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A. Warth
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MA 06 - Lung Cancer Biology I (ID 660)
- Event: WCLC 2017
- Type: Mini Oral
- Track: Biology/Pathology
- Presentations: 1
- Moderators:N. Motoi, Keith M Kerr
- Coordinates: 10/16/2017, 15:45 - 17:30, Room 501
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MA 06.06 - Assessment of RANK Prevalence and Clinical Significance in the NSCLC European Thoracic Oncology Platform Lungscape Cohort (ID 10006)
15:45 - 17:30 | Author(s): A. Warth
- Abstract
- Presentation
Background:
Receptor Activator of Nuclear Factor κappa-B (RANK) is a pathway involved in bone homeostasis. Recent evidence suggests that RANK signalling may also play a role in bone metastasis, and primary breast and lung cancers. The European Thoracic Oncology Platform (ETOP) Lungscape project allows evaluation of the prevalence of RANK expression and its clinical significance in a cohort of surgically-resected NSCLCs.
Method:
RANK expression was assessed on tissue microarrays (TMAs) using immunohistochemistry. Up to 4 cores per patient were analysed based on sample acceptance criteria. An H-Score (staining intensity + % cells stained) was used to assess RANK expression (positivity), as defined by at least 1 core with any degree of positive staining. Prevalence of RANK positivity and its association with clinicopathological characteristics, other cancer-related biomarkers (IHC ALK/MET/PTEN/PD-L1 expression and EGFR/KRAS/PIK3CA mutations) and patient outcome [Relapse-free Survival (RFS), Time-to-Relapse (TTR), Overall Survival (OS)] was explored in a subset of the ETOP Lungscape cohort. The prevalence of RANK overexpression (proportion of positive cancer cells ≥50%) was also investigated.
Result:
RANK expression was assessed in patients from 3 centers, a total of 402 from the 2709 patients of the Lungscape cohort, with median follow-up 44 months; 32.6% female, 40.8/54.2/5.0% adenocarcinomas (AC)/squamous cell carcinomas (SCC)/other, 44.8/28.4/26.9% with stage I/II/III, 20.6/57.7/18.9% current/former/never smokers (and 2.7% with unknown smoking status). Median was 74 months for both RFS and OS, while median TTR was not reached. Prevalence of RANK positivity was 26.6% (107 of the 402 cases), with 95% confidence interval (95%CI):22.4%-31.2%; significantly higher in AC: 48.2% (79 of 164 cases), 95%CI:40.3%-56.1%; vs SCC: 9.2% (20 of 218 cases), 95%CI:5.7%-13.8%; (p<0.001). RANK positivity was more frequent in females (38.9% vs 20.7% in males, p<0.001) and tumors≤4cm (30.7% vs 21.1% in tumors>4cm, p=0.031). Significant associations were also detected between RANK and PTEN expression in AC (RANK positivity 57.4% in PTEN expression vs 30.5% in PTEN loss; p=0.0011) and with MET status in SCC (RANK positivity 27.8% in MET+ vs 7.6% in MET-; p=0.016). No association with outcome was found. RANK overexpression was identified in 43 (10.7%; 95%CI: 7.9%-14.1%) cases.
Conclusion:
In this early-stage NSCLC cohort, RANK positivity (26.6% overall) is found to be significantly more common in adenocarcinomas (48.2%), females, patients with tumors of smaller size, with PTEN expression (in SCC) and MET positivity (in AC). No prognostic significance of RANK expression was found. Analysis of additional cases is ongoing and results will be presented.
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P1.15 - SCLC/Neuroendocrine Tumors (ID 701)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: SCLC/Neuroendocrine Tumors
- Presentations: 1
- Moderators:
- Coordinates: 10/16/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P1.15-011 - Longitudinal Mutation Monitoring in Plasma Without Matching Tumor Tissue by Deep Sequencing in Small Cell Lung Cancer (SCLC) (ID 9622)
09:30 - 16:00 | Author(s): A. Warth
- Abstract
Background:
SCLC is a devastating cancer with poor overall survival. Mutation profiles and treatment regimens differ significantly from non-small cell lung cancer (NSCLC). Here we demonstrate feasibility of monitoring patients with SCLC by deep sequencing from only 2 ml of plasma, without prior knowledge of the tumor tissue mutations relative to CT imaging.
Method:
Cell free DNA (cfDNA) was isolated from 64 longitudinal plasma samples (2ml) from 23 subjects with advanced SCLC using the cobas® cfDNA Sample Preparation Kit. The AVENIO ctDNA Surveillance kit (RUO, Roche, Pleasanton, CA, USA) with 197 genes detects SNVs, fusions, CNVs and InDels, and was used for sequencing the cfDNAs. Library preparation with 10-50ng cfDNA yielded a mean pre-capture library yield of 1,728ng. Mean % reads on-target was 65% with a mean deduped coverage of 3,397 fold. CT scans were reviewed to assess disease burden.
Result:
47 longitudinal plasma samples from 8 subjects were successfully analyzed without access to matched tumor tissue. Sixteen subjects with only one baseline plasma sample were excluded from further analysis. Subjects had 3-10 longitudinal plasma samples. Somatic variants were detected with allele frequency (AF) of >0.5% to 30% and 60-90% if they were present in cfDNA from at least three different time points. Germline variants were identified and removed if AFs were 40-60%, and >90%. All variants with frequencies >1% in ExAC were removed. Somatic variants were identified in TP53 (5), APC (2), NPAP1 (2), MKRN3 (2), BRAF, NFE2L2, CDKN2A, TIAM1, LRRTM1, NYP2, FAM135B, FAM71B, PIK3CG, KEAP1, DCAF12L1, PCDH15, EGFLAM. Tracking somatic variants in the longitudinal plasma samples allowed monitoring of treatment response at the molecular level for 6 of 8 subjects. In one subject with 10 longitudinal plasma samples mutations in five different genes were tracked at 1-3% AF before rising to 5- 20% at month 8 and 12-55% at month 9. Molecular progression was detected 1 month earlier than clinical progression by CT. Another subject had a TP53 splice mutation over 10 time points and through 3 lines of treatment and AF correlated with clinical response as measured by imaging.
Conclusion:
Subjects with advanced SCLC and mixed SCLC/NSCLC can be monitored at the mutation level using molecular barcoded duplex sequencing in longitudinal plasma samples. 2ml of plasma yielded sufficient cfDNA for testing with the Surveillance kit. Somatic mutation monitoring is possible without matching tumor tissue samples where longitudinal mutation profiles correlate with clinical response by CT imaging.
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P3.02 - Biology/Pathology (ID 620)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Biology/Pathology
- Presentations: 1
- Moderators:
- Coordinates: 10/18/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P3.02-032 - Spatial Heterogeneity of EGFR and KRAS Variant Allele Frequencies Correlates with Histological Patterns of Lung Adenocarcinomas (ID 8401)
09:30 - 16:00 | Author(s): A. Warth
- Abstract
Background:
Analysis of spatially distinct regions revealed a considerable histological and molecular heterogeneity of lung adenocarcinomas (ADCs). The predominant histological growth pattern and driver gene alterations (e.g. in EGFR and KRAS) have been shown to be of high prognostic and therapeutic relevance. This project aimed to examine the spatial distributions of EGFR and KRAS mutation frequencies in the various histological growth patterns of ADCs.
Method:
Central tumor sections from 19 ADCs were subdivided into 467 tumor segments of 5x5 mm. The segments were evaluated separately in order to enable a systematic analysis of histological and molecular markers within and between patients. We determined the predominant histological growth patterns and the variant allele frequencies (VAFs) of EGFR and KRAS in each segment by digital PCR. We further quantified the absolute cell counts and proportions of tumor and non-neoplastic cells in all segments in order to examine the cellular fractions and allow a precise normalization of VAFs.
Result:
Histopathological classification revealed morphological intratumor heterogeneity with more than one histological growth pattern in 16 of the 19 cases. The 467 malignant segments exhibited a mean tumor cell fraction of 28% with an extensive variability within and between the individual cases. The predominant solid pattern revealed the significantly lowest fraction of tumor cells. Furthermore, EGFR and KRAS VAFs were measured by digital PCR and normalized to the cellular fractions of the respective segment. While driver gene mutations were detected in > 99% of malignant segments, we found a heterogeneous spatial distribution of normalized VAFs: Some cases showed ubiquitously low or high mutant allele frequencies, others revealed regions with focally elevated frequencies and driver gene amplifications. In addition, we found a significant correlation between mutated allele frequencies and histological patterns. Micropapillary and solid patterns harboured higher mutant allele frequencies compared to lepidic and papillary histologies. Correlation analysis did not show an association between the tumor size and the normalized VAF or driver gene amplification.
Conclusion:
Our findings indicate that driver gene mutations are present with high levels of inter- and intratumor heterogeneity throughout all ADC samples tested. Allele frequencies correlated with histological growth patterns, but not with tumor size.
