Minimally invasive thymectomy: the best option for early and locally advanced epithelial thymomas

In this issue, Hwang et al. [1] present an interesting study comparing the outcomes of a minimally invasive approach (VATS) versus open surgery in the treatment of thymic epithelial tumours. For their purpose, a retrospective analysis of 1239 patients who underwent thymectomy between January 2000 and December 2013, were collected from the database of the Korean Association for Research on Thymus, involving 4 institutions. The analysis comprised univariable and multivariable analyses of unmatched data and a subsequent propensity score matching analysis comparing 2 groups of 378 patients with Masaoka–Koga stage I and II tumours, adjusting for age, sex, autoimmune symptoms, body mass index, tumour size and histologic type.

The authors observed that there were no significant differences in terms of overall survival, disease-free survival and R0 resection rates between the open and video assisted thoracic surgery (VATS) approaches. Operative time and postoperative length-of-stay were shorter in the VATS thymectomy group. In general, these results confirm what has been previously reported for Masaoka stage I thymomas, but extending also to stage II.

The authors should be congratulated for their outstanding number of cases analysed. Although their results are well known and have been reported previously, the present study is empowered by their high number of cases accrued and the consistent statistical analysis. Unfortunately, the present study suffers from the usual weakness of retrospective analyses and from their multicentric nature. It remains unclear whether some sort of variability in terms of preoperative, surgical and postoperative management persisted among participating centres. In addition, given the long period of study (14 years), it could have been desirable to compare early and late periods, given the fact that the skills with a minimally invasive approach would have improved with time, and this leads to a time and experience related bias.

Also, there is no information regarding the minimally invasive approach technique. Although most frequently approached by the right side, there might be cases of bilateral or subxiphoid approaches that could have had an influence on early postoperative outcomes, completeness of resection and recurrence rates.

Although minimized by the propensity score matching analysis, some selection bias is unavoidable. For instance, patients with myasthenia gravis underwent open approaches in all cases. This subgroup of patients presents differential clinical features that make them not comparable with non-myasthenic thymomas. In fact, we do not agree that the coexistence of myasthenia gravis should be a key factor to choose an open approach.

In addition, those patients converted from a minimally invasive to an open approach (either for bleeding or for anatomical resectability concerns) were allocated to the minimally invasive group in the analysis, and, possibly, it would have been more appropriate to be allocated in the open group, because operative time, hospital stay and chest tubes duration were more likely to be consistent with an open approach.

Of note, a high rate of operative complications was found in the open approach (9%) as opposed to 2.7% in the VATS approach group. Unfortunately, the authors did not provide detailed information on the type of operative complications observed.

Despite these drawbacks, the authors were able to demonstrate that, not only in Masaoka stage I thymomas but also in stage II, a VATS thymectomy may ensure a complete resection. Another recent propensity-matched study on patients undergoing either trans-sternal or minimally invasive thymectomy for stage I–II thymoma demonstrated less complications in the VATS thymectomy group, with most complications in the open approach being related to the sternotomy [2]. Although there are no randomized trials comparing VATS versus open thymectomy, 2 meta-analyses addressed the issue [3, 4]. Both studies demonstrated reduced postoperative blood loss, reduced postoperative pain scores, reduced overall complications rates and reduced postoperative hospital stay with VATS thymectomy compared with open thymectomy, while achieving microscopically complete resection and loco-regional recurrence rates similar than the open approach. Other investigators have observed similar outcomes with VATS thymectomy [5–8].

To summarize, the report by Hwang et al. [1] confirms that VATS thymectomy achieves the same long-term oncological outcomes in terms of overall survival and disease-free survival than the open approaches, while demonstrating less early complications and hospital stay, for both Masaoka stages I and II. This adds to the increasing evidence that Masaoka stages I–II can be safely resected by a minimally invasive approach with less operative morbidity than an open approach, while ensuring the highest standards in terms of long-term oncological outcomes and therefore should be taken as a first-choice approach when considering a thymectomy in these patients.

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