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

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-ALLs). 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-ALLs were CD10 + and without KMT2A (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.