Impact of Megakaryocyte Morphology on Prognosis of Persons with Myelodysplastic Syndromes

Purpose: To describe the morphological evolution of megakaryocytic dysplasia by developing a systematic classification and evaluate the impact of our classification of dys-megakaryopoiesis on prognosis of persons with MDS.

Patients and methods: 423 consecutive patients who had received no prior therapy with MDS diagnosed from January 2000 to April 2014 were enrolled. Follow-up data were available for 371 subjects (88%).  Date of last follow-up was December 15, 2014 or date of last contact.  Median follow-up was 22 months (range, 1¨C180 months).  Subjects with lower-risk MDS fall into Revised International Prognostic scoring systems (IPSS-R) categories of very low-, low-, and intermediate-risk groups and those with higher-risk category into the high- and very high-risk groups.  We performed CD41 immune staining and proposed a systematic classification of dys-megakaryopoiesis on bone marrow films: (1) micro-megakaryocytes (<12 µm); (2) micro-megakaryocytes (12-40 µm) with 1 nucleus; (3) micro-megakaryocytes (12-40 µm) with 2 nuclei; (4) micro-megakaryocytes (12-40 um) with multiple nuclei; (5) dys-morphic megakaryocytes (¡Ý40µm) with 1 nucleus; (6) dys-morphic megakaryocytes (¡Ý40 µm) with 2 nuclei; and (7) dys-morphic megakaryocytes (¡Ý40 µm) with multiple nuclei. To evaluate the prognostic impact of dys-megakaryopoiesis based on cell size we divided the seven subtypes into dys-megakaryopoiesis with and without micro-megakaryocytes.  Samples were also divided based on numbers of nuclei: (1) mono-nucleated dys-morphic megakaryocytes; (2) bi-nucleated dys-morphic megakaryocytes; and (3) multinucleated dys-morphic megakaryocytes.  The best discriminator cutoff point of each group was determined by the minimal P-value approach. The best discriminators were micro-megakaryocytes ¡Ý25%, dys-megakaryopoiesis except micro-megakaryocytes ¡Ý5%, mono-nucleated dys-megakaryopoiesis ¡Ý30% and bi-nucleated dys-megakaryopoiesis ¡Ý1%. In multi-nucleated megakaryopoiesis category, differences in survival at the optimal discriminator were not statistically significant (P=0.10).

Results:  Subjects in low- and high-risk cohorts were different with platelets (micro-megakaryocytes; P<0.001; dys-megakaryopoiesis except micro-megakaryocytes; P<0.001; mono-nucleated dys-megakaryopoiesis; P<0.001; bi-nucleated dys-megakaryopoiesis; P=0.028), bone marrow blasts (micro-megakaryocytes; P<0.001; dys-megakaryopoiesis except micro-megakaryocytes; P<0.001; mono-nucleated dys-megakaryopoiesis except micro-megakaryocytes; P<0.001; bi-nucleated dys-megakaryopoiesis;  P<0.001), WHO 2008 subtypes (dys-megakaryopoiesis; P=0.001; dys-megakaryopoiesis except micro-megakaryocytes; P<0.001; mono-nucleated dys-megakaryopoiesis P<0.001; bi-nucleated dys-megakaryopoiesis; P=0.014) and IPSS-R risk cohorts (micro-megakaryocytes; P<0.001; dys-megakaryopoiesis except micro-megakaryocytes; P<0.001; mono-nucleated dys-megakaryopoiesis; P<0.001; bi-nucleated dys-megakaryopoiesis; P=0.001). There was no significant difference in age, gender, hemoglobin concentration and blood neutrophils levels at diagnosis between low- and high-risk cohorts.  In addition, levels of micro-megakaryocytes and mono-nucleated megakaryocytes were significantly associated with IPSS-R cytogenetic category (P=0.002 and P=0.001).  A significant association with IPSS-R cytogenetic category was not found for subjects with dys-megakaryopoiesis except micro-megakaryocytes and bi-nucleated megakaryopoiesis (P=0.187 and P=0.654). In multivariate analyses, micro-megakaryocytes ¡Ý25% and mono-nucleated dys-morphic megakaryocytes ¡Ý30% were independent adverse prognostic factors (hazard ratio [HR]=1.56 [95% confidence interval [CI], 1.10, 2.20]; P=0.012 and 1.49 [1.05, 2.10]; P =0.024). These effects were greater than those for other boundaries except micro-megakaryocytes ¡Ý5% and bi-nucleated dys-morphic megakaryocytes ¡Ý1% (P=0.288 and P =0.133).

Conclusion: Our data suggest integration of micro-megakaryocytes and mono-nuclear dysmorphic megakaryocytes improves the predictive accuracy of the International Prognostic Scoring System-Revised (IPSS-R) scoring system.