BACKGROUND: Preclinical models show sequence-dependent synergy with the combination of temozolomide and irinotecan, and a Phase I trial has demonstrated the combination to be tolerable and active in children with relapsed solid tumors. Because responses were seen in patients with Ewing sarcoma (ES) on that trial, additional patients were treated with this combination following study completion. PROCEDURE: We reviewed data from all ES patients treated with temozolomide and irinotecan at four institutions, including seven patients treated on the above Phase I trial. RESULTS: Sixteen patients received a total of 95 courses, with a median of five courses per patient. All patients had either progressive disease (PD) during initial therapy (n = 5) or relapse within 2 years of diagnosis (n = 11). Twelve patients had metastatic disease at diagnosis, including 5 with bone and/or marrow metastases. Patients received oral temozolomide 100 mg/m(2)/day on days 1-5 plus intravenous irinotecan 10-20 mg/m(2)/day on days 1-5 and 8-12, with courses repeated every 21-28 days. We observed 1 complete, 3 partial, and 3 minor responses in 14 evaluable patients, with a median duration of response of 30 weeks. Planned 21-day courses were tolerable and no more toxic than 28-day courses. Myelosuppression was minimal despite heavy pretreatment. Grade 3-4 diarrhea occurred in 11% of courses and was related to higher irinotecan doses. Over 600 irinotecan doses were administered uneventfully at home. CONCLUSIONS: Temozolomide and protracted intravenous irinotecan given in 21-day courses was tolerable and active in patients with advanced ES. Home administration of irinotecan with temozolomide was safe and is reasonable palliative therapy. A formal Phase II study using a uniform dose and schedule is warranted to better define activity.