Comparison of the progression-free survival between robot-assisted thymectomy and video-assisted thymectomy for thymic epithelial tumors: a propensity score matching study

Background: Robotic system was recently introduced to assist surgeons in performing thymectomy. However, whether robot-assisted thoracoscopic thymectomy (RATT) could replace video-assisted thoracoscopic thymectomy (VATT) and be considered as a superior treatment for thymic epithelial tumors is still controversial. The aim of this study was to evaluate the progression-free survival (PFS) and shortterm clinical outcomes in patients undergoing RATT or VATT by comparing the matched two groups after performing propensity score analysis. Methods: We retrospectively reviewed the clinical data of 295 patients diagnosed with thymic epithelial tumors. There were 60 patients in RATT group and 235 in VATT group. Propensity score matching was done between two groups with variables of age, gender, tumor size, organization histologic classification, original Masaoka stages, presence of myasthenia gravis (MG) and adjuvant therapy. Sixty patients from the RATT group and 60 from the VATT group were matched, fitting the model. The PFS and short-term clinical outcomes of matched groups were compared. Results: After matching, the surgical time in RATT groups was significant shorter than that in VATT groups (P=0.042). Loco-regional recurrence and distal metastasis were detected in 4 patients with thymoma and 1 patient with thymic carcinoma in RATT group and in 25 patients with thymoma and 3 patients with thymic carcinoma in VATT group before matching. PFS were estimated in only thymoma cases. The PFS in RATT group (n=55) intended to be longer than that in VATT group (n=58) after matching (5-year PFS rate: 81.5% and 75.4%, respectively; log-rank P=0.095). Conclusions: RATT has the superiorities over VATT on short-term outcomes due to enabling surgeons to operate in a stable and comfortable environment. Meanwhile, RATT yielded a longer PFS compared with VATT, although the difference was not significant. Therefore, RATT could be considered as a standard approach for the treatment of thymic epithelial tumors.