ALK‐POSITIVE ANAPLASTIC LARGE CELL LYMPHOMA WITH VARIANT ALK‐FUSION PARTNER: A POPULATION‐BASED ANALYSES OF THE NHL‐BFM STUDY GROUP

Introduction: ALK-positive anaplastic large cell lymphomas (ALCL) are characterized by rearrangements involving the ALK gene on chromosome 2. The translocation t(2;5) (p23;q35) resulting in NPM1::ALK fusion is detected majority of ALCL. In 10%–20% ALCL, fused to various other partner genes. Compared NPM1::ALK, variant ALK-fusion proteins not expressed nucleus. frequency, distribution, and possible prognostic significance different genes have been analyzed population-based studies so far. We investigated all patients with ALCL exclusive cytoplasmic ALK-expression diagnosed a uniformly treated cohort NHL-BFM study group. Patients Methods: Between 2000 2017, 312 children adolescents were an Austria, Germany, Switzerland Czech Republic, included 99 trial or registry 2012. Reference pathology demonstrated ALK-staining 49 tumors. Formalin-fixed-paraffin-embedded frozen tumors 43/49 available for molecular analyses. Tumor-DNA was ALK-specific genomic capture high throughput sequencing assay. ALK-partner gene-specific RT-PCR assays used identify respective when tumor cDNA available. Results: 41 43 could be analyzed. 13 positive 28 had partner. TPM3::ALK (n = 9, 32%) ATIC::ALK 8, 29%) most common XPOI identified as novel patients´ characteristics expressing Variant::ALK comparable those fusions. five-year event-free survival (EFS) overall between 284 group Variant::ALK-expressing patients. However, none 9 relapsed, compared 5 relapses among 8 Conclusions: our ALCL-patients, less than 10% carried partners, 60% which TPM3 ATIC. staining patterns, positivity should excluded analysis. tendency relapse risk -positive ALCL-patients suggests that might confer aggressiveness drug resistance. research funded by: KNACK DEN KREBS Fördergemeinschaft Kinderkrebs-Zentrum Hamburg e.V. HAMBURGER STIFTUNG ZUR FÖRDERUNG DER KREBSBEKÄMPFUNG Keyword: diagnostic biomarkers No conflicts interests pertinent abstract.