P1631Machine-learning defined predictors of mortality in ischemic and non-ischemic heart failure patients undergoing CRT-P or CRT-D implantation

Background

Both Cardiac Resynchronization Therapy Pacemakers (CRT-P) and CRT Defibrillators (CRT-D) improve mortality in heart failure patients with reduced ejection fraction and wide QRS complex. However, not every patient benefits equally from each type of treatment and determinants of mortality may vary across the subgroups of patients with different etiologies and devices.

Purpose

Our aim was to investigate the differences in the predictors of long-term mortality in heart failure patients with different etiologies undergoing CRT-P or CRT-D implantation using machine learning.

Methods

We created 4 separate random forest models to predict 5-year all-cause mortality (models for ischemic and non-ischemic etiology in both CRT-P and CRT-D subgroups). A registry of 1650 patients (66±10 years, 1258 [76%] males, 751 [46%] CRT-D) was used as the training cohort for the prediction models. Forty-seven pre-implant parameters including cardiovascular risk factors and clinical variables were utilized to train our models. For each clinical parameter, we calculated the mean decrease in Gini impurity (dG). Based on the extent of decline, the 10 most important features were selected for each model. To keep the data comparable between the different models, we took the union of these features and plotted the results on radar charts.

Results

There were 879 (53%) deaths during the follow-up period. The mortality benefit of adding an Implantable Cardioverter Defibrillator could be observed only in ischemic patients (Hazard Ratio = 0.83, 95% Confidence Interval: 0.72–0.97, p<0.005), but not in the entire cohort or in patients with non-ischemic etiology. In patients with non-ischemic etiology, the pattern of mortality predictors were almost similar: in CRT-P patients the most important predictors were age, serum urea levels and left ventricular ejection fraction (LVEF) (dG: 0.114, 0.054 and 0.053, respectively) whereas in the CRT-D subgroup these factors were age, LVEF and serum sodium (dG: 0.116, 0.060 and 0.052, respectively). In CRT-P patients with non-ischemic etiology, the most relevant variables were age serum urea and LVEF in decreasing order (dG: 0.085, 0.060 and 0.050, respectively). The strongest predictors of mortality were age, hemoglobin and serum creatinine in ischemic patients with CRT-D (dG: 0.088, 0.060 and 0.052, respectively).

CRT-P vs. CRT-D by ischemic etiology

Conclusions

In patients with ischemic heart failure, CRT-D was associated with a mortality benefit compared to CRT-P. Our results also suggest that machine-learning may identify distinct patterns in clinical characteristics for a better mortality prediction. Taking these factors into consideration during the management of heart failure patients with CRT, risk stratification and outcomes could be improved.

Magnetic properties of artificially designed magnetic stray field landscapes in laterally confined exchange-bias layers

Magnetic stray fields generated by domain walls (DWs) have attracted significant attention as they might be employed for precise positioning and active control of micro- and nano-sized magnetic objects in fluids or in the field of magnonics. The presented work intends to investigate the near-field response of magnetic stray field landscapes above generic types of charged DWs as occurring in thin films with in-plane anisotropy and preferential formation of Néel type DWs when disturbed by external magnetic fields. For this purpose, artificial magnetic stripe domain patterns with three defined domain configurations, i.e. head-to-head (tail-to-tail), head-to-side, and side-by-side, were fabricated via ion bombardment induced magnetic patterning of an exchange-biased IrMn/CoFe bilayer. The magnetic stray field landscapes as well as the local magnetization reversal of the various domain configurations were analyzed in an external magnetic field by scanning magnetoresistive microscopy and compared to micromagnetic simulations.

Abstract P1-01-04: Mutational profiling of breast cancer brain metastases – matched pair analysis of next generation sequencing between primary breast cancer and later developed brain metastases

Background: Despite increased survival in patients with advanced breast cancer, breast cancer brain metastases (BCBM), remains a final frontier with a mean survival of 3-12 months. The biology facilitating BCBM is not fully understood.

Aims: To compare gene expression profiles in primary BC, and later diagnosed, surgically removed BCBM.

Material and Methods: A total of 58 BCBM and 46 breast tumors were analyzed with next generation sequencing (NGS). DNA was isolated from FFPE sectionsand then the Cancer Hotspot Panel v2 (ThermoFisher Scientific) covering 207-targeted regions in 50 cancer related genes was used. Template preparation and enrichment were performed with the IonChefTM Instrument (ThermoFisher Scientific). Eight barcoded samples were pooled per Ion 318 TM v2 BC chip and sequenced on the Ion PGMTM System (ThermoFisher Scientific).Alignment to the hg19 human reference genome and variant calling was performed by the Torrent Suite Software v5.2.0 (ThermoFisher Scientific) also IonReporterTM System (ThermoFisher Scientific) was used.

Results: 46 of the BCBM were matched with a primary breast cancer tumor. All but 12 tumors had the same IHC characteristic in the matched pairs. The most common transformation was Luminal A to Luminal B in 8 tumors. The other changes were triple negative subtype (TNBC) to Luminal B, HER2+ to Luminal B, Luminal A to TNBC and Luminal A to HER2+ with one case respectively. The BCBM had the following IHC profile: one tumor was luminal A (1%), 15 tumors were Luminal B (25%), 29 were TNBC (50%) and 14 HER2 overexpressing (24%). The preliminary NGS data shows that the most common mutation in BCBM was found in the tumor suppressor gene p53 (22/58, 38 %). Other common mutations were PIK3CA (17/58, 29%); KDR (16/58, 28%), KIT (9/58, 16%) and PTEN (2/58, 3%). The corresponding figures in the primary BC were p53 (15/46, 33%), PIK3CA (16/46, 35%), KDR (17/46, 37%), KIT (7/46, 15%) and no tumors with PTEN. The mutational spectra in the 50 cancer related genes were similar in the primary BC as in the BCBM with 1-5 different driver mutations but additional mutations were registered in 6/46 matched cases (13%). We fail to identify any specific differences in mutations between the different morphological subtypes (LumA/LumB/TNBC/HER2+) in the metastatic sample. In the NGS analysis of the metastases and primary tumors 3 different variations of p53 was detected.

Conclusions: In this large matched pairs of primary breast tumors and BCBM we show that the majority of BCBM have a similar gene profile as the primary BC. The most common aberrations were found in TP53, PIK3CA and KDR. Additional post analyses are under investigation and will be added to the results. It appears that brain metastases are not different from other metastases in that they remain fairly stable in their driver mutational profile. When the mutational profile changes there is addition of mutation rather than deletion. A clinical implication of these results could be to treat BCBM according to the mutational profile of the primary tumor which decreases the need for sampling of BCBM; something that if the patient is not eligible for surgery might otherwise prove complex.

Citation Format: Thulin A, Andersson C, Werner Rönnerman E, De Lara S, Chamalidou C, Schoenfeld A, Kovacs A, Enlund F, Linderholm BK. Mutational profiling of breast cancer brain metastases – matched pair analysis of next generation sequencing between primary breast cancer and later developed brain metastases [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-01-04.

Disturbed spermatogenic signaling in pituitary adenylate cyclase activating polypeptide-deficient mice

PACAP is a neuropeptide with diverse functions in various organs, including reproductive system. It is present in the testis in high concentrations, and in addition to the stage-specific expression within the seminiferous tubules, PACAP affects spermatogenesis and the functions of Leydig and Sertoli cells. Mice lacking endogenous PACAP show reduced fertility, but the possibility of abnormalities in spermatogenic signaling has not yet been investigated. Therefore, we performed a detailed morphological analysis of spermatozoa, sperm motility and investigated signaling pathways that play a role during spermatogenesis in knockout mice. No significant alterations were found in testicular morphology or motility of sperm in homozygous and heterozygous PACAP-deficient mice in spite of the moderately increased number of severely damaged sperms. However, we found robust changes in mRNA and/or protein expression of several factors that play an important role in spermatogenesis. Protein kinase A expression was markedly reduced, while downstream phospho-ERK and p38 were elevated in knockout animals. Expression of major transcription factors, such as Sox9 and phospho-Sox9, was decreased, while that of Sox10, as a redundant factor, was increased in PACAP-deficient mice. The reduced phospho-Sox9 expression was partly due to increased expression and activity of phosphatase PP2A in knockout mice. Targets of Sox transcription factors, such as collagen type IV, were reduced in knockout mice. In summary, our results show that lack of PACAP leads to disturbed signaling in spermatogenesis, which could be a factor responsible for reduced fertility in PACAP knockout mice, and further support the role of PACAP in reproduction.

Human leucocyte antigen class I and II imputation in a multiracial population

Human leucocyte antigen (HLA) genes play a central role in response to pathogens and in autoimmunity. Research to understand the effects of HLA genes on health has been limited because HLA genotyping protocols are labour intensive and expensive. Recently, algorithms to impute HLA genotype data using genome-wide association study (GWAS) data have been published. However, imputation accuracy for most of these algorithms was based primarily on training data sets of European ancestry individuals. We considered performance of two HLA-dedicated imputation algorithms - SNP2HLA and HIBAG - in a multiracial population of n = 1587 women with HLA genotyping data by gold standard methods. We first compared accuracy - defined as the percentage of correctly predicted alleles - of HLA-B and HLA-C imputation using SNP2HLA and HIBAG using a breakdown of the data set into an 80% training group and a 20% testing group. Estimates of accuracy for HIBAG were either the same or better than those for SNP2HLA. We then conducted a more thorough test of HIBAG imputation accuracy using five independent 10-fold cross-validation procedures with delineation of ancestry groups using ancestry informative markers. Overall accuracy for HIBAG was 89%. Accuracy by HLA gene was 93% for HLA-A, 84% for HLA-B, 94% for HLA-C, 83% for HLA-DQA1, 91% for HLA-DQB1 and 88% for HLA-DRB1. Accuracy was highest in the African ancestry group (the largest group) and lowest in the Hispanic group (the smallest group). Despite suboptimal imputation accuracy for some HLA gene/ancestry group combinations, the HIBAG algorithm has the advantage of providing posterior estimates of accuracy which enable the investigator to analyse subsets of the population with high predicted (e.g. >95%) imputation accuracy.

Clinical pregnancy following pre-implantation genetic diagnosis for cystic fibrosis

Pre-implantation genetic diagnosis (PGD) is an established alternative to prenatal testing for couples at risk of transmitting genetic disorders such as cystic fibrosis (CF).PGD screens pre-implantation embryos, allowing the safe transfer of those identified as unaffected. Awareness of CF carrier status in Ireland is increasing following the introduction of neonatal screening in 2011. PGD is the most acceptable reproductive strategy for many at risk Irish couples but until now the treatment necessitated travelling abroad. In 2012, the Irish Medicines Board licenced two Irish fertility clinics to carry out embryo biopsy for PGD. This is the first reported clinical pregnancy following PGD carried out in Ireland.