O2192: Thymic Carcinoma and Thymoma in Children, Adolescents, and Young Adults: A National Cancer Database Analysis of 1,069 Patients

Background: Thymic epithelial tumors (carcinoma and thymoma) are rare in young patients, with a paucity of data regarding clinical characteristics and outcomes. We aimed to evaluate clinical characteristics, treatment strategies, and survival outcomes for pediatric, adolescent, and young adult (YA) patients with thymic epithelial tumors.

Methods: The National Cancer Database was queried for thymic carcinoma and thymoma in patients (ages 0-39) from 2004-2019. Descriptive statistics were conducted for pediatric and YA patients with thymoma and thymic carcinoma. Univariable Cox regression was used to identify factors associated with overall survival. Variables with significant associations were included in a multivariable model. Kaplan-Meier analyses were performed for each tumor type, stratifying by age (pediatric/adolescent, aged 0-21 years, and YA, aged 22-39 years).

Results: We identified 1,069 pediatric and YA patients, of which 193 (18%) patients had thymic carcinoma (33 pediatric/adolescent and 160 YA) and 876 (82%) patients had thymoma (65 pediatric/adolescent and 811 YA). The overall cohort was 60% male. The average age for pediatric/adolescent patients was 17 years, and for YA patients was 33 years. Most patients were treated with surgical resection (77%) and the most common surgical approach was open (72%). Fewer than half of the patients received radiation (43%) or chemotherapy (45%). The 5-year survival rate for thymic carcinoma was 36.0% and for thymoma was 86.5%. In a multivariable model investigating predictors of overall survival, thymic carcinoma compared to thymoma was associated with worse survival (p < 0.001, HR 2.9), along with Masaoka stage 3 (p=0.001, HR 2.0), Masaoka stage 4 (p < 0.001, HR 3.0), receipt of chemotherapy (p=0.020, HR=1.5) and positive surgical margins (p=0.015, HR 1.6). In contrast, surgical resection was associated with improved survival (p < 0.001, HR 0.2), along with age (p=0.002, HR 0.97) (Table 1). In a sub-analysis of thymomas, there were no significant survival differences for pediatric/adolescent patients versus YA patients (p=0.17). For thymic carcinoma, pediatric/adolescent patients had significantly worse survival compared to YA patients (p=0.03) (Figure 1).

Conclusion: Advanced disease and thymic carcinoma are negative prognostic indicators for thymic epithelial tumors, while complete surgical resection is associated with improved survival. Notably, the overall survival for thymic carcinoma was poor, with pediatric patients experiencing worse survival compared to their YA counterparts for thymic carcinoma – a finding that did not apply to thymoma. By analyzing the largest cohort of pediatric patients with thymic carcinoma and thymoma, our study reveals important differences in prognostic factors and survival based on age and disease histology.