Faculty Bibliography

Histopathological investigations revealed acute-, subacute-, and chronic-type tissue responses, accompanied by inflammatory cell reaction in radiosurgery treated cerebral metastases originating from different primary cancers. Immunohistochemistry demonstrated that the preponderance of CD68-positive macrophages and CD3-positive T lymphocytes in the inflammatory infiltration developed in better controlled metastases ( > 5 months). In contrast, it was sparse or absent in poorly controlled neoplasms ( < 5 months) after radiosurgery. This inflammatory reaction may be stimulated by the ionizing energy, probably influenced by the general condition of the patients' immune system as well, and seems to play a role in local tumor control after focused radiation.

We discuss the current literature on the role of stereotactic radiosurgery in the multidisciplinary management of brain metastases and focus on the level of evidence that addresses key management questions. We reviewed the literature on the different roles of radiosurgery, radiotherapy, and resection, and in particular the 2009 Guidelines project of the Joint Section on Tumors of the AANS/CNS. Retrospective case series, matched cohort studies, and randomized trials show specific survival and local tumor control benefits after radiosurgery. Radiosurgery is an effective and safe minimally invasive option for patients with brain metastases. Randomized trials include tumors of different histologies which can detract from their relevance to specific tumor types.

We evaluated the role of Gamma Knife stereotactic radiosurgery in the multidisciplinary management of brain metastases ovarian and endometrial, prostate, thyroid, sarcoma, or unknown primary cancers. From a series of over 3,000 patients who had Gamma Knife radiosurgery for brain metastases we reviewed indications and outcomes in patients with less common cancer types. All tumor types responded favorably to radiosurgery. Patients with male and female genitourinary primaries tended to develop brain metastases late in their course and did worse. Patients with thyroid metastases appear to live much longer with a more indolent course. Radiosurgery is an effective and safe minimally invasive option for patients with brain metastases from these less common primary origins.

Stereotactic radiosurgery (SRS) is a well-established tool in the armamentarium for the treatment of metastatic tumors to the brain. Although SRS has proven to be highly effective in the management of brain metastases, it is not without risk. Despite selective targeting of lesions and the sharp dose fall-off associated with radiosurgical treatments, adverse radiation effects (AREs) can and do occur, albeit at a low rate, just as has been reported after conventional fractionated radiation therapy. One of the most vexing clinical scenarios for SRS practitioners is the distinction between ARE and tumor recurrence or progression after radiosurgery. Differentiation of these two entities is critical, as further treatment options range from oral medications to invasive surgical resection. In this review, we define AREs and discuss the possible mechanisms that produce them. Efforts to distinguish between ARE and tumor progression also are explored. Finally, a management algorithm for AREs is proposed.

Functional neurosurgery includes surgery conducted to ablate, augment, or modulate targets that lead to improvement in neurological function or behavior. Surgical approaches for this purpose include destructive lesioning with different mechanical or biologic agents or energy sources, non-destructive electrical modulation, and cellular or chemical augmentation. Our purpose was to review the role of stereotactic radiosurgery used for functional indications and to discuss future applications and potential techniques. Imaging and neurophysiological research will enable surgeons to consider new targets and circuits that may be clinically important. Radiosurgery is one minimal access approach to those targets.