Blood Cell Count Monitoring May Predict Progression of ET, PV to Secondary Myelofibrosis

Progressive anemia and thrombocytopenia in patients with polycythemia vera (PV) or essential thrombocythemia (ET) may help identify those patients whose disease is more likely to progress to secondary myelofibrosis (SMF), according to results of a retrospective study published in the American Journal of Hematology.

Chronic myeloproliferative neoplasms include primary myelofibrosis, which is characterized by replacement of normal bone marrow tissue with a buildup of scar tissue (fibrosis), as well as PV and ET.  Although both PV and ET can progress to SMF, the clinical characteristics and outcomes of patients with SMF are limited.

This study involved patients included in the Myelofibrosis Secondary to PV and ET Collaboration (MYSEC) cohort with SMF diagnosed between 1981 and 2017. At diagnosis of SMF, patients were classified as having either grade 2 bone marrow fibrosis (BMF2), defined as “a diffuse increase in reticulin with extensive intersections, and occasional bundles of collagen and/or osteosclerosis,” or grade 3 bone marrow fibrosis (BMF3) characterized by “coarse bundles of collagen, often associated with osteosclerosis.”

Of the 675 patients included in the study, 65.6% and 34.4% were classified with BMF2- and BMF3-related disease, respectively. Baseline characteristics, such as patient age, gender, disease-related symptoms, liver or spleen size, type of abnormal karyotype, percentage of marrow blasts, or the duration of time between the initial diagnosis of PV or ET and the subsequent diagnosis of SMF, were not correlated with grade of BMF.

However, compared with patients with disease classified as BMF3, those with disease classified as BMF2 were significantly more likely to have lower-risk disease according to the prognostic model from the MYSEC (MYSEC-PM; P <.0001). Conversely, a classification of BMF3 was correlated with an increased likelihood of a higher MYSEC-PM category.

Furthermore, on multivariate analyses, a prior diagnosis of ET (P =.006), lower platelet count (P =.0006), and lower hemoglobin level (P =.0002) were significantly associated with a BMF3 grade.

At a median follow-up of 11.0 years from progression of ET or PV to SMF, as well as 3.1 years following progression to SMF, treatment with cytoreductive therapy (P <.0001) and allogeneic stem cell transplantation (P <.0001) were more common in patients with BMF2- and BMF3-related disease, respectively, compared with those with disease characterized by the other BMF grade.

Notably, the median survival was lower for patients with disease graded as BMF3 (7.4 years) compared with those with BMF2-related disease (8.2 years; P =.011), However, on multivariate analyses that included adjustment for MYSEC-PM risk categories, BMF grade in patients with SMF was not significantly associated with patient survival, suggesting that BMF grade is not an independent prognostic factor for patients with SMF.

“The development of progressive anemia and thrombocytopenia during the course of PV and ET, besides suggesting an evolution into SMF, might [also be] a surrogate of BMF3 grade, eventually resulting in a worse outcome,” the study authors concluded, leading them to suggest that early detection of secondary myelofibrosis may be facilitated by regular blood cell count monitoring.

Reference

Mora B, Guglielmelli P, Rumi E, et al. Impact of bone marrow fibrosis grade in post-polycythemia vera and post-essential thrombocythemia myelofibrosis. A study of the MYSEC group. Am J Hematol. doi: 10.1002/ajh.25644