Introduction

Essential thrombocythemia (ET) is a rare blood cancer that causes the hyperproliferation of platelets within the blood by the bone marrow. This overproduction leads to an increased incidence of blood clots, increasing the risk for heart attacks and strokes. Risk stratification is essential in the understanding and treatment of patients, allowing for the understanding of individual patients’ risk factors and prognosis. Many treatments exist, including cytoreductive therapy, and the comprehensive analysis and investigation allows for the correct treatment methods to be used to maximise patient prognosis and increase quality of life.

Goals of management in ET

As ET is incurable, treatment focuses on the management of the disease and minimizing current symptoms and preventing further disease progression. The most common symptoms associated with the disease are chronic headaches, fatigue, dizziness, cold extremities, changes in vision, and itchy skin among others.¹ These symptoms are caused by the overproduction of platelets that block blood vessels and cause the triggering of pain signals. These blocked blood vessels also make it more difficult for blood to reach the fingers and toes, resulting in the discomfort caused by the condition.^2,3 Some of the goals of management of ET include ensuring that the condition does not develop further into secondary myelofibrosis, a form of acute leukemia, or another myeloproliferative condition.⁴ Secondary myelofibrosis is a condition that is characterized by the scarring of the bone marrow, impairing the ability of the bone marrow to make healthy blood cells. This further increases the abnormalities in the blood, causing worse and potentially new symptoms.⁵ In rare cases, ET can develop into acute myeloid leukemia (AML). AML is a cancer that affects white blood cells. The condition develops rapidly and can have devastating effects with a prognosis of ~15% after 5 years.⁶ Because of the possibility of disease progression, the control and management of the disease is paramount in preventing lower-prognosis outcomes for patients. This is made more possible as ET develops slowly and therefore changes in the condition happen more gradually and more easily able to be planned for and adjusted to. Management of ET involves the prescription of medications like blood thinners such as aspirin to prevent blood clots. Aspirin also aids in the management of pain caused by headaches, and long-term aspirin use can reduce the likelihood of heart attacks.⁸ Whilst understanding and investigating physical symptoms, patients’ psychological well-being must also be prioritized as they navigate the psychological burden of a chronic blood disorder.

Risk stratification and diagnosis

Risk stratification involves ensuring that all factors have been considered when identifying which patients are at higher risk of developing conditions or having an already diagnosed condition worsen. This typically involves a comprehensive analysis into all of the medical history of the 

patient, involving age, past medical history, currently prescribed medications, sex, and lifestyle habits. In the case of essential thrombocythemia, risk stratification involves investigating the most at-risk patients for medical intervention using specific age and previous medical history. Patients can be separated into high-risk and low-risk. These are determined based on the history of thrombosis in the patient and the patient’s age. Low-risk patients are classified as patients who are <60 years old, and have no history of thrombosis. High-risk patients are classified as patients who are >60 years old, and have a history of thrombosis.^9,10 There are still 

further considerations to make that don’t fall neatly into one of those two categories. These include understanding cardiovascular risk factors, such as hypertension, diabetes, and smoking. All of these must be monitored regardless of the previous category the patient fits in as these can all impact the chances of thrombosis. Furthermore, understanding the genetic background of patients is important as the presence of certain gene mutations can lend to more serious complications. A mutation in the JAK2 gene is common in patients as ~50% of patients with ET exhibit a mutation in this gene. The JAK2 gene is responsible for the activation of a janus kinase. These kinases play a crucial role in the development, differentiation and proliferation of certain cells, and in the case of ET, the mutation causes the body to make an abnormal count of blood cells.^11,12 The understanding of all of these different factors contributes to the diagnosis of the condition. Diagnosis methods vary, but typically begin with a routine blood test that checks for a high platelet count. A definitive diagnosis includes a bone marrow biopsy that investigates changes in the bone marrow and the size of platelet producing cells.¹³

Indications for cytoreductive therapy and other treatment methods

After diagnosis of the condition, a treatment path has to be chosen for patients. This is dependent on the risk level of the patients. High-risk patients are more commonly treated with cytoreductive therapy. Cytoreductive therapy is intended to reduce the number of platelets to limit the risk of future thrombosis in patients.¹⁵ Other factors that could influence the use of cytoreductive therapy include low-risk patients who have already tried the use of aspirin with minimal success, patients with frequent and difficult to manage symptoms, and the progression to splenomegaly. Splenomegaly is characterized by an enlarged spleen. This development is associated with an increased risk of thrombosis and pushes patients closer to the high-risk
categorization. Splenomegaly is a potentially dangerous development in ET patients and must be treated as such as it can potentially be a sign of disease evolution towards myelofibrosis, which is potentially life-threatening.¹⁶  Cytoreductive therapies include drugs like hydroxyurea and anagrelide and consistently help in ailing symptoms in high-risk patients but in low-risk patients without any of the other associated factors, it does not significantly help patients.¹⁷ Hydroxyurea is one of the main treatment methods used in cytoreductive therapy and it 

operates by preventing the formation of DNA by blocking an enzyme, which reduces the ability of the blood marrow to continuously produce platelets, thus reducing the number of platelets in the blood. The intention of hydroxyurea is not to cure the disease, but to prevent further thrombosis and potentially life-threatening complications.¹⁸ Anigrelide is another drug used to treat ET and it functions by preventing platelets from sticking together, this sticking together is known as aggregation and is how platelets form clots. Angeoplasty prevents the formation of these clots and leads to less congestion in the blood vessels.¹⁹ Treatment methods vary for patients but follow a rough guideline where low-risk, asymptomatic patients are not treated and undergo frequent monitoring, low-risk symptomatic patients are treated with aspirin, and high-risk patients or specific low-risk patients are treated with cytoreductive therapy.²⁰

Future directions

Future steps for essential thrombocythemia must focus on further developing risk stratification and developing more effective individualized methods for treatment. In cases where patients have a genetic component with a JAK2 mutation, there must be emphasis on identifying this specific problem and addressing it directly. Current research identifies JAK2 inhibitors as being potentially promising but they must be investigated further to understand whether the possible side effects are worth the positives they may bring.²¹ Focusing on other genetic mutations is also an area of interest, including CALR-specific mutations. 25% of patients with ET exhibit a mutation in this gene, so it would be particularly fruitful to be able to treat them effectively. The development of a monoclonal antibody that aims to target and prevent the consequences of the mutated protein. Current research is limited but the few studies that are being conducted look promising.²² Diagnosis is also a crucial part of understanding the disease further and use of artificial intelligence(AI) could help to aid diagnosis and in risk assessment.²³ 

Summary 

In conclusion, risk stratification is a crucial process that allows clinicians to understand what patients require cytoreductive therapy. High risk patients and those with other complications are suitable candidates. Low-risk patients can be managed by low dose aspirin. Potential genetic components call for further investigation and development of individualized treatment methods that could further enhance quality of life for patients. Managing ET relies on identifying through comprehensive analysis who requires cytoreductive therapy, tailoring therapy to both minimize 

risk and maximise positive outcomes and patient needs, and maintaining quality of life alongside disease control.