Higher rates of metastatic disease may explain the declining trend in Swedish paediatric rhabdomyosarcoma survival rates

AimPositive outcomes for paediatric rhabdomyosarcoma (RMS) were high in Sweden during the 1990s, but the last decade has seen decreasing trends in overall survival rates. We investigated the incidence, patient and disease characteristics, treatment and outcome of RMS to see whether any reason could be found for this decline. MethodsThis study included 210 children under the age of 15 who were diagnosed with RMS and whose details were recorded in the population-based Swedish Childhood Cancer Registry from 1984 to 2010. ResultsThe overall annual incidence of RMS was 4.9 per million, and the 5-year overall survival rates were 59 7% in 1984-1989, 78 +/- 5% in 1990-1999 and 71 +/- 5% in 2000-2010. When patients with localised disease were analysed separately, there was no difference in the 5-year survival rates between 1990 and 1999 (82 +/- 5%) and 2000-2010 (81 +/- 5%), but the outcome in 1984-1989 (53 +/- 8%) was significantly worse. The prevalence of metastatic disease was unexpectedly high during 2000-2010 (28%, p = 0.010), compared to an overall mean of 18% for the whole study period. ConclusionOur results suggest that a higher rate of metastatic disease may explain the declining trend in overall survival rates in paediatric RMS in Sweden over the last decade