"Donut's shape" radiosurgical treatment planning for large cystic metastatic brain tumors

Background Radiosurgical management of large cystic metastatic brain tumors represents a significant challenge. Nevertheless, modified dose planning has shown beneficial results in such cases. Method and Results: Donuts shape radiosurgical treatment planning is based on the chain-like application of multiple, small-sized isocenters for selective coverage of the contrast-enhancing tumor capsule and minimal irradiation of the central cystic area. Such an approach was used for the management of large cystic intracranial metastases, which were not accompanied by a significant mass effect and did not require immediate volume reduction. Treatment was done using Leksell Gamma Knife model C with automatic positioning system. The majority of treated lesions showed significant shrinkage after radiosurgery and no major complications were met. Conclusion: Large cystic metastatic brain tumors may be successfully treated with gamma knife radiosurgery alone using the proposed donuts shape dose planning with coverage of the contrast-enhancing tumor capsule by multiple small-sized isocenters.