PAX3/7–FOXO1 fusion status in older rhabdomyosarcoma patient population by fluorescent in situ hybridization

Abstract

In pediatric alveolar rhabdomyosarcoma, the PAX3-FOXO1 and PAX7-FOXO1 gene fusions are prognostic indicators, while little is known concerning this disease in older patients. To determine whether PAX3/7-FOXO1 fusion gene status correlates with outcome in adolescent, young adult, and adult rhabdomyosarcoma patients, the histological, immunohistochemical, and clinical characteristics of 105 patients followed at The University of Texas MD Anderson Cancer Center from 1957 to 2001 were evaluated. The samples were assembled into a tissue microarray, and fusion gene status was determined by fluorescence in situ hybridization using PAX3, PAX7, and FOXO1 loci-specific probes. The disease characteristics and specific gene fusion were correlated with patient outcomes using the log-rank test. Fifty-two percent of the samples exhibited a PAX3-FOXO1 fusion, 15% the PAX7-FOXO1 fusion, and 33% were negative for a rearrangement of these loci. The presence of PAX3/7-FOXO1 translocation was significantly associated with a higher frequency of metastatic disease. Although a statistically significant correlation between the PAX3/7-FOXO1 fusion gene status and overall survival was not identified, there was a trend toward better outcomes for patients with fusion-negative RMS. Therefore, identification of a FOXO1 fusion appears to be an interesting tool for predicting outcomes in older rhabdomyosarcoma patients and is worth further investigations in this rare subgroup of RMS population.