Heterogeneity In Lung Cancer Research Articles

Radiomics for Response and Outcome Assessment for Non-Small Cell Lung Cancer.

Routine follow-up visits and radiographic imaging are required for outcome evaluation and tumor recurrence monitoring. Yet more personalized surveillance is required in order to sufficiently address the nature of heterogeneity in nonsmall cell lung cancer and possible recurrences upon completion of treatment. Radiomics, an emerging noninvasive technology using medical imaging analysis and data mining methodology, has been adopted to the area of cancer diagnostics in recent years. Its potential application in response assessment for cancer treatment has also drawn considerable attention. Radiomics seeks to extract a large amount of valuable information from patients’ medical images (both pretreatment and follow-up images) and quantitatively correlate image features with diagnostic and therapeutic outcomes. Radiomics relies on computers to identify and analyze vast amounts of quantitative image features that were previously overlooked, unmanageable, or failed to be identified (and recorded) by human eyes. The research area has been focusing on the predictive accuracy of pretreatment features for outcome and response and the early discovery of signs of tumor response, recurrence, distant metastasis, radiation-induced lung injury, death, and other outcomes, respectively. This review summarized the application of radiomics in response assessments in radiotherapy and chemotherapy for non-small cell lung cancer, including image acquisition/reconstruction, region of interest definition/segmentation, feature extraction, and feature selection and classification. The literature search for references of this article includes PubMed peer-reviewed publications over the last 10 years on the topics of radiomics, textural features, radiotherapy, chemotherapy, lung cancer, and response assessment. Summary tables of radiomics in response assessment and treatment outcome prediction in radiation oncology have been developed based on the comprehensive review of the literature.

LncRNA TUC338 promotes invasion of lung cancer by activating MAPK pathway.

Lung cancer is highly heterogeneous and the 5-year survival rate is less than 15%. It is currently difficult to determine the heterogeneity of lung cancer and the underlying pathogenetic of metastasis. We aimed to investigate the effect of long non-coding RNA (lncRNA) TUC338 on the invasion of lung cancer by activating MAPK pathway and to understand the heterogeneity and metastasis mechanism of lung cancer. The expression of lncRNA TUC338 in 42 samples of lung cancer and paracancerous tissues were accessed by RT-qPCR. The relationship between the expression of lncRNA and clinicopathological parameters was analyzed. After overexpressing and interfering with lncRNA TUC338, effects of lncRNA TUC338 on cell proliferation and invasion were determined by cell counting kit-8 (CCK8) and transwell assay. The protein expression was evaluated by Western blot. Higher expression of TUC338 in lung cancer was observed in comparison with that in paracancerous tissues. The survival time of TUC338 was correlated with the expression of TUC338. Clinical data analysis revealed that the expression of TUC338 was correlated with the overall survival, tumor size and lymph node metastasis in patients, but not with age and gender. After interfering and overexpressing TUC338, it was found that the activity of lung cancer cells was decreased, as well as the invasion ability after interference with TUC338. After overexpression of TUC338, we found that lung cancer cell activity increased, as well as the invasion ability. By Western blot, we found that TUC338 can promote the development of lung cancer through regulating MAPK pathway. TUC338 was overexpressed in lung cancer, and its expression may have a relationship to the prognosis of lung cancer. MAPK pathway was involved in the invasion of lung cancer regulated by TUC338.

Lung cancer stem cells – the role in pathogenesis and progressive growth of cancer

Lung cancer is the main cause of cancer death worldwide. Rapid accurate diagnosis, recognition of risk factors and improvement of treatment efficacy represent the main challenges. An advanced stage of the disease at the time of diagnosis, observed in the majority of cases, makes the introduction of radical treatment impossible or ineffective. Immunotherapy was a breakthrough in achieving long-term survival in recent years. The reason for developing this type of treatment is to know the interaction between the host cells and tumor cells. Cancer stem cells theory is increasingly gaining greater significance in the world. The biological heterogeneity of lung cancer may be due to the presence of a small percentage of cancer stem cells (CSCs). CSCs are the results of genetic and epigenetic changes in normal stem cells, progenitor cells or differentiated cells. CSCs are functionally defined by their unlimited self-renewal capacity, multiple differentiation and their ability to imitate tumors. It is believed that CSCs determine unrestricted growth of tumors and their different morphology. Their ability to self-renew can be the cause of relapses even after long periods of remission. CSCs reside in niches, where they receive signals for differentiation and proliferation process. The identification of CSCs is based on the presence of specific molecules (CD133, CD44, CD90, ALDH, EpCAM). An important feature of CSCs is their resistance to conventional cancer treatment: radio therapy and chemotherapy. Presumably, CSCs are responsible for the synthesis of immunosuppressive particles, and recruiting other molecules, which have immunosuppressive properties. The paper presents the current state of knowledge on CSCs in lung cancer detailing adenocarcinoma.

Mutant-allele fraction heterogeneity is associated with non-small cell lung cancer patient survival.

Genetic intratumor heterogeneity is associated with tumor occurrence, development and overall outcome. The present study aims to explore the association between mutant-allele fraction (MAF) heterogeneity and patient overall survival in lung cancer. Somatic mutation data of 939 non-small cell lung cancer (NSCLC) cases were obtained from The Cancer Genome Atlas. Entropy-based mutation allele fraction (EMAF) score was used to describe the uncertainty of individual somatic mutation patterns and to further analyze the association with patient overall survival. Results indicated that association between EMAF and overall survival was significant in the discovery set [hazard ratio (H)R=1.62; 95% confidence interval (CI): 1.08–2.41; P=0.018] and replication set (HR=1.63; 95% CI: 1.11–2.37; P=0.011). In addition, EMAF was also significantly different in lung adenocarcinoma and squamous cell carcinoma. Furthermore, a significant difference was indicated in early-stage patients. Results from c-index analysis indicated that EMAF improved the model predictive performance on the 3-year survival beyond that of traditional clinical staging, particularly in early-stage patients. In conclusion, EMAF successfully reflected MAF heterogeneity among patients with NSCLC. Additionally, EMAF improved the predictive performance in early-stage patient prognosis beyond that of traditional clinical staging. In clinical application, EMAF appears to identify a subset of early-stage patients with a poor prognosis and therefore may help inform clinical decisions regarding the application of chemotherapy after surgery.

Relationship between MTA1 Expression and Prognosis of Chinese Lung Cancer Patients: A Meta-analysis

背景与目的已有的研究表明：在多种恶性肿瘤中发现转移相关蛋白1（metastasis associated protein 1, MTA1）发挥着促进肿瘤侵袭与转移的作用，且与肿瘤患者预后不佳有关。目前MTA1在肺癌中的预后作用仍有争议，故我们采用meta分析的方法评估其在肺癌患者中的预后价值。方法通过计算机检索PubMed、Embase、万方数据库、中国生物医学文献数据库、中国知网等数据库，收集纳入研究MTA1表达与肺癌预后关系的文献及相关数据，采用Stata 12.0软件进行数据分析，合并值为风险比（hazard ratio, HR）。结果总共纳入8项研究共712例中国肺癌患者，对这些研究进行异质性检验，发现存在异质性（I2=59.0%, P=0.017），故采用随机效应模型进行数据合并得HR=2.07（95%CI: 1.42-3.02, P < 0.001）。同时分层分析显示在非小细胞肺癌（non-small cell lung cancer, NSCLC）中各研究无明显异质性（I2=47.0%, P=0.093），采用固定效应模型合并得HR=1.66（95%CI: 1.27-2.18, P < 0.001）。结论MTA1高表达可能是中国NSCLC患者预后不良的一个指标，在肺癌及小细胞肺癌中的预后价值尚缺乏证据。

Simultaneous evolutionary expansion and constraint of genomic heterogeneity in multifocal lung cancer

Recent genomic analyses have revealed substantial tumor heterogeneity across various cancers. However, it remains unclear whether and how genomic heterogeneity is constrained during tumor evolution. Here, we sequence a unique cohort of multiple synchronous lung cancers (MSLCs) to determine the relative diversity and uniformity of genetic drivers upon identical germline and environmental background. We find that each multicentric primary tumor harbors distinct oncogenic alterations, including novel mutations that are experimentally demonstrated to be functional and therapeutically targetable. However, functional studies show a strikingly constrained tumorigenic pathway underlying heterogeneous genetic variants. These results suggest that although the mutation-specific routes that cells take during oncogenesis are stochastic, genetic trajectories may be constrained by selection for functional convergence on key signaling pathways. Our findings highlight the robust evolutionary pressures that simultaneously shape the expansion and constraint of genomic diversity, a principle that holds important implications for understanding tumor evolution and optimizing therapeutic strategies.

PD-L1 expression heterogeneity in non-small cell lung cancer: evaluation of small biopsies reliability.

Immunotherapy with checkpoint inhibitors, allowing recovery of effector cells function, has demonstrated to be highly effective in many tumor types and represents a true revolution in oncology. Recently, the anti-PD1 agent pembrolizumab was granted FDA approval for the first line treatment of patients with advanced non–small cell lung cancer (NSCLC) whose tumors show PD-L1 expression in ≥ 50% of neoplastic cells and as a second line treatment for patients with NSCLC expressing PD-L1 in ≥1% of neoplastic cells, evaluated with a validated assay. For the large majority of patients such evaluation is made on small biopsies. However, small tissue samples such as core biopsies might not be representative of tumors and may show divergent results given the possible heterogeneous immunoexpression of the biomarker. We therefore sought to evaluate PD-L1 expression concordance in a cohort of 239 patients using tissue microarrays (TMA) as surrogates of biopsies stained with a validated PD-L1 immunohistochemical assay (SP263) and report the degree of discordance among tissue cores in order to understand how such heterogeneity could affect decisions regarding therapy.We observed a discordance rate of 20% and 7.9% and a Cohen's κ value of 0.53 (moderate) and 0,48 (moderate) for ≥ 1% and ≥ 50% cutoffs, respectively.Our results suggest that caution must be taken when evaluating single biopsies from patients with advanced NSCLC eligible for immunotherapy; moreover, at least 4 biopsies are necessary in order to minimize the risk of tumor misclassification.

Lung Cancer Heterogeneity and New Strategies for Drug Therapy.

Lung cancer heterogeneity plays an important role in the development of drug resistance. Comprehensive molecular characterizations of lung cancer can describe hereditary and somatic gene changes, mutation, and heterogeneity. We discuss heterogeneity specificity, characterization, and roles of PIK3CD, TP53, and KRAS, as well as target-driven therapies and strategies applied in clinical trials based on a proposed precise self-validation system. The system is a specifically selected strategy of treatment for patients with cancer gene mutations and heterogeneity based on gene sequencing, following validation of the strategies in the patient's own cancer cells or in patient-derived xenografts using their own cancer cells isolated during surgery or biopsies. These results will be more precise if the drugs used in the strategies are selected through protein structure-guided compound screening or a DNA-encoded chemical library before validation in the patient's own cancer cells. Thus, a deeper understanding of heterogeneity mechanisms and improved validation of the therapeutic strategy will result in more precise treatments for patients.

Next-generation sequencing reveals novel resistance mechanisms and molecular heterogeneity in EGFR-mutant non-small cell lung cancer with acquired resistance to EGFR-TKIs

ObjectivesDespite initial responses to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) in EGFR mutant non-small cell lung cancer, patients invariably develop acquired resistance. In this study, we performed next-generation sequencing in pre- and post-EGFR-TKI tumor samples to identify novel resistance mechanisms to EGFR-TKIs. Material and methodsWe collected tumor tissues before EGFR-TKI treatment and after progression from 19 NSCLC patients to analyze genomic alterations in 409 cancer related genes. Bioinformatics analyses were used to identify mutations in which the allele frequencies are significantly changed, or newly appeared after progression. ResultsOverall, mutation rates and compositions were similar between pre- and post-EGFR-TKI tumors. We identified EGFR T790M as the most common mechanism of acquired resistance (63.2%). No pre-EGFR-TKI tumor had a preexisting T790M mutation, suggesting that tumors acquired T790M mutations following progression on EGFR-TKIs. Compared to T790M-positive tumors, T790M-negative tumors showed relatively high tumor mutation burden and shorter survival, suggesting T790M-negative patients as a potential candidate for immune checkpoint inhibitors. TP53 mutation was also significantly enriched in the T790M-negative tumors. Finally, we described here for the first time a novel missense mutation (T263P), which occurred concurrently with an activating G719A mutation, in the extracellular domain II of EGFR in a patient with poor response to erlotinib. Ba/F3 cells harboring EGFR T263P/G719A mutation showed higher sensitivity to afatinib, compared to gefitinib due to inhibition of EGFR/HER2 heterodimerization. ConclusionComprehensive genomic analysis of post-EGFR-TKI tumors can provide novel insight into the complex molecular mechanisms of acquired resistance to EGFR-TKIs.

Abstract 1722: Novel multiplex liquid biopsy detection of ALK and ROS1 rearrangements and intratumoral heterogeneity in lung cancer using circulating tumor cells (CTCs) isolated from NSCLC patient bloods and TR-CytoTrapNanoTM technology

Abstract Introduction: ALK and ROS1 rearrangements are common gene alterations found in subsets of patients with NSCLC. Identification of ALK and ROS1 rearrangement in NSCLC is critical for highly active targeted therapies aiming for these two main tumorigenic drivers. Due to the similarity of tyrosine kinase domains between ALK and ROS1, many ALK inhibitors are also functional in treatment of ROS1 subtype NSCLC. For example, crizotinib, which is a standard therapy for advanced ALK-rearranged NSCLC is highly effective in advanced ROS1-rearranged genotype NSCLC patients. The mutational analysis of these genes requires serial tumor biopsying from primary lesions, which requires high risk clinical procedures. Further, the current tissue-based diagnostics, such as fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) are known to be challenging technically with limited sensitivity, subjective interpretation and inaccuracy in monitoring the current tumor status. The TR-CytoTrapNanoTM CTC technology is a blood-based assay to utilize CTCs as a biosource for mRNA extraction to detect genetic alteration or gene expression profiles including ALK and ROS1 gene rearrangements. In this study, we determined the variant specific expression of ALK fusion transcripts (EML4-ALK, KIF-ALK, and TGF-ALK) and ROS1 fusion transcripts (EZR-ROS1, SDC4-ROS1, TPM3-ROS1, LRIG3-ROS1, GOPC-ROS1, CD74-ROS1, and SLC34A2-ROS1) using multiplex digital droplet polymerase chain reaction(ddPCR) technology. Method: The Peripheral Blood Mononuclear Cells isolated from NSCLC patient bloods run through the TR-CytoTrapNanoTM microfluidic system. The CTCs are enriched and captured on the chip surface conjugated with Anti-EpCAM targeting antibody, which specifically binds to CTCs of epithelial origin. Following lysis step facilitate total RNA release from trapped CTCs and then pure mRNAs are isolated using oligo-dT conjugated magnetic beads. The mRNAs are used for following ALK and ROS1 specific reverse transcription reaction to make cDNAs for either ALK or ROS1 fusion transcripts. The specific subtyping of ALK and ROS1 rearrangement are then validated using ddPCR. Results and Conclusion: We tested several liquid biopsies from ALK and ROS1 rearrangement positive patients and corresponding positive data to FISH assays using solid tumor biopsies. Interestingly, some of the CTCs harboring ALK and ROS1 rearrangement has shown high intratumor heterogeneity in the subtypes of fusion partners. we envision that our novel TR-CytoTrapNanoTM CTC ALK/ROS1 rearrangement Assay to monitor treatment response and recurrence in NSCLC patients will be used to monitor treatment response and disease recurrence following treatment with Tyrosine Kinase Inhibitors (TKIs). Note: This abstract was not presented at the meeting. Citation Format: sangjun lee. Novel multiplex liquid biopsy detection of ALK and ROS1 rearrangements and intratumoral heterogeneity in lung cancer using circulating tumor cells (CTCs) isolated from NSCLC patient bloods and TR-CytoTrapNanoTM technology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1722. doi:10.1158/1538-7445.AM2017-1722

Large-scale association analysis identifies new lung cancer susceptibility loci and heterogeneity in genetic susceptibility across histological subtypes.

SummaryWhile several lung cancer susceptibility loci have been identified, much of lung cancer heritability remains unexplained. Here, 14,803 cases and 12,262 controls of European descent were genotyped on the OncoArray and combined with existing data for an aggregated GWAS analysis of lung cancer on 29,266 patients and 56,450 controls. We identified 18 susceptibility loci achieving genome wide significance, including 10 novel loci. The novel loci highlighted the striking heterogeneity in genetic susceptibility across lung cancer histological subtypes, with four loci associated with lung cancer overall and six with lung adenocarcinoma. Gene expression quantitative trait analysis (eQTL) in 1,425 normal lung tissues highlighted RNASET2, SECISBP2L and NRG1 as candidate genes. Other loci include genes such as a cholinergic nicotinic receptor, CHRNA2, and the telomere-related genes, OFBC1 and RTEL1. Further exploration of the target genes will continue to provide new insights into the etiology of lung cancer.

Cancer: Tumours build their niche.

It emerges that tumour cells can give rise to non-dividing cells that form part of the supporting microenvironment known as the niche. These niche cells secrete proteins that drive tumour growth and progression. See Letters p.355 & p.360 Lung adenocarcinomas are aggressive tumours which are associated with poor treatment outcome. Tyler Jacks and colleagues now show that lung adenocarcinomas display two distinct subpopulations of tumour cells. One of these shows high levels of Wnt signalling and gives rise to the second one that produces Wnt ligands. The latter population fuels tumour growth of the former, showing that lung cancer cells can produce their own niche. These findings shed new light on the mechanisms underlying intratumoural heterogeneity which may have therapeutic implications. Small-cell lung cancers (SCLCs) with a neuroendocrine phenotype are aggressive tumours. In a mouse model of SCLC, Julien Sage and colleagues now show that activation of the Notch pathway can lead to cell fate switch of neuroendocrine cells to less proliferative non-neuroendocrine cells, generating intra-tumour heterogeneity. Non-neuroendocrine cells with activated Notch signalling in turn provide trophic support for neuroendocrine cells. Thus neuroendocrine tumour cells create their niche environment, which produces factors that act on neuroendocrine cells and promote tumour growth. Accordingly, targeting neuroendocrine cells with chemotherapeutics and non-neuroendocrine cells with Notch inhibitors cooperate in reducing tumorigenesis. This study sheds new light on the mechanisms underlying intratumoural heterogeneity in lung cancer and suggests that new combination treatments could be used to target SCLCs.

Critical roles of mucin-1 in sensitivity of lung cancer cells to tumor necrosis factor-alpha and dexamethasone.

Lung cancer is the leading cause of death from cancer. Mucins are glycoproteins with high molecular weight, responsible for cell growth, differentiation, and signaling, and were proposed to be correlated with gene heterogeneity of lung cancer. Here, we report aberrant expression of mucin genes and tumor necrosis factor receptors in lung adenocarcinoma tissues compared with normal tissues in GEO datasets. Mucin-1 (MUC1) gene was selected and considered as the target gene; furthermore, the expression pattern of adenocarcinomic cells (A549, H1650, or H1299 cells) was validated under the stimulation with tumor necrosis factor-alpha (TNFα) or dexamethasone (DEX), separately. MUC1 gene interference was done to A549 cells to show its role in sensitivity of lung cancer cells to TNFα and DEX. Results of our experiments indicate that MUC1 may regulate the influence of inflammatory mediators in effects of glucocorticoids (GCs), as a regulatory target to improve therapeutics. It shows the potential effect of MUC1 and GCs in lung adenocarcinoma (LADC), which may help in LADC treatment in the future.

Lung Cancer: A Wily Genetic Opponent

In two companion reports, the TRACERx consortium investigates tumor heterogeneity and evolution in early-stage non-small cell lung cancer. The studies highlight the prognostic value of copy-number heterogeneity assessment in tumor biopsies and circulating tumor DNA detection in plasma and suggest that tracking the evolution of lung cancers might aid clinical practice.

MA17.03 Identifying Genomic Alteration and Inter-Tumor Heterogeneity of Multiple Primary Lung Cancers by Targeted NGS of Tumor Tissue and ctDNA

MA17.03 Identifying Genomic Alteration and Inter-Tumor Heterogeneity of Multiple Primary Lung Cancers by Targeted NGS of Tumor Tissue and ctDNA

Say goodbye to Martini and Melamed: genomic classification of multiple synchronous lung cancer

It is said that all good things must come to an end. The paper “Genomic heterogeneity of multiple synchronous lung cancer” by Liu et al . may finally close the book on the Martini and Melamed criteria for establishing whether multiple synchronous lung cancers (MSLC) represent distinct primary tumors or intrapulmonary metastases (1).

P3.01-019 Desmoplasia is Associated with Poor Prognosis and Carcinoma-Associated Fibroblast Heterogeneity in Non-Small Cell Lung Cancer: Topic: Morphology

Cancer-associated fibroblasts (CAFs) are known to influence tumor development, progression and metastasis. Their characteristics and prognostic role in non-small cell lung cancer (NSCLC) patients have been recognized. However, the functional heterogeneity of CAFs between patients and its genetic basis is less understood. Two pathologists scored for desmoplasia on Hematoxylin-Eosin stained sections of resected lung tumors from two patient cohorts: one consisting of 171 NSCLC patients (128 adenocarcinoma, 43 squamous carcinoma) and the second of 24 primary cultures of CAFs. Percent area of desmoplasia among total tumor stroma was used to define high desmoplasia (HD) versus low desmoplasia (LD). The desmoplasia and survival analysis were assessed for 171 NSCLC patients. Gene expression data on RNA extracted from CAFs in contracted gels following 24 hours incubation was obtained using Illumina Human HT-12v4 Bead Chips array and was preprocessed and normalized using RMA and values were log2 transformed. Significant genes whose expression is strongly correlated (Spearman correlation coefficient and p value) with percent of desmoplasia were identified in both cohorts. The gene set enrichment analysis (GSEA) was applied to test for the enrichment of CAF cohort significant genes in 171 NSCLC cohort. Additionally, CAF significant genes were subjected to pathway enrichment analysis using Pathway Data Integration Portal ver. 2.5 (http://ophid.utoronto.ca/pahtDIP). The prognosis of adenocarcinoma patients with HD had poorer outcome in comparison to the patients with LD (disease free survival at 3 years 34% vs. 75% p=0.00045 and relapse rate 41% vs. 14%, p=0.0051). In the CAF cohort, the number of genes that are significantly associated with desmoplasia for enrichment are 356. Using GSEA, these genes were enriched in 171 NSCLC cohort (with a p value of 0.045). Protein-protein interaction (PPI) partners of these 356 genes were acquired using Integrated Interaction Database – IID (version 2016-03, http://dcv.uhnres.utoronto.ca/iid/). Obtained genes were then ranked according to their degree, i.e., number of PPIs. Top 44 (top 1%) of the genes were then selected to pathway enrichment analysis using pathDIP version 2.5. 245 pathways that significantly enriched by these 44 genes (FDR < 0.01) were obtained. Many of these pathways are known to be involved in lung cancer. We demonstrated that the prognosis of lung adenocarcinoma patients with HD had poorer outcome in comparison to the patients with LD. Furthermore, PPI analysis of CAF genes associated with HD reveals enrichment of many cancer-related pathways, suggesting their high relevance to lung cancer.

Evaluation of PET texture features with heterogeneous phantoms: complementarity and effect of motion and segmentation method

A major source of error in quantitative PET/CT scans of lung cancer tumors is respiratory motion. Regarding the variability of PET texture features (TF), the impact of respiratory motion has not been properly studied with experimental phantoms. The primary aim of this work was to evaluate the current use of PET texture analysis for heterogeneity characterization in lesions affected by respiratory motion. Twenty-eight heterogeneous lesions were simulated by a mixture of alginate and 18F-fluoro-2-deoxy-D-glucose (FDG). Sixteen respiratory patterns were applied. Firstly, the TF response for different heterogeneous phantoms and its robustness with respect to the segmentation method were calculated. Secondly, the variability for TF derived from PET image with (gated, G-) and without (ungated, U-) motion compensation was analyzed. Finally, TF complementarity was assessed. In the comparison of TF derived from the ideal contour with respect to TF derived from 40%-threshold and adaptive-threshold PET contours, 7/8 TF showed strong linear correlation (LC) (p < 0.001, r > 0.75), despite a significant volume underestimation. Independence of lesion movement (LC in 100% of the combined pairs of movements, p < 0.05) was obtained for 1/8 TF with U-image (width of the volume-activity histogram, WH) and 4/8 TF with G-image (WH and energy (ENG), local-homogeneity (LH) and entropy (ENT), derived from the co-ocurrence matrix). Their variability in terms of the coefficient of variance () resulted in (WH) = 0.18 on the U-image and (WH) = 0.24, (ENG) = 0.15, (LH) = 0.07 and (ENT) = 0.06 on the G-image. Apart from WH (r > 0.9, p < 0.001), not one of these TF has shown LC with Cmax. Complementarity was observed for the TF pairs: ENG–LH, CONT (contrast)–ENT and LH–ENT. In conclusion, the effect of respiratory motion should be taken into account when the heterogeneity of lung cancer is quantified on PET/CT images. Despite inaccurate volume delineation, TF derived from 40% and COA contours could be reliable for their prognostic use. The TF that exhibited simultaneous added value and independence of lesion movement were ENG and ENT computed from the G-image. Their use is therefore recommended for heterogeneity quantification of lesions affected by respiratory motion.

Mutation patterns in small cell and non-small cell lung cancer patients suggest a different level of heterogeneity between primary and metastatic tumors.

Several studies have shown heterogeneity in lung cancer, with parallel existence of multiple subclones characterized by their own specific mutational landscape. The extent to which minor clones become dominant in distinct metastasis is not clear. The aim of our study was to gain insight in the evolution pattern of lung cancer by investigating genomic heterogeneity between primary tumor and its distant metastases. Whole exome sequencing (WES) was performed on 24 tumor and five normal samples of two small cell lung carcinoma (SCLC) and three non-SCLC (NSCLC) patients. Validation of somatic variants in these 24 and screening of 33 additional samples was done by single primer enrichment technology. For each of the three NSCLC patients, about half of the mutations were shared between all tumor samples, whereas for SCLC patients, this percentage was around 95. Independent validation of the non-ubiquitous mutations confirmed the WES data for the vast majority of the variants. Phylogenetic trees indicated more distance between the tumor samples of the NSCLC patients as compared to the SCLC patients. Analysis of 30 independent DNA samples of 16 biopsies used for WES revealed a low degree of intra-tumor heterogeneity of the selected sets of mutations. In the primary tumors of all five patients, variable percentages (19-67%) of the seemingly metastases-specific mutations were present albeit at low read frequencies. Patients with advanced NSCLC have a high percentage of non-ubiquitous mutations indicative of branched evolution. In contrast, the low degree of heterogeneity in SCLC suggests a parallel and linear model of evolution.

439O Tracking spatiotemporal T790M heterogeneity in patients with EGFR-mutant advanced NSCLC after acquired resistance to EGFR TKIs

Background The evolution landscape of EGFR-mutant advanced NSCLC might be characterized by evolving traces of actionable EGFR mutations. With the approval of osimertinib, T790M has shifted from a resistant biomarker to an actionable biomarker for EGFR-mutant advanced NSCLC. However, T790M status might vary spatiotemporally and consequently hinder the initiation and clinical efficacy of third generation EGFR TKIs. Till now, the spatiotemporal traces of T790M under treatment pressure have not been fully elucidated. Methods We retrospectively reviewed T790M status and clinical courses of 114 patients who had multiple (>2) rebiopsies after acquired resistanceto EGFR TKIs from January 2010 to July 2016 in our institute. Tissue EGFR detection was performed by SNaPshot or ARMS. Plasma EGFR was detected by ARMS. Results The ratio of spatial T790M heterogeneity was 57%. In detail, 14 of 21 patients with synchronous rebiopsies at the same lesion and 20 of 39 patients with paired tissue and plasma rebiopsies showed T790M heterogeneity. 33% (10/30) of patients who had heterochronous rebiopsies at the same lesion revealed temporal T790M heterogeneity. Spatiotemporal T790M heterogeneity was observed in 53% (17/32) of patients who had heterochronous multiple sites rebiopsies. Of 24 patients with temporal or spatiotemporalT790Mheterogeneity(3withbothtypes),T790Mstatusin15switched from negative to positive after sequential treatments (7 first generation EGFR TKIs, 7 chemotherapy and 1 combined first generation EGFR TKIs and chemotherapy) and in 7 switchedfrompositivetonegativeaftersequentialtreatments(1thirdgenerationEGFR TKIs, 5 chemotherapy, 1 combined first generation EGFR TKIs and chemotherapy). 2 showed a cycle of T790M heterogeneity with a “positive-negative-positive” manner. Conclusions: T790M status could vary spatiotemporally at a ratio of 33-57% in patients with acquired resistance to previous EGFR TKIs, highlighting the necessity of repeated rebiopsies and dynamic monitor of T790M in this subpopulation. Moreover, this study provides a new insight of valuing actionable mutations when deciphering spatiotemporal genomic heterogeneity of lung cancer in clinical practice. Legal entity responsible for the study N/A Funding This study was supported by Guangzhou Science and Technology Bureau (No. 2014Y2-00050). Disclosure All authors have declared no conflicts of interest.