Cytogenetic classification in Korean multiple myeloma patients: prognostic significance of hyperdiploidy with 47-50 chromosomes and the number of structural abnormalities.

Chromosomal abnormalities are important prognostic factors for patients diagnosed with multiple myeloma (MM). We retrospectively reviewed the clinical and laboratory data of 525 MM patients to assess the abnormalities frequently found by conventional cytogenetic analysis and to determine their relationship to prognosis and clinical parameters. Samples from 222 (42.3%) patients had abnormal karyotypes. Hyperdiploidy-1 (>50 chromosomes), hyperdiploidy-2 (47-50 chromosomes), pseudodiploidy (46 with abnormalities), and hypodiploidy (<46 chromosomes) were found in 55, 44, 42, and 81 patients, respectively. The median overall survival (OS) was significantly shorter in patients with hyperdiploidy-2 (20.9 months), pseudodiploidy (19.9 months), and hypodiploidy (18.3 months) compared with patients with normal karyotype (66 months) and hyperdiploidy-1 (55.4 months) (P < 0.001). Among patients with chromosomal abnormalities, those with 1q amplification had a shorter median OS (17 vs. 25.1 months, P = 0.018). Patients with a chromosome 13 deletion in the pseudodiploidy group also had a shorter OS. A karyotype with more than six structural abnormalities was found to have the most significant independent prognostic value by multivariate analysis. These data show that hyperdiploidy with 47-50 chromosomes should be recategorized as an unfavorable risk group, and the number of structural abnormalities needs to be considered as an important factor for prognosis. In conclusion, our findings imply that subclassification of chromosomal abnormalities by conventional cytogenetics could be applied to the prognostic assessment of MM.