Just so we're all on the same page, here's what yr referencing:

Cytoreductive treatment with hydroxyurea has been shown to reduce the risk of thrombosis in patients with essential thrombocythemia (ET) and high-risk features, which include age >60 years or prior thrombosis or hemorrhage. But patients aged 40 to 59 years who lack high-risk features do not benefit from addition of hydroxyurea to aspirin, according to results of an open-label, randomized trial published in the Journal of Clinical Oncology. Compared with aspirin alone, the hydroxyurea/aspirin combination did not reduce rates of vascular events, leukemic transformation, or myelofibrotic transformation in patients with "intermediate-risk" ET.

Based on these results, the authors, led by Anna L. Godfrey, BMBCh, PhD MRCP, FRCPath, from Cambridge University Hospitals National Health Service (NHS) Foundation Trust, recommended that patients age 40 to 59 years without other clinical indications for treatment (such as previous thrombosis or hemorrhage) and with platelet counts < 1,500×109/L should not receive cytoreductive therapy.
https://ashpublications.org/ashclinicalnews/news/4232/No-Added-Benefit-When-Hydroxyurea-Is-Combined-With