Long term survivors in chronic granulocytic leukaemia: A study by the International CGL Prognosis Study Group

The purposes of the present work were to identify the initial characteristics associated with long-term survival in chronic granulocytic leukaemia (CGL) and to analyse the accuracy of prognostic models in identifying long-term survivors. 813 Philadelphia (Ph) chromosome-positive, nonblastic CGL patients from six American and European institutions, the majority treated conventionally, with a minimum follow-up >10 years, were studied. Stepwise logistic regression was performed to ascertain the association between the initial clinicohaematological variables and survival ≥ 8 years, and a prognostic index was derived. The usefulness of both Sokal's and the new prognostic index to identify long-term survivors was assessed by calculating their positive and negative predictive accuracies, sensitivity and specificity. Median survival of the series was 45 months (range 1-255), with 784 patients (96.4%) having died and 109 (13.4%) surviving 8 years or longer. Younger age, smaller spleen, platelets ≤ 600 x 10⁹/l, and lower blood blast percentage were associated with survival ≥ 8 years; platelets ≤ 600 x 10⁹/l and lower blood blast percentage were the predictive factors in patients 50 years old or younger. Two-thirds of long survivors belonged to Sokal's low-risk group, but the positive predictive accuracy and specificity for prolonged survival of Sokal's index were very low. This was also the case for the new predictive index. In 366 patients with information on the presence or not of additional karyotypic abnormalities at diagnosis, younger age, platelets ≤ 600 x 10⁹/l, lower blood blast percentage, and absence of additional cytogenetic abnormalities were associated with survival ≥ 8 years. The addition of the cytogenetic data improved the positive predictive accuracy and specificity of the model, albeit modestly. We conclude that, although most CGL long survivors show favourable prognostic features at presentation, clinicohaematological data do not allow a precise definition of such a subpopulation.