Molecular and hematologic relapses in adult patients with acute promyelocytic leukemia: a cohort study.

Objective: To evaluate factors predictive for relapse in a cohort of adult patients with acute promyelocytic leukemia monitored by molecular methods during consolidation and during at least one month of maintenance therapy.

Methods: The charts and laboratory data of 65 adult patients with acute promyelocytic leukemia treated according to the International Consortium on Acute Promyelocytic Leukemia 2006 protocol were reviewed. The identification of the promyelocytic leukemia-retinoic acid receptor-alpha gene rearrangement at diagnosis, post-induction, post-consolidation and during maintenance treatment was performed by qualitative and quantitative reverse transcription polymerase chain reaction.

Results: Eighty-nine patients were diagnosed with acute promyelocytic leukemia over a seven-year period and of these 65 were eligible for treatment with the protocol. Among the 45 patients who received consolidation and maintenance treatment, six (13%) relapsed, three of whom presented hematologic and three presented molecular relapse. The first relapses occurred at a median of 39 months. Relapsed patients were from all risk groups (low, intermediate and high) and both morphological types (M3 and M3variant) were found. Three of these patients are alive and in molecular remission after salvage treatment. There were no statistically significant differences regarding gender, age, risk group, morphology, promyelocytic leukemia breakpoint cluster region, use of all-trans retinoic acid, development of differentiation syndrome and number of days to complete remission between the patients who relapsed and those who did not.

Conclusion: Our results reinforce the importance of prolonged monitoring of acute promyelocytic leukemia patients using molecular methods to detect relapse early.