We report a study of an alternative treatment schedule of imatinib (IM) in chronic myeloid leukemia (CML). Seventy-six Philadelphia-positive (Ph+), BCR-ABL-positive patients aged 65 years or older who had been treated with IM for more than 2 years and who were in stable complete cytogenetic response (CCgR) and major molecular response (MMR) were enrolled in a single-arm study to test the effects of a policy of intermittent IM (INTERIM) therapy for 1 month on and 1 month off. With a minimum follow-up of 4 years, 13 patients (17%) lost CCgR and MMR and 14 (18%) lost MMR only. All these patients resumed continuous IM and all but one (lost to follow-up) regained CCgR and MMR. No patients progressed to accelerated or blastic phase or developed clonal chromosomal abnormalities in Ph+ cells or BCR-ABL mutations. In elderly Ph+ CML patients carefully selected for a stable CCgR (lasting >2 years), the policy of INTERIM treatment affected the markers of residual disease, but not the clinical outcomes (overall and progression-free survival). This trial was registered at www.clinicaltrials.gov as NCT 00858806.
Trial registration: ClinicalTrials.gov NCT00858806.