A Population-Based Study on the Treatment and Long-Term Outcomes of Thymoma: A 25-year Single Institution Retrospective Review

Abstract

<h3>Purpose/Objective(s)</h3> Thymomas are rare neoplasms arising from the thymic epithelium and there are a limited number of prospective studies in this setting to guide its management. The purpose of this study was to conduct a population-based analysis of patient and tumor factors associated with overall survival (OS) and progression-free survival (PFS) in patients with thymoma. <h3>Materials/Methods</h3> A retrospective review was performed on all thymoma patients diagnosed and treated between January 1994 and December 2019 at our center. Baseline demographic, tumor, surgery, radiotherapy, chemotherapy, and survival data were collected using our institution's cancer registry. Overall survival (OS) and progression-free survival (PFS) were analyzed using the Kaplan-Meier method. Cox regression analysis was used to identify risk factors for survival. <h3>Results</h3> 245 patients were identified for analysis. The median follow up was 77 months. A total of 214 patients underwent definitive surgery. Of these, 103 (48%) underwent surgery alone, 84 (34.2%) received adjuvant radiotherapy, 3 (1.4%) received adjuvant chemotherapy, and 6 (2.8%) received adjuvant concurrent chemoradiation. 10 (4.1%) patients underwent neoadjuvant chemotherapy followed by definitive surgery and 8 (3.7%) patients underwent neoadjuvant chemoradiation followed by definitive surgery. A total of 31 patients did not receive definitive surgery. Of these, 9 (29%) received concurrent chemoradiation, 5 (16.1%) received palliative chemotherapy, 7 (22.6%) received palliative radiotherapy, and 10 (32.3%) had supportive management. At presentation, 36 (16.8%) patients presented at Masaoka-Koga Stage I, 135 (63.1%) at stage II, 32 (15.0%) at stage III, and 11 (5.1%) at stage IV. Among the patients who received definitive radiotherapy, a median dose of 50 Gy was given. A median dose of 30 Gy was given for palliative radiotherapy. 91 (81%) patients had 3DCRT, 18 (15%) had VMAT and 5 (4%) patients were treated with IMRT. Preliminary analysis shows a 10-year OS and PFS rate of 74% and 70% respectively. The 10-year OS for stages I, II, III, and IV were 89%, 82%, 67%, and 44% respectively. The 10-year PFS for stages I, II, III, and IV were 89%, 78%, 64%, and 33% respectively. On multivariate analysis, worse OS was significantly associated with greater age at diagnosis (Hazard Ratio [HR], 1.03; 95% Confidence Interval [CI], 1.00-1.05; P=0.009), Masaoka Stage IV vs. Stage I (HR, 3.51; CI, 1.07-11.50, P=0.038), and no definitive surgery vs. definitive surgical management (HR, 3.47; CI, 1.10-10.98, P=0.034). Both age at diagnosis (HR, 1.04; CI 1.01-1.07, P=0.001) and stage IV vs stage I (HR, 11.20; CI, 3.45-36.38; P<0.001) were associated with worse PFS. <h3>Conclusion</h3> Thymoma is a clinically heterogenous disease with a wide variation in treatment practices. Survival rates in our population are comparable to previous published reports. Late Masaoka-Koga stage, age at diagnosis, and definitive surgical management are important prognostic factors for overall survival.