PF490 PRESENCE OF BRAFV600E MUTATION IN CHILDHOOD LCH CORRELATES WITH MULTISYSTEM DISEASE AND A POOR SURVIVAL

Abstract

Background:Reports in LCH have observed BRAFV600E mutation in 35–40% cases of LCH and have demonstrated its relation with poor outcome.Aims:The aim of the study was to detect the presence of BRAFV600E mutation in children with LCH and to correlate with survival.Methods:Retrospective, Single centre, Case‐control study. Biopsy or FNAC diagnosed and immunochemistry confirmed (CD1a and S‐100 +ve) cases of LCH over 5‐years were retrieved. RQ‐PCR as well as Sanger sequencing for BRAFV600E mutation was performed. Ten cases of non‐LCH histiocytic proliferations were run as controls.Results:Thirty‐five LCH cases enrolled. 4 cases were excluded due to poor quality of DNA and 2 due to lack of follow up. The mean age was 2.5 years (0.4–11 yrs). Unisystem involvement was noted in 13/28 (46.5%) cases and multisystem in 15/28 (53.5%), including 13 with risk organ involvement. Of the 28 samples run on RQ‐PCR, BRAFV600E mutation was identified in 6/28 (21%) cases. The copy number threshold (Ct) values of positive cases ranged from 25.8–34.1 with a mean of 30.2. Sanger sequencing in all 28 samples confirmed positivity in 5/6 cases. One case did not yield reportable reads. There were no false negatives noted. Ten events (36%) were recorded, including 4 (14%) disease relapse, 3 (11%) deaths and 3 (11%) with progressive disease. All patients positive for mutation had multisystem involvement (100%) (p 0.0348), an EFS at 3‐years of 17% vs. 72% in negative group (p 0.0110) and an OS of 32.5% vs. 82% (p 0.0330). The lower BRAFV600E positivity than west could be likely due to archival samples and degraded DNA.Summary/Conclusion:The frequency for BRAFV600E positivity was low (21%), however, all positive cases had multisystem involvement and a poor 3‐year survival, confirming BRAFV600E to be a poor prognostic marker.image