The use of radiographic response as the primary end point in phase II osteosarcoma trials may limit optimal detection of treatment response because of the calcified tumor matrix. We performed this study to determine if time to progression could be used as an end point for subsequent studies. Patients and MethodsWe performed a retrospective analysis of outcome for patients with recurrent/refractory osteosarcoma enrolled in one of seven phase II trials conducted by the Children's Oncology Group and predecessor groups from 1997 to 2007. All trials used RECIST or WHO radiographic response criteria and the primary end point of response rate. The following potential prognostic factors-age, trial, number of prior chemotherapy regimens, sex, and race/ethnicity-were evaluated for their impact on event-free survival (EFS). We used data from a phase II study (AOST0221) of patients with osteosarcoma who were given inhaled granulocyte-macrophage colony-stimulating factor with first pulmonary recurrence who had an EFS as well as biologic end point to determine the historical disease control rate for patients with fully resected disease. ResultsIn each included trial, the drugs tested were determined to be inactive on the basis of radiographic response rates. The EFS for 96 patients with osteosarcoma and measurable disease was 12% at 4 months (95% CI, 6% to 19%). There was no significant difference in EFS across trials according to number of prior treatment regimens or patient age, sex, and ethnicity. The 12-month EFS for the 42 evaluable patients enrolled in AOST0221 was 20% (95% CI, 10% to 34%). ConclusionThe EFS was uniformly poor for children with recurrent/refractory osteosarcoma in these single-arm phase II trials. We have now constructed baseline EFS outcomes that can be used as a comparison for future phase II trials for recurrent osteosarcoma.

HLH is a rare but potentially treatable illness with modern aggressive therapy. Though treatment is more standardized for HLH, the role of race and ethnicity as risk factors for development of disease and impact on outcome may warrant further investigation.

Low systemic exposure to oral mercaptopurine during maintenance therapy for acute lymphocytic leukemia in childhood adversely affects prognosis. Children should be studied at the beginning of maintenance therapy to establish the pharmacokinetics of mercaptopurine, and the dose should be tailored to achieve an appropriate systemic exposure.

Phase I trials in children with cancer represent a safe mechanism to determine the MTD, toxicity profile, and pharmacokinetics of new agents for use in children with cancer.