Annual Meeting Proceedings Part 1 - American Society of Clinical ...

10504 Oral Abstract Session, Mon, 8:00 AM-11:00 AM
Gene expression profiles of circulating tumor cells in metastatic breast
cancer patients. Presenting Author: Bianca Mostert, Department of Medical
Oncology, Erasmus University Medical Center, Daniel den Hoed Cancer
Center, Rotterdam, Netherlands
Background: A circulating tumor cell (CTC) count is an established
prognostic factor in metastatic breast cancer. Besides enumeration, CTC
characterization promises to further improve outcome prediction and
treatment guidance. We have previously shown the feasibility of measuring
the expression of a panel of 96 clinically relevant genes in CTCs in a
leukocyte background, and in the current study, we determined the
prognostic value of CTC gene expression profiling in metastatic breast
cancer. Methods: CTCs were isolated and enumerated from blood of 130
metastatic breast cancer patients prior to start of first-line systemic,
endocrine or chemotherapeutic, therapy. Of these, 103 were evaluable for
mRNA gene expression levels measured by quantitative RT-PCR in relation
to time to treatment switch (TTS). Separate prognostic CTC gene profiles
were generated by leave-one-out cross validation for all patients and for
patients with �5 CTCs per 7.5 mL blood, and cut-offs were chosen to
ensure optimal prediction of patients who might benefit from an early
therapy switch. Results: In the total cohort, of whom 56% received
chemotherapeutic and 44% endocrine therapy, baseline CTC count (�5
versus �5 CTCs/7.5 mL blood) predicted for TTS (Hazard Ratio (HR) 2.92
[95% Confidence Interval (CI) 1.71 – 4.95] P �0.0001). A 16-gene CTC
profile for all patients and a separate 9-gene CTC profile applicable for
patients with �5 CTCs were identified, which distinguished those patients
with TTS or death within 9 months from those with a more favorable
outcome. Test performance for both profiles was favorable; the 16-gene
profile had 90% sensitivity, 38% specificity, 50% positive predictive value
(PPV) and 85% negative predictive value (NPV), and the 9-gene profile
performed slightly better at 92% sensitivity, 52% specificity, 66% PPV and
87% NPV. In multivariate Cox regression analysis, the 16-gene profile was
the only factor independently associated with TTS (HR 3.15 [95%CI 1.35
– 7.33] P 0.008). Conclusions: Two CTC gene expression profiles were
discovered, which provide prognostic value in metastatic breast cancer
patients. This study further underscores the potential of molecular characterization
of CTCs.
10506 Oral Abstract Session, Mon, 8:00 AM-11:00 AM
DEAR1, a novel tumor suppressor, negative regulator of epithelialmesenchymal
transition, and prognostic factor in non-small cell lung
cancer. Presenting Author: Alfonso Quintas-Cardama, University of Texas
M. D. Anderson Cancer Center, Houston, TX
Background: DEAR1, also known as TRIM62, maps to 1p.35, a genomic
interval within which loss of heterozygosity occurs at high frequency in
carcinomas. DEAR1 has been proposed as a regulator of cell polarity in
vitro. Methods: We genetically engineered mice lacking DEAR1 alleles at
murine chromosome 4. To study the impact of DEAR1 loss in lung cancer,
DEAR1 deficient mice were crossed to mice carrying the latent mutant
K-ras G12D allele (K-ras LA1 ). Results: No survival difference was observed
between DEAR1 �/� and DEAR1 �/� mice (729 vs 699 days, p�0.98) but
they were markedly shorter than that of DEAR1 wild-type littermates (803
days, p�0.01). Over 90% of mice developed tumors, mainly adenocarcinomas,
including invasive and/or metastatic lung cancer in 23% of cases.
DEAR1-deficient K-ras LA1 mice had reduced life span compared with
DEAR1 �/� :K-ras �/LA1 littermates (184 vs 291 days, p�0.0001). The
survival of DEAR1 �/� :K-ras �/LA1 and DEAR1 �/� :K-ras �/LA1 mice were
similar (180 vs 153 days, p�0.38) and qPCR and IHC analyses suggested
loss of the wild-type DEAR1 allele. The survival of DEAR1-deficient
K-ras LA1
mice was also shorter than that of control p53�/� :K-ras�/LA1 mice
(240 days; p�0.01). The metastasis incompetent K-ras LA1 –positive LKR13
cell line after shRNA DEAR1 knock-down and cell lines derived from
DEAR1-deficient K-ras LA1 tumors recapitulated an invasive phenotype in
transwell migration and 3D culture assays and a metastatic phenotype on
SC or IV injection into immunocompetent wild-type littermates. The latter
was associated with epithelial-mesenchymal transition involving loss of
E-cadherin and DEAR1 expression and upregulation of vimentin, Twist,
and CD44. DEAR1 downregulation was very prevalent in a non-small cell
lung cancer (NSCLC) tissue array with 214 samples. Patients with early
stage NSCLC and loss of DEAR1 expression had a markedly shorter time to
relapse compared to those retaining DEAR1 expression (5.1 vs 2.87 years,
p�0.049) and worse 5-year relapse-free and overall survival rates.
Conclusions: DEAR1 is a novel tumor suppressor that negatively regulates
EMT and promotes lung cancer metastasis. DEAR1 loss is a poor prognostic
factor in NSCLC.
Tumor Biology
657s
10505 Oral Abstract Session, Mon, 8:00 AM-11:00 AM
Circulating DNA analysis and concordance with tumor section analysis in
the detection of KRAS and BRAF point mutations from metastatic
colorectal cancer. Presenting Author: Alain R. Thierry, Sysdiag UMR3145 -
CNRS, Montpellier, France
Background: We developed a specific method for circulating cell-free DNA
(ctDNA) enabling the detection of point mutations. CtDNA exists at high
level in patients with different types of cancer, and presents great potential
in regards, in particular, to its low invasiveness, rapid data turnaround and
cost effectiveness. We described here the first blinded prospective study on
the comparison of KRAS and BRAF mutational status data obtained from
the analysis of ctDNA and tumor section. Methods: Intplex is a refined
Q-PCR-based method specifically designed to analyze ctDNA. IntPlex
allows not only the detection of point mutations, but also the determination
of tumor-ctDNA concentration and fragmentation index simultaneously.
Intplex sensitivity is 0.01% (mutant to WT ratio) and is unprecedented
among Q-PCR-based methods. The study was conducted from a multicenter
cohort of 79 metastatic CRC patients not having received chemo- or
radio-therapy within the month prior to blood sample collection. Results:
Mutational status could not be determined in 9 samples with one of the two
methods. CtDNA analysis showed 100% specificity and 87% sensitivity for
KRAS detection (only three samples are misclassified) as compared to
tumor section analysis with 23/70 (33%) positive samples, the concordance
value being 96%. For BRAF mutation, the method exhibited a
specificity and a sensibility of 100% with 5/70 (7%) positive samples
(concordance of 100%). When combining KRAS and BRAF mutations,
100% specificity, 89% sensibility and 98% concordance were determined.
The three discordant samples may be explained by the malignant genotype
of primary tumor versus metastasis, or by the sensitivity of our detection
method. The mutation load (median, 12.4%) expressed as the proportion
of mutant allele in ctDNA is highly variable (0.037% to 69%) among
mutated samples showing a very high inter-individual heterogeneity.
Conclusions: Our blinded prospective multicenter study clearly showed for
the first time that tumor section analysis might be advantageously replaced
by ctDNA analysis, enlarging personalized medicine power for cancer
patients.
10507 Oral Abstract Session, Mon, 8:00 AM-11:00 AM
Rare epidermal growth factor receptor (EGFR) mutations in 10,117
patients with non-small cell lung cancer (NSCLC) evaluated by the French
ERMETIC IFCT network: Clinical, molecular, and survival data. Presenting
Author: Michele Beau-Faller, CHU Strasbourg, Strasbourg, France
Background: The EGFR exon 19 deletion and exon 21 L858R mutation are
associated with response to EGFR-TKI. However, the correlation with
response to EGFR-TKI remains unclear for rare exon 18 and 20 EGFR
mutations. We investigated the clinical features of NSCLC patients with
exon 18 and exon 20 EGFR mutations, analyzed response to EGFR-TKI and
patient’s survival. Methods: Between 2005 and 2011, all rare exon 18 and
20 EGFR mutations were collected from 10117 cases of NSCLC in 15 of
28 French NCI molecular genetic laboratories. Results: During the study
period, EGFR mutations were identified in 1048 (10.35%) out of the
10117 performed tests and 108 rare mutations (10.3%) were identified in
103 patients, including 25 never identified mutations. Among them, 48
mutations were localized at exon 18 and 60 at exon 20, with 3 out of the 4
identified T790M exon 20 mutations associated with L858R mutation.
Only 5 other rare mutations were associated with EGFR 19 or 21 mutations.
38 patients received EGFR-TKI (erlotinib, n�32; gefitinib, n�6). Among
the 36 evaluable patients, best response on TKI was progression in 18
patients (50%), stabilization in 11 (30.5%) and partial response in 7
(19.4%). Tumor control rate observed in exon 18 mutations was 61%
(8/13) and 50% (13/26) in exon 20 mutations. For the EGFR-TKI treated
patients, the median PFS was 6 months (2-53). Median OS was 15 months
(1-92), with no difference between the EGFR-TKI treated patients or not.
Conclusions: Prevalence of rare EGFR mutations was 1.06% of all tested
NSCLC and 10.35% of all EGFR mutations. Tumor control on TKI was
observed in half of the patients. Reports of NSCLC harboring rare mutations
are important to help the decision-making process in this subset of
patients.
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