Can doctors watch brain metastases instead of zapping them?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Patients must have histologically or cytologically confirmed metastatic non-hematologic malignancy. * Patients must have at least one new or progressive brain metastasis that has not received prior local therapy (surgery or radiation therapy). * Patients must have no active brain metastasis \>3cm in size. * Leptomeningeal disease is permitted * Patients with only non-measurable disease as defined by the RANO-BM criteria are permitted so long as the clinical determination of new or progressive disease has been made by the treating team. * Patients must have no symptoms attributable to active brain metastases. * At the time of enrollment, patients must be eligible for AND planning to begin a new line of systemic therapy with potential for CNS-efficacy. Determination of potential for CNS-efficacy will be determined based on the clinical judgement of the treating physicians. Patients must have had no prior exposure to the specific systemic therapy in question at the time of enrollment, though exposure to other medications from a similar class are acceptable at the discretion of the treating team. * Patient must be planning to defer radiation therapy to trial medical therapy regardless of enrollment on trial. * Must be age ≥ 18 years. * Patients must be willing to complete MoCA and FACT-BR assessments (refer to section 4.4.1). * Performance status: KPS performance status ≥50%. * Life expectancy of ≥3 months. * Ability to understand and willingness to sign a written informed consent document. Exclusion Criteria: * Patients who have only progressive growth of brain lesions that have previously been treated with surgery or radiation therapy. * Patients with active symptomatic brain metastases. * Patients requiring corticosteroids, anticonvulsants, or other palliative medications related to brain metastases. * Patients with conditions that exclude them from undergoing magnetic resonance imaging.