Characterization of Philadelphia-negative myeloproliferative neoplasm patients with chromosome 12 abnormalities.

Abstract

7112 Background: Chromosome 12 (Chr 12) abnormalities have been reported as infrequent events in myelofibrosis (MF). Structural abnormalities at 12q13-15 and 12q24 have been reported in primary MF (PMF), and understanding genes at these loci, such as Hmga2 and Lnk may help in the treatment of Philadelphia-negative (Ph-neg) myeloproliferative neoplasms (MPN). We sought to better characterize Ph-neg MPN patients (pts) with Chr 12 aberrations. Methods: We queried a database of pts with any Ph-neg MPN who were referred to MD Anderson Cancer Center from 1985 to 2012. We identified pts with Chr 12 abnormalities and reviewed available clinical information. We compared characteristics and outcomes of pts who had Chr 12 abnormalities with pts who had no Chr 12 abnormality. Results: Of 1,787 pts with Ph-neg MPN, 36 pts (2%) were found to have a Chr 12 abnormality. Of these, 31 (86%) had MF, 1 (3%) had polycythemia vera (PV), 3 (8%) had hypereosinophilic syndrome, and 1 (3%) had unspecified MPN. Fourteen pts (39%) had successive biopsies demonstrating evolving cytogenetic abnormalities. The percentage of pts with MF was significantly higher among patients with Chr 12 abnormalities (86% vs. 54%, p-value < 0.001). A larger fraction of MF pts with Chr 12 abnormalities had post-PV MF (PPMF) (31% vs. 14%, p-value < 0.001). Age, JAK2 status, and incidence and rate of leukemic transformation from MF were not significantly different between the two groups. Of the 31 Chr 12 pts with MF, 12 (39%) had an abnormality at 12q13, 8 (26%) at 12q24, 6 (19%) had trisomy 12, 5 (16%) at 12q15, and 6 (19%) had another Chr 12 abnormality. Four pts (13%) had a structural abnormality at >1 site along the long arm of Chr 12. Survival of Chr 12 MF pts as a whole or subdivided by chromosomal abnormality was not significantly different than MF pts without Chr 12 abnormalities. Conclusions: Our investigation into pts with Ph-neg MPN harboring Chr 12 abnormalities is the largest of its kind, and shows 3% of MF pts possessed some type of Chr 12 abnormality, most frequently at 12q13. We found that Chr 12 Ph-neg MPN pts were more likely to have MF and PPMF. Further investigation into the functional significance of these structural abnormalities is warranted.