Amplification of 1q21 and Other Abnormalities in Multiple Myeloma Patients from a Tertiary Hospital in Singapore

Much effort has been made to stratify multiple myeloma patients for targeted therapy. However, responses have been varied and improved patient stratifications are needed. Forty-five diagnostic samples from multiple myeloma patients (median age 65 years) were stratified cytogenetically as 15 having non-hyperdiploidy, 20 having hyperdiploidy and 10 having a normal karyotype. Fluorescence in situ hybridization (FISH) assays with FGFR3/IGH, CCND1/IGH, IGH/MAF, RB1 and TP53 probes on bone marrow samples showed that IGH rearrangements were the most common abnormality in the non-hyperdiploid group but these were also found among hyperdiploid patients and patients with normal cytogenetics. Of these, FGFR3/IGH rearrangements were most frequent. Deletion of RB1/monosomy 13 was the most common genetic abnormality across the three groups and was significantly higher among non-hyperdiploid compared to hyperdiploid patients. On the other hand, the study recorded a low incidence of TP53 deletion/monosomy 17. The FGFR3/IGH fusion was frequently seen with RB1 deletion/monosomy 13. FISH with 1p36/1q21 and 6q21/15q22 probes showed that amplification of 15q22 was seen in all of the hyperdiploid patients while amplification of 1q21, Amp(1q21), characterized non-hyperdiploid patients. In contrast, deletions of 1p36 and 6q21 were very rare events. Amp(1q21), FGFR3/IGH fusion, RB1 deletion/monosomy 13, and even TP53 deletion/monosomy 17 were seen in some hyperdiploid patients, suggesting that they have a less than favorable prognosis and require closer monitoring.