ED15.04 Radiation of Thymic Malignancies

Abstract

Radiation therapy (RT) plays an important role in the multimodality management of thymic malignancies. It can be employed in the neoadjuvant, adjuvant, definitive or palliative setting. Adjuvant RT is the most extensively studied setting for RT in thymic malignancies. After complete resection there is likely no role for adjuvant RT for patients with stage I thymomas, a possible role for patients with stage II thymomas, and likely a survival benefit in patients with stage III and IV thymomas. Several recent large database and population-based studies have detected a survival benefit for advanced thymomas, while the results for stage II thymomas have been mixed. For thymic carcinomas the impact of adjuvant RT appears more significant. Several large database and population-based studies have consistently reported a survival benefit with adjuvant RT for thymic carcinoma across various disease stages. For incompletely resected thymic tumors there is a stronger rationale for adjuvant RT based on emerging data and general oncologic principles. Neoadjuvant RT has been mostly explored in thymic carcinoma and demonstrated high response and operability rates. Definitive RT is an excellent treatment option for patients with unresectable thymic malignancies. While most thymic tumors are resectable, a subset of patients is technically or medically inoperable, due to invasion of critical structures or comorbidities. In general, thymic malignancies are radiosensitive, allowing for long-term local control rates. Palliative RT should be considered even in the recurrent or metastatic setting. Image-guided hypofractioned ablative RT may be used for oligometastatic disease as an alternative to surgical resection and has been shown to be a highly effective treatment modality with >90% long-term local control rates and minimal morbidity. Conventional palliative RT is an important modality to improve quality of life by alleviating pain, treating SVC syndrome, airway compression and other symptoms. Modern radiation therapy techniques such as 3D conformal radiation therapy or intensity-modulated radiation therapy should be used to minimize morbidity from treatment. Proton therapy may have advantages in certain clinical scenarios and is currently under investigation. ADJUVANT, radiation therapy, Thymic malignancies