Early detection of relapse by hypermetaphase fluorescence in situ hybridization after allogeneic bone marrow transplantation for chronic myeloid leukemia

Purpose: Standard G-band cytogenetic analysis (CG) provides information on approximately 25 metaphases for monitoring the presence of Philadelphia chr omosome positive (Ph+) cells in chronic myelogenous leukemia (CML) patients , making the detection of a low frequency of Ph+ cells problematic. The pur pose of this study wets to improve the detection of a low frequency of Phcells. Patients and Methods: We combined fluorescence in situ hybridization (FISH) with long-term colcemid exposure, capturing several hundred metaphases in bone marrow cultures (hypermetaphase FISH [HMF]). Using probes that identif y Ph+ cells, HMF was compared with CO analysis in the follow-up evaluations of 51 patients with CML at various time points after allogeneic bone marro w transplant (BMT). Results: Thirty-five patients never showed the presence of Ph+ cells by eit her method. In four patients, high frequencies of Ph+ cells were detected b y both methods. In the remaining 12 patients, Ph+ cells were detected by HM F at time points after BMT when they were not detected by CG. In seven of t he 12 patients, low but statistically significant frequencies of Ph+ cells (0.37% to 5.20%) were detected 3 months or later after BMT, and when no int ervention was initiated, all seven patients later relapsed. Based on those data, an eighth patient with mixed chimerism and a similar HMF-detected Ph frequency (1.8% at 27 months after BMT) was reinfused with donor lymphocyt es and achieved remission with 0% Ph+ cells studied by HMF (up to 50 months after BMT). Ph+ cells detected by HMF but not by CO less than 3 months aft er BMT disappeared on later examination in two of four patients. After dete ction of Ph+ cells by HMF only, the median time to cytogenetic progression (detection of Ph+ cells by CG) was 101 days. Conclusion: The results demonstrate the ability of HMF to detect low but cl inically relevant levels of leukemic cells not detected by CG in transplant patients. The data indicate that HMF can detect low levels of Ph+ cells be fore standard cytogenetics ata time that may be useful in monitoring diseas e status and planning clinical interventions. (C) 2000 by American Society of Clinical Oncology.