Novel prognostic groups in thymic epithelial tumors: assessment of risk and therapeutic strategy selection

To assess the role of multimodality treatment on patients with thymic epithelial tumors (TETs) (i.e., thymomas and thymic squamous cell carcinoma) and to define the prognostic classes according to the Masaoka and World Health Organization histologic classification systems.

Primary surgery was the mainstay of therapy. Extended thymectomy was performed in all cases. The cases were primarily staged according to the Masaoka system. Adjuvant radiotherapy was given to patients diagnosed with Masaoka Stage II, III, and IVA TET. Adjuvant chemotherapy was administered in selected cases.

We reviewed the records of 120 patients with TETs, with a mean follow-up of 13.8 years. Of the 120 patients, 98 (81.6%) received adjuvant radiotherapy. Of these 98 patients, Grade 1-2 pulmonary or esophageal toxicity was acute in 12 (12.2%) and late in 8 (8.2%). The median overall survival was 21.6 years. Of the 120 patients, 106 were rediagnosed and reclassified according to the World Health Organization system, and the survival rate was correlated with it. Three different prognostic classes were defined: favorable, Masaoka Stage I and histologic grade A, AB, B1, B2 or Masaoka Stage II and histologic grade A, AB, B1; unfavorable, Stage IV disease or histologic grade C or Stage III and histologic grade B3; intermediate, all other combinations. The 10- and 20-year survival rate was 95% and 81% for the favorable group, 90% and 65% for the intermediate group, and 50% and 0% for the unfavorable group, respectively. Local recurrence, distant recurrence, and tumor-related deaths were also evaluated.

The analysis of our experience singled out three novel prognostic classes and the assessment of risk identified treatment selection criteria.