Tumor perimeter and lobulation as predictors of pleural recurrence in patients with resected thymoma

Recurrence of resected thymoma frequently occurs during follow-up, with pleural recurrence as the most common type. The aim of our study was to identify risk factors for pleural recurrence after complete resection of thymoma by investigating clinical, radiological, surgical, and pathological findings.

Retrospective study was performed with 309 patients who had undergone complete resection of thymoma between January 2000 and December 2013. Among these cases, the patients were divided into the no pleural recurrence group (n=285) and the pleural recurrence group (n=24). Radiologic parameters such as maximum tumor diameter, tumor perimeter that contacted the lung (TPCL) and lobulated tumor contour were measured based on computed tomography. A multivariate analysis was performed to estimate risk factors for pleural recurrence including maximum tumor diameter, TPCL, lobulated tumor contour, World Health Organization (WHO) histologic classification, and Masaoka-Koga (M-K) stage.

The median follow-up period was 62 months. The pleural recurrence rate was 7.8% (24/309). After univariate analysis, longer maximum tumor diameter (p<0.001), longer TPCL (p<0.001), lobulated tumor contour (p=0.001), WHO histologic type B2, B3 (p=0.002), and M-K stage III/IV (p<0.001) demonstrated significant differences with risk factors of pleural recurrence. Multivariate analysis revealed that TPCL (per 1cm increase: hazard ratio [HR]: 1.040, 95% confidence interval [CI]: 1.019-1.061, p<0.001), lobulated tumor contour (HR: 5.883, CI: 1.201-28.824, p=0.029), WHO histologic classification B2/B3 (HR: 5.331, CI: 1.453-19.558, p=0.012) and advanced M-K stage (HR: 3.900, CI: 1.579-9.632, p=0.003) were significantly associated with pleural recurrence.

TPCL and lobulated tumor contour as well as WHO histologic classification and M-K stage were independent predictors of pleural recurrence after thymoma resection. Our study demonstrated that radiologic parameters could be useful predictor of pleural recurrence in patients with resected thymoma.