Using parametric model order reduction for inverse analysis of large nonlinear cardiac simulations

Predictive high-fidelity finite element simulations of human cardiac mechanics commonly require a large number of structural degrees of freedom. Additionally, these models are often coupled with lumped-parameter models of hemodynamics. High computational demands, however, slow down model calibration and therefore limit the use of cardiac simulations in clinical practice. As cardiac models rely on several patient-specific parameters, just one solution corresponding to one specific parameter set does not at all meet clinical demands. Moreover, while solving the nonlinear problem, 90% of the computation time is spent solving linear systems of equations. We propose to reduce the structural dimension of a monolithically coupled structure-Windkessel system by projection onto a lower-dimensional subspace. We obtain a good approximation of the displacement field as well as of key scalar cardiac outputs even with very few reduced degrees of freedom, while achieving considerable speedups. For subspace generation, we use proper orthogonal decomposition of displacement snapshots. Following a brief comparison of subspace interpolation methods, we demonstrate how projection-based model order reduction can be easily integrated into a gradient-based optimization. We demonstrate the performance of our method in a real-world multivariate inverse analysis scenario. Using the presented projection-based model order reduction approach can significantly speed up model personalization and could be used for many-query tasks in a clinical setting.

Greatly enhanced performance of AlGaN-based deep ultraviolet light emitting diodes by introducing a polarization modulated electron blocking layer

Carrier transport in AlGaN-based deep ultraviolet (DUV) light emitting diodes (LEDs) with the wavelength of 273 nm has been investigated by introducing polarization modulated electron blocking layer (EBL) that adopts an Al composition and thickness graded multiple quantum barriers (MQB) structure. The experimental result shows that the maximum light output power and external quantum efficiency for the proposed structure at the current of 250 mA are 9.6 mW and 1.03% respectively, severally increasing by 405% and 249% compared to traditional one, meanwhile, the efficiency droop at 250 mA is also dramatically reduced from 42.2% to 16.6%. Further simulation analysis indicates that this graded MQB-EBL enhances the potential barrier height for electrons and meanwhile reduces that for holes, hence effectively suppresses the electron leakage, and at the same time significantly improves the hole injection efficiency. As a result, the whole performance of the LED with the proposed MQB-EBL is dramatically improved.

P104 One year failure rates for de novo ventriculo-peritonealshunts in under 3- month-old children

Objectives

Historically VPS failure and infection rates are higher for neonates than for older children. We compared our one year VPS failure and infection rates in under 3-month-olds with those of older children.

Design

A retrospective, single centre study comparing 1 year survival and infection rates of VPS in under 3-month-olds verses older children.

Subjects

58 children under 3 months of age underwent VPS insertion between January 2007 and December 2016.

Methods

Data was collected by three independent reviewers from electronic files and case notes. Data was analysed using descriptive statistics and one year shunt survival curves were produced.

Results

For children under 3 months there was a 29.3% one-year shunt failure rate, of which 2 were shunt infections (3.4%). In patients greater than 3 months, the shunt malfunction rate was 23.4% and the infection rate was 4.3%. There were no shunt-related mortalities in either group.

Conclusions

Children under 3-months-old undergoing VPS insertion should not automatically expect an increased 1 year failure or infection rate compared with older children. Reasons for this may be increased sub-specialisation, improved neonatal care and use of antibiotic impregnated catheters.

Cumulative cortisol exposure in the third trimester correlates with postpartum mothers' neural response to emotional interference

Prolonged stress affects the central nervous system, rendering individuals vulnerable to a wide range of mental health disorders. 76 healthy postpartum mothers were studied by means of functional magnetic resonance imaging within 6 days of childbirth. The subjects were required to perform the emotional Stroop task involving happy and anxious word-face combinations. Hair samples were collected to determine cumulative hair cortisol concentration (HCC) in the third trimester. HCC was found to be negatively correlated with the recruitment of the dorsal anterior cingulate cortex (ACC) and the midcingulate cortex (MCC). In response to the emotional interference of only anxious target faces, a negative correlation was seen between HCC and the bilateral orbitofrontal cortex, extending to the rostral ACC and the MCC. Women with lower HCC recruited brain areas relevant to emotional cognitive control, indicating that lower HCC helps preserve conflict monitoring and resolution capacities and thus benefits mental health in pregnancy.

Abstract P3-06-01: Clonal evolution and heterogeneity in breast tumors treated with neoadjuvant HER2-targeted therapy

Background: Understanding to what extent a breast tumor's genetic composition may change over the course of a few months of neoadjuvant therapy has implications for optimal therapeutic approach. However, genomic changes observed across treatment may result from either treatment-induced clonal evolution or geographically disparate sampling of a heterogeneous tumor. We sought to characterize the geographic heterogeneity in primary breast tumors, and to incorporate this information into analysis of clonal evolution with neoadjuvant therapy.

Methods: We assembled the largest cohort to date of multi-region (n=2-3) whole-exome sequenced (WES) or whole-genome sequenced untreated primary breast tumors with matched normal and adequate tumor purity for analysis: four tumors with data generated for this study and five tumors compiled from three previous studies. We also generated the first cohort of multi-region (n=2-6) WES breast tumors post-neoadjuvant HER2-targeted therapy and chemotherapy, sequencing one region from a pre-treatment diagnostic specimen, multiple regions from the post-treatment surgical specimen, and matched normal for five HER2+ breast tumors that did not achieve a pathologic complete response. We used an agent-based model of spatial tumor growth to investigate whether the mutational patterns we observed with treatment were consistent with pre-existing heterogeneity or treatment-induced selection.

Results: In untreated primary breast tumors, on average 30% (range 1-70%) of apparently clonal mutations from a single region were absent or rare in a second, spatially disparate region (high-frequency regional, or HFR). Intra-tumor heterogeneity was similar post-treatment (HFR 28%, range 10-54%), and was higher in breast tumors than in previously analyzed colon, brain, lung, and esophageal tumors. Simulation studies confirmed that with high heterogeneity as observed in breast tumors, analysis of one pre-treatment and one post-treatment region could not distinguish treatment-induced clonal evolution from pre-existing heterogeneity; however, obtaining at least two post-treatment regions allowed for detection of clonal shifts with treatment. Analysis of multi-region data revealed that clonal replacement occurred with neoadjuvant therapy in two of the five tumors. Candidate causes of therapeutic resistance included amplifications in CCND1, ERBB4, and MYC in one subclone, and functional protein-altering mutations in ERCC2, SMO, and WT1 in another. Mathematical modeling suggested that these putative resistant subclones comprised 0.02-12.5% of the overall pre-treatment cell population, substantially larger than previous estimates of resistant tumor clone size.

Conclusions: WES data from multiple regions of untreated and treated primary breast tumors revealed considerable heterogeneity that remained present throughout treatment with chemotherapy and HER2-targeted therapy, even while major clonal sweeps took place in a minority of tumors. Obtaining at least two samples for analysis from breast tumors post-neoadjuvant therapy may reveal the tumor's evolutionary path and, especially as increasing numbers of molecular and immune therapeutic targets are identified, inform new clinical strategies.

Citation Format: Caswell-Jin JL, McNamara K, Reiter JG, Sun R, Hu Z, Ma Z, Suarez CJ, Tilk S, Raghavendra A, Forte V, Chin S-F, Bardwell H, Provenzano E, Caldas C, Lang J, West R, Tripathy D, Press MF, Curtis C. Clonal evolution and heterogeneity in breast tumors treated with neoadjuvant HER2-targeted therapy [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 P3-06-01.

Abstract P1-15-02: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Schwab R, Clark A, Yau C, Wolf D, Chien AJ, Majure M, Ewing C, Wallace A, Roesch E, Helsten T, Forero A, Stringer-Reasor E, Vaklavas C, Nanda R, Jaskowiak N, Boughey J, Haddad T, Han H, Lee C, Albain K, Isaacs C, Elias A, Ellis E, Shah P, Lang J, Lu J, Tripathy D, Kemmer K, Yee D, Haley B, Korde L, Edmiston K, Northfelt D, Viscusi R, Khan Q, I-SPY 2 Consortium, Symmans WF, Perlmutter J, Hylton N, Rugo H, Melisko M, Wilson A, Singhrao R, Asare S, van't Veer L, DeMichele A, Berry D, Esserman L. Withdrawn [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 P1-15-02.

One year failure rates for de-novo ventriculo-peritoneal shunts in under 3-month-old children

Introduction: Ventriculo-peritoneal shunts (VPS) are still the mainstay treatment for hydrocephalus in children. It is generally accepted that VPS failure and infection rates are higher for neonates than for older children. We compared our 1-year failure and infection rates in under 3-month-old children compared with older children in our department. Results: We identified 58 children under 3 months of age who underwent VPS insertion between January 2007 and December 2016. They had a 29.3% (17) shunt failure rate over the first year. There were two confirmed shunt infections (3.4%). Discussion: The 1-year shunt failure rate at our institution for VPS insertion in children over 3 months is 26.1% and the infection rate is 4.3% (9). The literature suggests that the outcome for VPS in younger children is worse than for older children. Our work shows similar outcomes for all children compared to those under 3 months at time of VPS insertion alone. Conclusion: Children under 3-months-old undergoing VPS insertion should not automatically expect an increased 1-year failure or infection rate compared with older children. The reasons for this may be as a result of increased subspecialisation, the more widespread use of antibiotic-impregnated catheters and improved neonatal care.

Characterization of immune responses to anti-PD-1 mono and combination immunotherapy in hematopoietic humanized mice implanted with tumor xenografts

Background

The success of agents that reverse T-cell inhibitory signals, such as anti-PD-1/PD-L1 therapies, has reinvigorated cancer immunotherapy research. However, since only a minority of patients respond to single-agent therapies, methods to test the potential anti-tumor activity of rational combination therapies are still needed. Conventional murine xenograft models have been hampered by their immune-compromised status; thus, we developed a hematopoietic humanized mouse model, hu-CB-BRGS, and used it to study anti-tumor human immune responses to triple-negative breast cancer (TNBC) cell line and patient-derived colorectal cancer (CRC) xenografts (PDX).

Methods

BALB/c-Rag2^nullIl2rγ^nullSIRPα^NOD (BRGS) pups were humanized through transplantation of cord blood (CB)-derived CD34+ cells. Mice were evaluated for human chimerism in the blood and assigned into experimental untreated or nivolumab groups based on chimerism. TNBC cell lines or tumor tissue from established CRC PDX models were implanted into both flanks of humanized mice and treatments ensued once tumors reached a volume of ~150mm³. Tumors were measured twice weekly. At end of study, immune organs and tumors were collected for immunological assessment.

Results

Humanized PDX models were successfully established with a high frequency of tumor engraftment. Humanized mice treated with anti-PD-1 exhibited increased anti-tumor human T-cell responses coupled with decreased Treg and myeloid populations that correlated with tumor growth inhibition. Combination therapies with anti-PD-1 treatment in TNBC-bearing mice reduced tumor growth in multi-drug cohorts. Finally, as observed in human colorectal patients, anti-PD-1 therapy had a strong response to a microsatellite-high CRC PDX that correlated with a higher number of human CD8+ IFNγ+ T cells in the tumor.

Conclusion

Hu-CB-BRGS mice represent an in vivo model to study immune checkpoint blockade to human tumors. The human immune system in the mice is inherently suppressed, similar to a tumor microenvironment, and thus allows growth of human tumors. However, the suppression can be released by anti-PD-1 therapies and inhibit tumor growth of some tumors. The model offers ample access to lymph and tumor cells for in-depth immunological analysis. The tumor growth inhibition correlates with increased CD8 IFNγ+ tumor infiltrating T cells. These hu-CB-BRGS mice provide a relevant preclinical animal model to facilitate prioritization of hypothesis-driven combination immunotherapies.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0518-z) contains supplementary material, which is available to authorized users.