemic adaptive immune activation potentially more robust than cryoablation with/without ipilimumab.

Antibody-drug conjugates in breast cancer: overcoming resistance and boosting immune response

Antibody-drug conjugates (ADCs) have emerged as a revolutionary therapeutic class, combining the precise targeting ability of monoclonal antibodies with the potent cytotoxic effects of chemotherapeutics. Notably, ADCs have rapidly advanced in the field of breast cancer treatment. This innovative approach holds promise for strengthening the immune system through antibody-mediated cellular toxicity, tumor-specific immunity, and adaptive immune responses. However, the development of upfront and acquired resistance poses substantial challenges in maximizing the effectiveness of these therapeutics, necessitating a deeper understanding of the underlying mechanisms. These mechanisms of resistance include antigen loss, derangements in ADC internalization and recycling, drug clearance, and alterations in signaling pathways and the payload target. To overcome resistance, ongoing research and development efforts are focused on urgently identifying biomarkers, integrating immune therapy approaches, and designing novel cytotoxic payloads. This Review provides an overview of the mechanisms and clinical effectiveness of ADCs, and explores their unique immune-boosting function, while also highlighting the complex resistance mechanisms and safety challenges that must be addressed. A continued focus on how ADCs impact the tumor microenvironment will help to identify new payloads that can improve patient outcomes.

A phase Ib trial of pembrolizumab plus paclitaxel or flat-dose capecitabine in 1st/2nd line metastatic triple-negative breast cancer

Chemoimmunotherapy with anti-programmed cell death 1/ligand 1 and cytotoxic chemotherapy is a promising therapeutic modality for women with triple-negative breast cancer, but questions remain regarding optimal chemotherapy backbone and biomarkers for patient selection. We report final outcomes from a phase Ib trial evaluating pembrolizumab (200 mg IV every 3 weeks) with either weekly paclitaxel (80 mg/m² weekly) or flat-dose capecitabine (2000 mg orally twice daily for 7 days of every 14-day cycle) in the 1st/2nd line setting. The primary endpoint is safety (receipt of 2 cycles without grade III/IV toxicities requiring discontinuation or ≥21-day delays). The secondary endpoint is efficacy (week 12 objective response). Exploratory aims are to characterize immunologic effects of treatment over time, and to evaluate novel biomarkers. The trial demonstrates that both regimens meet the pre-specified safety endpoint (paclitaxel: 87%; capecitabine: 100%). Objective response rate is 29% for pembrolizumab/paclitaxel (n = 4/13, 95% CI: 10-61%) and 43% for pembrolizumab/capecitabine (n = 6/14, 95% CI: 18-71%). Partial responses are observed in two subjects with chemo-refractory metaplastic carcinoma (both in capecitabine arm). Both regimens are associated with significant peripheral leukocyte contraction over time. Response is associated with clinical PD-L1 score, non-receipt of prior chemotherapy, and the H&E stromal tumor-infiltrating lymphocyte score, but also by a novel 27 gene IO score and spatial biomarkers (lymphocyte spatial skewness). In conclusion, pembrolizumab with paclitaxel or capecitabine is safe and clinically active. Both regimens are lymphodepleting, highlighting the competing immunostimulatory versus lymphotoxic effects of cytotoxic chemotherapy. Further exploration of the IO score and spatial TIL biomarkers is warranted. The clinical trial registration is NCT02734290.

Organoid generation from mouse mammary tumors captures the genetic heterogeneity of clinically relevant copy number alterations

Breast cancer metastases exhibit many different genetic alterations, including copy number amplifications. Using publicly available datasets, we identify copy number amplifications in metastatic breast tumor samples and using our organoid-based metastasis assays, and we validate FGFR1 is amplified in collectively migrating organoids. Because the heterogeneity of breast tumors is increasingly becoming relevant to clinical practice, we demonstrate our organoid method captures genetic heterogeneity of individual tumors.

Risk‐reducing mastectomy decisions among women with mutations in high‐ and moderate‐ penetrance breast cancer susceptibility genes

Background

Women harboring mutations in breast cancer susceptibility genes are at increased lifetime risk of developing breast cancer and are faced with decisions about risk management, including whether to undergo high‐risk screening or risk‐reducing mastectomy (RRM). National guidelines recommend BRCA1 or BRCA2 mutation carriers consider RRM, but that carriers of moderate penetrance mutations (e.g., ATM or CHEK2) should be managed based on family history. We aimed to investigate determinants of decision for RRM, and hypothesized that mutation status, age, family history, partner status, and breast cancer would impact RRM decision making.

Methods

We performed a retrospective study assessing RRM decisions for 279 women.

Results

Women with BRCA and moderate penetrance gene mutations, a personal history of breast cancer, or a first degree relative with a history of breast cancer were more likely to undergo RRM. Breast cancer status and age showed an interaction effect such that women with breast cancer were less likely to undergo RRM with increasing age.

Conclusion

Although national guidelines do not recommend RRM for moderate penetrance carriers, the rates of RRM for this population approached those for BRCA mutation carriers. Further insights are needed to better support RRM decision‐making in this population.

Event-free survival by residual cancer burden after neoadjuvant pembrolizumab + chemotherapy versus placebo + chemotherapy for early TNBC: Exploratory analysis from KEYNOTE-522

503

Background: KEYNOTE-522 (NCT03036488) tested the benefit from adding pembrolizumab (pembro) to chemotherapy (chemo) in patients (pts) with early TNBC. The primary results showed statistically significant and clinically meaningful improvements in pCR and EFS with pembro.Prior studies have shown the prognostic value of the residual cancer burden (RCB) method to quantify the extent of residual disease after neoadjuvant chemo. In this exploratory analysis, we assessed EFS by RCB in KEYNOTE-522. Methods: 1174 pts with previously untreated, nonmetastatic, stage T1c/N1-2 or T2-4/N0-2 TNBC were randomized 2:1 to pembro 200 mg Q3W or placebo (pbo) given with 4 cycles of paclitaxel + carboplatin, then 4 cycles of doxorubicin or epirubicin + cyclophosphamide. After definitive surgery, pts received pembro or pbo for 9 cycles or until recurrence or unacceptable toxicity. Dual primary endpoints are pCR and EFS. RCB was assessed by the local pathologist at the time of surgery. The association between RCB categories (RCB-0, -1, -2, -3, corresponding to increasingly larger residual cancer) and EFS was assessed based on a Cox regression model with treatment as a covariate. Results: Median follow-up was 39.1 months at data cutoff (23 MAR 2021). Pembro shifted RCB to lower categories across the entire spectrum (Table). The HRs (95% CI) for EFS were 0.70 (0.38 - 1.31) for RCB-0 (equivalent to pCR), 0.92 (0.39 - 2.20) for RCB-1, 0.52 (0.32 - 0.82) for RCB-2, and 1.24 (0.69 - 2.23) for RCB-3. The most common EFS event in both arms was distant recurrence, which occurred in fewer pts in the pembro arm in all RCB categories. Conclusions: Increased RCB score was associated with worse EFS. Pts with residual disease had lower RCB values in the pembro arm, including fewer pts with RCB-3. Pembro + chemo prolonged EFS vs chemo alone in the RCB-0, -1, and -2 categories; the small sample size limits interpretation in the RCB-3 category. The small subset of pts with extensive residual disease (RCB-3) in both arms, 5.1% and 6.7%, respectively, had a poor prognosis. These results highlight the importance of neoadjuvant treatment with pembro for improving survival in pts with early TNBC, and identified a subset of pts for whom additional therapies will be needed. Clinical trial information: NCT03036488. [Table: see text]

A single-arm, phase 2 study of perioperative ipilimumab, nivolumab, and cryoablation in women with hormone receptor-negative, HER2-negative, early-stage/resectable breast cancer

TPS617

Background: Local tumor destruction with cryoablation (cryo) induces inflammation and releases antigens that can activate tumor-specific immune responses. Pre-clinically, cryo with checkpoint inhibition augmented tumor-specific immune responses and prevented recurrence. Clinically, we established that peri-operative (peri-op) cryo with ipilimumab (ipi) +/- nivolumab (nivo) was not only safe in patients (pts) with operable, early stage breast cancer (ESBC) but also generated robust intra-tumoral and systemic immune responses. In this phase 2 study, we evaluate the disease specific impact of peri-op ipi/nivo/cryo in women with residual triple negative breast cancer (TNBC) after neoadjuvant chemotherapy (NAC), a subset at high risk of early relapse. Methods: Eligible pts are ≥18y, with ER < 10%, PR < 10%, HER2 negative (per ASCO/CAP definition), ≥ 1.0 cm, residual operable disease after taxane-based NAC. Approximately 80 pts will be enrolled and treated with ipi/nivo/cryo followed by breast surgery and adjuvant nivo. Pts undergo percutaneous, image-guided cryo with concurrent research core biopsy 7-10 days prior to surgery and will receive ipi (1mg/kg IV) with nivo (240mg IV) 1 to 5 days prior to cryo. After surgery, pts will receive 3 additional doses of nivo at 240mg IV Q2 weeks. Adjuvant capecitabine is recommended for all patients per local standard-of-care. Patients will be stratified by NAC platinum administration, NAC anthracycline administration, and clinical nodal status (positive versus negative). The primary endpoint is 3-year Event Free Survival (EFS). Secondary endpoints include Invasive Disease-Free Survival (IDFS), Distant Disease-Free Survival (DDFS), overall survival (OS) and safety. Exploratory correlative studies will be performed on tumor and serum to characterize the immunologic impact of the intervention and to explore predictors of efficacy and toxicity. Clinical trial information: NCT03546686.

Interplay between B cell and GABA metabolism (GABAm) and association with immune evasion in breast carcinoma (BC)

1097

Background: GABAergic signaling has been reported to play a pivotal role in breast cancer (BC) tumorigenesis and metastasis, however, its role in immune modulation remains unclear. Recent in vitro and in vivo studies (Zhang et al., Nature, 2021) report the role of B cell-derived GABA metabolites in promoting anti-inflammatory macrophages (MM), thus limiting anti-tumor immunity. In this study, we aim to characterize the interplay between B cells and the GABAm pathway, as well as their associated immune infiltrates and cytokines. Methods: BC tumors (n = 9455) were analyzed by next generation sequencing (NextSeq, 592 Genes and WES, NovaSEQ) and whole transcriptome sequencing (WTS, NovaSeq) at Caris Life Sciences. Gene set variation analysis (GSVA) scores were used for GABAm pathway activity (GMPA). IFN score to test the likelihood of a tumor’s response to anti PD1 therapy and Immune cell fraction (quanTIseq) were assessed by mRNA analysis. Wilcoxon-Mann-Whitney test was applied (p without, q with multiple comparison correction). Correlation coefficients were calculated using spearman correlation. Results: GMPA demonstrated a statistically significant positive correlation with B cells fraction (r = 0.24, p < 0.0001). When stratified by classical molecular subtypes, the positive correlations were exclusive to HR+ and HER2+ BC, and absent in TNBC. GMPA was the most enriched in HR+ BC, followed by HER2+ and TNBC. BC tumors with high B cell infiltration were then grouped into GMPA-high (B+G+, cutoff > median for both) or GMPA-low (B+/G-), which likely represented tumors with B cell-derived high and low GMPA group, respectively. The GMPA-high group demonstrated significantly less fractions of MM1 (2.8 vs 3.7) and CD8+ T cells (0.8 vs 1.2) but greater MM2 (5.3 vs 4.9). mRNA levels of the MM2 marker IL10, a proposed marker of immune evasion, was significantly overexpressed in the B+/G+ group compared to the B+/G- group (fold change, FC = 1.39). mRNA levels of GAD1, a GABA-generating enzyme, were higher in B+/G+ than B+/G- (FC = 7.19). B+/G+ group had notably less IFN score than B+/G- group (-0.37 vs -0.27). When further stratified into molecular subtypes, concurrent more MM2 (5.4 vs 5.2) and less CD8+ T cell (0.74 vs 0.91) fractions were found in B+/G+ compared to B+/G- in HR+ tumors, but not in HER2+ or TNBC tumors. B+/G+ group also demonstrated a lower IFN score (-0.38 vs -0.32) in HR+ tumors. Additionally, IL10 and GAD1 were consistently overexpressed in B+/G+ regardless of subtype, reaching FC 7.9 in HR+ tumors. q < 0.0001 for all comparisons. Conclusions: Our study is the largest clinical dataset to demonstrate the association of interplay between B cell and GABAm with immunogenicity. Our results support the potential role of B cell-derived GABAm metabolites in immune modulation in BC in a subtype-specific manner. Targeting small metabolites to modulate immune evasion in BC warrants further investigation.

Phase 1 pilot study with dose expansion of chemotherapy in combination with CD40 agonist and Flt3 ligand in metastatic triple-negative breast cancer

TPS1126

Background: Only a subset of patients with metastatic triple-negative breast cancer demonstrate response to currently approved PD-1 immune checkpoint blockade, and few have durable responses. Antigen presentation defects may be a reason for this low response because deficiency of antigen-presenting DC1 dendritic cells is associated with poor anti-tumor immunity. CD40 agonists are a class of agents that activate antigen presenting cells including dendritic cells and B cells and also repolarize macrophages. Flt3 ligand is a growth factor that increases dendritic cells. In line with this, we recently demonstrated in pre-clinical models that the combination of liposomal-doxorubicin chemotherapy, a CD40 agonist, and a Flt3 ligand improves outcomes of breast cancer compared to alternate combinations. Methods: This is a single arm phase I pilot study of liposomal-doxorubicin, CDX-1140 (CD40 agonist), and CDX-301 (Flt3 ligand) combination therapy in patients with metastatic or unresectable locally advanced metastatic triple-negative breast cancer. Patients will be randomized to 3 lead-in arms (triplet therapy, doublet immunotherapy only, liposomal-doxorubicin only) prior to receiving full triplet therapy with fresh tissue biopsies before and after the lead-in treatment. CDX-301 will be discontinued after 2 cycles; liposomal-doxorubicin and CDX-1140 will be continued until disease progression or clinically limiting toxicities. Primary endpoint is determination of a recommended phase 2 dose based on treatment-related adverse events including dose-limiting toxicities. Secondary endpoints include anti-tumor immune response after triplet therapy, after immunotherapy alone, and after liposomal-doxorubicin alone; median progression-free survival, overall response rate, duration of response, and clinical benefit rate. Key eligibility criteria are unresectable stage III or stage IV triple-negative breast cancer (ER ≤10%, PR ≤10%, HER2/neu negative), 1st to 3rd line metastatic treatment setting (1st line patients need to be PD-L1 negative by 22C3 assay), measurable disease by RECIST 1.1 criteria, consent for pre-treatment and on-treatment biopsies of amenable soft tissue tumor lesions, no prior treatment with an anti-CD40 antibody or a Flt3 ligand, no anthracycline treatment in the metastatic setting, no prior progression while on anthracycline-based therapy or within 6 months of completing neoadjuvant chemotherapy, and no history of non-infectious pneumonitis or current pneumonitis. This trial will enroll up to 45 patients across multiple sites. Clinical trial information: NCT05029999.

Neoadjuvant HER2-targeted therapy +/- immunotherapy with pembrolizumab (neoHIP): An open-label randomized phase II trial

TPS624

Background: Immune checkpoint inhibition (ICI) is synergistic with HER2-directed therapy in pre-clinical models. Clinically, pembrolizumab (K)-mediated ICI plus HER2-directed therapy with trastuzumab (H) was safe and demonstrated modest activity in H-resistant HER2-positive (HER2+) metastatic breast cancer. Because ICI may confer more robust activity when administered earlier in the course of disease, H and K administered in the curative-intent, treatment-naive setting may allow for de-escalation of cytotoxics; confer life-long, tumor-specific immunity; and ultimately, improve cure rates. Moreover, the synergy of H and K with paclitaxel (T) may overcome the need for dual HER2-blockade with H plus pertuzumab (P). In this randomized, multicenter, phase II, open-label trial the efficacy and safety of neoadjuvant THP vs THP-K vs TH-K are explored. Methods: 174 patients (pts) ≥18y with previously untreated, stage II-III, HER2+ breast cancer will be randomized and stratified by clinical nodal status (positive vs. negative) and hormone receptor status (positive vs. negative). In arm A, pts receive T at 80mg/m2 weekly for 12 weeks, H at 8mg/Kg (loading dose) and then 6mg/Kg every 3 weeks x 3 doses, P at 840 mg (loading dose) and then 420mg/Kg every 3 weeks x 3 doses (THP). In arm B, pts receive THP plus K at 200mg every 3 weeks x 4 doses (THP-K). In arm C, pts receive TH-K. Definitive surgery is 3-6 weeks after the last dose. After surgery, pts are treated per the treating physician’s discretion including radiotherapy per local clinical standard. Pts whose tumors are hormone-receptor positive will receive hormone therapy per local standard-of-care. The primary end point is pathologic complete response (pCR) rate in the breast and axilla (ypT0/Tis ypN0). Secondary end points include pCR rate by ypT0ypN0 and ypT0/Tis, residual cancer burden index, event free survival, breast conserving surgery rate, safety and overall survival. Exploratory correlative studies will characterize potential immune biomarkers predictive of efficacy and/or toxicity. Clinical trial information: NCT03747120.

Association of 27-gene IO score with outcome in a phase Ib trial of pembrolizumab (pembro) plus chemotherapy (CT) in metastatic triple-negative breast cancer (mTNBC)

1082

Background: The IO score is a is a 27-gene signature developed to classify the tumor immune microenvironment derived from the 101-gene TNBCtype genomic classifications. The IO score predicts clinical outcome following immune checkpoint inhibitor therapy in NSCLC and bladder cancer, and recently was shown to predict benefit by pCR of atezolizumab plus CT over neoadjuvant CT alone in early stage TNBC (NeoTRIPaPDL1 trial). The IO score has not yet been evaluated in mTNBC or with pembro in breast cancer. Methods: We report preliminary associations of IO score with response from a phase Ib trial (NCT02734290). mTNBC subjects received 1st/2nd line pembro (200mg IV q3wk) plus investigator’s choice paclitaxel (80mg/m2 IV q1wk, n = 15) or capecitabine (2000mg PO BID x 7d, q2wk, n = 14). Baseline (n = 23) and on-treatment (at wk 6, n = 10) biopsies were analyzed for IO score and genomic subtype by RNA exome sequencing. Objective response rate (ORR, partial or complete response, 12 weeks) and survival was determined among response-evaluable subjects (n= 21). Tumor PD-L1 was assessed by IHC (combined positive score, CPS > 10%). The IO signature was analyzed as a binary classifier (IO+/IO-) and as a continuous variable (IO score). Results: 39% of evaluable subjects were IO+ (n =9/23). IO+ was associated with improved clinical outcome, including ORR (IO+ 43%, IO- 29%), median progression free survival (mPFS, IO+ 138d, IO- 79d), and median overall survival (mOS, IO+ 687d, IO- 305d). IO+/IO- classification and IO scores were stable across serial biopsies (Cohen’s kappa = 0.74, r = 0.84). IO score was not strongly correlated with PD-L1 CPS (r = 0.27) or sTILs (r =.09). PD-L1-/IO+ tumors constituted 31% (n = 5/16) of PD-L1- cases and exhibited favorable outcome (ORR 40%, mPFS 162d, mOS 556d). IO score and ORR varied across TNBCtype classifications (BL1 subtype: 50% ORR, 66% IO+; BL2 subtype: 0% ORR, 66% IO+; LAR subtype: 50% ORR, 0% IO+, MSL subtype: 33% ORR, 60% IO+). Conclusions: IO score is associated with favorable outcome following pembro + CT, and may identify PD-L1-negative cases that respond to pembro + CT. Further investigation in larger datasets is warranted to ascertain the clinical utility of IO score in this setting. Funding: Drug support and funding provided by Merck Sharpe & Dohme as part of the Merck Investigator Studies Program. Clinical trial information: NCT02734290.

Brain radiotherapy, tremelimumab-mediated CTLA-4-directed blockade +/- trastuzumab in patients with breast cancer brain metastases

Breast cancer brain metastases (BCBM) are a common and devastating complication of metastatic breast cancer with conventional systemic therapies demonstrating limited effectiveness. Consequently, radiotherapy (RT) ± surgery remains the cornerstone of BCBM management. Because preclinical and clinical evidence indicate that immune checkpoint blockade (ICB) may synergize with RT to promote systemic tumor regression, we explored the safety and efficacy of RT and concurrent tremelimumab-mediated cytotoxic T-lymphocyte associated protein 4 (CTLA-4) ICB with tremelimumab ± HER2-directed therapy with trastuzumab for BCBM. Eligible patients had BCBM indicated for brain RT. A Simon two-stage design was adopted to evaluate the efficacy of tremelimumab and RT in 20 patients with human epidermal growth factor receptor normal (HER2−) BCBM. The safety of concurrent RT, tremelimumab, and trastuzumab was evaluated in a cohort of 6 HER2+ patients. The primary endpoint was 12-week non-central nervous system (CNS) disease control rate (DCR). Secondary endpoints included safety, survival, and CNS response. Exploratory correlatives included characterization of peripheral blood immune responses among exceptional responders. Tremelimumab plus RT ± trastuzumab was tolerated with no treatment-related grade 4 adverse events reported. The 12-week non-CNS DCR was 10% (2/20) in the HER2− cohort and 33% (2/6) in the HER2+ cohort. One patient with HER2+ disease experienced a durable partial response with evidence of peripheral T-cell activation. Thus, tremelimumab and RT ± trastuzumab was tolerated. Although modest clinical activity was observed in the HER2- efficacy cohort, encouraging responses were observed in the HER2+ safety cohort. Consequently, a trial to determine efficacy in HER2+ BCBM is planned.

Clinical Trial Registration Number: NCT02563925.

Abstract PD6-06: Comprehensive characterization of neurotransmitters and neuronal signaling gene alterations in invasive breast cancers

BACKGROUNDIt has been reported that the sympathetic nervous system and associated neurotransmitters (NTs) play a pivotal role in driving breast cancer (BC) tumorigenesis and metastasis, however, comprehensive characterization of these pathways in BC is lacking. The purpose of this study was to retrospectively characterize NTs and neuronal signaling (NTNS) gene alterations in a large real-world BC cohort. METHODS A total of 6464 BC tumors were analyzed by next generation sequencing (NextSeq, 592 genes and WES, NovaSEQ, 720 genes) and whole transcriptome sequencing (WTS, NovaSeq) at Caris Life Sciences. Gene set variation analysis (GSVA) scores were calculated (positive: higher gene expressions in a selected gene set compared to genes outside that gene set in each tumor specimen, vice versa for negative) to assess expression of major NTNS genes, including GABA, nicotinic (NIC), muscarinic (MUS), dopamine (DA), reelin (RELN), and glial cell line-derived neurotrophic factor (GDNF). GSVA scores were compared by histologic subtype, primary or metastatic site, and hormone receptor (HR) and HER2 status with corrected Wilcoxon-Mann-Whitney testing. All significance levels were p&lt;0.01. RESULTS The 6464 BC specimens in this cohort included 2520 primary sites and 3944 metastasis (mets) (liver: 1012; lymph node: 714; bone: 575; lung: 420; brain: 196). Predictive biomarker status in this cohort was HR+/HER2-: 3705; HR+/HER2+: 238; HR-/HER2+: 189; TNBC: 1654. Invasive ductal carcinomas (IDC) were the most common histologic subtype and demonstrated significantly higher GSVA scores for RELN and NIC pathways with respect to invasive lobular carcinomas (ILC) (Table). TNBC tumors had significantly higher enrichment overall (GABA, -0.04 vs -0.14; RELN, -0.05 vs -0.31; DA, -0.03 vs -0.08; MUS, 0.13 vs -0.16; NIC, 0.01 vs -0.12; and GDNF, 0.04 vs -0.04). HR-/HER2+ had significantly higher scores in GABA, -0.04 vs -0.14; RELN, -0.03 vs -0.31; MUS, 0.12 vs -0.16; and NIC, -0.01 vs -0.12 genes. Brain mets had significantly enriched pathway scores for GABA, 0.30 vs -0.13; MUS, 0.15 vs -0.08; and NIC, 0.13 vs -0.09 compared to primary tumors. Similarly, GABA,0.09 vs -0.13; DA, 0.07 vs -0.05; MUS, 0.17 vs -0.08; and NIC, 0.02 vs -0.09 pathways were enriched in bone mets compared to those from primary tumors. CONCLUSION Our results demonstrate that NTNS pathways are significantly enriched in IDC, TNBC tumors, and particularly in brain and bone mets. Our data advance the current understanding of the role of NTNS pathways in BC tumorigenesis and metastasis. Further investigation on genetic. determinants and signaling alternations associated with the observed NTNS pathway deregulation is warranted and could inform the development of novel therapeutic strategies. Significant comparisons with Bonferroni corrected p values are shown with an asterisk.

Citation Format: Irene Kang, Krutika Deshpande, Sarah Persing, Jun Yin, Joanne Xiu, Wolfgang Michael Korn, Jia Zeng, Evanthia T Roussos-Torres, Janice Lu, Darcy Spicer, Stephen F Sener, Antoinette R Tan, Ashley Sumrall, David SB Hoon, Cynthia X Ma, Carey K Anders, Heather L McArthur, Reva Basho, Heinz-Josef Lenz, Josh Neman. Comprehensive characterization of neurotransmitters and neuronal signaling gene alterations in invasive breast cancers [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 PD6-06.

Abstract PD10-01: The PEARL trial: Pre-operative pembrolizumab with radiation therapy in early stage triple negative breast cancer

Background: Anti-PD(L)1 in addition to neoadjuvant chemotherapy (NAC) can achieve pathologic complete response (pCR) rates of up to 65% in patients with early stage triple negative breast cancer (TNBC). However, patients with non-pCR can have dismal prognosis. Innovative strategies that render the tumor microenvironment more sensitive to anti-PD(L)1 may confer benefit. Preclinical studies have shown that hypofractionated radiation therapy (RT) delivered to an in-situ breast tumor, when combined with immune checkpoint blockade, stimulates anti-tumor immune responses and induces long-term, tumor-specific memory. Here, we report the first results of a phase II study that established the feasibility and efficacy of this approach in the pre-operative treatment setting for TNBC. Methods: Fifty patients with stage I-III TNBC, defined as ER&lt;10%,PR&lt;10%, HER2-negative, were enrolled between 12/17-4/21. Study treatment consisted of one cycle (C1) of pembro (200 mg iv q 3wks), followed by cycle 2 (C2) of pembro + RT (24Gy) delivered to a breast primary, followed by NAC regimen per MD choice, surgery and adjuvant therapy. Paired tumor biopsies and blood were collected at 3 serial time points: 1) baseline (pre-treatment); 2) after pembro C1; 3) after pembro C2 + RT (prior to initiation of NAC). All patients received breast and axillary surgery and postoperative RT to the chest wall and regional lymph nodes. Dual primary endpoints were: 1) feasibility, defined by the number of patients who did not necessitate a &gt;4-week delay in initiating NAC after pembro C2 + RT; 2) change in tumor infiltrating lymphocyte (TIL) score. Secondary endpoints included pCR, defined as ypT0/TisypN0, in addition to toxicity and cosmesis evaluations. Results: To date, 50 patients are evaluable with a median follow up of 12 months (range 6-12). Median age of cohort is 55y (range 26-76). The majority (92%) were clinical stage II; 2% stage I and 6% stage III. 34% of the cohort had biopsy-proven, node positive disease. All patients received a taxane, 52% carboplatin and 74% anthracycline. 12% did not complete the planned course of NAC due to toxicities. No patients experienced a delay in initiating NAC. 50% received breast-conserving surgery and 50% mastectomy. Grade 1 or 2 toxicities consisted of fatigue (76%), nausea (66%), maculopapular rash (32%), diarrhea (38%), colitis (2%), hypothyroidism (8%) and peripheral neuropathy (40%). Four patients had grade 3 toxicities that were attributable to pembro: hyponatremia(1), colitis (1), adrenal insufficiency(1) and pneumonitis (1). Three patients had grade 4 neutropenia which were not attributable to pembro. The overall rate of pCR was 74% (37/50). Among the 13 patients with non-pCR, 0% were RCB 1, 16% RCB 2 and 10% RCB 3. Among the 17 N+ patients, 13 converted to ypN0, 1 ypN1mic and 3 ypN1a. No patients progressed during treatment. Changes in TIL count, PD-L1 and other biomarkers after pembro +/- RT and their association with treatment response, will be presented at the meeting. Conclusions: The novel combination of pre-operative pembro followed by the addition of RT to pembro prior to NAC is not only feasible, but also achieves pCR rates that are higher-than-expected compared to the pembro arm of KEYNOTE-522. AEs were consistent with known safety profiles of each agent. If confirmed by larger, randomized studies, this combination will be paradigm-changing for the treatment of TNBC.

Citation Format: Heather L McArthur, Stephen Shiao, Scott Karlan, Reva Basho, Farin Amersi, Michele Burnison, Amin Mirhadi, Alice Chung, Cathie T Chung, Catherine Dang, Heather Richardson, Armando E Giuliano, Nimmi Kapoor, Brigid Larkin, Hector Godinez, Samantha A Dunn, Negin Habibi Khameneh, Simon Knott, Philomena McAndrew, Monica Mita, Dorothy J Park, Christina Abaya, Jonathan H Chen, Amy Ly, Veerle Bossuyt, Alice Ho. The PEARL trial: Pre-operative pembrolizumab with radiation therapy in early stage triple negative breast cancer [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 PD10-01.

Changes in T-cell subsets and clonal repertoire during chemoimmunotherapy with pembrolizumab and paclitaxel or capecitabine for metastatic triple-negative breast cancer

BACKGROUND

Chemoimmunotherapy is a standard treatment for triple-negative breast cancer (TNBC), however, the impacts of different chemotherapies on T-cell populations, which could correlate with clinical activity, are not known. Quantifying T-cell populations with flow cytometry and T-cell receptor (TCR) immunosequencing may improve our understanding of how chemoimmunotherapy affects T-cell subsets, and to what extent clonal shifts occur during treatment. TCR immunosequencing of intratumoral T cells may facilitate the identification and monitoring of putatively tumor-reactive T-cell clones within the blood.

METHODS

Blood and tumor biopsies were collected from patients with metastatic TNBC enrolled in a phase Ib clinical trial of first or second-line pembrolizumab with paclitaxel or capecitabine. Using identical biospecimen processing protocols, blood samples from a cohort of patients treated for early-stage breast cancer were obtained for comparison. Treatment-related immunological changes in peripheral blood and intratumoral T cells were characterized using flow cytometry and TCR immunosequencing. Clonal proliferation rates of T cells were compared based on intratumoral enrichment.

RESULTS

When combined with pembrolizumab, paclitaxel and capecitabine resulted in similar time-dependent lymphodepletions across measured peripheral T-cell subsets. Their effects were more modest than that observed following curative-intent dose-dense anthracycline and cyclophosphamide (ddAC) (average fold-change in CD3⁺ cells, capecitabine: -0.42, paclitaxel: -0.56, ddAC: -1.21). No differences in T-cell clonality or richness were observed following capecitabine or paclitaxel-based treatments. Regression modeling identified differences in the emergence of novel T-cell clones that were not detected at baseline (odds compared with ddAC, capecitabine: 0.292, paclitaxel: 0.652). Pembrolizumab with paclitaxel or capecitabine expanded T-cell clones within tumors; however, these clones did not always expand within the blood. Proliferation rates within the blood were similar between clones that were enriched and those that were not enriched within tumors.

CONCLUSION

Chemoimmunotherapy for metastatic TNBC with pembrolizumab and capecitabine or paclitaxel resulted in similar peripheral T-cell subset lymphodepletion without altering T-cell clonal diversity. Regression modeling methods are applicable in immune monitoring studies, such as this to identify the odds of novel T-cell clones emerging during treatment, and proliferation rates of tumor-enriched T-cell clones.

Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immunotherapy for the treatment of breast cancer

Breast cancer has historically been a disease for which immunotherapy was largely unavailable. Recently, the use of immune checkpoint inhibitors (ICIs) in combination with chemotherapy for the treatment of advanced/metastatic triple-negative breast cancer (TNBC) has demonstrated efficacy, including longer progression-free survival and increased overall survival in subsets of patients. Based on clinical benefit in randomized trials, ICIs in combination with chemotherapy for the treatment of some patients with advanced/metastatic TNBC have been approved by the United States (US) Food and Drug Administration (FDA), expanding options for patients. Ongoing questions remain, however, about the optimal chemotherapy backbone for immunotherapy, appropriate biomarker-based selection of patients for treatment, the optimal strategy for immunotherapy treatment in earlier stage disease, and potential use in histological subtypes other than TNBC. To provide guidance to the oncology community on these and other important concerns, the Society for Immunotherapy of Cancer (SITC) convened a multidisciplinary panel of experts to develop a clinical practice guideline (CPG). The expert panel drew upon the published literature as well as their clinical experience to develop recommendations for healthcare professionals on these important aspects of immunotherapeutic treatment for breast cancer, including diagnostic testing, treatment planning, immune-related adverse events (irAEs), and patient quality of life (QOL) considerations. The evidence-based and consensus-based recommendations in this CPG are intended to give guidance to cancer care providers treating patients with breast cancer.

Chemotherapy and Targeted Therapy for Patients With Human Epidermal Growth Factor Receptor 2-Negative Metastatic Breast Cancer That is Either Endocrine-Pretreated or Hormone Receptor-Negative: ASCO Guideline Update

PURPOSE

This guideline updates recommendations of the ASCO guideline on chemotherapy and targeted therapy for patients with human epidermal growth factor receptor 2-negative metastatic breast cancer (MBC) that is either endocrine-pretreated or hormone receptor (HR)-negative.

METHODS

An Expert Panel conducted a targeted systematic literature review guided by a signals approach to identify new, potentially practice-changing data that might translate into revised guideline recommendations.

RESULTS

The Expert Panel reviewed abstracts from the literature review and retained 14 articles.

RECOMMENDATIONS

Patients with triple-negative, programmed cell death ligand-1-positive MBC may be offered the addition of immune checkpoint inhibitor to chemotherapy as first-line therapy. Patients with triple-negative, programmed cell death ligand-1-negative MBC should be offered single-agent chemotherapy rather than combination chemotherapy as first-line treatment, although combination regimens may be offered for life-threatening disease. Patients with triple-negative MBC who have received at least two prior therapies for MBC should be offered treatment with sacituzumab govitecan. Patients with triple-negative MBC with germline BRCA mutations previously treated with chemotherapy may be offered a poly (ADP-ribose) polymerase inhibitor rather than chemotherapy. Patients with HR-positive human epidermal growth factor receptor 2-negative MBC for whom chemotherapy is being considered should be offered single-agent chemotherapy rather than combination chemotherapy, although combination regimens may be offered for highly symptomatic or life-threatening disease. Patients with HR-positive MBC with disease progression on an endocrine agent may be offered treatment with either endocrine therapy with or without targeted therapy or single-agent chemotherapy. Patients with HR-positive MBC with germline BRCA mutations no longer benefiting from endocrine therapy may be offered a poly (ADP-ribose) polymerase inhibitor rather than chemotherapy. No recommendation regarding when a patient's care should be transitioned to hospice or best supportive care alone is possible.Additional information is available at www.asco.org/breast-cancer-guidelines.

ALEXANDRA/IMpassion030: A phase 3 study of standard adjuvant chemotherapy with or without atezolizumab in patients with early-stage triple-negative breast cancer

TPS597

Background: Early stage triple negative breast cancer (TNBC) is associated with a high risk of distant relapse. Because TNBC does not currently have specific targeted agents approved for use in the early setting, it is treated primarily with chemotherapy. TNBC may be more immunogenic than other subtypes of breast cancer. Atezolizumab (an anti–PD-L1 antibody), in combination with nab-paclitaxel has been approved in >70 countries for the treatment of PD-L1-positive unresectable locally advanced or metastatic TNBC based on the results of the randomized phase 3 IMpassion130 trial. The phase 3 IMpassion031 study, evaluating atezolizumab in combination with chemotherapy (nab-paclitaxel followed by doxorubicin and cyclophosphamide) in comparison to placebo plus chemotherapy as neoadjuvant treatment demonstrated a statistically significant and clinically meaningful improvement in pCR in both PD-L1 positive and PD-L1 negative tumors. ALEXANDRA/IMpassion030 is a global, prospective, randomized, open-label, phase 3 trial currently investigating the efficacy, safety and pharmacokinetic profile of adjuvant atezolizumab plus standard anthracycline/taxane adjuvant chemotherapy versus chemotherapy alone in early stage TNBC. Methods: ALEXANDRA/IMpassion030 will randomize 2300 patients with operable stage II-III TNBC, confirmed by central pathology review. Patients are stratified by type of surgery, nodal status, and centrally assessed PD-L1 status. Adjuvant chemotherapy consist of weekly paclitaxel 80 mg/m2 for 12 weeks followed by dose dense anthracycline (epirubicin 90 mg/m2 or doxorubicin 60 mg/m2) and cyclophosphamide 600 mg/m2 for 4 doses every 2 weeks or the same chemotherapy regimen (T-EC/AC) given concomitantly with atezolizumab 840 mg every 2 weeks followed by maintenance atezolizumab 1200 mg every 3 weeks until completion of 1 year of atezolizumab. The primary endpoint is invasive disease-free survival (iDFS) and secondary endpoints include, iDFS in the PD-L1 selected tumour status (IC1/2/3) and node-positive subpopulations, overall survival, safety, patient functioning and health related quality of life (HRQoL). Tumor tissue and blood samples will be collected for biomarker research. The first site was activated on May 4 2018, and approximately 373 sites in 30 countries are currently participating in this trial. This trial is sponsored by F. Hoffmann-La Roche Ltd and conducted in partnership with the Breast International Group, Frontier Science and Technology Research Foundation, Institute Jules Bordet and Alliance Foundation Trials. Clinical trial information: NCT03498716.

Advances in Combining Radiation and Immunotherapy in Breast Cancer

Breast irradiation has long been utilized in the adjuvant or metastatic setting to eliminate microscopic disease or to palliate existing disease, respectively. However, preclinical data have demonstrated that radiation can also alter the tumor microenvironment and induce antitumor immune responses. As a result, multiple clinical studies have been undertaken and have reported synergy between radiation and immune checkpoint blockade across various cancer types. Given recent clinical successes with immune checkpoint blockade in both early-stage and metastatic breast cancer, there has been substantial interest in combining radiation and immunotherapy to enhance local and systemic immune responses. Herein, we review the preclinical rationale for combining radiotherapy and immunotherapy, the early clinical trials that have adopted this strategy in breast cancer, and the landscape of ongoing relevant clinical trials. Finally, we propose future directions based on promising preclinical studies that integrate radiation, checkpoint blockade, and novel agents for the treatment of breast cancer.

Immunomodulatory Activity of a Colony-stimulating Factor-1 Receptor Inhibitor in Patients with Advanced Refractory Breast or Prostate Cancer: A Phase I Study

PURPOSE

Tumor-associated macrophages correlate with increased invasiveness, growth, and immunosuppression. Activation of the colony-stimulating factor-1 receptor (CSF-1R) results in proliferation, differentiation, and migration of monocytes/macrophages. This phase I study evaluated the immunologic and clinical activity, and safety profile of CSF-1R inhibition with the mAb LY3022855.

PATIENTS AND METHODS

Patients with advanced refractory metastatic breast cancer (MBC) or metastatic castration-resistant prostate cancer (mCRPC) were treated with LY3022855 intravenously in 6-week cycles in cohorts: (A) 1.25 mg/kg every 2 weeks (Q2W); (B) 1.0 mg/kg on weeks 1, 2, 4, and 5; (C) 100 mg once weekly; (D)100 mg Q2W. mCRPC patients were enrolled in cohorts A and B; patients with MBC were enrolled in all cohorts. Efficacy was assessed by RECIST and Prostate Cancer Clinical Trials Working Group 2 criteria.

RESULTS

Thirty-four patients (22 MBC; 12 mCRPC) received ≥1 dose of LY3022855. At day 8, circulating CSF-1 levels increased and proinflammatory monocytes CD14^DIMCD16^BRIGHT decreased. Best RECIST response was stable disease in five patients with MBC (23%; duration, 82-302 days) and three patients with mCRPC (25%; duration, 50-124 days). Two patients with MBC (cohort A) had durable stable disease >9 months and a third patient with MBC had palpable reduction in a nontarget neck mass. Immune-related gene activation in tumor biopsies posttreatment was observed. Common any grade treatment-related adverse events were fatigue, decreased appetite, nausea, asymptomatic increased lipase, and creatine phosphokinase.

CONCLUSIONS

LY3022855 was well tolerated and showed evidence of immune modulation. Clinically meaningful stable disease >9 months was observed in two patients with MBC.

A phase III trial of nivolumab with neoadjuvant chemotherapy and adjuvant endocrine therapy in ER+/HER2- primary breast cancer: CheckMate 7FL

TPS604

Background: Patients (pts) diagnosed with primary estrogen receptor-positive (ER+), human epidermal growth factor 2-negative (HER2−) breast cancer (BC) of high grade and/or low ER expression are at increased risk of relapse, despite current standard of care (SoC). Promising data assessing programmed death-1 (PD-1) inhibition coupled with neoadjuvant chemotherapy for pts with high-risk ER+, HER2− BC noted improved pathologic complete response (pCR), which is identified as a valid surrogate endpoint for long-term clinical outcomes. Methods: CheckMate 7FL (NCT04109066) is a randomized, double-blind, placebo-controlled, multicenter, global phase 3 study evaluating nivolumab (NIVO) vs placebo (PBO) in combination with neoadjuvant chemotherapy and adjuvant endocrine therapy (ET) in pts with high-risk, ER+, HER2− primary BC. Eligible pts are male or female, aged ≥18 years with newly diagnosed grade 2 with ER expression of 1–9%, or grade 3, T1c-2, cN1-2 (tumor size ≥2 cm) or T3-T4, cN0-cN2 ER+, HER2− BC. Pts eligible for neoadjuvant chemotherapy and surgery, with adequate organ function, ECOG PS of 0 or 1, and tissue available for biomarker assessments will be enrolled. Approximately 1200 pts will be randomized 1:1 to NIVO or PBO, stratified by programmed death ligand 1 (PD-L1) expression, tumor grade (2 or 3), axillary nodal status (+ or −), and anthracycline + cyclophosphamide schedule (Q3W or Q2W). In the neoadjuvant phase, pts will receive NIVO 360 mg Q3W or PBO + paclitaxel 80 mg/m2 QW for four 3-week cycles, followed by NIVO 360 mg Q3W (or 240 mg Q2W) or matching PBO in combination with either doxorubicin 60 mg/m2 or epirubicin 90 mg/m2 and cyclophosphamide 600 mg/m2 Q3W or Q2W for 4 cycles. Pts will undergo surgery after completion of the neoadjuvant phase. Following surgery, pts will enter the adjuvant phase and receive NIVO 480 mg Q4W or PBO for 7 cycles + investigator’s choice of ET per local SoC. Primary endpoints are pCR (ypT0/is, ypN0) and event-free survival. Secondary endpoints include overall survival, disease-free survival, distant-metastasis-free survival, safety, pCR (ypT0 ypN0 and ypT0/is) rates, overall response rates, residual cancer burden, and quality of life. Interim analyses are planned. The study is currently enrolling. Clinical trial information: NCT04109066 .

Combination Immunotherapy Strategies in Breast Cancer

Purpose of Review

We summarize combination immunotherapy strategies for the treatment of breast cancer, with a focus on metastatic disease. First, a general overview of combination approaches is presented according to breast cancer subtype. Second, additional review of promising combination approaches is presented.

Recent Findings

Combination strategies utilizing chemotherapy or radiotherapy with immune checkpoint inhibition are being evaluated across multiple phase III trials. Dual immunotherapy strategies, such as dual immune checkpoint inhibition or combined co-stimulation/co-inhibition, have supportive preclinical evidence and are under early clinical investigation. Modulation of the immune microenvironment via cytokines and vaccination strategies, as well as locally focused treatments to enhance antigenic responses, are active areas of research.

Summary

Pre-clinical and translational research sheds new light on numerous ways the immune system may be modulated to fight against cancer. We describe current and emerging combination approaches which may improve patient outcomes in metastatic breast cancer.

A phase 2 clinical trial assessing the efficacy and safety of pembrolizumab and radiotherapy in patients with metastatic triple-negative breast cancer

BACKGROUND

The current study was conducted to evaluate the efficacy and safety of pembrolizumab-mediated programmed cell death protein 1 inhibition plus radiotherapy (RT) in patients with metastatic triple-negative breast cancer who were unselected for programmed death-ligand 1 expression.

METHODS

The current study was a single-arm, Simon 2-stage, phase 2 clinical trial that enrolled a total of 17 patients with a median age of 52 years (range, 37-73 years). An RT dose of 3000 centigrays (cGy) was delivered in 5 daily fractions. Pembrolizumab was administered intravenously at a dose of 200 mg within 3 days of the first RT fraction, and then every 3 weeks ± 3 days until disease progression. The median follow-up was 34.5 weeks (range, 2.1-108.3 weeks). The primary endpoint of the current study was the overall response rate (ORR) at week 13 in patients with unirradiated lesions measured using Response Evaluation Criteria in Solid Tumors (RECIST; version 1.1). Secondary endpoints included safety and progression-free survival. Exploratory objectives were to identify biomarkers predictive of ORR and progression-free survival.

RESULTS

The ORR for the entire cohort was 17.6% (3 of 17 patients; 95% CI, 4.7%-44.2%), with 3 complete responses (CRs), 1 case of stable disease, and 13 cases of progressive disease. Eight patients died prior to week 13 due to disease progression. Among the 9 women assessed using RECIST version 1.1 at week 13, 3 (33%) achieved a CR, with a 100% reduction in tumor volume outside of the irradiated portal. The CRs were durable for 18 weeks, 20 weeks, and 108 weeks, respectively. The most common grade 1 to 2 toxicity (assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events, version 4.0) was dermatitis (29%). Four grade 3 adverse events were attributed to pembrolizumab: fatigue, lymphopenia, and infection. No were no grade 4 adverse events or treatment-related deaths reported.

CONCLUSIONS

The combination of pembrolizumab and RT was found to be safe and demonstrated encouraging activity in patients with poor-prognosis, metastatic, triple-negative breast cancer who were unselected for programmed death-ligand 1 expression. Larger clinical trials of checkpoint blockade plus RT with predictive biomarkers of response are needed.

Immunotherapy in Triple-Negative Breast Cancer: Present and Future

Purpose of Review

Immunotherapy is emerging as an effective treatment option for metastatic triple-negative breast cancer. In this review, we summarize clinical data of immunotherapy in triple-negative breast cancer and comment on future directions in the field.

Recent Findings

IMpassion130 was a phase III trial that demonstrated progression-free survival benefit, and potentially overall survival benefit, of first-line chemotherapy (nab-paclitaxel) plus anti-programmed death ligand 1 (PD-L1) atezolizumab, among PD-L1-positive metastatic triple-negative breast cancers. Studies are ongoing to evaluate other combination therapies with immune checkpoint blockade in TNBC, and to evaluate efficacy in PD-L1-negative tumors and in later lines of therapy.

Summary

Immunotherapy is now a standard option in the treatment of triple-negative breast cancer. Ongoing trials may expand the degree of clinical benefit. Further work is ongoing to identify novel predictive biomarkers, which in the future may enable a personalized approach of combination immunotherapy.

Current Landscape of Immunotherapy in Breast Cancer: A Review

Importance

There is tremendous interest in using immunotherapy to treat breast cancer, as evidenced by the more than 290 clinical trials ongoing at the time of this narrative review. The objective of this review is to describe the current status of immunotherapy in breast cancer, highlighting its potential in both early-stage and metastatic disease.

Observations

After searching ClinicalTrials.gov on April 24, 2018, and PubMed up to June 30, 2018, to identify breast cancer immunotherapy trials, we found that immune checkpoint blockade (ICB) is the most investigated form of immunotherapy in breast cancer. Use of ICB as monotherapy has achieved objective responses in patients with breast cancer, with higher rates seen when administered in earlier lines of therapy. For responding patients, those responses are durable. More recent data suggest clinical efficacy when ICB is given in combination with chemotherapy. Ongoing studies are evaluating combination strategies pairing ICB with additional chemotherapeutic agents, targeted therapy, vaccines, and local ablative therapies to enhance response. To date, robust predictive biomarkers for response to ICB have not been established.

Conclusions and Relevance

It is anticipated that combination therapy strategies will be the way forward for immunotherapy in breast cancer, with an improved understanding of tumor, microenvironment, and host factors informing treatment combination decisions. Thoughtful study design incorporating appropriate end points and correlative studies will be critical in identifying optimal strategies for enhancing the immune response against breast tumors.

Pembrolizumab (pembro) with paclitaxel (taxol) or capecitabine (cape) as early treatment of metastatic triple-negative breast cancer (mTNBC)

1015

Background: Atezolizumab (anti-PD-L1) plus nab-paclitaxel was shown to improve outcomes in mTBNC in a phase III clinical trial. Subjects were required to be > 12 months from curative-intent therapy in this trial. It remains unknown whether non-taxane chemo + anti-PD-1/L1 will be beneficial in mTNBC, or whether this approach is effective in rapidly-progressing patients ( < 12 mo from curative-intent therapy). Methods: mTNBC patients were enrolled in a phase Ib study of anti-PD-1 (pembro, 200mg IV q3w) plus physician’s choice chemo (cape: n = 14, 2000mg BID, 7d on/7d off; or taxol: n = 14, 80mg/m2 q1w). Primary/secondary objectives were to evaluate safety/tolerability (primary) and RECIST1.1 response (w12). The exploratory objective was to explore for differences in immunomodulation according to chemo choice. Mixed effects models were employed to compare the longitudinal effects of chemo on peripheral immune cells (flow cytometry) and T-cell diversity (Immunoseq assay). Results: Enrollment of the trial is complete (n = 28), with 100% of evaluable patients tolerating therapy (n = 22) as of 2/1/2019. Cape ORR was 43% (5 PR, 1 CR, 2 SD) with median PFS = 155d. Taxol ORR was 25% (1 CR, 1 PR, 3 SD) with median PFS = 99d. Subjects enrolled < 12 months from curative-intent therapy had numerically lower response (ORR = 27%, 1 CR, 2 PR, 3 SD) than subjects without rapid progression (ORR = 45%, 1 CR, 4 PR, 2 SD). No significant differences in immunomodulation were observed according to chemo type, however both cape & taxol were associated with declines in T-cell quantity (CD4 p < .02, CD8 p < .04) and Immunoseq T-cell fraction over time. Conclusions: Pembro plus cape or taxol is safe with encouraging efficacy, however activity may be lower in the setting of rapid progression following curative-intent chemo. Cape+pembro efficacy is favorable with no measurable differences in immunomodulation, and therefore cape may be preferred as a chemo backbone in selected patients. Both cape and taxol are associated with iatrogenic declines in T-cell quantity, which may explain the observed dropoff in anti-PD-1/L1 activity in later lines. Clinical trial information: NCT02734290.

ALEXANDRA/IMpassion030: A phase III study of standard adjuvant chemotherapy with or without atezolizumab in early-stage triple-negative breast cancer

TPS598

Background: Early stage triple negative breast cancer (TNBC) is associated with a high risk of distant relapse. Because TNBC does not currently have specific targeted agents approved for use in the early setting it is treated primarily with chemotherapy. TNBC may be more immunogenic than other subtypes of breast cancer and promising clinical activity has been reported with the anti–PD-L1 antibody, atezolizumab, in Phase 1/1b metastatic TNBC trials. Furthermore, the randomized phase 3 IMpassion130 study demonstrated enhanced anti-tumor activity when atezolizumab was co-administered with chemotherapy in the first line metastatic setting, with benefit mainly observed in PD-L1+ cohort. ALEXANDRA/IMpassion030 will evaluate the efficacy and safety of atezolizumab in combination with standard anthracycline/taxane adjuvant chemotherapy in early TNBC patients. Methods: ALEXANDRA/IMpassion030 is a global, prospective, randomized, open-label, phase 3 trial investigating the efficacy, safety and pharmacokinetic profile of adjuvant atezolizumab plus standard chemotherapy versus chemotherapy alone in early TNBC. In total, 2300 patients with operable stage II or III TNBC, confirmed by central pathology review, will be randomized. Patients are stratified by type of surgery, nodal status, and centrally assessed PD-L1 status. Adjuvant treatment will consist of weekly paclitaxel 80 mg/m2 for 12 weeks followed by dose dense anthracycline (epirubicin 90 mg/m2 or doxorubicin 60 mg/m2) and cyclophosphamide 600 mg/m2 for 4 doses every 2 weeks or the same chemotherapy regimen (T-EC/AC) given concomitantly with atezolizumab 840 mg every 2 weeks followed by maintenance atezolizumab 1200 mg every 3 weeks until completion of 1 year of atezolizumab. The primary end-point is invasive disease-free survival (iDFS) and secondary end-points include iDFS by PD-L1 and lymph node status, overall survival, safety, patient functioning and health related quality of life (HRQoL). Tumor tissue and blood samples will be collected for biomarker research. The first patient was enrolled on August 2nd 2018, and approximately 430 sites are expected to be opened globally in 30 countries. Clinical trial information: NCT03498716.

Nimbus: A phase II study of nivolumab plus ipilimumab in metastatic hypermutated HER2-negative breast cancer

TPS1115

Background: A previous study from our group showed that approximately 9% of metastatic breast cancer (MBC) is hypermutated, defined as a tumor mutational burden (TMB) ≥10 Mutations/Megabase (Mut/Mb). The aim of this study is to evaluate if patients with hypermutated HER2-negative MBC benefit from the combination of nivolumab plus ipilimumab. Methods: This is an open-label, single-arm, multicenter, phase 2 study assessing the efficacy of nivolumab 3 mg/Kg intravenously (IV) every 14 days plus Ipilimumab 1 mg/Kg IV every 6 weeks in subjects with hypermutated metastatic HER2-negative breast cancer. Patients with measurable HER2-negative MBC, TMB ≥10 Mut/Mb assessed by a cancer-gene panel evaluating > 300 genes and performed in a CLIA-certified laboratory, and 0-3 prior lines of chemotherapy in the advanced setting are eligible. The primary objective is overall response rate according to RECIST 1.1. Secondary objectives include the safety and tolerability of the combination, progression-free survival, and overall survival. The study will follow a two-stage design. In the first stage 14 patients will be enrolled. If there is at least one patient with objective response, accrual will continue to the second stage where an additional 16 patients will be enrolled. If there are at least 4 patients with an objective response among the 30 patients, the regimen will be considered worthy of further study. If the true response rate is 5%, the chance the regimen is declared worthy of further study is less than 5%. If the true response rate is 25%, the chance that the regimen is declared worthy of further study is > 90%. Tumor biopsies, peripheral blood, and stool collection are mandatory and will be obtained at baseline, on treatment (end of cycle 1), and at disease progression and will be assessed for potential biomarkers of treatment response. The trial was activated in February 2019, and accrual should be completed in 18 months. Clinical trial information: NCT03789110.

Phase 1 study of LY3022855, a colony-stimulating factor-1 receptor (CSF-1R) inhibitor, in patients with metastatic breast cancer (MBC) or metastatic castration-resistant prostate cancer (MCRPC)

2548

Background: Tumor-associated macrophages (TAM) correlate with increased invasiveness, growth, and immunosuppression. Activation of CSF-1R results in proliferation, differentiation, and migration of monocytes/macrophages. CSF-1R inhibition with LY3022855 (LY), a human immunoglobulin G subclass 1 (IgG1) monoclonal antibody (mAB), may have favorable anti-tumor effects. We evaluated the safety and clinical response of LY monotherapy. Methods: Patients (pts) with advanced refractory MBC and MCRPC received LY intravenously in 6-week cycles in cohorts: A) 1.25 mg/kg every 2 weeks [Q2W]; B) 1.0 mg/kg on Weeks 1, 2, 4, and 5; C) 100 mg once weekly; D)100 mg Q2W. MCRPC pts were enrolled in cohorts A and B; MBC pts were enrolled in all cohorts. Anti-tumor activity was assessed using RECIST v1.1 by radiological imaging every 6 weeks. Results: Thirty-four pts (22 MBC; 12 MCRPC) received ≥1 dose of LY. Median age was 57.0 years (range: 32.0–81.0) for MBC pts and 72.5 years (range: 58.0–84.0) for MCRPC pts. Baseline Eastern Cooperative Oncology Group performance status was 0 (n = 13, 38.2%), 1 (n = 18, 52.9%), or 2 (n = 3, 8.8%). MBC pts were hormone receptor (HR) positive (n = 20), HR negative (n = 1), or unknown (n = 1); 3 MBC pts received concurrent hormone therapy. Common treatment-related adverse events of any grade were fatigue (38.2%), decreased appetite (26.5%), nausea (26.5%), increased lipase (23.5%), and increased creatine phosphokinase (20.6%). No complete or partial response was observed. Stable disease (SD) was observed in 5/22 MBC pts (duration 82–302 days) and 3/7 evaluable MCPRC pts (duration 50–124 days). Two MBC pts (9%; Cohort A) had durable SD > 9 months and 1 pt had palpable reduction in a nontarget neck mass. Circulating CSF1 and IL-34 increased at Day 8 suggestive of target engagement. Pharmacokinetics of LY were consistent with other IgG1 mAbs. Conclusions: LY3022855 was well tolerated and showed evidence of target engagement. Clinically meaningful SD > 9 months was observed in 2 MBC pts. Tumor biomarker analyses are underway. Clinical trial information: NCT02265536.

Preoperative checkpoint inhibition (CPI) and cryoablation (Cryo) in women with early-stage breast cancer (ESBC)

592

Background: Checkpoint inhibition (CPI) combined with local strategies that cause local tumor destruction, such as cryo may augment tumor specific immunity and improve survival. We previously demonstrated in 18 ESBC patients (pts) that pre-operative (pre-op) cryo with ipilimumab (ipi) is not only safe but also generates robust local and systemic immune responses (NCT01502592). Given the added activity of dual CPI in other tumors, we undertook a second pilot study of pre-op ipi/nivolumab (nivo)/cryo to confirm the safety of this combination and the impact on immune biomarkers. Methods: In both pilot studies, eligible pts had operable ≥1.5cm invasive HER2 negative ESBC. CPI was administered 8-15d prior to, and cryo was performed 7-10d prior to, standard-of-care (SOC) surgery. Toxicity evaluation continued for 12wks after drug administration. Blood for immune correlates was obtained at baseline, cryo, surgery and 2-4 weeks thereafter. Tumor samples were obtained at cryo and surgery. Flow-cytometry of peripheral lymphocytes was compared to previously reported ipi/cryo responses. Results: After a median follow-up of 66 months all 18 ESBC ipi/cryo pts, including 3 TNBC pts, are recurrence free. In the ipi/nivo/cryo study, the safety primary endpoint was met when 5 pts underwent SOC surgery without delay. Ipi/nivo/cryo was well tolerated overall. One pt on an aromatase inhibitor had grade 4 liver toxicity 8 weeks after surgery. One pt, 3 weeks after her SOC surgery, developed grade 1 hyperthyroidism, preventing a secondary axillary dissection from proceeding as scheduled. Robust activation of peripheral CD4+ and CD8+ T cells peaked at week 2 post ipi/nivo with the majority of activated CD8+ T cells expressing PD1. Comparing the correlatives of the ipi/nivo/cryo study with the prior ipi/cryo study, we observed higher expression of activation markers (Ki-67, ICOS, CTLA-4, LAG-3) on peripheral T cells and downregulation of suppressor cells. Conclusions: Ipi/cryo-treated pts, including 3 TNBC pts, remain recurrence free after > 5y. Combining cryo with ipi/nivo preop is feasible, safe, and associated with greater T cell activation than ipi/cryo alone. These results informed an ongoing randomized phase 2 study of pre-op ipi/nivo/cryo versus SOC in women with residual TNBC after neoadjuvant chemotherapy (NCT03546686). Clinical trial information: NCT02833233.

KEYNOTE-756: Randomized, double-blind, phase 3 study of pembrolizumab vs placebo combined with neoadjuvant chemotherapy and adjuvant endocrine therapy for high-risk, early-stage estrogen receptor–positive, human epidermal growth factor receptor 2–negative (ER+/HER2−) breast cancer

TPS601

Background: Although ER+/HER2− breast cancer (BC) has better overall prognosis than other subtypes, a high-risk subpopulation is characterized by high-grade tumors, decreased sensitivity to endocrine therapy (ET), higher responsiveness to chemotherapy (CT), and worse prognosis. Based on prior studies, increased pathological complete response (pCR) rates after neoadjuvant CT may have a substantial impact for patients with high-risk, early-stage HR+/HER2− BC. KEYNOTE-756 (ClinicalTrials.gov, NCT03725059) is a global, randomized, double-blind, phase 3 study of pembrolizumab (vs placebo) + CT as neoadjuvant treatment followed by pembrolizumab (vs placebo) + ET as adjuvant treatment for patients with high-risk, early-stage ER+/HER2− BC. Methods: Patients with T1c-2 cN1-2 (tumor size ≥2 cm) or T3-4 cN0-2 grade 3, invasive, ductal ER+/HER2− BC will be stratified by lymph node involvement (positive vs negative), tumor PD-L1 status (positive [CPS≥1] vs negative [CPS < 1]), ER positivity (ER+ ≥10% vs ER+ < 10%), and anthracycline dosing schedule (every 3 weeks [Q3W] vs Q2W), then randomized 1:1 to neoadjuvant treatment with pembrolizumab 200 mg Q3W or placebo combined with paclitaxel (80 mg/m2 Q1W) for 4 cycles followed by doxorubicin (60 mg/m2) or epirubicin (100 mg/m2), each with cyclophosphamide (600 mg/m2) Q2/3W for 4 cycles. After definitive surgery (± radiation therapy, as indicated), patients will receive adjuvant treatment of pembrolizumab (200 mg Q3W) or placebo for 9 more administrations combined with ET, which can be given for up to 10 years. There will be no crossover between treatment arms when moving from neoadjuvant to adjuvant treatment. Dual primary endpoints are pCR rate (ypT0/Tis ypN0) and event-free survival (EFS). Secondary endpoints include ypT0/Tis and ypT0 ypN0 pCR rates in all patients and all 3 pCR definitions in those with PD-L1+ tumors, EFS in patients with PD-L1+ tumors, overall survival, safety, and health-related quality of life. Interim analyses are planned. Enrollment is currently ongoing. Clinical trial information: NCT03725059.

A network approach to developing immuno-oncology combinations in Canada

Immune checkpoint inhibitors have revolutionized care for many cancer indications, with considerable effort now being focused on increasing the rate, depth, and duration of patient response. One strategy is to combine immune strategies (for example, ctla-4 and PD-1/L1-directed agents) to harness additive or synergistic efficacy while minimizing toxicity. Despite encouraging results with such combinations in multiple tumour types, numerous clinical challenges remain, including a lack of biomarkers that reliably predict outcome, the emergence of therapeutic resistance, and optimal management of immune-related toxicities. Furthermore, the selection of ideal combinations from the myriad of immune, systemic, and locoregional therapies has yet to be determined. A longitudinal network-based approach could offer advantages in addressing those critical questions, including long-term follow-up of patients beyond individual trials. The molecular cancer registry Personalize My Treatment, managed by the Networks of Centres of Excellence nonprofit organization Exactis Innovation, is uniquely positioned to accelerate Canadian immuno-oncology (io) research efforts throughout its national network of cancer sites. To gain deeper insight into how a pan-Canadian network could advance research in io combinations, Exactis invited preeminent clinical and scientific advisors from across Canada to a roundtable event in November 2017. The present white paper captures the expert advice provided: leverage longitudinal patient data collection; facilitate network collaboration and assay harmonization; synergize with existing initiatives, networks, and biobanks; and develop an io combination trial based on Canadian discoveries.

Abstract OT3-04-02: Neoadjuvant Her2-targeted therapy +/- immunotherapy with pembrolizumab (neoHIP): An open label randomized phase II trial

Background: In preclinical models HER2-directed therapy administered with checkpoint blockade is synergistic. Clinically, trastuzumab administered with pembrolizumab-mediated checkpoint blockade in trastuzumab-resistant HER2-positive metastatic breast cancer was safe and demonstrated modest activity. However, because checkpoint blockade can confer improved responses when administered earlier in the course of disease, trastuzumab with pembrolizumab administered in the curative-intent, treatment-naive setting may confer life-long, tumor-specific immunity and ultimately, improve cure rates. Moreover, the potential synergy of trastuzumab and pembrolizumab with paclitaxel may overcome the need for dual HER2-blockade. The neo-HIP study is a randomized, multicenter, phase II, open-label trial to evaluate the efficacy and safety of weekly paclitaxel, trastuzumab plus pertuzumab (THP) vs weekly THP plus pembrolizumab (THP-K) vs a HER2 monotherapy regimen (TH-K) as neoadjuvant treatment in patients with HER2-positive early stage invasive breast cancer.

Methods:Patients ≥18 years old with previously untreated, non-metastatic, stage II-III, HER2-positive (by ASCO/CAP guidelines) breast cancer are eligible. Patients with inflammatory breast cancer or bilateral primary tumors are excluded. Adequate organ function and ECOG PS 0-1 are required. Approximately 174 patients will be randomly assigned to 1 of 3 arms with stratification by clinical nodal status (positive vs. negative) and hormone receptor status (positive vs. negative). In arm A, patients will receive T at 80mg/m2 weekly for 12 weeks, H at 8mg/Kg (1 loading dose) and then 6mg/Kg IV every 3 weeks x 3 doses, P at 840mg (1 loading dose) and then 420mg/Kg IV every 3 weeks x 3 doses (THP). In arm B, patients will receive the same regimen as arm A with the addition of pembrolizumab 200mg IV every 3 weeks x 4 doses (THP-K). In arm C, patients will receive the same regimen as arm B, but without pertuzumab (TH-K). Definitive surgery will be 3-6 weeks after the last treatment dose. After surgery, patients in all arms willbe treated per the treating physician's discretion. After completion of post-operative chemotherapy, patients will receive radiotherapy per local clinical standard and those patients whose tumors are hormone-receptor positive will receive hormone therapy as per local standard-of-care. The purpose of this phase II study is to identify whether Arm B (THP-K) and/or Arm C (TH-K) demonstrate a clinically significant improvement in pCR rate when compared with Arm A (THP). The primary end point is pCR rate in the breast and axilla (ypT0/Tis ypN0). Secondary end points include pCR rate by ypT0ypN0 and ypT0/Tis, residual cancer burden index, event free survival, breast conserving surgery rate, safety and overall survival. Exploratory correlative studies will characterize the immunologic responses to the interventions and explore potential predictors of efficacy and toxicity.

Citation Format: McArthur HL, Leal JHS, DiLauro Abaya C, Basho R, Coleman H, Shiao S, Knott S, Tighiouart M, Dadmanesh F, Giuliano A, Verma S. Neoadjuvant Her2-targeted therapy +/- immunotherapy with pembrolizumab (neoHIP): An open label randomized phase II 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 OT3-04-02.

Abstract OT2-06-05: A randomized phase II study of peri-operative ipilimumab, nivolumab and cryoablation versus standard peri-operative care in women with residual triple negative early stage/resectable breast cancer after standard-of-care neoadjuvant chemotherapy

Background: Triple negative breast cancer (TNBC) is a biologically distinct subtype with high risk of early relapse, particularly for patients who do not achieve a pathological complete response (pCR) after neoadjuvant chemotherapy (NAC), with an event free survival of &lt; 60% at 3 years. Physical disruption of tumors with cryoablation (cryo) induces inflammation and releases antigens that can activate tumor-specific immune responses. In pre-clinical studies, the combination of cryo with checkpoint inhibition augmented tumor-specific immune responses and prevented cancer recurrence. In clinical studies, the combination of pre-operative ipilimumab (ipi)- +/- nivolumab (nivo)-mediated checkpoint blockade with cryo was safely administered in women with operable, early stage breast cancer and generated intra-tumoral and systemic immune responses (NCT01502592, NCT02833233). In this multi-center, randomized study, we evaluate the disease specific impact of peri-operative ipi, nivo and cryo versus standard care in women with residual TNBC after neoadjuvant taxane-based chemotherapy (NCT03546686).

Methods:Eligible pts are aged ≥18 years, with ER, PR and HER2 negative operable tumors ≥ 1.0 cm after neoadjuvant taxane-based chemotherapy. Approximately 160 patients will be randomized to one of two arms: standard-of-care breast surgery (control arm) or ipi/nivo/cryo followed by standard-of-care breast surgery (intervention arm). Subjects randomized to the intervention arm will undergo percutaneous, ultrasound- (or MRI-) guided cryoablation with concurrent research core biopsy 7-10 days prior to surgery, and will receive a pre-operative infusion with ipilimumab at the dose of 1mg/kg IV, and nivolumab 240mg flat dose IV (1 to 5 days prior to cryoablation). After surgery, patients will receive three additional doses of nivolumab 240mg flat dose IV Q2 weeks. Adjuvant capecitabine is recommended for all participants and will be administered per standard-of-care at the treating physician's discretion. Patients will be stratified by prior platinum administration, prior anthracycline administration, and clinical nodal status (positive versus negative) at enrollment. The primary endpoint is 3-year Event Free Survival (EFS). Secondary end points include Invasive Disease-Free Survival (IDFS), Distant Disease-Free Survival (DDFS), overall survival (OS) and safety. Exploratory correlative studies will be performed on tumor and serum to characterize the immunologic impact of the intervention and to explore predictors of efficacy and toxicity.

Citation Format: McArthur HL, Comen EA, Solomon S, Rodine M, DiLauro Abaya C, Leal JHS, Patil S, Norton L. A randomized phase II study of peri-operative ipilimumab, nivolumab and cryoablation versus standard peri-operative care in women with residual triple negative early stage/resectable breast cancer after standard-of-care neoadjuvant chemotherapy [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 OT2-06-05.

Abstract P2-09-07: Preoperative pembrolizumab (Pembro) with radiation therapy (RT) in patients with operable triple-negative breast cancer (TNBC)

Background: Radiation therapy (RT) induces immune-mediated cell death and could generate a rich supply of tumor antigens if administered in the pre-operative, curative-intent setting. The addition of PD-1 mediated checkpoint blockade to pre-operative RT could thus, generate robust anti-tumor immune responses, induce long-term tumor-specific memory, and ultimately, improve cure rates. This study aims to establish the safety of pre-operative pembrolizumab (pembro)-mediated immune modulation with a RT “boost” equivalent in patients with operable triple negative breast cancer (TNBC) for whom lumpectomy and adjuvant RT are planned (NCT03366844). Serial research biopsies permit interrogation of conventional biomarkers including tumor infiltrating lymphocytes (TILs) and novel immune correlates as potential predictors of response to pembro alone versus pembro with RT.

Methods: Ten women with operable, primary TNBC &gt;2cm for whom breast-conserving therapy is planned are being enrolled in this single-institution pilot study. Study treatment consists of 1 cycle of pre-operative pembro (200 mg IV) alone, followed 3 weeks later by a RT boost (24 Gy/3 fractions) to the primary breast tumor concurrently with pembro (+/- 5 days). Curative-intent, standard-of-care, neoadjuvant chemotherapy (NAC) or breast-conserving surgery is then undertaken within 8 weeks of study enrollment (i.e. within 5 weeks of pembro #2). Adjuvant RT is administered per standard-of-care after surgery, but without a boost dose. Research blood and fresh tumor biopsies are obtained at baseline and after cycles 1 and 2 of pembro. Co-primary endpoints are: 1) safety/tolerability, as defined by the number of patients who do not necessitate a delay in standard-of-care chemotherapy or surgery and 2) change in TIL score. Secondary endpoints include safety/toxicity up to 19 weeks after study enrollment, pCR rates and disease-free survival. Correlative analysis will include single-cell RNA sequencing of the tumor immune infiltrate and multispectral immunohistochemistry

Results: Seven patients enrolled between 12/19/17 and 7/1/18. As of 7/1/18, 5 patients have completed the experimental pembro/RT phase of the trial and are currently completing standard-of-care NAC; 1 patient is currently being treated in the experimental pembro/RT phase; and 1 patient with a cT2N0 tumor at baseline achieved a pathologic complete response (pCR, ypT0/Tis ypN0) after completing the experimental pembro/RT phase followed by anthracycline- and taxane-based NAC. No grade 3 or 4 toxicities have been observed during pembro/RT in the 6 patients completing the experimental phase to date. Three additional patients will be enrolled

Conclusions: This is the first trial of curative-intent, pre-operative checkpoint blockade with RT in breast cancer and the strategy appears to be well tolerated to date. At the time of presentation, safety, change in TIL score, and pCR rates for all patients completing the experimental and NAC phases of the study will be reported.

Citation Format: McArthur HL, Basho R, Shiao SL, Park D, Mita M, Chung A, Arnold B, Martin C, Dang C, Karlan S, Knott S, Giuliano A, Ho A. Preoperative pembrolizumab (Pembro) with radiation therapy (RT) in patients with operable 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 P2-09-07.

Abstract P2-09-03: Updated efficacy of first or second-line pembrolizumab (pembro) plus capecitabine (cape) in metastatic triple negative breast cancer (mTNBC) and correlations with baseline lymphocyte and naïve CD4+ T-cell count

Background: In mTNBC, anti-PD-1/L1 monotherapy is most effective when administered early in the course of disease, with recent trials demonstrating overall response rates (ORR) of 23-26% in the first-line setting and 5-6% in later lines. This may reflect iatrogenic lymphopenia from preceding cytotoxic chemotherapy. Furthermore, curative-intent chemotherapy is associated with prolonged suppression of naïve CD4+ cells, a T-cell subset that may play a critical role in the generation of de novo anti-tumor immune responses. We present the final clinical results of a pilot study evaluating the safety and efficacy of combining pembrolizumab plus standard-of-care capecitabine in the first/second-line mTNBC setting. We also explore potential associations between clinical benefit and lymphopenia, preceding chemotherapy, and absolute naïve CD4+ counts.

Methods: In a pilot study, we evaluated the tolerability and preliminary efficacy of concurrent pembro (200mg IV q21 day) plus investigator-selected 1st/2nd line paclitaxel (80mg/m2 IV weekly) or oral cape (2,000mg BID, weekly 1 on/1 off). The primary endpoint was tolerability, defined as the proportion of subjects receiving &gt;6 weeks concurrent therapy without dose discontinuation with toxicities reported per CTCAE v4.0. The secondary endpoint was 12-week objective response rate (ORR) by RECIST1.1. Exploratory endpoints included peripheral blood cell enumeration by real-time flow cytometry and routine clinical laboratory. Naïve CD4+ cells were defined as CD45+ CD3+ TCRab+ CD4+ CD45RA+ CCR7+. Here, we report the results of the pilot phase of the cape cohort (NCT02734290).

Results: Twelve of 14 subjects were treated in the first-line setting. All subjects (14/14, 100%) tolerated cape+pembro for &gt;6 weeks, with toxicities consistent with monotherapy cape experience (diarrhea: grade I-II 50%, grade III 7%; hand-foot: grade I-II 71%) that improved with dose-reduction as needed. At 12 weeks, the ORR was 6/14 (42.9%), and the clinical benefit rate (ORR + stable disease) was 8/14 (57.1%). Depressed absolute lymphocyte count at baseline (ALC&lt;1.0/uL: 33% CBR; ALC≥1.0/uL: 75% CBR) and recent exposure to cytotoxic chemotherapy (&lt;6 months: 33% CBR; &gt;6 months: 75% CBR) were associated with reduced clinical benefit. By flow cytometry, subjects experiencing clinical benefit had higher baseline absolute naïve CD4+ counts (average 283 cells/uL v. 93 cells/uL, p=.069).

Conclusions: This study met the primary endpoint of safety for cape plus pembro in mTNBC, with encouraging clinical activity. These data are supportive of further studies evaluating combination chemotherapy plus anti-PD-1/L1 mTNBC. We observed greater clinical benefit in subjects with non-suppressed ALC, less exposure to recent chemo, and higher baseline naïve CD4+ counts, suggesting that iatrogenic immunosuppression can impair response to immune checkpoint therapy in mTNBC. These findings should be confirmed in ongoing randomized trials of immune checkpoint +/- chemotherapy in mTNBC, and should be considered in the design of future clinical trials.

Citation Format: Page DB, Pucilowska J, Bennetts L, Kim I, Sanchez K, Martel M, Conlin A, Moxon N, Mellinger S, Acheson A, Kemmer K, Mitri Z, Vuky J, Ahn J, Abaya C, Manigault T, Basho R, Urba WJ, McArthur HL. Updated efficacy of first or second-line pembrolizumab (pembro) plus capecitabine (cape) in metastatic triple negative breast cancer (mTNBC) and correlations with baseline lymphocyte and naïve CD4+ T-cell count [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 P2-09-03.

Optimizing (neo)adjuvant treatment of HER2-positive breast cancer

The development of human epidermal growth factor 2 (HER2)-directed therapy has resulted in significant improvement in outcomes for patients with early-stage HER2-overexpressing (HER2+) breast cancer. In recent years, newer HER2-directed agents and novel treatment strategies have been developed with ongoing improvements in overall outcomes. However, with the addition of newer agents, there is an increasing need to risk stratify patients to maximize efficacy and minimize toxicity of treatment. De-escalation of therapy with the potential to shorten the duration of adjuvant therapy and minimize chemotherapy administration in patients with favorable disease can be considered. On the other hand, escalation of therapy with the addition of novel HER2-directed agents and extended duration of therapy in patients at high risk of relapse can help improve long-term cure rates. Herein, we discuss recent developments in neoadjuvant and adjuvant strategies for the treatment of potentially curable HER2+ breast cancer.

Immunotherapy in Breast Cancer: the New Frontier

PURPOSE OF REVIEW

This review summarizes current immunotherapies in breast cancer, with an emphasis on immune checkpoint inhibitors and vaccines.

RECENT FINDINGS

Combination immunotherapy with checkpoint inhibitors and cytotoxic therapies have shown promising results. Active clinical trials are ongoing in both early stage and metastatic settings for triple negative, HER2+, and hormone-positive breast cancer patients.

SUMMARY

Ongoing challenges remain in defining biomarkers that predict response to immunotherapy, determining the optimal combination immunotherapies, and enhancing the immunogenicity of breast cancer subtypes.

A single-arm, phase II study assessing the efficacy of pembrolizumab (pembro) plus radiotherapy (RT) in metastatic triple negative breast cancer (mTNBC)

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Background: Overall response rates of 13-19% have been reported with checkpoint inhibitor monotherapy in chemotherapy-resistant, PD-L1-positive mTNBC. RT is frequently used to enhance local control in mTNBC and has been reported to induce distant (abscopal) tumor responses when combined with immunotherapy. In this study, we evaluate the safety and efficacy of RT combined with a programmed cell death protein 1 (PD-1) inhibitor, pembro, in a single-arm, two-stage, phase II study in mTNBC. Methods: Eligible women had biopsy-proven mTNBC, ECOG performance status 0-2, and ≥2 measurable sites of metastatic disease with at least one site requiring RT. A total RT dose of 3000 cGy was delivered in 5 daily fractions. Pembro 200 mg was given intravenously within 3 days of first RT fraction, then every 3 weeks +/-3 days until disease progression. The primary endpoint was overall response rate at week 13 in the non-irradiated lesions by RECIST v1.1. Secondary endpoints included safety and overall survival. Tumor biopsies were obtained at baseline and at week 7. PD-L1 expression was not required for study entry. Results: Of the 17 women enrolled, the median age was 52 y (range 37-73y). and the median number of prior chemotherapies received for metastatic disease was 3 (range 0 to 8). Of the 8 women not evaluable at 13 weeks: 5 died secondary to disease-related complications (at weeks 2, 6, 7, 8, and 9) and 3 came off study due to disease progression prior to week 13. Of the 9 women evaluable at week 13, 3 (33%) had a partial response, 1 (11%) had stable disease and 5 (56%) had disease progression. The 3 partial responses represented 60%, 54%, and 34% decreases in tumor burden by RECIST v1.1 and were durable for 31, 21, and ongoing at 22 weeks, respectively. The stable disease response was durable for 22 weeks. Common toxicities were mild and included fatigue, myalgia and nausea. Conclusions: The combination of pembro and RT is well-tolerated. This is a poor prognosis population with 5/17 (29%) of patients dying within 12 weeks of study entry. However, durable responses were observed outside of the RT field in 3/9 (33%) patients who were unselected for PD-L1 expression and evaluable at 13 weeks. Clinical trial information: NCT02730130.

Characteristics and Prognostic Factors for Patients With HER2-overexpressing Breast Cancer and Brain Metastases in the Era of HER2-targeted Therapy: An Argument for Earlier Detection

BACKGROUND

Although brain metastases (BM) are associated with poor prognosis, patients with human epidermal growth factor receptor 2 (HER2) overexpressing (HER2⁺) breast cancer (BC) with BM who are treated with anti-HER2 therapy have a relatively longer survival after BM diagnosis compared with other subtypes and HER2⁺ patients previously untreated with anti-HER2 therapy. It is unclear if previously reported prognostic factors are applicable to patients with HER2⁺ BC in the era of HER2-targeted therapy.

PATIENTS AND METHODS

We evaluated 100 consecutive patients with HER2⁺ BC with BM who underwent radiation therapy as primary BM treatment from January 2001 to December 2011 at Memorial Sloan Kettering Cancer Center by retrospective review. Patient characteristics at the time of BM diagnosis and their associations with time from BM to death were evaluated by Kaplan-Meier curves, log-rank tests, and Cox proportional hazard models.

RESULTS

Significantly better survival from BM was noted for patients with higher performance status, fewer BM lesions, continued use of HER2-targeted therapy after BM diagnosis, and better controlled extracranial metastatic disease. Absence of neurologic symptoms at BM diagnosis was significantly associated with fewer lesions, decreased use of whole brain radiotherapy, and longer survival in univariate and multivariate analysis (multivariate hazard ratio, 3.69; 95% confidence interval, 1.69-8.07).

CONCLUSION

Our finding supports the continued use of HER2-targeted therapy after BM diagnosis. In addition, future research on the clinical impact of detecting asymptomatic BM in patients with HER2⁺ BC, in terms of improving prognosis, quality of life, and avoidance of whole brain radiotherapy, is warranted.

Monosomy 17 in potentially curable HER2-amplified breast cancer: prognostic and predictive impact

PURPOSE

HER2 copy number by fluorescence in situ hybridization (FISH) is typically reported relative to the centromere enumeration probe 17 (CEP17). HER2/CEP17 ratio could be impacted by alterations in the number of chromosome 17 copies. Monosomy of chromosome 17 (m17) is found in ~ 1900 cases of early-stage HER2-positive breast cancer annually in the United States; however, the efficacy of HER2-directed trastuzumab therapy in these patients is not well characterized. Here, we retrospectively identified HER2-amplified, stage I-III breast cancers with m17 and characterized the impact of trastuzumab treatment.

METHODS

From January 1, 2000 to June 1, 2011, we identified 99 women with HER2-amplified m17 breast cancers, as defined by a CEP17 signal of < 1.5 per nucleus and a HER2/CEP17 ratio of ≥ 2.0.

RESULTS

Most HER2-amplified m17 patients were treated with trastuzumab plus chemotherapy (51%, n = 50), whereas 31% (n = 31) received chemotherapy alone and 18% (n = 18) received no chemotherapy. The 4-year overall survival (OS) was superior with trastuzumab compared to chemotherapy alone or no chemotherapy (100 vs. 93 vs. 81%, respectively; p = 0.005). OS was not influenced by estrogen/progesterone-receptor (ER/PR) status, tumor stage, or degree of FISH positivity. A proportion of patients who would be considered HER2-negative by standard immunohistochemistry staging criteria (0-1+) were HER2 amplified by FISH.

CONCLUSIONS

In the largest series reported to date, patients with HER2-amplified m17 cancers treated with trastuzumab have outcomes comparable to patients from the large phase III adjuvant trastuzumab trials who were HER2-positive, supporting the critical role of HER2-directed therapy in this patient population.

Combined Radiation Therapy and Immune Checkpoint Blockade Therapy for Breast Cancer

PURPOSE

Treatment with checkpoint inhibitors has shown durable responses in a number of solid tumors, including melanoma, lung, and renal cell carcinoma. However, most breast cancers are resistant to monotherapy with checkpoint inhibitors. Radiation therapy (RT) has been shown to have a number of immunostimulatory effects, including priming the immune system, recruiting immune cells to the tumor environment, and altering the immunosuppressive effects of the tumor microenvironment. RT therefore represents a promising adjuvant therapy to checkpoint blockade in breast cancer.

METHODS AND MATERIALS

We review the data from the checkpoint blockade studies on breast cancer reported to date, the mechanisms by which RT potentiates immune responses, the preclinical and clinical data of checkpoint blockade and RT combinations, and the landscape of current clinical trials of RT and immune checkpoint inhibitor combinations in breast cancer.

RESULTS

Clinical trials with checkpoint blockade therapy have demonstrated response rates of up to 19% in breast cancer, and many of the responses are durable. Preclinical data indicate that RT combined with checkpoint inhibition synergizes not only to enhance antitumor efficacy but also to induce responses outside of the radiation field. Thus multiple clinical trials are currently investigating the combination of checkpoint inhibition with RT.

CONCLUSIONS

The use of combination strategies that incorporate chemotherapy and/or local strategies such as RT may be needed to augment responses to immune therapy in breast cancer. Preclinical and clinical results show that RT in combination with checkpoint blockade may be a promising therapeutic option in breast cancer.

Impact of neoadjuvant HER2-directed therapy on HER2 status in breast cancer

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Background: Neoadjuvant chemotherapy (NAC) with HER2-directed therapy has become standard-of-care for most women with potentially curable HER2-positive (HER2+) breast cancer and is associated with a high pathologic complete response (pCR) rate. The HER2 status of residual disease after NAC is not well characterized and could potentially inform clinical decisions about additional systemic therapy. We describe tumoral HER2 status before and after NAC with HER2-directed therapy. Methods: An institutional database was screened to identify patients with stage 1-3 HER2+ breast cancer by fluorescence in situ hybridization (FISH) and/or immunohistochemistry (IHC) who received NAC with HER2-directed therapy followed by resection between 2011 and 2015. Clinicopathologic data was collected. Change in HER2 status by FISH and IHC following treatment was described. Results: 99 patients were identified. Median age was 49 years (range 26-85). Pre-treatment median HER2/CEP17 copy number ratio (CNR) for all tumors was 6.3 (range 1.9-20.7) by FISH and 84 (84.8%) tumors were IHC 3+. 44 (44.4%) patients achieved a pCR. Of the 55 patients with residual disease, 35 had sufficient residual tumor to evaluate HER2 status and 14/35 (40%) were HER2- by FISH and IHC (table). Tumors converting from HER2+ to HER2- had lower pre-treatment median HER2 copy numbers (11.9, range 4.6-22) compared to tumors that remained HER2+ (18.3, range 5.1-48.6; p=0.04) after neoadjuvant therapy. Additionally, pre-treatment median HER2/CEP17 CNR was lower among tumors that converted from HER2+ to HER2- (3.0, range 2.2-8.2) compared to those remaining HER2+ (6.8, range 2-15.7; p=0.02). Conclusions: While pCR rates are high with NAC and HER2-directed therapy, many patients still have residual tumor. In this cohort, 40% of patients with evaluable residual disease after NAC had HER2+ tumors that became HER2-. HER2 conversion was associated with lower pre-treatment HER2 copy numbers and HER2/CEP17 CNR. Conversion from HER2+ to HER2- in patients undergoing neoadjuvant therapy may have clinical significance and biological implications. [Table: see text]