Perspectives on surgical treatment for thymic epithelial tumors: a narrative review.

Background and Objective: Thymic epithelial tumors are relatively rare; thus, mostly retrospective studies and a few prospective randomized controlled trials have been conducted on the treatment and the biomarkers, with no standard therapy established. Indications for extended thymectomy, robot-assisted thoracic surgery, and multidisciplinary treatment are controversial. Here, we considered the prospects of surgical treatment and the possibility of immune checkpoint inhibitor (ICI) treatment for thymic epithelial tumors. Methods: This is a narrative review; PubMed was searched using a set of keywords related to thymoma and its proposed treatments over the last 5 years. Key Content and Findings: Thymic epithelial tumors are associated with autoimmune diseases. They are relatively rare, and their pathology remains unclear. Therefore, accumulating more case reports is important. Surgical resection is generally considered for both diagnosis and treatment. If the tumor has a strong tendency to invade surrounding areas, such as thymic carcinoma/thymoma, the diagnosis may be confirmed preoperatively by needle biopsy, and induction chemotherapy may be selected. Surgical resection is the most effective treatment, and complete resection is important. In cases where complete resection is difficult, multidisciplinary treatment is performed. Although there are various obstacles, using ICIs may prove effective for treatment both as preoperative and postoperative chemotherapy in the future, as shown for other cancers. Programmed cell death-ligand 1 (PD-L1) is an immunoinhibitory molecule that suppresses T cells activation, leading to tumor progression. Overexpression of PD-L1 in some cancers is associated with poor clinical outcomes. However, the role of PD-L1 expression as a prognostic factor remains controversial. Therefore, various biomarkers other than PD-L1 have been identified. Conclusions: We reviewed the latest treatments for thymic epithelial tumors. If new therapeutic agents such as ICIs and molecular-targeted drugs are developed, this review suggests that surgery will become more important not only as therapy but also as part of multidisciplinary treatment that includes tissue collection.