Surveillance of thymic epithelial tumors (TETs)-a narrative review.

Background and Objective: Surveillance after thymic epithelial tumors (TETs) is widely recommended yet poorly studied. While this is not a situation unique to TETs, we seek to evaluate the rational of surveillance after treatment of TETs and summarize current available guidelines. Methods: A literature review was conducted in PubMed/MEDLINE and Google Scholar databases. Articles were included if they discussed the following: (I) the epidemiology and natural history of TETs; (II) the diagnosis of recurrent TETs; (III) the treatment and outcomes of recurrent TETs; (IV) current available guidelines for surveillance or follow-up after treatment of TETs. Key Content and Findings: TETs are rare group of neoplasms that include thymoma, thymic carcinoma and neuroendocrine neoplasms. Thymomas have excellent overall survival but can recur over longer periods of time compared to other malignancies. Thymic carcinoma and neuroendocrine neoplasms have less favorable outcomes but still have prolonged survival even at advanced stages. Moreover, recurrence tends to be asymptomatic and localized to the chest and pleura, making it amenable to local treatments such as surgery and/or radiation. As such, TETs may be positioned to benefit from surveillance but also present unique challenges regarding surveillance. There are no prospective studies addressing surveillance in TETs, but at least 5 guidelines have made recommendations that mostly recommend computed tomography (CT) of the chest in variable frequencies and durations. Most agree that the duration for thymoma surveillance should be 10 years or longer. Thymic malignancies are frequently associated with paraneoplastic syndromes which can be a symptom of recurrence, and knowledge of these disorders should be a component of surveillance. Conclusions: Surveillance after treatment for TETs is felt to be beneficial, but there is a paucity of evidence directly studying this. Currently available guidelines do offer some direction based on expert opinion. Given the rare occurrence of TETs and recurrences after treatment, pooling of data such as the International Thymic Malignancy Interest Group (ITMIG) database to study follow up will be necessary to develop more effective surveillance strategies.