Late toxicity comparison of alkylating-based maintenance regimen with cyclophosphamide (VAC) vs ifosfamide (VAI) in Ewing sarcoma survivors treated in the randomized clinical trial Euro-EWING99-R1 in France.

In Euro-EWING99-R1 randomized trial, cyclophosphamide was shown to be noninferior to ifosfamide in the consolidation of standard-risk Ewing sarcoma (SR-EWS) after a common induction with VIDE (vincristine-ifosfamide-doxorubicin-etoposide). We present the results of the late effects analysis of VAC (vincristine-dactinomycin-cyclophoshamide) vs VAI (vincristine-dactinomycin-ifosfamide) conducted in Euro-EWING99-R1 French cohort. Of 267 French randomized patients, 204 were alive and free-of-relapse at 5-years including 172 with available long-term follow-up data concerning cardiac, renal and/or gonadal functions (sex-ratio M/F = 1.3, median age at diagnosis = 14 years): 84 randomized in VAC (median cumulative doses: cyclophosphamide = 9.7 g/m2 , ifosfamide = 59.4 g/m2 ) and 88 in VAI (ifosfamide = 97.1 g/m2 ). With a median follow-up of 10 years (range = 5-17), five late relapses and five second malignancies were recorded. The 10-year event-free survival among 5-year free-of-relapse survivors was similar between VAC and VAI (93% vs 95%, P = .63). We estimated the 10-year cumulative probabilities of cardiac and kidney toxicities at 4.4% (95% confidence interval [95% CI] = 1.1%-7.6%) and 34.8% (95% CI = 26.8%-42.0%), respectively. Cardiac toxicity cumulative probability was similar in both arms, whereas kidney toxicity was higher in VAI (at 10 years, 43.0% vs 25.7%, P = .02), resulting from significant difference in glomerular toxicity (31.1% vs 13.1%, P < .01). At 10 years, gonadal toxicity was observed in 27% and 28% of pubertal men and women, respectively, without significant difference between VAC and VAI. Kidney and gonadal toxicities represent major issues in Euro-EWING99-R1, with significantly higher risk of kidney toxicities with VAI, without significant gonadal toxicity reduction. These results support the need to limit cumulative doses of both alkylating agents and to use mixed regimen as in VIDE-VAC or VDC/IE (vincristine-doxorubicin-cyclophoshamide/ifosfamide-etoposide).