P28: Pridictors and management for the primary IVa thymoma

Background: We aimed to evaluate the multimodality treatment of prognostic for the patients with IVa thymoma.

Methods: We enrolled 50 consecutive patients with primary IVa thymoma (WHO) treated in the Chest Hospital, China from January 2006 to December 2013. The median age was 45 years (range: 25–70 years). The distribution of WHO pathological type was B1 3 (6%), B2 14 (28%), B3 25 (50%), B thymoma but indetermination 8 (16%), respectively. The media maximum diameter of the primary tumor and pleural tumor were 8.5 cm (range: 3–22 cm) and 2.2 cm (range: 0.5–5 cm). For the initial treatment, 32 (64%) patients underwent extended surgery. A total of 22 patients received chemotherapy and 35 patients received subsequent mediastinal radiotherapy (MRT) or plural radiotherapy (PRT).

Results: The median follow-up interval from the initial diagnosis was 37 months (range, 12–94 months). Five-year survival was 51%. Pleura was the most common site of recurrence and progress (14 patients in the surgery group, 45%). There were significant differences for 5-year-survival between the patients with or without surgery (62.6% for surgery vs. 35.6% for non-surgery patients, P=0.011) and between the patients with or without radiotherapy (60.7% for RT vs. 33% for no-RT patients, P=0.00). In univariate analysis, the complete resection of the primary mediastinum tumor, the resection of the plural tumor, surgical management and PRT showed an good effect of on OS. In multivariate analysis, only plural radiation was associated with prolonged survival (P=0.041). For the surgery group, the plural metastasis number more than four on the CT before surgery was significant risk factors for recurrence, while the non-complete resection of the primary mediastinum tumor was significant risk factors for overall survival. For the non-surgery group, radiation (include MRT and PRT) was the only independent factors predicting long-term survival. Chemotherapy was associated neither with improved progression-free survival for the non-surgery group (P=0.771) nor with freedom-from-recurrence for the surgery group.

Conclusions: For the patients of primary Iva stage thymoma, our retrospective analysis showed that complete resection of the primary mediastinum tumor and PRT were associated with better outcome. Nevertheless, there were adjuvant PRT after surgery and PRT aimed at the recurrent plural when recurrence in our date. We have no idea when and how PRT take part in the treatment progress. Further prospective studies are warranted to clarify the role of RT in the treatment of these patients.

Keywords: Stage IVa thymoma; complete resection; plural radiotherapy; mediastinal radiotherapy