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Hydroxyurea vs. Pegylated Interferon in Essential Thrombocythemia and Polycythemia Vera
The most effective first-line treatment for patients with essential thrombocythemia (ET) and polycythemia vera (PV) is unknown. Hydroxyurea (HU) is the most commonly used treatment for high-risk patients. However, over the last decade, reports of hematological and molecular responses in patients treated with pegylated interferon-α (peg-IFN) have renewed enthusiasm for this agent.
In an international, randomized, controlled trial, investigators compared the safety and efficacy of peg-IFN and HU in 168 high-risk patients with ET or PV. High risk was defined as presence of at least one of the following: age >60; thrombosis history; bleeding (ET only); platelet count >1000 x 109/L in PV and >1500 x 109/L in ET; vasomotor symptoms; splenomegaly; diabetes; or hypertension. The primary endpoint was complete response (CR), defined as normalization of blood counts, spleen size, and disease-related symptoms.
Among the findings:
- CR at 12 months was similar in the HU and peg-IFN groups (37% and 35%; P=0.80).
- Median spleen size reduction was similar in the HU and peg-IFN groups (−5% and −6%).
- Cumulative incidence of thrombosis was 2% in each group.
- Histopathological bone marrow response was significantly more common in the HU group (23% vs. 5%).
- Molecular responses were observed in both the HU and peg-IFN groups (−5.3% and −10.7%).
- Adverse events were more common in the peg-IFN group than the HU group, including depression (15% vs. 3%) and grade 3 or higher events (46% vs. 28%).
The authors conclude that both peg-IFN and HU are effective front-line treatments for ET and PV. The study has limitations, as the trial was closed well before enrollment was met due to lack of availability of peg-IFN. The surprising finding here is that HU had comparable efficacy to peg-IFN with regard to CR, even with improved histopathological responses. Before this study, peg-IFN was considered a promising agent that could modify the natural history of the disease. Unfortunately, as demonstrated here, it is difficult to prove disease modification in ET and PV due to the rarity of disease-defining events such as thrombosis or progression. However, longer follow-up is essential for judging the merits of peg-IFN, as effectiveness is time dependent — response rates improved at months 24 and 36 compared with HU.
Mascarenhas J et al.
Title: A randomized, phase 3, trial of interferon-α versus hydroxyurea in polycythemia vera and essential thrombocythemia.
Source: Blood 2022 Jan 10; [e-pub]. (Abstract/FREE Full Text)