CLL-656 Multiplex ligation-dependent probe amplification (MLPA): Utility as a first line screening tool for detection of clinically relevant genomic aberrations in CLL

Abstract

Objective: In Chronic lymphocytic leukemia (CLL), genomic aberrations play an important role in prognostication and treatment strategies. Current techniques based on karyotyping or FISH for detection of chromosomal abnormalities are laborious, timeconsuming and expensive. The present study was thus carried out to assess the sensitivity of Multiplex ligation-dependent probe amplification (MLPA) and to detect the frequency and association of genomic aberrations with clinical outcome in Indian CLL patients. Patients: CLL patients were investigated for aberrations at 13q14, 11q22, 17p13 and trisomy12 by iFISH (n=272; Metasystems, Germany) and MLPA ((n=345; MRC Holland, The Netherlands). Data for both iFISH and MLPA was available for 114 cases. The survival status was analyzed in 503 cases (OS: n=503, TTFT: n=341 (Rai stage 0-2) categorized on the basis of FISH and/or MLPA. The statistical analysis was carried out using Sigma Plot software (version 15.0). Results: Chromosomal aberrations were detected in a total of 69% cases with del(13q) in 32%, del(11q) in 3.7%, trisomy 12q in 12%, and del(17p) in 8% cases as sole abnormality. Concomitant presence of two abnormalities in same patient was detected in 11.5% cases. In group with coexistence of ≥2 aberrations, del(13q) was a major clone (n=45) indicating it as a primary event followed by del(11q) (n=39) and del(17p) (n=37). Comparison of MLPA results with FISH (n=114), resulted in a concordance of 89% cases; discordance was observed for 2, 2, 4 and 5 cases for trisomy 12, del(11q), del (17p) and del(13q) respectively. Del(17p) discordant cases suggest inability of MLPA in detection of ≤15% positive fraction. OS(n=503) and TTFT(n=341) were significantly lower in high risk [(del(17p)] and mid risk [(del(11q) and del(12q)] cases as compared to low risk cases [del(13q) and no abnormality)]. Discussion: A significant proportion (69%) of Indian CLL population harbor one or the other genomic aberrations. Although the frequencies differ slightly from previous reports, the distribution pattern is similar. High concordance between MLPA and FISH indicate that MLPA represents a high-throughput, cost-effective and comprehensible technique that can be used as a first-line screening for categorization of CLL patients into prognostically different genetic subtypes.