Abstract 4634
Background
Several studies in BRAFV600E colorectal cancers (CRC) have failed to replicate the efficacy of BRAF inhibitors in treatment of BRAFV600E melanomas (Mel), suggesting the existence of different resistance mechanisms as well as molecular and biological differences between the 2 tumor types. Herein, we examine these differences.
Methods
Tumor samples submitted to Caris Life Sciences for NGS DNA sequencing (592 gene panel) and RNA sequencing (54 gene panel) between the years 2015 and 2019 were retrospectively studied. Only microsatellite stable (MSS) tumors with either BRAFV600E mutation or wild type (WT) BRAF status were included in this initial analysis. Chi-square tests determined differences.
Results
A total of 8409 tumor samples were analyzed: CRC (N = 7453: BRAFV600E=373; WT = 7080) and Mel samples (N = 956: BRAFV600E=274; WT = 682). The most frequently mutated genes in BRAFV600E CRC were TP53 (81%), APC (26%), and SMAD4 (22.4%), compared to CDKN2A (22%), PTEN (13%), and TP53 (13%) in BRAFV600E Mel. Molecular alterations that are significantly more frequent in BRAFV600E CRC vs BRAFV600E Mel but not significantly different between BRAF WT CRC vs BRAF WT Mel included RSPO3 fusions (CRC=22.6% vs Mel=0%, P = 0.027); RNF43 deletions (2.0% vs 0%, p = 0.019); and mutations in RNF43 (18.8% vs 0%, P < 0.001), AKT1 (3.5% vs 0.4%, p = 0.008), and MTOR (2.4% vs 0.4%, p = 0.037). RSPO3 fusions and RNF43 mutations/deletions are mutually exclusive. Significantly more frequent alterations in BRAFV600E Mel compared to BRAFV600E CRC (but not in either WT) included deletions in PTEN (7% vs 3%, p = 0.005) and mutations in PTEN (12.9% vs 5.4%), MITF (1.9% vs 0%), STK11 (1.5% vs 0%), ERCC2 (1.1% vs 0%), FANCC (1.2% vs 0%), and CDK4 (1.5% vs 0%) (p < 0.05 for all).
Conclusions
BRAFV600E CRC carry molecular alterations that are distinct from BRAFV600E Mel. RSPO3 fusions and RNF43 alterations are prevalent in BRAFV600E CRC tumors in a mutually exclusive manner, suggesting that Wnt pathway activation via genetic alterations in upstream Wnt pathway regulators may play an important role in BRAFV600E CRC tumorigenesis and resistance to BRAF inhibitors. Drug combinations that target both the MAPK and Wnt pathways may warrant further investigation.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
M.E. Salem: Travel / Accommodation / Expenses: Caris Life Sciences. J. Xiu: Full / Part-time employment: Caris Life Sciences. A. Grothey: Travel / Accommodation / Expenses: Caris Life Sciences. R.M. Goldberg: Research grant / Funding (self), Travel / Accommodation / Expenses: Caris Life Sciences. Z. Gatalica: Full / Part-time employment: Caris Life Sciences. R. Feldman: Full / Part-time employment: Caris Life Sciences. M. Saul: Full / Part-time employment: Caris Life Sciences. W..M. Korn: Full / Part-time employment: Caris Life Sciences. A.F. Shields: Research grant / Funding (institution), Travel / Accommodation / Expenses: Caris Life Sciences. J.L. Marshall: Advisory / Consultancy: Caris Life Sciences. H.J. Lenz: Travel / Accommodation / Expenses: Caris Life Sciences. All other authors have declared no conflicts of interest.
Resources from the same session
3524 - Cabazitaxel For Octogenarian Patients With Metastatic Castration-Resistant Prostate Cancer (MCRPC).
Presenter: Paolo Tralongo
Session: Poster Display session 3
Resources:
Abstract
5637 - External Validation of a Prognostic Score in First-Line Metastastic Castration-Resistant Prostate Cancer (mCRPC)
Presenter: David Lorente
Session: Poster Display session 3
Resources:
Abstract
3228 - Treatment outcomes of 3rd treatment in a real-world metastatic castration resistant prostate cancer (mCRPC) population: results from the Dutch CAPRI-registry
Presenter: Jessica Notohardjo
Session: Poster Display session 3
Resources:
Abstract
4695 - Pelvic lymph node dissection and its extent on survival benefit in prostate cancer patients with a risk of lymph node invasion>5%: a propensity score matching analysis from SEER database
Presenter: Junru Chen
Session: Poster Display session 3
Resources:
Abstract
4438 - Multi-institutional evaluation of therapeutic management for oligometastatic cancer prostate recurrence with choline-PET/CT
Presenter: Morgane Guibert-broudic
Session: Poster Display session 3
Resources:
Abstract
4574 - Safety of new androgen receptor inhibitors (ARi) in patients with nonmetastatic castration-resistant prostate cancer (nmCRPC): a network meta-analysis of randomized controlled trials (RCT)
Presenter: Amelia Altavilla
Session: Poster Display session 3
Resources:
Abstract
3816 - Real-world use of radium-223 for treatment of metastatic castration resistant-prostate cancer (mCRPC): results from the Dutch CAPRI registry
Presenter: Malou Kuppen
Session: Poster Display session 3
Resources:
Abstract
5180 - A phase 2a study of radium-223 dichloride (Ra-223) alone or in combination with abiraterone acetate or enzalutamide in metastatic castration-resistant prostate cancer (mCRPC)
Presenter: Daniel Petrylak
Session: Poster Display session 3
Resources:
Abstract
1067 - Adding ADT to PSMA-PET/CT-guided SBRT for oligometastatic prostate cancer improves distant progression-free survival
Presenter: Carole Mercier
Session: Poster Display session 3
Resources:
Abstract
5529 - Safety and efficacy of Ac-225-PSMA-617 in metastatic castration resistant prostate cancer (mCRPC) after failure of Lu-177-PSMA
Presenter: Robert Tauber
Session: Poster Display session 3
Resources:
Abstract