Results of a cohort study of patients with myeloproliferative neoplasms (MPNs) show that spleen stiffness, as measured by elastography, may be correlated with the extent of bone marrow fibrosis, as well as clinical outcome. These findings were presented in the Journal of Clinical Medicine.
Myeloproliferative neoplasms, including essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF) are Philadelphia chromosome-negative disorders associated with clonal proliferation of myeloid cells in the bone marrow.
In particular, MF is associated with fibrosis or the buildup of scar tissue in the bone marrow. Furthermore, PV, primarily characterized by an overproduction of erythrocytes, and ET, associated with an overproduction of platelets, can progress to secondary MF.
Elastography is a medical imaging technique, primarily involving either ultrasound or magnetic resonance imaging, which offers an advantage over anatomical imaging methods in that it can detect the presence of stiffness in soft tissues, a manifestation of many disease conditions.
A major aim of this study was to measure the elastic properties of the spleen and liver in patients with ET, PV, and primary myelofibrosis (PMF) or secondary MF, as well as healthy volunteers, to determine whether stiffness in these organs was associated with the presence of marrow fibrosis, particularly in the setting of PMF.
This study included 70 consecutive patients with MPNs from the Hematology Unit at the University of Pisa, Italy, as well as 20 healthy nurse or physician volunteers. Of the patients with MPNs, PMF, secondary MF, PV, and ET was present in 41.3%, 21.3%, 24.3%, and 14.3%, respectively. Ultrasonographic and elastosonographic imaging evaluation of the liver and spleen of these patients, as well as other assessments, including bone marrow biopsy and blood cell counts, were performed.
Some of the key findings of this study included the following:
- Significantly higher levels of spleen stiffness were observed in patients with MF (P =.011) and PV (P =.035) compared with patients with ET
- Significantly higher levels of spleen stiffness were observed in patients with MF (P <.0001) and PV (P =.002) compared with healthy controls
- The presence of spleen stiffness correlated with more advanced bone marrow fibrosis (P <.0001)
- Progression-free survival (PFS) was significantly shorter in those with MF characterized by spleen stiffness above a particular cutoff value (hazard ratio [HR], 3.2; P =.012)
- In patients with MF, spleen stiffness was higher in those with more advanced fibrotic stages compared with patients with disease characterized as prefibrotic or early-fibrotic (P <.0001)
- Liver stiffness was significantly greater when patients with MF were compared with healthy controls (P =.001), but not when those with PV (P =.999) or ET (P =1.01) were compared with healthy controls
- No other variables (eg, age, body mass index, blood cell counts, mutational status) were associated with spleen stiffness level
Based on the findings, the study authors commented that assessment of spleen stiffness may serve as “a surrogate marker of [bone marrow fibrosis]” and “may drastically reduce the need for multiple invasive bone marrow biopsies.”
“We can conclude that organ stiffness adds valuable information to the clinical work-up of MPNs and could be employed to define patients at a higher risk of progression,” the study authors noted.
Benedetti E, Tavarozzi R, Morganti R, et al. Organ stiffness in the work-up of myelofibrosis and Philadelphia-negative chronic myeloproliferative neoplasms. J Clin Med. Published online July 8, 2020. doi:10.3390/jcm9072149