Pediatric Treatment Guidelines for Philadelphia Positive (Ph+) Acute Lymphoblastic Leukemia (ALL): What Are They in today’s Imatinib Era?

Abstract Background: The treatment of pediatric Philadelphia positive (Ph+) leukemias in the era of the tyrosine kinase inhibitors (TKI) continues to evolve with the role of allogeneic hematopoietic cell transplantation (allo-HCT) in these high-risk patients becoming more controversial. Ph+ acute lymphoblastic leukemia (ALL) prior to imatinib in both pediatric and adult patients has often involved intensive chemotherapy, including consolidative allo-HCT. Whether treatment strategies in 2008 have changed for these Ph+ leukemias in pediatrics, from heavily allo-HCT based to TKI based medical therapy, is presently unclear. Methods: Thirty-two pediatric centers across the United States and Canada were surveyed regarding current treatment practices for Ph+ ALL in order to explore treatment practices in 2008. The survey targeted primary pediatric oncologists and bone marrow transplant physicians regarding their treatment approach for Ph+ ALL in terms of upfront therapy, utility of allo-HCT, use of TKI (including their role in the post-HCT setting) and how response to therapy was monitored. Results: Twenty-three of the thirty-two centers completed the survey to provide a completion rate of 72% (Table 1). Twenty-two of the 27 physicians (81%) reported they do not classify patients by risk group according to age and presenting WBC (e.g. low-, intermediate- or high-risk) but rather use response to therapy to identify high risk patients, initially treating all Ph+ ALL patients the same. Eighty-one percent of survey responders recommended allo-HCT in first remission, when a matched sibling donor was available, for Ph+ ALL. Regarding the use of TKI in the post-HCT setting, 13 of 27 (48%) physicians reported using imatinib as maintenance therapy post-HCT as a means to prevent relapse. All physicians reported using PCR techniques for bcr-abl of either bone marrow, peripheral blood or both to monitor treatment response with frequencies ranging from monthly to every six months. Conclusion: Treatment of pediatric Ph+ ALL appears variable and center dependent. Classifying patients into low-, intermediate- or high-risk disease based on age and presenting WBC was not shown to be standard practice but rather using treatment response to identify high-risk patients. This survey identified a trend toward less allo-HCT in 2008 for Ph+ ALL compared to years past. Despite the trend toward less HCT, the treatment consensus in 2008 for pediatric Ph+ ALL remains MSD allo-HCT when available. Use of imatinib was recognized by all survey responders as standard of care in upfront therapy for Ph+ ALL, but the use of imatinib or other TKI in the post-HCT setting as maintenance therapy remains in question. Prospective pediatric clinical trials will be necessary to determine the optimal strategy for the Ph+ diseases. Table 1. Pediatric Centers British Columbia's Children's Hospital Children's Hospital of Pittsburgh Children's Memorial Medical Center–Northwestern Cincinnati Children's Hospital Medical Center City of Hope Columbia Presbyterian College of Phys & Surgeons Doernbecher Children's Hospital-OHSU Duke University Medical Center Mayo Clinic Medical College of Wisconsin Nationwide Children's Hospital Schneider Children's Hospital St. Jude Children's Research Hospital Stollery Children's Hospital–Edmonton Texas Children's Cancer Center at Baylor College of Medicine The Children's Hospital of Philadelphia The University of Chicago Comer Children's Hospital University of California at San Diego/Rady Children's Hospital San Diego UCSF School of Medicine University of Florida University of Michigan–C.S. Mott Children's Hospital University of Minnesota Children's Hospital, Fairview Washington University–St. Louis