Follow-up of complete cytogenetic remission in patients with chronic myeloid leukemia after cessation of interferon alfa.

PURPOSE: A small proportion of patients with chronic myeloid leukemia (CML) achieve a complete cytogenetic response (CCR), defined as the disappearance of Philadelphia (Ph) chromosome-positive metaphases, after treatment with interferon alfa (IFN). In this population of patients, the question of whether treatment should then be withdrawn is not yet resolved. PATIENTS AND METHODS: In the present study, we followed 15 patients who stopped IFN after achieving CCR. In nine patients IFN was stopped in view of adverse reactions (n = 8) or patient's choice (n = 1). For the remaining six patients, the treatment was stopped because no BCR/ABL rearrangement could be detected by reverse transcriptase polymerase chain reaction (RT-PCR) in four successive analyses using peripheral-blood samples.
RESULTS: Loss of CCR and survival were not statistically different (P =.48; P =.7) for the 15 patients who stopped IFN compared with 41 other CCR patients who continued IFN therapy in our institution. The median follow-up after discontinuation of IFN treatment was 36 months (range, 6 to 108 months). Seven patients (47%) (females, or CCR > 24 months and RT-PCR negative before IFN cessation; P <.0001) did not relapse. Eight other patients (53%) relapsed (lost CCR) within 3 to 33 months of treatment discontinuation. One of them relapsed in major cytogenetic remission (MCR) and was still in MCR 87 months after stopping therapy without any treatment.
CONCLUSION: It is possible to stop IFN treatment at least in some patients with CML who achieve a prolonged period of CCR. This study also illustrates the hypothesis that persistence of low numbers of Ph-positive cells does not necessarily imply hematologic relapse.