Prognostic Correlation between Tumor Volume and Complete Resection of Thymoma at Different Masaoka-Koga Stages.

OBJECTIVE: Thymoma is a slow-growing epithelial tumor of thymus gland. Its size is associated with its prognosis. The aim of this study was to analyze the prognostic correlation of tumor volume and complete resection of thymoma at different Masaoka-Koga stages.

METHODS: A retrospective study was carried out, using the data of 502 patients who underwent complete resection of thymectomy at Zhongshan Hospital, Fudan University, in Shanghai, China, from February 2009 to February 2016. The characteristics of the patients were collected. Using Masaoka-Koga staging system, patients were divided into four different subcohorts: Stage I, stage II, stage III and stage IVa/IVb. The relationship between tumor volume and postoperative recurrence was analyzed for each subcohort, using receiver operating curves, cutoff values were obtained. and patients were grouped according to the cutoff values. Survival analysis was performed with the help of Kaplan-Meier method, and the difference between the two survival curves was compared using log-rank test. Whether tumor volume could be used as an independent risk factor for thymoma prognosis was analyzed, using a univariate Cox proportional hazards model.

RESULTS: The area under the curve was 0.718, 0.740, 0.798, and 0.804 for the stage I, II, III, and IVa/IVb subcohorts, respectively, and the cutoff values of tumor volume for predicting recurrence were 47.90 cm3 , 53.70 cm3 , 76.35 cm3 , and 89.05 cm3 , respectively. Patients with tumor volumes greater than the cutoff values had significantly shorter recurrence-free survival than those with tumor volumes less than the cutoff values ( p < 0.001). The results of the univariate Cox proportional hazards model indicated that tumor volume was an independent risk factor for thymoma prognosis and for postoperative prognosis of thymoma in Masaoka-Koga stage I ( p < 0.001).

CONCLUSIONS: Tumor volume is significantly correlated with the postoperative prognosis of thymoma in Masaoka-Koga stage I and can serve as an independent risk factor for predicting postoperative tumor recurrence.