Canterbury DHB


Hydroxyurea-Refractory and -Intolerant ET

Patients are considered refractory if:

The optimal second-line therapy is unclear and there is a lack of large-scale controlled clinical trials. The situation in New Zealand is further complicated by the lack of funding for treatments commonly recommended by overseas experts.


Anagrelide is a common second-line therapy for ET in New Zealand.

The PT-1 trial4 found anagrelide plus aspirin to be inferior to hydroxyurea plus aspirin, although the platelet counts were similar in both groups. Patients who received anagrelide had higher rates of arterial thrombosis, major haemorrhage, and myelofibrotic transformation, but lower rates of venous thrombosis.

The ANAHYDRET study4 did not find anagrelide to be inferior to hydroxyurea, but the patients' numbers and follow-up were both less than in the PT-1 trial. The non-inferiority design in this study has also been questioned.

Anagrelide has been used in conjunction with hydroxyurea. Fibrosis has been seen with anagrelide, and was reversible in a small number of patients. Some experts recommend follow-up trephine biopsies every 2–3 years.

See Beer PA, Green AR (2009)4 for further reading about treatment and treatment rationale.

Pegylated interferon-2-alpha

This has shown similar efficacy in ET to PV, and may be considered preferable in patients <40 years – although it is not funded in New Zealand. See Hydroxyurea-Refractory and -Intolerant PV for additional information.

Pipobroman, phosphorus-31 and bulsulfan

These are other options that can be considered, especially in older patients who are refractory to hydroxyurea and anagrelide. See Hydroxyurea-Refractory and -Intolerant PV for additional information.

About this Canterbury DHB document (6217):

Document Owner:

Bridgett McDiarmid (see Who's Who)

Last Reviewed:

August 2018

Next Review:

April 2021


Note: Only the electronic version is controlled. Once printed, this is no longer a controlled document. Disclaimer

Topic Code: 6217