Targeted therapies for the treatment of chronic myeloid leukemia have become common, even enabling some patients to achieve a deep molecular response that allows them to discontinue use altogether.
Two second-generation tyrosine kinase inhibitors (TKIs) for pediatric patients who are positive for the Philadelphia (Ph) chromosome and in chronic phase are available in the United States (dasatinib and nilotinib), as is the first-generation TKI imatinib.1,2 Not all TKIs are available worldwide, however, and numerous questions remain regarding the long-term outcomes of TKIs in the pediatric population.3 As was recently published in Cancer Therapy Advisor, without established treatment guidelines, most clinicians apply adult guidelines, but that may change with the results from a long-term, large cohort study on imatinib in the pediatric population.4
CML-PAED-II enrolled 156 patients under the age of 18 with newly diagnosed CML (146 of whom were diagnosed with chronic phase, 3 with accelerated phase, and 7 with blastic phase disease).4 In this study, all patients received imatinib up-front (300 mg/m2, 400 mg/m2, or 500 mg/m2, respectively). All patients were recruited from March 2004 through December 2015. There was a 97% (95% CI, 94.2-99.9%) event-free survival by 18 months in those with chronic phase disease. Further, complete cytogenetic response by month 12 and major molecular response by month 18 were achieved in 98%, 63%, and 59% of the patients, respectively. Secondary endpoints included time to progression, overall survival (OS), time to loss of response, and treatment-related toxicities, among others. A total of 38 patients (27%) experienced imatinib failure, and 28 of 148 patients (19%) underwent stem cell transplantation (SCT).
“With pediatric CML, the long-term follow-up is crucial to ensure the survival curves are really stable,” Richard Aplenc, MD, PhD, MSCE, of the Children’s Hospital of Philadelphia (CHOP) in Pennsylvania, told Cancer Therapy Advisor. “One of the strengths of this study is that their OS is a 5-year time frame.”
“None of the TKIs are curative in nature and most will be taken for a lifetime,” Shweta Bansal, pediatric oncologist in Mumbai, India, said.5
The “very large number of patients who were treated at multiple centers over an extended period of time with strong follow-up data provides a level of weight and credibility to the authors’ findings and helps make those findings more generalizable,” Dr Aplenc said, but the low numbers of accelerated and blast phase patients means the study results do not provide additional guidance on decision-making for those populations.
“It is helpful, however, to have another piece of literature saying these patients can be treated with TKIs initially,” he said.