Rethinking the Definition of High Risk in Pediatric Salivary Gland Carcinoma

Objective: Indications for adjuvant radiation in pediatric salivary gland carcinoma rely on high-risk criteria extrapolated from adult data. We sought to determine whether adult-derived high-risk criteria were prognostic in children aged ≤21 years or young adults aged 22 to 39 years. Study Design: Cross-sectional analysis of a hospital-based national registry. Setting: Patients were identified from the National Cancer Database between 2004 and 2015. Methods: High-risk criteria were defined as adenoid cystic histology, intermediate/high grade, T3/T4, positive margins, and/or lymph node involvement. Exact matching was used to adjust for differences in baseline characteristics between pediatric and young adult patients. Results: We identified 215 pediatric patients aged ≤21 years, 317 patients aged 22 to 30 years, and 466 patients aged 31 to 39 years. Within the pediatric cohort, there was no significant difference in overall survival (OS) between low- and high-risk groups (5-year OS, 100% vs 98.5%; P =.29). In contrast, within the young adult cohorts, there was a significant difference in OS between low- and high-risk groups in patients aged 22 to 30 years (5-year OS, 100% vs 96.1%; P =.01) and 31 to 39 years (5-year OS, 100% vs 88.5%; P <.001). When high-risk patients were matched 1:1 on high-risk criteria and race, pediatric patients were associated with better OS than those aged 22 to 30 years (P =.044) and those aged 31 to 39 years (P =.005). Conclusion: Children have excellent OS, irrespective of adult-derived high-risk status. These findings underscore the need to understand how age modifies clinicopathologic risk factors.