AB022. Retrospective evaluation of cardiac toxicity during irradiation of thymic malignancies

Background: Cardiac toxicities of thymic irradiations are relatively unknown because of to the rarity of the indication but are very important to study due to the long overall survival of this population. The objective of this study is to evaluate the occurrence of cardiac events in patients irradiated for thymic malignancies, in relation to the doses delivered to the cardiac structures.

Methods: All patients treated with radiotherapy for thymic tumors between 2012 and 2024 in the Department of Radiotherapy of the CHU de Bordeaux were retrospectively included. We collected the doses received by the heart, coronary arteries and by the pericardium (V30, V40, V45 and V50) by performing a specific pericardial contour defined as an internal expansion of 3 mm from the cardiac contour. More specific structures were analyzed a posteriori according to the post-therapeutic toxicity.

Results: Of the 52 patients identified, 43 were included in the final analysis (9 patients excluded because irradiated outside the thymic compartment). The majority of tumors were thymomas (58%) or squamous cell carcinomas (30%). Before treatment, 79% of patients had at least one cardiovascular risk factor. Radiotherapy was adjuvant in 88% of cases (positive margins: 60%) with a median dose of 53.2 [45–66] Gy. Exclusive radiotherapy with concomitant chemotherapy was performed in 7% of patients {median dose of 51 [50–66] Gy}, and palliative intent in 2 patients. Nine patients (21%) presented with a cardiac event: 2 arrhythmias, 1 valvular pathology, 1 infarction, 2 proven pericardial toxicities and 3 atypical chest pain possibly of pericardial origin. Doses received by conduction nodes or pathological valve structures in affected patients were less than 15 Gy making the imputability to radiotherapy uncertain. The patient who required inter-ventricular coronary angioplasty had received the prescription dose of 50 Gy in the artery. In patients with a pericardial or related event, the doses received by the pericardium were significantly higher than in the population without the event: V30Gy at 20.2% vs. 10.8%, V40Gy at 15.4% vs. 8.2%, V45Gy at 11.2% vs. 7%, V50Gy at 8.3% vs. 5%, and mean cardiac dose at 14.4 vs. 10.3 Gy.

Conclusions: Radiotherapy of thymic tumors can induce cardiac toxicity, particularly pericardial toxicity, which appears to be correlated with the dose received by the heart and pericardium. This can lead to personalized reinforced cardiac follow-up for identified persons at risk.

Keywords: Radiation oncology; thymus malignancies; cardiac toxicities