The impact of peripheral blood values and bone marrow findings on prognosis for patients with essential thrombocythemia and polycythemia vera

The Philadelphia chromosome-negative (Ph-) chronic myeloproliferative neoplasms include the three well-known clinical entities polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Over time, patients with ET and PV may develop myelofibrosis (MF), and all three entities carry a risk of transformation into acute myeloid leukemia (AML). In a population-based survey during 1983-1999, we studied a total of 358 patients who were diagnosed with ET and PV in the city of Gothenburg, Sweden. At the time of diagnosis, evaluable bone marrow biopsy material was available from 280 of these patients. The current work was aimed at investigating the impact of peripheral blood counts, spleen size, and bone marrow biopsy findings at diagnosis on long-term survival and the risk of development of AML or MF in this well-defined unselected population. The variables evaluated were venous blood hemoglobin concentration, packed cell volume, white blood cell count, platelet count, and splenic enlargement; as to bone marrow biopsies, interest was focused on reticulin content, focal or generalized collagen formation, bone marrow cellularity, and megakaryocyte profile number. Over the median observation time of 15 yr, the patients with ET did not demonstrate any significant difference as to survival compared to the normal Swedish population (hazard ratio, 1.23; 95% confidence interval, 0.97-1.51; p = 0.089). The patients with PV, on the other hand, had a significantly shorter survival compared to general population (hazard ratio, 1.66; 95% confidence interval, 1.38-1.99; p < 0.001). A lower hemoglobin concentration at diagnosis of ET predicted poorer survival (p = 0.0281), whereas patients with PV with splenic enlargement at diagnosis had a shorter survival (p = 0.037). In the patients with ET, the risk of transformation to either MF or AML was significantly associated with low hemoglobin concentration and high white cell count at diagnosis (p = 0.0037 and 0.0306, respectively). An increased reticulin content and hypercellularity in the bone marrow at diagnosis were also independent risk factors (p = 0.0359 and 0.0103, respectively). The risk of transformation in patients with PV was significantly associated with splenic enlargement and increase in bone marrow reticulin content (p = 0.0028 and 0.0164, respectively).