3734 - Long-Term Treatment Outcomes and Late Toxicity between Childhood and Adult Nasopharyngeal Carcinoma in the Era of IMRT

S. Shiran, X. Huang, K. Wang, J. Wang, Y. Zhang, Y. Qu, X. Chen, J. Zhang, J. Luo, R. Wu, and J. Yi; Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China

Purpose/Objective(s): To make a comparison between childhood nasopharyngeal carcinoma (NPC) and adult NPC patients regarding treatment outcomes and late toxicities in the era of IMRT. Materials/

Methods: A total of 140 childhood and adolescent NPC patients aged =21 years treated at our institution between January 2004 and November 2019 were reviewed. A propensity score matching method was used to screen 280 matched adult NPC patients at a ratio of 1:2. Treatment outcomes and late sequelae between child and adult groups were compared.
Results: Compared with adult NPC, childhood and adolescent NPC exhibited distinct differences in clinical features with more advanced stages, more sensitive to radiotherapy and more favorable prognosis. The 5-year overall survival (OS), progression-free survival (PFS), locoregional relapse rate (LRR) and distant metastasis (DM) rates for the child group versus the adult group were 83.1% versus 71.9% (P=0.001), 71.6% versus 60.9% (P=0.023), 3.1% versus 12.6% (P=0.002), and 25.8% versus 29.3% (P=0.498), respectively. After neoadjuvant chemotherapy (NACT), 63.9% of childhood and adolescent NPC patients achieved complete response (CR) or partial response (PR), while in adult group, a CR/PR was observed in 51.4% patients. It is interesting to note that, in childhood and adolescent patients who receive NACT, there were no differences according to OS, PFS, LRR and DM when comparing CR/PR patients with those individuals with SD/PD. However, the response to NACT was a significant prognostic factor in adult group regarding OS (P=0.017), PFS (P<0.001) and DM (P<0.001). More patients in child group were successfully salvaged compared with patients in adult group (42.1% versus 21.7%, P=0.015). The 2-year and 5-year PFS-2 (PFS-2 was defined as the duration from the date of first progression until further progression) were 56.7% and 36.4% in child group versus 35.9% and 19.5% in adult group (P=0.012). Late toxicities showed higher incidence in adult group regarding xerostomia (P=0.015), neck fibrosis (P=0.014) and temporal lobe necrosis (P=0.060), but lower incidence in hypothyroidism (P=0.030) when compared with child group.
Conclusion: Childhood and adolescent NPC patients have better survival outcomes than adult patients, regardless of the higher proportion of locoregionally advanced disease. The low locoregional relapse rate indicated young patients are more sensitive to radiotherapy. Compared with adult patients, there is a higher rate of successful salvage treatment in children and adolescents. Late toxicity profiles were differed between child patients and adult patients.