Allison Gandey

December 11, 2006

December 11, 2006 (Orlando) — Clinicians have a new biological prognostic indicator that is more specific than the classic risk factors of older age and risk of thrombosis. Researchers presenting at the American Society of Hematology (ASH) 48th Annual Meeting and Exposition say doctors should start testing for a mutation in the Janus tyrosine kinase 2 gene. "Our data support a meaningful correlation between the proportion of mutant JAK2 and the degree of symptoms seen in polycythemia patients," lead investigator Alessandro Vannucchi, MD, from the University of Florence, in Italy, told journalists attending a news conference. "Testing can be done quite easily and can be performed at any good molecular laboratory."

Presenting at a plenary session at the meeting, Dr. Vannucchi emphasized to attendees that about 75% of patients with a V617F mutation to the JAK2 genes are considered high risk irrespective of age or thrombotic activity.

"There has been much excitement in the scientific and medical communities since the discovery last year of JAK2's role in a number of blood disorders," American Society of Hematology president, Kanti Rai, MD, from the Long Island Jewish Medical Center and Albert Einstein College of Medicine, in New York, told reporters. "This study further defines the place of this gene in polycythemia vera and may revolutionize the way we diagnose and treat patients with this disorder."

While introducing the study at the session, Kenneth Kaushansky, MD, from the University of California, San Diego, said that it has been tempting to speculate about elevated levels of JAK2 and prognosis. "It makes sense," he noted, and he praised Dr. Vannucchi's team for providing a "clear diagnostic approach."

The investigators looked at 135 polycythemia patients who were evaluated for JAK2 mutations within 6 months of diagnosis and followed for a median of 2 years. Detectable amounts of the mutated gene were found in 83% of the patients.

During an interview with Medscape, Dr. Vannucchi recommended that physicians start testing patients for JAK2 . "I would recommend that we initiate the tests now," he said. "It's not difficult, and the first step might be to test for the mutation — a simple positive or negative." Dr. Vannucchi argues that JAK2 testing should become routine. "We of course should prove cost-effectiveness through further study, but I am confident it will be."

Proposed Risk Stratification System for Polycythemia Vera
Risk Category
Variable
High
Over 60 years of age
Previous thrombosis
V617F allele >75%
Intermediate
None of the above but presence of a cardiovascular risk factor
Low
None of the above

The researchers report that an increase in mutant alleles is associated with more frequent pruritus and splenomegaly at diagnosis. They also found that JAK2 was associated with a greater need for chemotherapy combined with phlebotomy for the control of the disease and a higher incidence of thrombosis at follow-up.

ASH 48th Annual Meeting and Exposition: Abstract 5. Presented December 10, 2006.


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