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Polycythemia vera (PV) is a Philadelphia-negative chronic myeloproliferative neoplasm (MPN) characterized by clonal expansion of erythrocytes.1 This leads to thrombotic complications and the risk of progression to post-PV myelofibrosis or blast phase.1
Currently, hydroxyurea (HU) is the most used cytoreductive therapy, but it is associated with poor responses and toxicity in a significant proportion of patients. Moreover, the predictors of a complete response (CR) with HU and its prognostic implications are yet to be defined.1 The impact of different types of suboptimal responses in patients switching to ruxolitinib (RUX) is also unclear.1
Palandri et al.1 recently published in Cancers, a real-world, retrospective study (PV-NET) identifying factors associated with CR during HU treatment, along with whether the type of HU responses would influence a patient’s decision to switch to RUX. The MPN Hub is pleased to summarize the key findings here.
This is an observational, retrospective cohort study across 22 hematologic centers. A total of 563 patients diagnosed with PV according to the World Health Organization 2016 definition between 1985 and 2000 and treated with HU for ≥12 months were included.
Table 1. Patient characteristics*
Characteristics |
Complete responders (n = 166) |
Poor responders (n = 397) |
p value |
---|---|---|---|
Median age (range), years |
70 (47–87) |
65 (21–89) |
<0.001 |
Sex, male (%) |
39.8 |
55.4 |
0.001 |
Median platelet count (range), ×109/L |
500 (159–1279) |
449 (138–1209) |
0.004 |
Median leukocyte count (range), ×109/L |
10 (3.3–30.3) |
10.1 (1–27.3) |
0.70 |
Median hemoglobin (range), g/dL |
|||
Male |
18.6 (15.8–23.6) |
18.7(12–23.4) |
0.59 |
Female |
17.8 (15.3–22) |
17.5 (13.2–21.9) |
0.09 |
Median hematocrit (range), % |
|||
Male |
55 (48.9–72.5) |
56.3 (38–73) |
0.70 |
Female |
54 (47.6–71.7) |
54.1 (39–72) |
0.99 |
Palpable spleen†, % |
15.8 |
39.4 |
<0.001 |
Pruritus, % |
17 |
39.9 |
<0.001 |
Thromboses pre-/at diagnosis, % |
23.5 |
25.7 |
0.58 |
Median HU dose‡ (range), g/d |
0.8 (0.2–2) |
0.5 (0.2–2) |
<0.001 |
Median HU dose ≥1 g/d, g/d |
49.6 |
26.17 |
<0.001 |
HU, hydroxyurea. *Adapted from Palandri, et al.1 †548 evaluable patients. ‡506 evaluable patients. |
Figure 1. Response rates in patients treated with HU*
*Adapted from Palandri, et al.1
Figure 2. A) Response rates of patients who experienced a poor response to HU; B) Percentage of patients who experienced a poor response to HU who either remained on HU or switched to RUX*
HU-POOR, patients who experienced a poor response and remained on hydroxyurea; HU-RUX, patients who switched from hydroxyurea to ruxolitinib; NR, no response; PR, partial response.
*Adapted from Palandri, et al.1
Figure 3. Adverse events according to HU dose*
AE, adverse event; HU, hydroxyurea.
*Adapted from Palandri, et al.1
This real-world, retrospective cohort study highlights the importance of optimizing HU dosing. Although higher HU dosing achieves greater rates of CR it also increases the risk of TRAEs. In addition, the study also demonstrates the lack of an association between CR and reduced thrombotic risk. Therefore, HU dosing should be determined based on individual patient needs. Furthermore, a large proportion of stable poor responders continued HU treatment, emphasizing the need to improve overall therapeutic strategy. However, due to the retrospective nature, this study was limited by factors such as patient selection, uncontrolled drug prescription, inadequate recognition of poor response to HU, and inadequate drug compliance assessment.
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