Factors influencing outcome in thymic epithelial tumors (TET).

Abstract

7108 Background: TET represent a heterogeneous collection of rare tumors, thymoma and thymic carcinoma (TC). Prognosis is often based on WHO histology and Masaoka Stage (MS) with small series often lacking long-term follow-up or advance stage disease. We examined predictors of relapse, disease-free survival (DFS) and overall survival (OS) based on WHO classification and MS. Methods: A retrospective analysis was performed on patients(pts) with TET seen at IUSCC from 1976 to 2011 with available tissue blocks. MS, WHO histology, demographics, autoimmune co-existence and non-TET neoplasms were correlated with DFS and OS (via Kaplan-Meier analysis). Results: Of 251 pts identified, MS at diagnosis was I(n=74), II(n=43), III(n=71), IVa(n=38), IVb(n=12) and indeterminate (n=13). The histology were thymoma (n=195) and TC (n=56). Median age was 51(10-88) and (M:F =121:130). Autoimmune disease was present (n=82) (myasthenia gravis n=52) and non-TET neoplasms (n=36). Therapy after diagnosis included surgery alone (n=115), radiation (n=29), chemo (n=71), chemo-radiotherapy (n=29), indeterminate(n=7). Median follow up was 69 months (1 to 399.5). DFS for stages I,II,III at 5 years was 83%, 71% and 39%; DFS was associated with MS (p<.001) and WHO classification (p=.028). The 5yr and 10yr OS for stages I, II, III, IVa, IVb were 90%, 94%, 80%, 55%, 14% and 65%, 52%, 53%, 28%, 0%. The 5yr OS for WHO classification were: A/AB-89%, B1/B2/B3-98% and C-30% and 10yr survivals were 89%, 62%, 0%. OS was associated with MS (p<.01) , WHO classification (p<.001) and autoimmune disease (p=.03). Late relapses (>5yr) occurred in 13 (23%) pts, including 3 with Stage I and 2 with WHO A classification. Conclusions: MS, WHO classification and autoimmune disorders were statistically significant with OS and with DFS for MS and WHO. TC prognosis is significantly worse than thymoma. The improved OS with autoimmune disease requires further investigation but raises the possibility of benefit derived from earlier diagnosis and/or heightened immune surveillance. These data support the notion that all TET, regardless of histologic subtype or clinical stage, are malignant with a capacity for metastasis. As relapses beyond 5 years are common, lifelong follow-up for TET is recommended.