[Application of interphase fluorescence in situ hybridization for determination of the tumor load in chronic myeloid leukemia].

BACKGROUND & OBJECTIVE: It is essential to evaluate the tumor burden accurately in assessing the degree of response of chronic myeloid leukemia for design of treatment model. The aim of this study was to explore the sensitivity and specificity of interphase fluorescence in situ hybridization (I-FISH) technique in monitoring the tumor load of chronic myeloid leukemia (CML) during treatment.

METHODS

Ten cases of normal bone marrow cells were examined using I-FISH technique to define the normal cut-off value. Bone marrow cells from 20 CML patients in treatment were assayed with I-FISH, conventional cytogenetic G-banding (CCG) analysis, and reverse transcriptase polymerase chain reaction (RT-PCR). The tumor load was monitored in a quantitative way.

RESULTS

The false-positive bone marrow cells were 0.6%-2.0% in control group by I-FISH; the normal cut-off value was 2.45%. Among 20 CML patients after being treated with IFN-alpha or bone marrow transplantation, Ph(+) clone were detected in 9 cases by CGG with positive cell rate ranging from 16.7% to 100%. However, combining with the cutoff value, bcr-abl(+) cells were found in 16/20(80%) cases by I-FISH with positive cell rate ranging from 2.8% to 99.6%. These 16 patients were assayed with RT-PCR, and 13(81.3%) among them showed bcr-abl mRNA positive.

CONCLUSION

I-FISH can be used as a sensitive and specific tool to monitor the change of tumor load in CML during treatment; meanwhile, the results acquired from I-FISH would be more accurate than that from CCG and RT-PCR.