Rhabdomyosarcoma in Adults: A Retrospective Analysis of Case Records Diagnosed between 1979 and 2018 in Western Denmark.

Introduction: Adult rhabdomyosarcoma is a rare tumour that has an inferior survival compared to the paediatric patient population. The reason for this consistently worse outcome remains mostly unknown. It has been suggested that this disparity may be related to biological and/or treatment-related factors, which in the literature has been shown to be distributed differently among paediatric and adult patients. The aim of this study was to clarify treatment outcome and clinicopathological factors for adult patients with rhabdomyosarcoma that were treated in Aarhus, Denmark, since 1979.

Methods: By searching the Aarhus Sarcoma Registers, data for all rhabdomyosarcoma patients, aged 18 years or more, between 1979 and 2018, were retrieved and analysed.

Results: Data from 50 patients were collected. No patients were lost to follow-up. For the entire cohort, 5- and 10-year overall survival rates were 30% and 18%, respectively. The median age was 46.5 years, and the median overall survival was 2.3 years. Tumour histology was embryonal 18%, alveolar 22%, pleomorphic 44%, and not otherwise specified 16%. The tumour site was unfavourable in more than 80% of the patients. Significant factors associated with inferior overall survival were histology and disease stage, although histological subtype was not significant in the multivariate model. Five-year overall survival was 40% for localised disease versus 15% for metastatic disease.

Conclusion: Rhabdomyosarcoma in adults has a poorer prognosis than paediatric rhabdomyosarcoma and other high-grade sarcomas in adults. Adult rhabdomyosarcoma should continue to be treated aggressively, but new and tailored treatment strategies are needed to improve the long-term outcome. Previous predictors of poor survival in paediatric patients were valid in adults except for age, site (favourable versus unfavourable), and tumour size.