Predictors of recurrence in thymic tumors: Importance of invasion, World Health Organization histology, and size

Objective: This study sought to define predictors of recurrence after resection of thymic tumors. Methods: A single-institution retrospective study was performed of 179 patients who underwent resection of a thymic tumor from 1972 through 2003. Results: Resection was complete in 90% (161/179) of patients. After a median follow-up of 115 months, the recurrence rate was 11% (20/179), the tumor-related death rate was 7.8% (14/179), and the overall death rate was 36.3% (65/179). Tumor recurrence correlated with advanced stage and histology (P < .0001). The difference in recurrence between Masaoka stage I (0) and II(1.7% [1/59]) was insignificant. Recurrence rates correlated with World Health Organization tumor type: A and AB, 0%; B1 and B2, 8% (4/51); B3, 27% (14/51); and C, 50% (2/4; P < .0001). Tumor size separation into quintiles demonstrated a step-up of recurrence at 8 cm (< 8 cm, 1.8% [2/113]; >= 8 cm, 28% [18/64]; P <.003). Multivariate Cox modeling demonstrated that Masaoka stage (odds ratio, 5.70; P <.001), World Health Organization histology (odds ratio, 5.77; P =.003), and size (odds ratio, 1.16; P = .001) were independent predictors of recurrence. Conclusion: The Masaoka staging system could be collapsed to 3 degrees of invasion by combining stages I and II. The World Health Organization histologic type can be simplified for clinical. use into A (A, AB), early B (B 1, 132), advanced B (133), and C tumors. Size of 8 cm or larger is an independent risk factor, even when patients with Masaoka stage III tumors are considered alone, and might identify candidates for preoperative therapy.