Fractionated Radiosurgery Alone for Thirty-seven Brain Metastases: Not Everything that can be Counted Counts

There is an ongoing debate as to the maximum number of brain metastases that can safely and practically be treated with a single course of radiosurgery. Despite evidence of durable local control and favorable overall survival when treating 10 or more brain metastases with radiosurgery alone, some institutions and guidelines still limit radiosurgery to an arbitrary number of metastases. As demonstrated by this case report, the number of lesions is not so important when the patient's life expectancy is otherwise good and body tumors are controllable. In the current era of effective targeted therapies, multi-year survival with brain metastases is increasingly common. Treating 37 brain metastases simultaneously in a five-fraction stereotactic course is technically feasible and in this case, resulted in 100% local and distant control in the brain for 18 months ongoing without any additional brain radiation. We discuss patient selection factors when treating large numbers of brain metastases, and present a possible class solution when using five daily fractions of 6 Gray (Gy) with a single plan and isocenter.