Long term disease-free survival and T cell and antibody responses in women with high-risk Her2+ breast cancer following vaccination against Her2

<p>Abstract</p> <p>Background</p> <p>The HER2-inhibiting antibody trastuzumab, in combination with chemotherapy, significantly improves survival of women with resected, HER2-overexpressing breast cancers, but is associated with toxicities including a risk of cardiomyopathy. Additionally, the beneficial effect of trastuzumab is expected to decrease once the drug is discontinued. We proposed to address these concerns by using cancer vaccines to stimulate HER2 intracellular domain (ICD)-specific T cell and antibody responses.</p> <p>Methods</p> <p>Subjects with stage II (≥ 6 +LN), III, or stage IV breast cancerwith > 50% HER2 overexpressing tumor cells who were disease-free after surgery and adjuvant therapy were eligible. Vaccines consisted of immature, cultured DC (n = 3), mature cultured DC (n = 3), or mature Flt3-ligand mobilized peripheral blood DC (n = 1) loaded with ICD, or tetanus toxoid, keyhole limpet hemocyanin or CMV peptide as controls, and were administered intradermally/subcutaneously four times at 3 week intervals. ICD-specific T cell and antibody responses were measured. Cardiac function was determined by MUGA or ECHO; long term disease status was obtained from patient contact.</p> <p>Results</p> <p>All seven patients successfully underwent DC generation and five received all 4 immunizations. There were no toxicities greater than grade 1 or ejection fraction decrements below normal. Delayed-type hypersensitivity (DTH) reactions at the injection site occurred in 6/7 patients and HER2 specificity was detected by cytokine flow cytometry or ELISPOT in 5 patients. At more than 5 years of follow-up, 6/7 had detectable anti-ICD antibodies. One patient experienced a pulmonary recurrence at 4 years from their study immunizations. This recurrence was resected and they are without evidence of disease. All patients are alive and disease-free at 4.6–6.7 years of follow-up.</p> <p>Conclusion</p> <p>Although this was a small pilot study, the well-tolerated nature of the vaccines, the lack of cardiac toxicity, significant immunogenicity, and a 100% 4.5-year survival rate suggest that vaccination with HER2 ICD protein-containing DC is appropriate for further study in this population.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov NCT00005956</p

Cancer Yield of Mammography, MR, and US in High-Risk Women: Prospective Multi-Institution Breast Cancer Screening Study

PURPOSE: To prospectively determine cancer yield, callback and biopsy rates, and positive predictive value (PPV) of mammography, magnetic resonance (MR) imaging, and ultrasonography (US) in women at high risk for breast cancer. MATERIALS AND METHODS: The study was approved by the institutional review board and was HIPAA compliant, and informed consent was obtained. We conducted a prospective pilot study of screening mammography, MR, and US in asymptomatic women 25 years of age or older who were genetically at high risk, defined as BRCA1/BRCA2 carriers or with at least a 20% probability of carrying a BRCA1/BRCA2 mutation. All imaging modalities were performed within 90 days of each other. Data were analyzed by using exact confidence intervals (CIs) and the McNemar test. RESULTS: A total of 195 women were enrolled in this study over a 6-month period, and 171 completed all study examinations (mammography, US, and MR). Average age of the 171 participants was 46 years +/- 10.2 (standard deviation). Sixteen biopsies were performed and six cancers were detected, for an overall 3.5% cancer yield. MR enabled detection of all six cancers; mammography, two; and US, one. The diagnostic yields for each test were 3.5% for MR, 0.6% for US, and 1.2% for mammography. MR, US, and mammography findings prompted biopsy in 8.2%, 2.3%, and 2.3% of patients, respectively. None of the pairwise comparisons were statistically significant. The PPV of biopsies performed as a result of MR was 43%. CONCLUSION: Screening MR imaging had a higher biopsy rate but helped detect more cancers than either mammography or US. US had the highest false-negative rate compared with mammography and MR, enabling detection of only one in six cancers in high-risk women

Real-word incidence and management of durable complete response in de novo metastatic HER2-positive breast cancer.

e13017 Background: HER2-directed therapies enable a small number of patients with de novo HER2+ metastatic breast cancer (MBC) to achieve long term durable responses (DR). However, clinic-pathologic factors that correlate with DRs in de novo HER2+ MBC are unknown. Expert opinion dictates indefinite HER2-directed therapies for patients who achieve DRs, but real-world examples of this practice, especially the effect on cardiotoxicity, are lacking in the literature. Methods: This is a retrospective case control study of patients with de novo HER2+ MBC who received treatment with trastuzumab at two NCI designated cancer centers between the years 2012-2017. Patients were included if ≥2 years of follow up data were available or if patients were deceased. DRs are defined as radiographic complete or partial response without progression or death at any point after diagnosis. Controls are patients with evidence of radiographic progression or death any point after diagnosis. Age at diagnosis, ER/PR status, site of metastasis, and initial treatment were analyzed. An un-paired T test for age and fisher exact test for categorical variables were used. Results: A total of 96 patients with de novo HER2+ MBC, 28 with DRs and 68 with progression, were identified. Average follow up length for patients with DR was 90 months (range 27-224 months). Patients who progressed had a mPFS of 17.5 months and a mOS of 60 months. Results are shown in Table. Additionally, six patients (6.3%) developed reduced ejection fraction, one with DR, five with progression. Nine patients have been receiving trastuzumab for over ten years with no evidence of disease. Only one patient opted to discontinue this therapy a year after complete response and is disease free five years from diagnosis. Conclusions: Nearly a third of patients with de novo metastatic HER2+ MBC in our dataset achieved DR. Factors that predict DRs include single organ involved by metastatic disease and more intensive upfront chemotherapy including trastuzumab and pertuzumab. The majority of patients with DR continued HER2 directed therapy indefinitely with minimal cardiotoxicity. In the absence of predictive biomarkers of DRs, indefinite trastuzumab administration is common practice for these patients. [Table: see text] </jats:p

Combination mTORC1/2 and BCL- X_L inhibition in endocrine and CDK4/6-resistant estrogen receptor-positive breast cancer.

e14653 Background: Endocrine therapy plus CDK 4/6 inhibition has led to impressive improvements in progression-free survival in patients with advanced, estrogen receptor positive (ER+)/HER2-negative (HER2-) breast cancer. Resistance inevitably emerges, leaving patients with few proven therapeutic options. Our group has recently found that treatment of PIK3CA mutant ER+/HER2- breast cancer with inhibitors of mTORC1/2 and BCL-XL causes impressive synergistic growth suppression and apoptosis induction compared to either agent alone in vitro and in vivo. We sought to assess activity in clinically relevant models of PIK3CA mutant ER+ breast cancer with acquired resistance to endocrine therapy and CDK4/6 inhibition. Methods: Using orthotopic MCF-7 xenograft tumors (ER+/ PIK3CA mutant) that were evolved through serial passaging in vivo to develop tamoxifen resistance (TamR), we developed models of resistant disease. TamR xenograft- bearing mice were then treated for 4-6 weeks with palbociclib (50 mg/kg qd), fulvestrant (100mg/kg qw), or the combination. Mice in each treatment group were divided into two groups following the initial development of resistance, defined by steady growth for 1-2 weeks: one receiving vehicle and the other receiving low dose MLN0128 0.3 mg/kg qd (mTORC1/2 inhibitor) + ABT-737 25 mg/kg qd (BCL-XL /BCL-2 inhibitor). Results: Combination BCL-XL (ABT-737) + mTORC1/2 (MLN0128) inhibition significantly inhibited growth in tamoxifen (p = 0.0045), fulvestrant/tamoxifen (p = 0.0035), palbociclib/tamoxifen (p = 0.0155), and palbociclib/tamoxifen/fulvestrant (0.005) resistant tumors compared to controls. These results were observed without significant animal toxicity, dose-limiting thrombocytopenia secondary to BCL-XL inhibition, or toxicity to normal breast epithelial cells. We have observed tumor regressions in multiple models using doses five- to 12-fold lower than the equivalent doses required to cause clinically meaningful thrombocytopenia in humans and large animal models. Conclusions: Our data establish the rationale for investigating the combination of BCL-XL and mTORC1/2 inhibition in a clinical trial of advanced PIK3CA mutant, ER+/HER2- breast cancer after progression on CDK 4/6 and endocrine therapy. Preclinical work is ongoing with novel inhibitors of BCL-XL. </jats:p

Identification of pathogenic <i>ROS1</i> alterations in cell-free DNA (cfDNA) from patients with breast cancer.

1031 Background: ROS1 is an important proto-oncogene involved in the development of various cancers for which we have FDA approved therapies. While activation of the ROS1 tyrosine kinase receptor has been reported in 1-2% of lung cancers, the frequency and type of ROS1 alterations in breast cancer have not been fully explored. We previously described the incidence of ROS1 alterations from breast cancer tissue. The purpose of this study was to identify the incidence of ROS1 genomic alterations occurring in cfDNA from patients with breast cancer. Methods: We queried 16,053 breast cancer samples from the Guardant Health breast cancer database between June 2015 - October 2019 to identify the incidence of ROS1 alterations detected in cfDNA in breast cancer. We identified fusion partner genes and classified each alteration type into the following categories: fusion, single nucleotide variants (SNVs), and indels. Radical amino acid changes occurring at conserved regions across the ROS1 gene were identified. In vitro analyses were used to investigate the effect of ROS1 nonsynonymous mutations on the ROS1 protein. We made associations with ROS1 alterations and co-occurring mutated genes. Results: Nonsynonymous ROS1 alterations from the Guardant Health breast cancer database were found in 162 samples from 142 patients in the 16,053-patient cohort (1%). Alterations found included: 1 (0.6%) ROS1-SLC35F1 fusion, 155 (95.7%) SNVs, and 6 (3.7%) indels. Of the 155 SNVs, we identified 23 (14.8%) mutations occurring in the ROS1 kinase, of which, 20 (12.9%) occurred at highly conserved regions and 15 (9.6%) harbored radical amino acid changes. The top 5 co-occurring mutations in samples with ROS1 alterations were TP53 (50%), PIK3CA (44%), ESR1 (27%), EGFR (21%), and FGFR1 (18%). Conclusions: A modest incidence of ROS1 genomic alterations occurs in cfDNA from patients with breast cancer. New somatic alterations in the ROS1 gene were identified from Guardant Health that were not detected in publicly available databases. A portion of mutations occurred at highly conserved regions across the ROS1 gene suggesting these may be more actionable than currently recognized. In vitro analyses of ROS1 gene activation from these newly discovered somatic alterations are being investigated with results to be reported. Co-occurring mutations reveal a unique genotype associated with ROS1 alterations that may play a biologic role in ROS1-mediated pathogenesis. </jats:p

Identification of pathogenic <i>CDK12</i> alterations in cell-free DNA (cfDNA) from patients with breast cancer.

1028 Background: Cyclin dependent kinase 12 ( CDK12) has both tumor suppressive and proto-oncogenic potential in metastatic breast cancers (MBC). CDK12 may be an important biomarker and target in MBC. However, a comprehensive genomic analysis of CDK12 alterations from cfDNA in MBC has not been investigated and the genomic impact of CDK12 alterations across the MBC spectrum is unknown. The purpose of this study was to identify the incidence of CDK12 genomic alterations occurring in cfDNA from patients with MBC and elucidate which CDK12 alterations may impact CDK12 kinase activity. Methods: We queried 13,070 MBC samples from the Guardant Health database between April 2019 – November 2020 to identify the incidence of CDK12 alterations detected in cfDNA. We classified each alteration type as: missense mutations, indels, or truncations. Amino acid changes occurring at conserved regions across multiple species were identified. Three-dimensional biochemical in silico analyses with ChimeraX were used to determine which CDK12 alterations may impact CDK12 kinase activity. To gain further biologic insights into CDK12 altered MBC we made associations with CDK12 alterations and co-occurring mutated genes. Results: Nonsynonymous CDK12 alterations from the Guardant Health database were found in 317 samples from a cohort of 13,070 patients indicating an overall incidence of 2.43%. Alterations included: 239 (75.4%) missense mutations; 26 (8.2%) indels; and 52 (16.4%) truncations. We identified 62 alterations within the kinase domain with all occurring at highly conserved regions across species. The most frequent hotspot mutation identified was I76M/T, occurring in 11 unique breast cancers. Three-dimensional analyses indicate that CDK12 alterations within the hinge, HRD, DFG, catalytic spine, and regulatory spine may impact CDK12 kinase activity. The significantly co-occurring mutations from the Guardant Health breast cancer database in samples with CDK12 alterations were ARID1A, APC, RB1, and PTEN. Conclusions: A modest incidence of CDK12 genomic alterations occur in cfDNA from patients with breast cancer. Novel somatic alterations in CDK12 were identified from Guardant Health that were not detected in the public domain. A portion of these occurred at highly conserved regions across species suggesting these specific CDK12 mutations may impact CDK12 kinase expression and be actionable therapeutic targets in breast cancers. Three dimensional analyses of the CDK12 gene further illustrate which specific alterations may induce CDK12 kinase expression or lead to inactivation. Co-occurring mutations reveal a unique genotype associated with CDK12 alterations that may play a biologic role in CDK12-mediated breast cancer pathogenesis. Preclinical studies to determine the prognostic and therapeutic implication of CDK12 alterations in MBC are warranted. </jats:p

Dora: A randomized phase II multicenter maintenance study of olaparib alone or olaparib in combination with durvalumab in platinum responsive advanced triple-negative breast cancer (aTNBC).

TPS1113 Background: PARP inhibition (PARPi) with olaparib is approved in HER2-negative germline BRCA mutant (g BRCAm) metastatic breast cancer. Maintenance PARPi in relapsed platinum-sensitive ovarian cancer improves median PFS regardless of gBRCA mutation status. Preclinical work has shown that platinum response strongly correlates with olaparib response in breast cancer models; hence, maintenance therapy trials are underway in aTNBC. PARPi modulates immune responses and enhances immunogenicity in many preclinical models. We hypothesize that olaparib either alone or in combination with the PD-L1 inhibitor durvalumab will have clinical efficacy as maintenance therapy in aTNBC subjects who have responded to platinum-based chemotherapy. Methods: DORA is a randomized, international, multicenter, phase II study designed to explore the efficacy of olaparib or olaparib in combination with durvalumab as maintenance therapy in platinum-sensitive aTNBC. 60 subjects will be enrolled following a minimum of 3 cycles of treatment with platinum-based (cisplatin or carboplatin) chemotherapy as a single agent or combination therapy in the first or second-line setting. Subjects deriving clinical benefit (CR / PR / SD) from platinum-based therapy will be eligible and randomized in a 1:1 ratio. Patients in arm 1 will receive olaparib orally 300mg BID continuously and in arm 2 will receive olaparib orally 300mg BID continuously in combination with durvalumab 1500mg IV every 4 weeks. Assessment of tumor response will be done every 8 weeks. Primary endpoint: progression-free survival. Secondary endpoints: overall survival, clinical benefit rate, safety. Correlative analyses: pre-treatment archival/fresh biopsy samples are mandated. Post-treatment tissue biopsy is requested. Serial ctDNA will be collected at baseline, staging, and progression to correlate with response and track emerging genomic alterations in a platinum sensitive cohort under the pressure of PARP inhibition. Whole exome DNA sequencing, IHC for PDL-1 and TILs will be performed on tissue samples. ClincalTrials.gov Identifier: NCT03167619. (Moore K, et al "SOLO-1: Phase III trial of maintenance olaparib following platinum-based chemotherapy in newly diagnosed patients with advanced ovarian cancer and a BRCA1/2 mutation" ESMO 2018; Abstract LBA7-PR). Clinical trial information: NCT03167619. </jats:p

Nuclear basic fibroblast growth factor regulates triple-negative breast cancer chemo-resistance

INTRODUCTION: Chemotherapy remains the only available treatment for triple-negative (TN) breast cancer, and most patients exhibit an incomplete pathologic response. Half of patients exhibiting an incomplete pathologic response die within five years of treatment due to chemo-resistant, recurrent tumor growth. Defining molecules responsible for TN breast cancer chemo-resistance is crucial for developing effective combination therapies blocking tumor recurrence. Historically, chemo-resistance studies have relied on long-term chemotherapy selection models that drive genetic mutations conferring cell survival. Other models suggest that tumors are heterogeneous, being composed of both chemo-sensitive and chemo-resistant tumor cell populations. We previously described a short-term chemotherapy treatment model that enriches for chemo-residual TN tumor cells. In the current work, we use this enrichment strategy to identify a novel determinant of TN breast cancer chemotherapy resistance [a nuclear isoform of basic fibroblast growth factor (bFGF)]. METHODS: Studies are conducted using our in vitro model of chemotherapy resistance. Short-term chemotherapy treatment enriches for a chemo-residual TN subpopulation that over time resumes proliferation. By western blotting and real-time polymerase chain reaction, we show that this chemotherapy-enriched tumor cell subpopulation expresses nuclear bFGF. The importance of bFGF for survival of these chemo-residual cells is interrogated using short hairpin knockdown strategies. DNA repair capability is assessed by comet assay. Immunohistochemistry (IHC) is used to determine nuclear bFGF expression in TN breast cancer cases pre- and post- neoadjuvant chemotherapy. RESULTS: TN tumor cells surviving short-term chemotherapy treatment express increased nuclear bFGF. bFGF knockdown reduces the number of chemo-residual TN tumor cells. Adding back a nuclear bFGF construct to bFGF knockdown cells restores their chemo-resistance. Nuclear bFGF-mediated chemo-resistance is associated with increased DNA-dependent protein kinase (DNA-PK) expression and accelerated DNA repair. In fifty-six percent of matched TN breast cancer cases, percent nuclear bFGF-positive tumor cells either increases or remains the same post- neoadjuvant chemotherapy treatment (compared to pre-treatment). These data indicate that in a subset of TN breast cancers, chemotherapy enriches for nuclear bFGF-expressing tumor cells. CONCLUSION: These studies identify nuclear bFGF as a protein in a subset of TN breast cancers that likely contributes to drug resistance following standard chemotherapy treatment

The prevalence of germline mutations among patients with solid tumors with genomic alterations identified on tumor testing: Results from a tertiary care academic center molecular tumor board.

1516 Background: The proportion of germline versus somatic mutations identified on genomic tumor testing of solid malignancies is not well characterized. We compared somatic and germline testing results in patients with breast, ovarian, pancreatic or prostate cancer with a genomic alteration identified on tumor testing. Methods: Retrospective chart review was performed using a tertiary care academic center’s database of somatic tumor testing results obtained via FoundationOne and Guardant testing. Patients with breast, ovarian, pancreatic or prostate cancer who had a genomic alteration identified on tumor testing, including pathogenic and VUS variants, in BRCA1or BRCA2, CHEK2, ATM, BRIP1, RAD51C, RAD51D, PALB2and CDH1and who had also received germline testing were identified. Analysis was performed to assess prevalence of germline results. The association between mutant allele fraction (MAF) and germline mutation status was also assessed. Results: Results: 124 patients with breast, ovarian, pancreatic or prostate cancer were identified who had a genomic alteration of interest also tested for via germline testing. 54 (32.5%) of tumor mutations were also identified on germline testing. Proportion of genomic results that were germline was wide, ranging from 0-85.7% depending on the gene and variant classification (Table). Germline mutations were present in 36.4% of breast, 25% of ovarian, 53.3% of pancreatic, and 20.9% of prostate cancer patients who had a tumor alteration present. Alterations that were found to be concordant in both somatic and germline testing had an average MAF of 0.54, and alterations identified on somatic testing only had an average MAF of 0.30. Conclusions: Our findings suggest that approximately one-third of genomic alterations on tumor testing will be of germline origin. However, concordance rates may be gene and variant dependent. Higher MAF may be associated with germline alteration status, but further evaluation is needed. Thus, while information provided by genomic tumor testing may be suggestive of a correlating germline mutation, no single alteration type or MAF value is reliably predictive. [Table: see text] </jats:p