Therapeutic Approach to Young Patients With Low-Risk Essential Thrombocythemia: Primum Non Nocere.

The Oncology Grand Rounds series is designed to place original reports published in the Journal into clinical context. A case presentation is followed by a description of diagnostic and management challenges, a review of the relevant literature, and a summary of the authors' suggested management approaches. The goal of this series is to help readers better understand how to apply the results of key studies, including those published in Journal of Clinical Oncology, to patients seen in their own clinical practice. A 51-year-old woman was diagnosed with essential thrombocythemia (ET) the previous year (April 2016) when she was incidentally found to have increased platelets (747 × 109/L) during a yearly physical examination. Her past medical history was significant only for mild hypertension, which was well controlled with a low dose of a β-blocker. There was no history of thromboembolic events. A JAK2V617F mutation was detected in her peripheral blood. A repeated platelet count 1 month later showed increased platelets of 871 × 109/L and she began hydroxyurea. One year later, she presented to our clinic with a white cell count of 8.9 × 109/L, hemoglobin 14 g/dL, and platelets 846 ×109/L while receiving hydroxyurea 500 mg one day alternating with 1000 mg the next day and aspirin 81 mg once per day. The differential as well as other laboratory findings were within normal limits. She had chronic mild to moderate itching, but otherwise denied symptoms referable to ET. Her physical examination was notable for the absence of palpable hepatosplenomegaly. Bone marrow aspiration and biopsy revealed normocellular marrow with hyperplastic megakaryocytes in clusters, no reticulin fibrosis, and 2% blasts, compatible with ET. Molecular testing confirmed JAK2V617F mutations at a variant allele frequency of 12% without any other mutations (81-gene panel), and her karyotype was diploid. She visited the clinic to discuss the next steps in her treatment.