Faculty Bibliography

There is incomplete understanding of genetic heterogeneity and clonal evolution during cancer progression. Here we use deep whole-exome sequencing to describe the clonal architecture and evolution of 20 pediatric B-acute lymphoblastic leukaemias from diagnosis to relapse. We show that clonal diversity is comparable at diagnosis and relapse and clonal survival from diagnosis to relapse is not associated with mutation burden. Six pathways were frequently mutated, with NT5C2, CREBBP, WHSC1, TP53, USH2A, NRAS and IKZF1 mutations enriched at relapse. Half of the leukaemias had multiple subclonal mutations in a pathway or gene at diagnosis, but mostly with only one, usually minor clone, surviving therapy to acquire additional mutations and become the relapse founder clone. Relapse-specific mutations in NT5C2 were found in nine cases, with mutations in four cases being in descendants of the relapse founder clone. These results provide important insights into the genetic basis of treatment failure in ALL and have implications for the early detection of mutations driving relapse.

BACKGROUND:Infants with acute lymphoblastic leukemia (ALL) have a poor prognosis. Intensification of therapy has resulted in fewer relapses but increased early deaths, resulting in failure to improve survival. PROCEDURE/METHODS:AALL0631 is a Phase 3 study for infants (<366 days of age) with newly diagnosed ALL. Induction initially (Cohort 1) consisted of 3 weeks of therapy based on COG P9407. Due to excessive early mortality, induction was amended to a less intensive 5 weeks of therapy based on Interfant-99. Additionally, enhanced supportive care guidelines were incorporated with hospitalization during induction until evidence of marrow recovery and recommendations for prevention/treatment of infections (Cohort 2). RESULTS:Induction mortality was significantly lower for patients in Cohort 2 (2/123, 1.6%) versus Cohort 1 (4/26, 15.4%; P = 0.009). All induction deaths were infection related except one due to progressive disease (Cohort 2). Sterile site infections were lower for patients in Cohort 2 (24/123, 19.5%) versus Cohort 1 (15/26, 57.7%; P = 0.0002), with a significantly lower rate of Gram positive infections during induction for patients in Cohort 2, P = 0.0002. No clinically significant differences in grades 3-5 non-infectious toxicities were observed between the two cohorts. Higher complete response rates were observed at end induction intensification for Cohort 2 (week 9, 94/100, 94%) versus Cohort 1 (week 7, 17/25, 68%; P = 0.0.0012). CONCLUSION/CONCLUSIONS:De-intensification of induction therapy and enhanced supportive care guidelines significantly decreased induction mortality and sterile site infections, without decreasing complete remission rates.

BACKGROUND: Infants with acute lymphoblastic leukemia (ALL) present with aggressive disease and a poor prognosis. Early relapse within 6-9 months of diagnosis is common. Approximately 75% of infants have MLL-rearranged (MLL-R) ALL with event free survival (EFS) ranging from 20% to 30%. Children's Oncology Group (COG) P9407 used shortened (46 weeks), intensified therapy to address early relapse and poor EFS. PROCEDURE: P9407 therapy was modified three times for induction toxicity resulting in three cohorts of therapy. One hundred forty-seven infants were enrolled in the third cohort. RESULTS: We report an overall 5-year EFS and OS of 42.3 +/- 6% and 52.9 +/- 6.5% respectively. Poor prognostic factors included age /=50,000/mul. For infants 90 days (P < 0.0001). Among infants >90 days of age, 5-year EFS rates were 43.8 +/- 8% for MLL-R versus 69.1 +/- 13.6% for MLL-germline ALL (P < 0.0001). CONCLUSIONS: Age