Stereotactic Radiation for Growing/Changing Brain Metastases With Same-Day Radiation Planning and Treatment With Margin Reduction

Adaptively designed radiation, which adjusts a given radiation plan for real time changes in patient position or anatomy, has become a standard approach within many oncologic entities to combat the effect of shifts between simulation and treatment. Adaptively planned SRS/SRT with same day brain MRI and treatment delivery offers potential to quantify the impact of treatment planning time while also reducing margins and potentially improving rates of local recurrence and radiation necrosis. This trial aims to explore the viability of adaptively designed SRS/SRT with same day planning and treatment in combination with tighter planning margins in both controlling brain metastases locally and minimizing the risk of radiation necrosis in a phase 2 randomized study. Participants will have a preliminary stereotactic treatment plan created from a diagnostic brain MRI indicating the need for treatment. The preliminary plan will undergo departmental-standard physics, therapy, and quality assurance checks, spanning a total of 1-2 weeks, after which the patient will return for treatment. On the day of treatment (SRS) or start of treatment (SRT), a repeat MRI brain will be performed for planning purposes on an MRI simulator. A synthetic computed tomography (CT) scan will be generated from the new MRI. The previously generated contours and plan will be adapted to the new MRI and the fused synthetic CT. Lastly, the treatment will be delivered. The primary objective is to assess the percentage of patients that demonstrate tumor beyond the standard planning margin (1.0mm PTV) at the time of stereotactic treatment. An important secondary objective is to quantify local recurrence and radiation necrosis rates in patients treated with same day simulation and treatment, based on randomization to a PTV of 0mm or 1.0mm.