Molecular and clinical characterization of BRAF mutations in pancreatic ductal adenocarcinomas (PDACs).

Authors

null

Michelle Guan

Cedars-Sinai Medical Center, Los Angeles, CA

Michelle Guan , R Joseph Bender , Michael J. Pishvaian , David Charles Halverson , Richard Tuli , Samuel Jacob Klempner , Zev A. Wainberg , Aatur D. Singhi , Emanuel Petricoin III, Andrew Eugene Hendifar

Organizations

Cedars-Sinai Medical Center, Los Angeles, CA, Perthera, Inc., Mclean, VA, Georgetown University Lombardi Comprehensive Cancer Center, Washington, DC, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA, The Angeles Clinic and Research Institute, Los Angeles, CA, UCLA David Geffen School of Medicine, Los Angeles, CA, University of Pittsburgh Medical Center, Pittsburgh, PA, George Mason University, Manassas, VA

Research Funding

Other

Background: The activation of the RAS/RAF/MEK/ERK pathway is critical for the proliferation, survival, and tumorigenesis of PDACs. Oncogenic mutations in KRAS (90%) or BRAF (3%) are recurrent genomic alterations, but their co-occurrence is not well described. We reviewed BRAF alterations and clinical outcomes in consecutive PDAC patients (pts). Methods: Perthera, Inc. deploys an IRB-approved registry that was utilized in partnership with PanCAN’s “Know Your Tumor” program. Perthera uses CAP/CLIA accredited multi-Omic profiling, including next generation DNA sequencing (NGS, Foundation Medicine) and proteomics/immunohistochemistry (Neogenomics Inc. and Caris Life Sciences, Inc.). We used a Fisher's exact test with multiple testing correction to compare frequencies of mutations and protein over-/under-expression between BRAF-mutated (n = 21) and BRAF wild type pts (n = 745). Results: Of 766 pancreatic cancer pts, 21 pts were identified with BRAF mutations. 18 pts were diagnosed with PDAC, 1 pancreatoblastoma, 1 pancreatic acinar cell carcinoma, and 1 mixed acinar neuroendocrine carcinoma. Amongst the 18 PDAC pts with BRAF mutations, nine variations were found: V600E (5/18), BRAF fusion (4/18), N486_P490del (3/18), T310I (1/18), K601N (1/18), G596R (1/18), exon 2-10 deletions & S467L (1/18), equivocal amplification of BRAF (1/18), and a BRAF inframe deletion (1/18). KRAS was mutated in 6% of BRAF mutated PDACs, compared to 94% in BRAF wild type PDACs (p < 0.001). Amongst KRAS wild type PDACs, 53% of CDKN2A mutated pts had BRAF mutations vs. only 15% of CDKN2A wild type cases (p < 0.05). Two BRAF mutated pts from the database were given BRAF inhibitors. A sustained response to the combination dabrafenib and trametinib was observed in a BRAF V600E mutated PDAC pt, while no response was seen in a pt with concurrent KRAS G12A & BRAF K601N mutations who received trametinib. Conclusions: BRAF mutations are significantly and inversely correlated with KRAS alterations. The most common BRAF alteration, V600E mutation, was found to be mutually exclusive with the KRAS mutation. Clinical trials targeting BRAF alterations in KRAS wild type pancreatic cancer appears warranted.

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Abstract Details

Meeting

2018 Gastrointestinal Cancers Symposium

Session Type

Poster Session

Session Title

Poster Session B: Cancers of the Pancreas, Small Bowel, and Hepatobiliary Tract

Track

Cancers of the Pancreas, Small Bowel, and Hepatobiliary Tract

Sub Track

Prevention, Diagnosis, and Screening

Citation

J Clin Oncol 36, 2018 (suppl 4S; abstr 214)

DOI

10.1200/JCO.2018.36.4_suppl.214

Abstract #

214

Poster Bd #

A11

Abstract Disclosures

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