Described herein are methods of treating cancer by administering a therapeutically effective amount of at least one texaphyrin metal complex or a pharmaceutically acceptable derivative, and performing stereotactic radiosurgery to the patient. In some embodiments, at least one texaphyrin metal complex or a pharmaceutically acceptable derivative is administered while the patient is undergoing a radiation therapy. Also described herein are methods for detecting various cancerous tumors, lesions, or metastases in a patient by administering an effective amount of at least one texaphyrin metal complex or a pharmaceutically acceptable derivative before a patient undergoes stereotactic radiosurgery. Also described herein are methods for visualizing tumors not otherwise visualized; methods for detecting the margins of a tumor; and methods for improving the targeting of the SRS radiation.