Elective Nodal Irradiation as Adjuvant Radiotherapy for Advanced Thymomas and Thymic Carcinomas

We evaluated the clinical outcome of patients with stage III to IV thymomas (Ts) or stage II to IV thymic carcinomas (TCs) treated with complete thymectomy and local radiation therapy (LRT, targeting the tumor bed and anterior mediastinal areas only) or elective nodal irradiation (ENI, targeting the entire mediastinal and supraclavicular regions).

Data from 47 patients diagnosed with Ts or TCs and treated with surgery and adjuvant RT from May 2002 to May 2015 were analyzed. The standard RT dose was 50.4 Gy in 28 fractions; patients with a positive resection margin received a further 4 to 10 Gy. Survival outcomes determined at 5 years included local recurrence-free survival, regional recurrence-free survival, distant metastasis-free survival, and overall survival.

Five-year local recurrence-free survival was similar in both groups (LRT, 94.7% vs. ENI, 96.2%; P = .849). Significant differences were seen in 5-year regional recurrence-free survival (LRT, 55.1% vs. ENI, 83.7%; P = .006); however, tumor size was seen to be a significant factor (< 7 cm, 95.2% vs. ≥ 7 cm, 48.9%; P < .001), and the LRT group contained a greater proportion of patients with ≥ 7-cm tumors (70% vs. 33%). Multivariate analysis demonstrated that tumor size was the only significant prognostic factor (P < .001). No differences in 5-year overall survival were seen (LRT, 91.7% vs. ENI, 100%; P = .106).

ENI may not be indicated in all cases, as additional benefit in reducing recurrence or improving survival was not predominant. LRT seems to be a feasible option with favorable patient outcomes.