Second Clinical Scenario - Progressive Disease Despite Hematocrit Control

Dr. Vachhani presents the second clinical scenario involving a 68-year-old woman with 6-year PV history and prior deep vein thrombosis at diagnosis. Additional comorbidities include type 2 diabetes, hyperlipidemia, and obesity, with close primary care and cardiology follow-up for cardiovascular risk management. She has received hydroxyurea cytoreductive therapy for several years, maintaining hematocrit consistently below 45%, representing well-managed hematocrit control unlike the previous case.

However, over nine months, laboratory monitoring revealed increasing white blood cell counts (now 16,000), with imaging demonstrating progressive splenomegaly. Clinically, she reported worsening fatigue, night sweats, early satiety, and declining quality of life. Attempts at hydroxyurea dose escalation resulted in cytopenias and gastrointestinal side effects requiring dose reduction, creating therapeutic challenges where splenomegaly and new symptoms persist while dose escalation cannot be achieved due to toxicity.

Dr. El Chaer characterizes this case as instructive, illustrating limitations of hematocrit-centric thinking. While the patient's hematocrit has remained consistently below 45% for years, which historically would have been considered controlled disease, every other meaningful disease control metric indicates uncontrolled disease. Adequate control in current practice requires hematocrit below 45% without phlebotomy dependency, white blood cell counts within acceptable ranges and not rising (this patient exceeds 16,000, well above the 11,000-13,000 alarm threshold), stable spleen size (this patient has progressive splenomegaly), stable or improving symptom burden (this patient has worsening fatigue, night sweats, early satiety, declining quality of life), and absence of dose-limiting toxicity preventing adequate cytoreduction (this patient has cytopenias and gastrointestinal intolerance forcing dose reduction).

Dr. Vachhani emphasizes the importance of considering disease progression possibilities in patients losing treatment response. Progressive splenomegaly, new symptoms like night sweats, and increasing white blood cell counts despite stable hydroxyurea dosing suggest potential progression to myelofibrosis. This clinical presentation warrants bone marrow biopsy assessment for progression evaluation versus same-stage PV becoming harder to treat. Indications for considering PV progression to post-PV myelofibrosis include minor criteria components of post-PV myelofibrosis diagnostic criteria: new blood blasts, new splenomegaly, rising lactate dehydrogenase (particularly relevant for post-ET myelofibrosis but applicable to post-PV myelofibrosis), or development of anemia when previous phlebotomies or higher hydroxyurea doses were previously required.

Dr. El Chaer explains that this case demonstrates both hydroxyurea resistance and intolerance by ELN criteria definitions, providing compelling arguments for treatment change. Resistance criteria include increasing white blood cell count despite hydroxyurea therapy, progressive splenomegaly despite therapy, and failure to maintain adequate hematocrit control despite adequate hydroxyurea dosing without phlebotomy dependence. Intolerance criteria include cytopenia development requiring dose reduction and gastrointestinal effects that are dose-limiting, preventing titration to adequate doses.