Secondary acute lymphoblastic leukaemia is constitutional and probably not related to prior therapy

Summary Very little is known about secondary acute lymphoblastic leukaemia (s‐ ALL ). This retrospective analysis studied a cohort of s‐ ALL patients treated at a single centre between 1994 and 2013, while comparing therapy‐associated ALL (t‐ ALL ) and antecedent malignancy ALL (am‐ ALL ) patients. Thirty‐two patients with s‐ ALL were identified. The overall incidence was 9·4% among ALL adults while T‐cell s‐ ALL was rare (12% of s‐ ALL s). The median time interval between two malignant diagnoses was 5·3 years (range: 0·1–28). In contrast to previous reports, most of the s‐ ALL s were CD 10 +  and without KMT 2A ( MLL ) abnormalities. The overall survival ( OS ) rates of the entire cohort at 12 and 24 months from ALL diagnosis was 49% and 25%, respectively. Most patients ( n  = 23, 72%) received prior chemo‐/radio‐therapy for their first malignancy (t‐ ALL ) and only 9 (28%) did not (am‐ ALL ). No significant difference was found in the incidence of B‐/T‐ lineage ALL , extramedullary disease, blood count, and the rate of Philadelphia‐positive ALL , nor in the rates of complete remission ( P  = 0·55) and OS ( P  = 0·97). This similarity, together with high incidence of family malignancy in both groups, raise the possibility that s‐ ALL patients may have an inherent predisposition to malignancies and a history of previous therapy may be of lesser importance in the pathogenesis of s‐ ALL .