Failure patterns for thymic carcinoma with completed resection and postoperative radiotherapy

We aimed to evaluate the pattern and risk factors of disease failure in patients with thymic carcinoma after complete resection and postoperative radiotherapy (PORT).

We retrospectively analyzed 127 patients with thymic carcinoma who underwent PORT after complete resection between 2003 and 2020 in our center. Data on clinical characteristics and radiation fields were collected. Failure patterns were recorded as locoregional (disease appearing in the tumor bed or regional lymph nodes), pleural, or distant failure (including hematogenous metastasis and nonregional lymph node metastasis).

All patients underwent tumor bed irradiation. During a median follow-up period of 64 months, disease failure was observed in 51 patients (40.2 %). The 5-year disease-free survival (DFS) and overall survival rates were 58.9 % and 85.0 %, respectively. The sequence of failure patterns was distant (n = 41, 32.3 %), pleural (n = 28, 22.0 %), and locoregional failure (n = 19, 15.0 %). Of the locoregional failure patients, failures occurred in-field in three patients (2.4 %), marginal failure in one patient (0.8 %), out-of-field failure in nine patients (7.1 %), synchronous in-field and out-of-field failures in two patients (1.6 %), synchronous marginal and out-of-field failures in two patients (1.6 %), and unknown failure fields in two patients (1.6 %). Multivariate analysis showed that Masaoka stage (hazard ratio [HR], 3.88; p = 0.000) and adjuvant chemotherapy (HR, 0.47; p = 0.015) were independent predictors of DFS.

The most common failure was distant, the Masaoka stage and adjuvant chemotherapy were independent predictors of DFS, and low locoregional failure-supported tumor bed irradiation was sufficient for patients with thymic carcinoma after complete resection.