Comparative Analysis of Targeted RNA-Seq and Optical Genome Mapping for Detecting Gene Rearrangements in Acute Leukemia.

Background/

Objectives

Gene rearrangements involving oncogenes are major drivers in acute leukemia, influencing disease classification, prognosis, and therapeutic decision-making. Targeted RNA sequencing (RNA-Seq) panels capable of detecting intergenic and intragenic fusions across multiple genes are increasingly used in diagnostic settings. However, comparative evaluation with orthogonal technologies remains limited. Material and

Methods

We compared the performance of a 108-gene anchored multiplex PCR (AMP)-based RNA-Seq panel with that of Optical Genome Mapping (OGM) in 467 acute leukemia cases. The cohort included 360 cases of acute myeloid leukemia (AML), 89 B-lymphoblastic leukemia (B-ALL), 12 T-lymphoblastic leukemia (T-ALL), and 6 cases of mixed phenotype acute leukemia (MPAL).

Results

Results of both methods were concordant in 175 (74.7%) of 234 detected gene/rearrangement fusions. The concordance rate varied significantly across different leukemia types, ranging from 80.2% in B-ALL to 41.7% in T-ALL (p < 0.001) OGM uniquely detected 37 of 234 (15.8%) clinically relevant rearrangements, whereas RNA-Seq exclusively identified 22 of 234 (9.4%). Enhancer-hijacking lesions, including MECOM and BCL11B rearrangements, CDK6::MNX1, and IGH rearrangements, had a markedly lower concordance (20.6%) compared with all other aberrations (93.1%) (p < 0.001). Conversely, some gene fusions arising from intrachromosomal deletions were interpreted by OGM as simple deletions rather than rearrangements or fusions.

Conclusions

Targeted RNA-Seq was effective for detecting chimeric fusion transcripts and showed slightly better performance in identifying fusions resulting from deletions. However, OGM was effective for detecting enhancer-hijacking events that do not generate fusion transcripts. Both methods are complementary for the workup of acute leukemia cases.