The International Working Group for Myeloproliferative Neoplasms (MPN) Research and
Treatment (IWG-MRT) meets annually to organize clinical research projects and develop
consensus criteria. The IWG-MRT recently published a series of papers that clarified the
natural history of WHO-defined essential thrombocythemia (ET) and its distinction from
prefibrotic myelofibrosis (MF).10 (link), 11 (link), 12 , 13 , 14 (link), 15 (link),
16 (link), 17 (link), 18 (link), 19 (link) During the 2010
IWG-MRT meeting in Florence, Italy, center and patient eligibility criteria for a large
international study in PV were discussed and followed up by a request for participation.
Study eligibility criteria included strict adherence to the 2008 WHO diagnostic
criteria,9 (link) availability of clinical and
laboratory information obtained within 1 year of diagnosis and before institution of
cytoreductive therapy, diagnosis date after 1970 and age ⩾18 years old.
After approval from their respective institutional review board, seven centers from
Italy, Austria and the United States collectively submitted diagnostic and follow-up
information on 1818 patients, locally diagnosed with ‘WHO-defined PV'. The two
principle investigators (AT and TB) reviewed all submitted cases and, based on diagnostic
accuracy9 (link) and the above stipulated
eligibility criteria, selected 1545 patients for further analysis (Supplementary Table 1 ). Conventional criteria were used for diagnosis of
post-PV acute myeloid leukemia (AML),9 (link) whereas
post-PV MF was annotated by the coinvestigators from each center with recommendations of
adherence to uniform criteria.20 (link) Conventional
laboratory methods were used by each institution for JAK2 mutation screening,
measurement of serum erythropoietin level and detection of endogenous erythroid
colonies.
All analyses were conducted using The Stat View (SAS Institute, Cary, NC, USA), JMP (SAS
Institute) or SAS version 9.2 (SAS Institute) statistical packages. Pre-receiver operating
characteristic (ROC) plots were used to determine cutoff levels for continuous variables
of interest.21 (link) Differences in the distribution
of continuous variables between categories were analyzed by Mann–Whitney or
Kruskal–Wallis test. Patient groups with nominal variables were compared by
χ2 test. Overall survival analysis was considered from the date
of diagnosis to date of death (uncensored) or last contact (censored). Observed survival
was compared with the expected survival of the age- and sex-matched US total population.
The rate of post-PV AML was calculated as the cumulative incidence of transformation,
accounting for the competing risk of death.22 (link)All survival curves were prepared by the Kaplan–Meier method and compared by the
log-rank test. Cox proportional hazard regression model was used for multivariable
analysis. P-values <0.05 were considered significant.
Treatment (IWG-MRT) meets annually to organize clinical research projects and develop
consensus criteria. The IWG-MRT recently published a series of papers that clarified the
natural history of WHO-defined essential thrombocythemia (ET) and its distinction from
prefibrotic myelofibrosis (MF).10 (link), 11 (link), 12 , 13 , 14 (link), 15 (link),
16 (link), 17 (link), 18 (link), 19 (link) During the 2010
IWG-MRT meeting in Florence, Italy, center and patient eligibility criteria for a large
international study in PV were discussed and followed up by a request for participation.
Study eligibility criteria included strict adherence to the 2008 WHO diagnostic
criteria,9 (link) availability of clinical and
laboratory information obtained within 1 year of diagnosis and before institution of
cytoreductive therapy, diagnosis date after 1970 and age ⩾18 years old.
After approval from their respective institutional review board, seven centers from
Italy, Austria and the United States collectively submitted diagnostic and follow-up
information on 1818 patients, locally diagnosed with ‘WHO-defined PV'. The two
principle investigators (AT and TB) reviewed all submitted cases and, based on diagnostic
accuracy9 (link) and the above stipulated
eligibility criteria, selected 1545 patients for further analysis (
post-PV acute myeloid leukemia (AML),9 (link) whereas
post-PV MF was annotated by the coinvestigators from each center with recommendations of
adherence to uniform criteria.20 (link) Conventional
laboratory methods were used by each institution for JAK2 mutation screening,
measurement of serum erythropoietin level and detection of endogenous erythroid
colonies.
All analyses were conducted using The Stat View (SAS Institute, Cary, NC, USA), JMP (SAS
Institute) or SAS version 9.2 (SAS Institute) statistical packages. Pre-receiver operating
characteristic (ROC) plots were used to determine cutoff levels for continuous variables
of interest.21 (link) Differences in the distribution
of continuous variables between categories were analyzed by Mann–Whitney or
Kruskal–Wallis test. Patient groups with nominal variables were compared by
χ2 test. Overall survival analysis was considered from the date
of diagnosis to date of death (uncensored) or last contact (censored). Observed survival
was compared with the expected survival of the age- and sex-matched US total population.
The rate of post-PV AML was calculated as the cumulative incidence of transformation,
accounting for the competing risk of death.22 (link)All survival curves were prepared by the Kaplan–Meier method and compared by the
log-rank test. Cox proportional hazard regression model was used for multivariable
analysis. P-values <0.05 were considered significant.
