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P. Chesnut
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MINI 13 - Genetic Alterations and Testing (ID 120)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:Y. Koh, R.K. Thomas
- Coordinates: 9/08/2015, 10:45 - 12:15, 205+207
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MINI13.01 - Clinicopathological Profiles of ROS1 Positive Patients Screened by FISH (ID 1450)
10:45 - 10:50 | Author(s): P. Chesnut
- Abstract
- Presentation
Background:
ROS1 fusion variants represent an important subset of oncogenic driver mutations in approximately 0.7 – 3.4% of non-small cell lung cancers. Since the frequency of ROS1 positive lung cancer patients is relatively low, it is unclear whether there are significant clinicopathologic associations for positive cases. Thus far, ROS1 positive patients tend to be younger and never-smokers with tumors displaying adenocarcinoma histology. This study describes a further cohort of ROS1 positive lung cancer patients in an effort to identify clinicopathologic associations.
Methods:
The data represent a retrospective analysis of the clinicopathological profiles of primary and metastatic lung cancer patients tested for ROS1 gene rearrangements by break-apart (BA) FISH at the University of Colorado School of Medicine.
Results:
The cohort consisted of 452 patients enriched for triple-negative (EGFR-, KRAS- and ALK-) non-squamous cell carcinomas screened for ROS1 rearrangements using the BA FISH assay. Nineteen cases (4.2%) were identified as positive for rearrangement, the majority (68%) of which were female, with a mean cohort age of 54.9 years (range 30-79); as compared to negative cases which included 56% female patients (P= 0.1083), and had a mean cohort age of 62.9 (range 21-90) (P= 0.0058). Seventeen out of the 19 ROS1 positive tumors were classified as adenocarcinomas, one was diagnosed as adenosquamous carcinoma, and the histology on one specimen was not otherwise specified (NOS). Among 12 individuals with information on pathologic stage at diagnosis, the majority (75%) were stage IV. The prevalent FISH pattern for rearrangement was a split 5’ and 3’ signal (68%) with the remaining specimens showing primarily single 3’ signals (21%) or a mix of split and single 3’ signals (11%).
Conclusion:
The ROS1 positive tumors in this cohort were primarily classified as adenocarcinomas, diagnosed at an advanced stage, in patients significantly younger and more likely to be women, although the sample set was biased for non-squamous lesions thereby limiting the application of this information to squamous cell lung carcinoma. The higher prevalence of ROS1 positive cases in this cohort compared to unselected cohorts is best explained by the inclusion of specimens with known negative status for EGFR and KRAS mutations and ALK fusions. As such, these data are in agreement with previous descriptions of ROS1 positive cohorts. Screening for ROS1 rearrangements in lung cancer patients displaying adenocarcinoma histology and negative for EGFR, KRAS and ALK activating events should identify a higher frequency of ROS1 rearranged tumors compared to unselected approaches and facilitate this subset of patients to be treated with targeted ROS1 inhibitors.
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ORAL 37 - Novel Targets (ID 146)
- Event: WCLC 2015
- Type: Oral Session
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:S.S. Ramalingam, E. Thunnissen
- Coordinates: 9/09/2015, 16:45 - 18:15, Mile High Ballroom 4a-4f
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ORAL37.06 - Defining MET Copy Number Driven Lung Adenocarcinoma Molecularly and Clinically (ID 2379)
17:39 - 17:50 | Author(s): P. Chesnut
- Abstract
- Presentation
Background:
Increases in MET copy number define an oncogenic driver state sensitive to MET inhibition (Camidge et al, ASCO 2014). However, the level at which the genomic gain is relevant remains uncertain. When testing is performed by fluorescence in situ hybridization (FISH), variable cut-points in both mean MET/cell and MET/CEP7 ratio have been used. Partially overlapping datasets from the Lung Cancer Mutation Consortium (LCMC1) and Colorado Molecular Correlates (CMOCO) Laboratory were explored for a distinct MET-copy number driven lung adenocarcinoma subtype.
Methods:
MET was assessed by FISH. Data from non-adenocarcinomas and EGFR mutant patients with acquired resistance to an EGFR inhibitor were excluded. Positivity criteria were mean MET/cell ≥5 (low ≥5-<6, intermediate ≥6-<7, high ≥7) or MET/CEP7 ≥1.8 (low ≥1.8-≤2.2, intermediate >2.2-< 5, high ≥5). MET metrics were compared by race, sex, smoking status, stage at diagnosis, number of metastatic disease sites, site of metastases, presence of other known drivers (EGFR, KRAS, ALK, ERBB2, BRAF, NRAS, ROS1 and RET), response to first line chemotherapy and overall survival using Fisher’s exact tests, chi-square tests, Spearman correlations and log-rank tests, as appropriate. Statistical significance was set at the 0.05 level without adjustment for multiple comparisons.
Results:
1164 unique adenocarcinomas were identified (60% female, 85% Caucasian, 66% ex/current smokers). MET/CEP 7 data was available on 1164 and mean MET/cell on 700. 52/1164 (4.5%) had MET/CEP7 ≥1.8 (48% female, 83% Caucasian, 69% smokers). 50/52 (98%) had ≥1 other oncogenic driver tested (25/50 (50%) positive). 113/700 (16%) had mean MET/cell ≥ 5 (57% female, 82% Caucasian, 58% smokers). 109/113 (96%) had ≥ 1 other oncogenic driver tested (73/109 (67%) positive). Among patients with ≥1 additional driver oncogene tested, alternate drivers in low, indeterminate and high categories of mean MET/cell were 44/60 (67%), 17/24 (70%) and 12/28 (43%) respectively and for MET/CEP7: 16/29 (55%), 9/18 (50%) and 0/4 (0%) respectively. MET positive with additional drivers were excluded from further analyses. Men exceeded women in MET/CEP7 (men 4% vs women 1.6%, p = 0.019) and mean MET/cell positive cases (men 9.6% vs women 5.4%, p = 0.058). 6.4% of adrenal metastasis cases were MET/CEP7 positive vs 2% all other sites, p=0.031. Mean MET/cell: 12% adrenal vs 5% other sites, p=0.082. MET/CEP7 or mean MET/cell positive and negative groups did not differ by other variables (p > 0.05).
Conclusion:
The proportion of ‘MET positive’ adenocarcinomas varies by definition and positivity cut-point. Mean MET/cell ≥5 defines nearly 4x more positives than MET/CEP7 ≥1.8 and no mean MET/cell positive category was free from overlap with other drivers. As only high MET/CEP7 had no overlap with other drivers, MET/CEP7 ≥ 5 is the clearest candidate for a pure MET-copy number driven state, however cases free from other drivers do exist at lower MET positivity levels. MET/CEP7 positive cases free from other known drivers are more likely to be male, but unlike other known oncogenic states, race and smoking status are not significant in determining positivity. MET positivity may have a specific biological phenotype, being more likely to present with adrenal metastases.
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