Population-based survival of pediatric rhabdomyosarcoma of the head and neck over four decades.

Objectives: Clinical trials have reported increases in the survival of pediatric rhabdomyosarcoma (RMS) from 25% in 1970 to 73% in 2001. The purpose of this study was to examine whether survival of pediatric patients with RMS of the head and neck improved at the US population level.

Methods: A population-based cohort of patients with rhabdomyosarcoma of the head and neck aged 0-19 years in the Surveillance, Epidemiology, and End Results (SEER) registry from 1973 to 2013 was queried. The cumulative incidence competing risks (CICR) method was used to estimate risk and survival trends.

Results: 718 cases were identified for analysis. Survival rates at 1-, 5-, and 10-years after diagnosis were 91.2%, 73.2%, and 69.4% respectively. Survival rates at 1 year after diagnosis increased from 82.6% to 93.1% during the study period. In the subdistributional hazard analysis, there was a significantly improved disease-specific risk of death in the first year after diagnosis. Overall risk of death did not improve significantly. Favorable prognostic factors included age <10 years at diagnosis, smaller tumor size, absence of distant metastasis, localized tumors, earlier stage at presentation, grossly complete surgical resection, and embryonal or botryoid histology.

Conclusions: Disease-specific survival in the first year following diagnosis improved, but the change in overall survival at the population level was not statistically significant. These findings should be interpreted in light of the inclusion of patients with distant metastasis at diagnosis, who have poor prognoses, together with the limited statistical power afforded in studies of rare diseases.