Therapy‐related acute lymphoblastic leukemia is more frequent than previously recognized and has a poor prognosis

BACKGROUND: Acute lymphoblastic leukemia (ALL) occurring in patients with a history of prior chemotherapy/radiotherapy exposure has been previously reported to be rare, accounting for <2.5% of ALL cases. METHODS: All cases of adult ALL with a history of prior cytotoxic or radiation therapy at a leukemia referral center over a 13-year period were analyzed. RESULTS: Twenty-three cases, representing 6.9% of all ALL cases, were identified. Of these, 17 (74%) had at least 1 high-risk feature; 8 (35%) had MLL rearrangements, and 4 were BCR-ABL(+) . MLL rearrangements were correlated with CD15 expression and absence of CD10, and also tended to have a shorter mean latency period and more prior topoisomerase II exposure. Twenty-one patients received induction therapy, and 18 (86%) achieved a complete response, 17 with 1 induction. Six patients have relapsed and died, and 4 others died of other complications, 2 of these postallogeneic stem cell transplantation. Median disease-free survival (DFS) and overall survival (OS) were 27 and 13.6 months, respectively, and 3-year DFS and OS were 37.1% and 37.6%, respectively. CONCLUSIONS: The frequency of therapy-related ALL is higher than previously reported and has a poor prognosis, probably related to the high frequency of adverse risk features.