Temporal trends in pediatric cancer mortality: rare cancers lag behind more common cancers.

Temporal trends demonstrate improved survival for many types of common pediatric cancer. Studies have not examined improvement in very rare pediatric cancers or compared these improvements to more common cancers. In this cohort study of the Surveillance, Epidemiology, and End Results (SEER) registry, we examined patients from 1975 to 2016 who were 0-19 years of age at the time of diagnosis. Cancers were grouped by decade of diagnosis and 3 cancer frequency groups: Common, Intermediate, and Rare. Trends in mortality across decades and by cancer frequency were compared using Kaplan-Meier curves and adjusted Cox proportional hazards models. A total of 50,222 patients were available for analysis, with the top 10 cancers grouped as Common (67%), 13 cancers grouped with Intermediate (24%), and 37 cancers as Rare (9%). Rare cancers had higher rates of children who were older and Black. 5-year survival increased from 63% to 86% across all cancers from the 1970s to the 2010s. The hazard ratio (HR) for mortality decreased from the reference point of 1 in the 1970s to 0.27 (95% CI: 0.25-0.30) in the 2010s in Common cancers, while the HR only dropped to 0.60 (0.49-0.73) over that same period for rare cancers. Pediatric oncology patients have experienced dramatic improvement in mortality since the 1970s, with mortality falling by nearly 75% in common cancers. Unfortunately, rare pediatric cancers continue to lag behind more common and therefore better studied cancers, highlighting the need for a renewed focus on research efforts for children with these rare diseases.