Complete cytogenetic conversion in chronic myelocytic leukemia patients undergoing interferon alpha therapy:...

Fifteen chronic myelocytic leukemia patients in durable complete cytogenetic conversion (CCC) under interferon therapy, were monitored every three to six months by bone marrow (BM) karyotypes and/or reverse-transcription polymerase chain reaction (RT-PCR) on peripheral blood (PB) leukocytes (by a nested primer approach using two rounds of amplification, 30 cycles each). Special care was taken to minimize the risk of contamination. The median time of follow-up after first CCC was 12 months (range, 6-30). Thirty five BM karyotypes were performed. Only three patients demonstrated the transient reappearance of a few Philadelphia-positive metaphases, while other patients remained in CCC. Forty five PB samples were studied by RT-PCR. In two patients, no BCR/ABL transcript could be detected in three consecutive samples. In the 13 other cases, RT-PCR was intermittently negative, indicating a level of residual leukemic cells close to the threshold of sensitivity of the technique.