Polymerase chain reaction: a method for monitoring tumor cell purge by long-term culture in BCR/ABL positive acute lymphoblastic leukemia.

We report the successful purging of leukemia cells bearing the Philadelphia chromosome and BCR/ABL transcripts by long-term marrow culture (LTC), and subsequent grafting of the purged marrow in a case of refractory acute lymphoblastic leukemia. The efficiency of the purge was evaluated by polymerase chain reaction (PCR) for BCR/ABL transcripts. In two LTCs initiated in the blastic stage, we demonstrated the selective effect of three culture media (serum dependent, serum-free (SF) supplemented or not with IL3 and GM-CSF) on the proliferative potential of normal hematopoietic (CFU-GM/BFU-E) and leukemic progenitors (CFU-ALL). BCR/ABL positive cells disappeared after 3 to 4 weeks of culture. The addition of IL3 and GM-CSF to the SF medium enhanced the growth of CFU-GM/BFU-E and shortened the purging period. We therefore carried out a LTC in the presence of IL3 and GM-CSF with marrow harvested in morphological remission. BCR/ABL positivity was detected at the outset, although no leukemia cells could be identified. The BCR/ABL was no longer found by PCR in the 7 and 14 day LTCs. The patient, consolidated by high dose polychemotherapy and total body irradiation, was infused with the 14 day LTC. This study indicates that PCR is a useful and sensitive technique for monitoring tumor cell reduction after LTC prior to autografting.