Chemotherapy Definitions and Policies for Thymic Malignancies

Abstract

Thymic malignancies are rare epithelial tumors that may be aggressive and difficult to treat.1 Thymomas are usually localized to the anterior mediastinum and are frequently eligible for upfront surgical resection, which is the mainstay of the curative-intent treatment.1 However, approximately 30% of patients present with an advanced tumor at the time of diagnosis, with invasion of neighboring organs, dissemination to the pleura, the pericardium, or less frequently extrathoracic organs. In such cases, chemotherapy has been used both to reduce the tumor burden—possibly allowing subsequent surgery or radiotherapy—and to achieve prolonged disease control. Recurrence after resection may be similarly treated with chemotherapy. Thymic carcinomas, although rare, are usually already advanced at the time of presentation, and systemic therapy is important for almost all of these patients. Knowledge regarding chemotherapy for thymic tumors has mainly been based on retrospective series,2–9 although several prospective trials have also been conducted.10–21 These studies have clearly demonstrated the chemosensitivity of thymoma, and to a lesser extent thymic carcinoma, to various cytotoxic agents and combinations. However, details of patient selection are often lacking (either disease extent or general condition), and the intent of the treatment sequence is often vague. Adoption of a common language and definition of terms is crucial for the International Thymic Malignancies Interest Group (ITMIG) effort to develop a international prospective database of thymic tumors. The article by Huang et al.22 provides definitions for survival and endpoints for recurrences assessment and discusses how to measure response to treatment. Herein, we discuss additional points with regard to chemotherapy, including treatment sequence, general modalities, and impact of corticosteroids.