Ploidy status rarely changes in myeloma patients at disease progression.

Hyperdiploid and non-hyperdiploid multiple myeloma represents distinct biological entities characterized by different patterns of genetic changes. We sought to determine whether ploidy category (non-hyperdiploid versus hyperdiploid) remains stable over time from diagnosis to progression. Of the 43 patients studied (39 by flow cytometry DNA index and 4 by a FISH-based index), only five (12%) altered their ploidy status at progression. In three of these patients, the change may possibly be attributable to technical artifacts because of the low absolute change in DNA index. For those who retain their ploidy subtypes, the DNA index change minimally (3.75+/-4.87%). It would appear that the initiating genetic events underlying hyperdiploid and non-hyperdiploid MM that marks them out as distinct entities continue to dominate and persist during disease evolution and progression.