Chronic myelocytic leukemia patients achieving complete cytogenetic conversion under interferon alpha therapy:...

We report minimal residual disease evaluation in 18 chronic myelocytic leukemia patients who achieved a durable complete cytogenetic conversion (CCC) under interferon alpha (IFN) therapy. Monitoring was performed 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 during follow-up. A median of five BM karyotypes were performed per patient (range: 3-11). The estimated chances of maintaining a major cytogenetic response (either CCC or less than 35% Ph positive metaphases were 93 +/- 13% (95% CI) at 36 months. One patient lost his cytogenetic response. A median of seven RT-PCR reactions were performed per patient (range: 1-11). A residual disease was detectable even in cases with long periods of CCC. However, in two patients, RT-PCRs were often negative; one, who had four successive negative RT-PCR was taken off IFN therapy and did not receive any other treatment; later in this case, RT-PCRs were again positive, but CCC was maintained for 39 months. Of the three 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 metaphases, 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 remnant effect.