Thirty-six patients with Philadelphia chromosome–positive acute lymphoblastic leukemia (Ph+ ALL) were studied for the presence of the bcr-abl fusion mRNA transcript after an allogeneic matched related (N = 12), partially matched related (N = 4), matched unrelated (N = 14), autologous (N = 5), or syngeneic (N = 1) bone marrow transplant (BMT). Seventeen were transplanted in relapse, and 19 were transplanted in remission. Twenty-three patients had at least one positive bcr-abl polymerase chain reaction (PCR) assay after BMT either before a relapse or without subsequent relapse. Ten of these 23 relapsed after a positive assay at a median time from first positive PCR assay of 94 days (range, 28 to 416 days). By comparison, only 2 relapses occurred in the 13 patients with no prior positive PCR assays; both patients had missed at least one scheduled follow-up assay and were not tested 2 months and 26 months before their relapse. The unadjusted relative risk (RR) of relapse associated with a positive PCR assay compared with a negative assay was 5.7 (95% confidence interval 1.2 to 26.0, P = .025). In addition, the data suggest that the type of bcr-abl chimeric mRNA detected posttransplant was associated with the risk of relapse: 7 of 10 patients expressing the p190 bcr-abl relapsed, compared with 1 of 8 who expressed only the p210 bcr-abl mRNA (P = .02, log-rank test). The RR of p190 bcr-abl positivity compared to PCR-negative patients was 11.2 (confidence interval 2.3-54.8, P = 0.003), whereas a positive test for p210 bcr-abl was apparently not associated with an increased relative risk. In separate multivariable models, PCR positivity remained a statistically significant risk factor for relapse after separately adjusting for donor (unrelated and partially matched v matched, autologous, and syngeneic), remission status at the time of transplant, the presence of acute graft-versus-host disease (GVHD), and type of conditioning regimen (total body irradiation dose of ≤1,200 cGy v <1,200 cGy). The PCR assay appears to be a useful test for predicting patients at high risk of relapse after BMT and may identify patients who might benefit from therapeutic interventions. The finding that the expression of p190 bcr-abl may portend an especially high risk of relapse suggests a different clinical and biologic behavior between p190 and p210 bcr-abl.
We studied 346 patients after bone marrow transplantation (BMT) for chronic myeloid leukemia (CML) for the presence of the bcr-abl transcript detected by the polymerase chain reaction (PCR) to understand the frequency and implication of a positive test. A total of 634 samples of BM and/or peripheral blood were obtained for PCR analysis between 3 and 192 months after BMT. A positive PCR test at 3 months post-BMT was not statistically significantly associated with an increased risk of relapse compared with PCR-negative patients. However, a positive PCR assay at 6 months and beyond was highly associated with subsequent relapse. The Kaplan-Meier estimate of relapse for patients testing PCR-positive at 6 to 12 months was 42% versus 3% for PCR-negative patients (P < .0001). The Kaplan-Meier estimate of survival at 4 years for the PCR-positive patients was 74% compared with 83% for the PCR-negative group (P = .002). Multivariable analysis indicated that a PCR-positive result at 6 to 12 months post-BMT, the type of BMT donor (allogeneic matched donor v mismatched or unrelated), and the presence of acute GVHD were independent risk factors for subsequent relapse. The relative risk (RR) for relapse for patients PCR-positive at 6 to 12 months post-BMT was 26.1 (95% confidence interval, 8.9 to 76.1, P < .0001). The outcome of long-term patients (> 36 months post-BMT) who tested PCR-positive was much better, as 15 of 59 (25%) tested positive for bcr-abl, but only one patient relapsed. There was a 91% concordance between PCR tests of simultaneously obtained BM and peripheral blood. These analyses show that the PCR assay of the bcr-abl fusion transcript 6 to 12 months post-BMT is an independent predictor of subsequent relapse which provides an opportunity for early therapeutic intervention.
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