Essential thrombocythaemia (ET)
Essential thrombocythaemia is a slow blood cancer in which the marrow makes too many platelets. Most people need only aspirin and monitoring; those at higher risk of clots take a drug to lower the platelet count, usually hydroxyurea or interferon, with anagrelide in reserve.
Overview
Essential thrombocythaemia is a classical myeloproliferative neoplasm defined by a sustained platelet count above 450 x 10^9/L with a marrow full of large, mature megakaryocytes and no other explanation. About 60 percent carry JAK2 V617F, 20 to 25 percent a CALR mutation and 3 to 5 percent an MPL mutation; the rest are triple negative. Many people have no symptoms and are found on a routine blood count; others have headaches, visual disturbance, burning red hands and feet (erythromelalgia) or, at high platelet counts, paradoxical bleeding. Treatment is set by the IPSET-thrombosis score, which weighs age, prior clot, JAK2 status and cardiovascular risk: very low-risk patients may need nothing, low-risk patients take low-dose aspirin, and high-risk patients add cytoreduction with hydroxyurea or interferon, with anagrelide second line. The PT-1 trial showed hydroxyurea plus aspirin beats anagrelide plus aspirin on arterial clots and bleeding. Progression to myelofibrosis happens in a minority over decades and to acute leukaemia in a few percent. Bomedemstat, an LSD1 inhibitor, is in a phase 3 trial against hydroxyurea, and antibodies against mutant CALR are the first treatments aimed at the clone itself.
State of the art
- Most people with ET live a near-normal lifespan; the treatment question is who needs more than aspirin, and IPSET-thrombosis answers it better than platelet count alone.
- Hydroxyurea remains first line for high-risk disease because PT-1 showed fewer arterial clots and less bleeding than anagrelide.
- Interferons give molecular responses in JAK2- and CALR-mutated ET and are the choice in younger patients and pregnancy.
- Bomedemstat is the first new cytoreductive drug in a phase 3 trial against hydroxyurea in two decades.
- Mutant-CALR antibodies (INCA033989 and others) are the first treatments that target the ET clone itself, in early trials.
Anatomy and lymph node drainage
Leukaemias, myeloma and MDS live in the marrow and blood; lymphomas grow in lymph nodes and spleen. The node stations are the disease map, not a route of spread, and staging counts them.
- Bone marrow (leukaemia, MDS, MPN, myeloma)JAK2 V617F-mutated (about 60 percent; higher thrombosis risk) · CALR-mutated (20 to 25 percent; higher platelets, lower thrombosis risk) · MPL-mutated (3 to 5 percent) · Prefibrotic primary myelofibrosis (a look-alike separated by marrow histology since WHO 2016)
- Lymph node germinal centre (lymphomas)
- Spleen
- Blood (leukaemic phase)
- Lytic bone lesions (myeloma)
- Skin and extranodal sites
- cervical
- axillary
- mediastinal
- para-aortic and mesenteric
- inguinal
In lymphoma the node stations are the disease itself; staging (Ann Arbor / Lugano) counts how many regions and sides of the diaphragm are involved.
Same organ: Acute myeloid leukaemia, Acute lymphoblastic leukaemia, Chronic lymphocytic leukaemia, Chronic myeloid leukaemia (CML), Diffuse large B-cell lymphoma, Follicular lymphoma, Hodgkin lymphoma, Mantle cell lymphoma, Multiple myeloma, Non-Hodgkin lymphoma (all types), Myelodysplastic syndromes / neoplasms (MDS), Myeloproliferative neoplasms (PV, ET, myelofibrosis), Polycythaemia vera (PV), Waldenström macroglobulinaemia, Hairy cell leukaemia, Peripheral T-cell lymphomas (including cutaneous T-cell lymphoma), Blastic plasmacytoid dendritic cell neoplasm (BPDCN), Burkitt lymphoma, HIV-associated (AIDS-related) lymphomas, Chronic myelomonocytic leukaemia and MDS/MPN overlap neoplasms, Systemic mastocytosis, Erdheim-Chester disease, Rosai-Dorfman disease and other histiocytic neoplasms, Langerhans cell histiocytosis (LCH), Post-transplant lymphoproliferative disorder (PTLD)
Show survival figures (1)
Averages across everyone diagnosed, often years ago. Your stage, subtype, age, fitness and the treatment you receive matter more than the average, and the numbers are improving quickly.
- Around one to two new cases per 100,000 people a year, with a second peak in women in their thirties; life expectancy is close to normal for most, and the risks are clots, bleeding and slow progression to myelofibrosis.
- AI in radiologyEstablished
- cfDNA fragmentomicsEstablished
- Colorectal cancer screening (colonoscopy, FIT, stool DNA, blood)Standard of care
- DNA methylation profilingEstablished
- HCC surveillance in cirrhosis (ultrasound + AFP)Standard of care
- High-risk pancreatic surveillance (CAPS / PRECEDE)Established
- A 28-day national pathway for people with a positive multi-cancer blood test
- A breath test to rule out cancer in people with vague symptoms
- A cancer blood test for older people arriving at A&E with unexplained symptoms
- A legislated, publicly reported 28-day standard from urgent referral to diagnosis
- A live national dashboard of stage at diagnosis as the scorecard for early detection
- A single 'cancer check at 60' appointment bundling all screening tests
Background: Alpha-fetoprotein (AFP), Barrett's oesophagus, CA 19-9, Early detection, Faecal immunochemical test (FIT). Also on OnCo: Symptoms and red flags · Early detection roadmap.
Cases by country
No country-level case numbers. This cancer is not mapped to a GLOBOCAN site.
Full blood count, JAK2, CALR and MPL testing, bone marrow biopsy to confirm ET and exclude prefibrotic myelofibrosis, and exclusion of reactive causes (iron deficiency, inflammation, infection, splenectomy).
Observation alone in very low risk (under 60, no clot, JAK2-negative); low-dose aspirin for low risk and for anyone with microvascular symptoms, once acquired von Willebrand deficiency is excluded at very high platelet counts.
Cytoreduction to a platelet count under 400 x 10^9/L: hydroxyurea first line (PT-1), pegylated or ropeginterferon alfa-2b preferred under 60 and in pregnancy, anagrelide second line.
Switch to interferon or anagrelide; ruxolitinib did not beat best available therapy in MAJIC-ET but relieves symptoms.
Managed as myelofibrosis: JAK inhibitors for spleen and symptoms, transplant for fit higher-risk patients.
Subtypes & biomarkers
top- JAK2 V617F-mutated (about 60 percent; higher thrombosis risk)
- CALR-mutated (20 to 25 percent; higher platelets, lower thrombosis risk)
- MPL-mutated (3 to 5 percent)
- Triple negative (10 to 15 percent)
- Prefibrotic primary myelofibrosis (a look-alike separated by marrow histology since WHO 2016)
- Platelet count above 450 x 10^9/L
- JAK2 V617F, CALR exon 9 and MPL W515 mutations
- IPSET-thrombosis score (age over 60, prior thrombosis, JAK2 V617F, cardiovascular risk factors)
- Marrow histology to exclude prefibrotic myelofibrosis
- Acquired von Willebrand deficiency at platelet counts above 1,000 x 10^9/L (bleeding risk with aspirin)
How often this target appears
- 1934Epstein and Goedel describe haemorrhagic thrombocythaemia
The first account of a primary platelet disorder with bleeding and clotting.
- 1951Dameshek groups the myeloproliferative disorders
- 2005JAK2 V617F found in half of ET
- 2005PT-1: hydroxyurea beats anagrelide
In 809 high-risk patients hydroxyurea plus aspirin gave fewer arterial clots, less bleeding and less progression to myelofibrosis than anagrelide plus aspirin.
- 2013CALR mutations discovered
Klampfl and Nangalia find CALR exon 9 mutations in most JAK2-negative ET and myelofibrosis.
- 2016WHO separates prefibrotic myelofibrosis from ET
Marrow histology now distinguishes true ET from early myelofibrosis, which carries a worse outlook.
- 2017MAJIC-ET: ruxolitinib not superior
Ruxolitinib matched but did not beat best available therapy after hydroxyurea failure, though it eased symptoms.
- 2023Bomedemstat enters phase 3
Merck starts the Shorespan-007 trial against hydroxyurea in high-risk ET.
What is in development for Essential thrombocythaemia (ET), drawn from the whole corpus: 3 items. Drugs are grouped by the most advanced trial phase they have reached anywhere; approved treatments sit under standard of care. Technologies are the methods being tested for this cancer, trials are the studies recorded here, and ideas are proposals not yet in a trial.
Drugs in phase 3 · 1
Trials reported · 2
- MAJIC-ET · phase 2 · 2017 · negative
- PT-1 (Primary Thrombocythaemia 1) · phase 3 · 2005 · positive
Open problems and what is being done
No treatment has been shown to prevent progression to myelofibrosis or leukaemia.
Very low-risk patients receive nothing and low-risk patients aspirin, but the evidence for aspirin in CALR-mutated low-risk disease is thin and bleeding may outweigh benefit.
Prefibrotic myelofibrosis is still often misdiagnosed as ET, and the two need different counselling.
Pregnancy management rests on small series; interferon is preferred but randomised data are lacking.
Trials
topTrials recruiting now
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Landmark trials
Expert centres
topExpert centres
- via Myeloproliferative neoplasms (PV, ET, myelofibrosis), Ruxolitinib
Questions to ask
topQuestions to ask your oncologist about Essential thrombocythaemia
Newly diagnosed
- What is my exact diagnosis, stage, and grade, and which tests established them?Why: Everything else follows from an accurate stage and subtype.
- Which biomarkers have been tested on my tumour (for example Platelet count above 450 x 10^9/L, JAK2 V617F, CALR exon 9 and MPL W515 mutations, IPSET-thrombosis score, Marrow histology to exclude prefibrotic myelofibrosis, Acquired von Willebrand deficiency at platelet counts above 1,000 x 10^9/L), and what were the results?Why: These results decide eligibility for targeted therapy, immunotherapy, and trials.
- Which subtype is my cancer, and does that change the recommended treatment?Why: Recognised subtypes for this cancer include JAK2 V617F-mutated, CALR-mutated, MPL-mutated.
- Is germline (inherited) genetic testing recommended for me or my family?Why: Inherited variants can change treatment and matter for relatives.
Diagnosis
- For my situation (diagnosis), which of the standard options do you recommend and why?Why: Guideline options include: Full blood count, JAK2, CALR and MPL testing, bone marrow biopsy to confirm ET and exclude prefibrotic myelofibrosis, and exclusion of reactive causes (iron deficiency, inflammation, infection, splenectomy).
Very low and low risk
- For my situation (very low and low risk), which of the standard options do you recommend and why?Why: Guideline options include: Observation alone in very low risk (under 60, no clot, JAK2-negative); low-dose aspirin for low risk and for anyone with microvascular symptoms, once acquired von Willebrand deficiency is excluded at very high platelet counts.
- Am I a candidate for Aspirin, and what side effects should I expect?Why: Knowing the expected toxicities helps you plan work, family, and supportive care.
High risk (over 60 with JAK2 or prior clot)
- For my situation (high risk (over 60 with jak2 or prior clot)), which of the standard options do you recommend and why?Why: Guideline options include: Cytoreduction to a platelet count under 400 x 10^9/L: hydroxyurea first line (PT-1), pegylated or ropeginterferon alfa-2b preferred under 60 and in pregnancy, anagrelide second line.
- Am I a candidate for Hydroxyurea (hydroxycarbamide), Ropeginterferon alfa-2b, Anagrelide, and what side effects should I expect?Why: Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of PT-1 (Primary Thrombocythaemia 1) apply to someone like me?Why: Trial populations differ from individual patients; ask how closely you match.
Hydroxyurea resistance or intolerance
- For my situation (hydroxyurea resistance or intolerance), which of the standard options do you recommend and why?Why: Guideline options include: Switch to interferon or anagrelide; ruxolitinib did not beat best available therapy in MAJIC-ET but relieves symptoms.
- Am I a candidate for Anagrelide, Ruxolitinib, and what side effects should I expect?Why: Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of MAJIC-ET apply to someone like me?Why: Trial populations differ from individual patients; ask how closely you match.
Progression to myelofibrosis
- For my situation (progression to myelofibrosis), which of the standard options do you recommend and why?Why: Guideline options include: Managed as myelofibrosis: JAK inhibitors for spleen and symptoms, transplant for fit higher-risk patients.
- Am I a candidate for Ruxolitinib, and what side effects should I expect?Why: Knowing the expected toxicities helps you plan work, family, and supportive care.
Any stage
- Are there clinical trials I could join, for example of Bomedemstat, Ropeginterferon alfa-2b?Why: Trials are how the next standard of care is set; asking early keeps options open.
- Would a second opinion at a high-volume centre change anything, and can you help arrange it?Why: Rare or high-stakes decisions benefit from a centre that treats many similar patients.
- What supportive care (symptom control, nutrition, exercise, mental health, financial help) is available from the start?Why: Supportive care improves quality of life and helps patients complete treatment.
- I read that “No treatment has been shown to prevent progression to myelofibrosis or leukaemia”. How does that affect my plan?Why: Open problems are where trials and second opinions matter most.
- I read that “Very low-risk patients receive nothing and low-risk patients aspirin, but the evidence for aspirin in CALR-mutated low-risk disease is thin and bleeding may outweigh benefit”. How does that affect my plan?Why: Open problems are where trials and second opinions matter most.
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Direct links plus the targets, companies, and technologies of this cancer's products.
technologies
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2drugs
7companies
4terms
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2Latest papers
topQuery for this cancer: (TITLE:"Essential thrombocythaemia" OR ABSTRACT:"Essential thrombocythaemia" OR TITLE:"Essential thrombocythemia" OR ABSTRACT:"Essential thrombocythemia" OR TITLE:"Primary thrombocythaemia" OR ABSTRACT:"Primary thrombocythaemia" OR TITLE:"Essential thrombocytosis" OR ABSTRACT:"Essential thrombocytosis") AND (treatment OR therapy OR trial OR survival OR diagnosis). Results are unfiltered search hits about Essential thrombocythaemia (ET), not a curated reading list.
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