Background: Little was known about the therapeutic result of rhabdomyosarcomas (RMSs) and other malignant tumors until the end of the last century in China. Very few prospective clinical research results have been reported. We designed a RS-99 protocol under close cooperation of a multidisciplinary team including surgeons, radiologists, pathologists, and pediatric oncologists at Shanghai Children's Medical Center. This study aimed to improve the prognosis of childhood solid tumors and analyze the results of different tumors with the same protocol, including RMSs, the Ewing sarcoma family of tumors (ESFTs), and ex-cranial germ cell tumors (GCTs).

Methods: Sixty-six patients with malignant solid tumors [RMS (n=30), GCT (n=22), and ESFT (n=14)] were enrolled on the RS-99 protocol from October 1998 to October 2006. They were 34 girls and 32 boys aged 9 to 194 months. The protocol involved surgery, radiotherapy and chemotherapy which included VCP (vincristine, cis-diaminedichloroplatinum, and cyclophosphamide) and IEV (etoposide, vincristine and ifosfamide) for the low-risk group, AVCP (adriamycin, vincristine, cis-diaminedichloroplatinum, and cyclophosphamide) and IEV for the intermediate-risk group and high-risk group. Peripheral blood stem cell transplantation was suggested for the high-risk group. Radiotherapy was only given for RMS and ESFT. Differences in survival between the groups were determined by comparison of entire survival curves and tested by the Kaplan-Meier method and the log-rank tests.

Results: The 5-year event-free survival (EFS) for the whole group (RMS, ESFT and GCT) was 60%. The 5-year EFS for children with RMS was 35% (95% CI 16-54), GCT was 79% (95% CI 70-88) and ESFT was 72% (95% CI 58-86). The 5-year EFS showed that the patients with RMS in the retroperitoneum-pelvis did not have a better result than those with tumors in other sites (P=0.604). The histological classification of RMS exerted prognostic influence on the estimated 5-year EFS (P=0.04). Tumor stage and risk group were also contributive to prognosis (P=0.008). For GCT patients, the primary sites of tumors and their histological classification did not influence the therapeutic result (P=0.814). The 5-year EFS was 100% in stage I and II versus 62% in stage III and IV patients (P=0.02). Because of the small number of patients, we did not analyze the prognostic factors for patients with ESFT. No organ failure or functional impairment occurred in the patients enrolled in the RS-99 protocol. One ESFT patient developed a second cancer.

Conclusions: The RS-99 protocol is well tolerated and is reasonable for the 3 different tumors. Risk-based grouping protocol design is needed and the protocol for high risk RMS should be revised.

Key words: children; Ewing sarcoma; germ cell tumor; rhabdomyosarcoma

World J Pediatr 2010;6(1):43-49