Alveolar Rhabdomyosarcoma (RMA) are characterised by chromosomal translocations fusing the PAX3 or PAX7 gene with FKHR in ~85%. Previous studies have suggested that PAX3/7-FKHR fusion types are related to prognosis. In order to prove these findings we performed a retrospective analysis of the PAX-FKHR fusion status and its relation to outcome in patients treated in the CWS trials.

Between 1986 and 2004, out of 446 RMA patients treated in four consecutive CWS trials (CWS-86, -91, -96 or -2002-P), tumor samples from 121 patients with adequate quality for analysis of PAX-FKHR fusion status by RT-nested PCR were available. Survival analysis depending on clinical risk factors and fusion status was performed using the Kaplan-Meier Method, the log rank test and the Cox regression model.

There were no major differences in distribution of known risk factors in the analysed cohort of 121 patients compared to all patients enrolled in the CWS trials. PAX-FKHR fusions were detected in 83%: 72 PAX3-, 29 PAX7-FKHR fusions. Patients with PAX3-FKHR positive tumors more often showed a pattern of adverse clinical risk factors (age > 10 years, primary metastases, lymph node involvement) than the PAX7-FKHR positive group. The 5-year event free survival rate of patients with initially metastatic tumors positive for either of the two fusion transcripts was significantly lower compared with the fusion transcript negative cohort and the non-analysed RMA patients. There was no significant outcome difference between patients with PAX3-FKHR and PAX7-FKHR positive tumors in uni- and multivariate analysis.

In the present analysis, which is to our knowledge the largest reported so far, PAX-FKHR fusion type was no significant predictor for prognosis, thus not supporting results of previous studies.