MR-guided stereotactic radiosurgery of an intracardiac tumoral thrombus using comprehensive motion management

Lung cancer is often complicated by hypercoagulability, with intracardiac thrombi not an uncommon consequence. While radiotherapy can be a treatment option, effective intracardiac irradiation can be technically challenging. We present the case of a 54-year-old non-small-cell lung cancer (NSCLC) patient treated for a recurrent left atrial tumoral thrombus. The patient responded well after a first course of chemo-immuno radiotherapy. Follow up imaging showed a metabolic reactivation of the left atrial thrombus. The patient subsequently underwent an 18 Gy stereotactic radiosurgery using a 1.5 T Unity MR-Linac (Elekta AB, Sweden, Stockholm) using comprehensive motion management (CMM) to account for respiratory motion. Treatment was well tolerated. Complete metabolic response was observed 2 months after treatment. This case represents the first ever reported use of CMM on a 1.5 T MR-Linac to target an intracardiac lesion.