CHRONIC MYELOCYTIC-LEUKEMIA PATIENTS ACHIEVING COMPLETE CYTOGENETIC CONVERSION UNDER INTERFERON-ALPHA THERAPY - MINIMAL RESIDUAL DISEASE FOLLOW-UP

We report minimal residual disease evaluation in 18 chronic myelocytic leukemia patients who achieved a durable complete cytogenetic convers ion (CCC) under interferon alpha (IFN) therapy. Monitoring was perform ed every 3-6 months using bone marrow (BM) karyotypes and/or two-step reverse transcription polymerase chain reaction (RT-PCR) on peripheral blood samples. Median follow-up after first CCC was 47 months (range 15-69). All patients maintained complete hematological remission durin g follow-up. A median of five BM karyotypes were performed per patient (range: 3-11). The estimated chances of maintaining a major cytogenet ic response (either CCC or less than 35% Ph positive metaphases) were 93 +/- 13% (95% CI) at 36 months. One patient lost his cytogenetic res ponse. A median of seven PT-POP reactions were performed per patient ( range: 1-11). A residual disease was detectable even in cases with lon g periods of CCC. However, in two patients, RT-PCRs were often negativ e; one, who had four successive negative RT-PCR was taken off IFN ther apy and did not receive any other treatment; later in this case, RT-PC Rs were again positive, but CCC was maintained for 39 months. Of the t hree who were taken off IFN and no longer treated, two maintained CCC (39+ and 33+ months); the third had a recurrence of 7% Ph-positive met aphases, and later returned to CCC. These results confirm that in most well-responding patients, the disease is not eradicated. However, it seems that the clonogenic potential of the residual leukemic clone is low. In patients taken off IFN therapy, IFN may have a particular remn ant effect.