Narrative review of indication and management of induction therapy for thymic epithelial tumors.

Background and Objective: Thymic epithelial tumors (TETs) are rare and originate from the thymus. Thymomas and thymic carcinomas are the most common types of TETs. Of the two, thymomas tend to have a better prognosis and are typically localized, while thymic carcinomas have a worse prognosis and are more likely to spread. The Masaoka-Koga staging system is commonly used to determine the stage of TETs. Complete resection is the preferred treatment option, but treating locally advanced TETs can be challenging due to the invasion of surrounding structures. In such cases, induction therapy is administered to downstage the tumors and enable complete resection. We conducted this narrative review to evaluate the current progress in induction treatment for locally advanced TETs. Methods: The literature search was performed using PubMed and Web of Science in June 2023. Prospective and retrospective published trials, systemic and narrative reviews, and meta-analyses were included. Key Content and Findings: Induction chemotherapy is often used as a preoperative treatment for advanced TETs. Platinum and anthracycline-based chemotherapy regimens are commonly used for treating thymoma (response rate, 37-100%), and complete resection is highly common. Treatment with cisplatin and etoposide, carboplatin and paclitaxel, docetaxel and cisplatin have also demonstrated effectiveness, particularly in patients with thymic carcinoma or thymoma who cannot tolerate anthracycline regimens. The emergence of immunotherapy and targeted therapies may provide additional options for the treatment of TETs. Induction radiotherapy, as the sole treatment for TETs, is not widely practiced due to concerns about potential damage to surrounding tissues. However, combining modern radiation techniques with surgery has shown promising results in selected patients. Induction chemoradiotherapy, which combines chemotherapy and radiation, is an emerging approach for treating TETs. Despite the lack of randomized trials comparing chemotherapy with chemoradiotherapy, concurrent chemoradiation with radiation doses of 40-50 Gy is often considered the optimal induction therapy for thymic carcinoma patients or in more advanced special situations, such as great vessel invasion. Conclusions: Overall, the optimal treatment for locally advanced TETs remains controversial. Induction therapy, including chemotherapy, radiotherapy, or chemoradiotherapy, is administered to downstage tumors and improve resectability. The choice of treatment depends on individual factors such as tumor stage, histology, and overall patient condition. However, further research and well-designed studies are needed to determine the most effective treatment strategies for locally advanced TETs.