Long Term Follow-up of Ph+ CML Patients Achieving Complete Cytogenetic Response (CCgR) with Interferon Based Therapy - GIMEMA Protocol CML0509

Abstract 786

Interferon alpha (INFα) either alone or in combination with Ara-C was the frontline therapy of Ph+ chronic myeloid leukaemia (Ph+ CML) between 1980 and 2000. INFα prolonged survival as compared to conventional chemotherapy and it was the first drug able to induce complete cytogenetic responses (CCgRs). Patients achieving a CCgR by INFα ± Ara C were less than 10–15%, but they represent fascinating elite of patients who are the most likely candidates for prolonged survival and possibly for cure. The last update of the largest European cohort of 317 CML patients who had obtained a CCgR on IFNα was reported in 2001 (Bonifazi et al., Blood, 2001). Briefly, the median time to first CCgR was 19 months, the 10 year survival rate from first CCgR was 72% and the survival probability for patients with low Sokal risk was 84%. In this study, the contribution of the Italian Cooperative Study Group on CML was of 119 cases. Although INFα was used more than 20 years ago, obtaining information on this selected category of CCgR–INFα responding patients in the Imatinib era may be interesting both from the biological and clinical point of view. We report here the preliminary results of an observational study aimed to update the overall survival (OS), the progression free survival (PFS) to accelerated-blastic phase (ABP) and the CCgR duration in 92 Ph+ CML patients who were treated in Italy with an INFα based therapy between 1986 and 2001 and who obtained a CCgR at least once. In this selected cohort of patients, the median time to first CCgR was 24 months (range, 3–143), and the median duration of the first CCgR was 87 months (3-252). The overall survival (OS) calculated from diagnosis, from start of IFNα and from the time of the first CCgR was 185 months (range, 74–334), 179 months (range, 74–287) and 154 months (range, 51–274), respectively. This is the longest follow-up of Ph+ CML patients who obtained a CCgR with an IFNα-based therapy. Out of 92 patients in CCgR, 71 (77%) cases stopped IFNα and 21 (23%) continued to be treated with IFNα. Out of the 71 cases who stopped IFNα, 38 (53%) cases lost CCgR and 3 (4%) cases died because of progression to ABP; 15 (21%) maintained CCgR without any other therapy and 18 (25%) maintained CCgR but shifted to Imatinib. Among the latter 33 patients maintaining the CCgR, 4 cases died because of CML unrelated causes. Out of the 21 cases who continued to be treated with IFNα, 18 (86%) currently maintain the CCgR and are alive and well, while 3 lost CCgR and died (2 cases for ABP). These data show that there are at least 33/92 (36%) patients who are alive and well and are maintaining a CCgR, either with continued IFNa treament (18 cases) or after IFNα treatment discontinuation (15 cases) but who have never been treated with Imatinib or any other tyrosine kinase inhibitor (TKI). We are now analyzing molecular data and we are collecting peripheral blood and bone marrow samples for correlative biological studies aimed to characterize the peculiar genetic and epigenetic features of these patients

Work supported by European LeukemiaNet and Cofin 2009