Assessing the Prognostic Significance of Histologic Response in Osteosarcoma: A Comparison of Outcomes on CCG-782 and INT0133-A Report From the Children's Oncology Group Bone Tumor Committee.

BACKGROUND: The prognostic value of histologic response for osteosarcoma may have changed with induction chemotherapy schedules over time. We hypothesized that the increased intensity of induction therapy provided on INT0133 compared to the Children's Cancer Group study CCG-782 would diminish the impact of histologic response on the risk of events after definitive surgery. METHODS: Retrospective analysis was performed for patients aged <22 with newly diagnosed nonmetastatic osteosarcoma enrolled on CCG-782 and INT0133. Clinical factors were evaluated for association with response and outcome. Good response was defined as <5% viable tumor at resection. Associations of response, study, and postdefinitive surgery event-free survival (EFS-DS) were determined using Cox proportional hazard models. EFS-DS was estimated by Kaplan-Meier methodology. RESULTS: Data were available for 814 patients (206 CCG-782, 608 INT0133). For good responders, 10-year EFS-DS (±SE) was 75.4% ± 7.7% for CCG-782 and 70.8% ± 3.1% for INT0133. For poor responders, 10-year EFS-DS was 39.9% ± 4.9% for CCG-782 and 58.4% ± 3.1% for INT0133. Histologic response predicted outcome across studies (P < 0.0001). Significant interaction between study and histologic response was observed for EFS-DS (P = 0.011). Using proportional hazards regression, INT0133 poor responders had less risk of events compared to CCG-782 poor responders (relative hazard ratio (RHR) = 0.6:1), but good responders on INT0133 had a greater risk of events compared to CCG-782 good responders (RHR = 1.53:1). CONCLUSION: We observed an inverse relationship between the predictive value of tumor necrosis and intensity of induction therapy, raising questions about the true prognostic value of histologic response. This highlights the need for novel markers to develop strategies for treatment in future trials.

Dexamethasone versus prednisone and daily oral versus weekly intravenous mercaptopurine for patients with standard-risk acute lymphoblastic leukemia: a report from the Children's Cancer Group.

Conventional therapy for childhood acute lymphoblastic leukemia (ALL) includes prednisone and oral 6-mercaptopurine. Prior observations suggested potential advantages for dexamethasone over prednisone and for intravenous (IV) over oral 6-mercaptopurine, which remain to be validated. We report the results of a randomized trial of more than 1000 subjects that examined the efficacy of dexamethasone and IV 6-mercaptopurine. Children with National Cancer Institute standard-risk ALL were randomly assigned in a 2 x 2 factorial design to receive dexamethasone (6 mg/m(2)/d) for 28 days in induction, plus taper, compared with prednisone (40 mg/m(2)/d). The second randomized assignment was for daily oral or weekly IV 6-mercaptopurine during consolidation. During maintenance, 5 days of the randomized steroid was given monthly, at the same dose, and all patients received daily oral 6-mercaptopurine. During delayed intensification, all patients received a dexamethasone dosage of 10 mg/m(2)/d for 21 days, with taper. Intrathecal (IT) methotrexate was the sole central nervous system-directed therapy. Patients randomly assigned to receive dexamethasone had a 6-year isolated central nervous system-relapse rate of 3.7% +/- 0.8%, compared with 7.1% +/- 1.1% for prednisone (P =.01). There was also a trend toward fewer isolated bone marrow relapses with dexamethasone. The 6-year event-free survival (EFS) was 85% +/- 2% for dexamethasone and 77% +/- 2% for prednisone (P =.002). EFS was similar with oral or IV 6-mercaptopurine; however, patients assigned to IV 6-mercaptopurine had decreased survival after relapse.