N50: Age-Related Efficiency Of BRAF V600E Mutational Testing For The Exclusion Of Lynch Syndrome In MSI Colorectal Cancers

H. Bläker1, A. Ahadova2, J. Chang-Claude3, A. Arnold4, M. von Knebel Doeberitz2, H. Brenner3, M. Hoffmeister3, M. Kloor2

1 – Institute of Pathology, Charite Berlin. 2 – University Hospital Heidelberg. 3 – German Cancer Research Center. 4 – Charite Berlin.

 

Aim: For distinguishing Lynch syndrome patients from sporadic microsatellite unstable (MSI) patients, BRAF V600E testing has become one of the most important tools. In order to analyze the discriminatory power of BRAF mutations in different age groups, we looked at the age distribution of BRAF mutations in MSI colorectal cancers.

Method: Age at diagnosis and BRAF mutation status were retrieved for unselected series of MSI colorectal cancers (n=151) from publicly available databases (DFCI) and the DACHS cohort.

Results: The prevalence of BRAF V600E mutations in MSI cancers strongly increased with age at diagnosis, with 87% of BRAF mutations occurring after the age of 65. There was no patient with a BRAF mutation under the age of 50, and the youngest patient with a BRAF mutation was 52 year old.

Conclusion: Our data demonstrate that BRAF mutation testing to exclude Lynch syndrome has very limited value in patients younger than 50, as the likelihood of detecting BRAF mutation in a patient under 50 is close to 0%. Reports of BRAF mutations in 1-2% of cancers from proven Lynch syndrome mutation carriers call into question the role of BRAF mutations as a bona-fide exclusion marker for Lynch syndrome.

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