Managing stage IV thymic carcinoma-a narrative review of radiation therapy strategies and options.

Background and Objective: Thymic carcinoma is a type of thymic epithelial tumor that is rare and aggressive. Compared to patients with thymoma, patients with thymic carcinoma experience worse overall survival, progression-free survival and earlier relapses. Patients with stage IV thymic carcinoma most commonly have disease involving the pleural or pericardium, but distant spread outside the thorax is also possible. The purpose of this review is to describe radiation therapy strategies and options for patients with stage IV thymic carcinoma. Methods: Due to the rare nature of thymic tumors, the literature on stage IV thymic carcinoma is limited. As a result, most of the data on stage IV thymic carcinoma is based on retrospective reviews and heterogenous populations. Key Content and Findings: The management of stage IV thymic carcinoma is multidisciplinary and depends on many factors including the patient's performance status, extent of disease, biology of the disease and intent of treatment. Systemic therapy, surgical resection, observation, and radiation therapy are often considered. Radiation can be used for palliation of symptoms, prevention of impending symptoms, and potentially for prolongation of disease control particularly in patients with oligometastatic or oligoprogressive disease. The type of radiation used in patients with stage IV thymic carcinoma depends on the intent of treatment, location of the disease, size of the target, and proximity to organs that are sensitive to radiation. Various techniques such as 3D conformal radiation therapy (3DCRT), stereotactic body radiation therapy (SBRT), intensity modulated radiation therapy (IMRT), proton beam therapy, and hemi-thoracic intensity-modulated pleural radiation therapy (IMPRINT) may be considered depending on these factors. Conclusions: In patients with stage IV thymic carcinoma, radiation therapy is an effective modality for palliation of symptoms, prevention of impending symptoms, and potentially for prolongation of disease control. Due to the rare nature of the disease, additional data and research are required to better understand the impact and appropriateness of various treatment approaches in patients with thymic carcinoma. Because the management of stage IV thymic carcinoma can involve multiple different modalities depending on the patient's individual case, a multidisciplinary approach is critical for optimal patient care.