Faculty Bibliography

PURPOSE: To evaluate the outcomes after a single stereotactic radiosurgery procedure for the care of patients with 4 or more intracranial metastases. METHODS AND MATERIALS: Two hundred five patients with primary malignancies, including non-small-cell lung carcinoma (42%), breast carcinoma (23%), melanoma (17%), renal cell carcinoma (6%), colon cancer (3%), and others (10%) underwent gamma knife radiosurgery for 4 or more intracranial metastases at one time. The median number of brain metastases was 5 (range, 4-18) with a median total treatment volume of 6.8 cc (range, 0.6-51.0 cc). Radiosurgery was used as sole management (17% of patients), or in combination with whole brain radiotherapy (46%) or after failure of whole brain radiotherapy (38%). The median marginal radiosurgery dose was 16 Gy (range, 12-20 Gy). The mean follow-up was 8 months. RESULTS: The median overall survival after radiosurgery for all patients was 8 months. The 1-year local control rate was 71%, and the median time to progressive/new brain metastases was 9 months. Using the Radiation Therapy Oncology Group recursive partitioning analysis (RPA) classification system, the median overall survivals for RPA classes I, II, and III were 18, 9, and 3 months, respectively (p < 0.00001). Multivariate analysis revealed total treatment volume, age, RPA classification, and marginal dose as significant prognostic factors. The number of metastases was not statistically significant (p = 0.333). CONCLUSION: Radiosurgery seems to provide survival benefit for patients with 4 or more intracranial metastases. Because total treatment volume was the most significant predictor of survival, the total volume of brain metastases, rather than the number of metastases, should be considered in identifying appropriate radiosurgery candidates.

OBJECTIVE: The obliteration response of an arteriovenous malformation (AVM) to radiosurgery is strongly dependent on dose and volume. For larger volumes, the dose must be reduced for safety, but this compromises obliteration. In 1992, we prospectively began to stage anatomic components in order to deliver higher single doses to symptomatic AVMs >15 ml in volume. METHODS: During a 17-year interval at the University of Pittsburgh, 1040 patients underwent radiosurgery for a brain AVM. Out of 135 patients who had multiple procedures, 37 patients underwent prospectively staged volume radiosurgery for symptomatic otherwise unmanageable larger malformations. Twenty-eight patients who were managed before 2002 were included in this study to achieve sufficient follow-up in assessing the outcomes. The median age was 37 years (range, 13-57 yr). Thirteen patients had previous hemorrhages and 13 patients had attempted embolization. Separate anatomic volumes were irradiated at 3 to 8 months (median, 5 mo) intervals. The median initial AVM volume was 24.9 ml (range, 10.2-57.7 ml). Twenty-six patients had two stages and two had three-stage radiosurgery. Seven patients had repeat radiosurgery after a median interval of 63 months. The median target volume was 12.3 ml. (range, 4.2-20.8 ml.) at Stage I and 11.5 ml. (range, 2.8-22 ml.) at Stage II. The median margin dose was 16 Gy at both stages. Median follow-up after the last stage of radiosurgery was 50 months (range, 3-159 mo). RESULTS: Four patients (14%) sustained a hemorrhage after radiosurgery; two died and two patients recovered with mild permanent neurological deficits. Worsened neurological deficits developed in one patient. Seizure control was improved in three patients, was stable in eight patients and worsened in two. Magnetic resonance imaging showed T2 prolongation in four patients (14%). Out of 28 patients, 21 had follow-up more than 36 months. Out of 21 patients, seven underwent repeat radiosurgery and none of them had enough follow- up. Of 14 patients followed for more than 36 months, seven (50%) had total, four (29%) near total, and three (21%) had moderate AVM obliteration. CONCLUSIONS: Prospective staged volume radiosurgery provided imaging defined volumetric reduction or closure in a series of large AVMs unsuitable for any other therapy. After 5 years, this early experience suggests that AVM related symptoms can be stabilized and anticipated bleed rates can be reduced.

Recent research has exploited the inherent bending of a bevel-tipped needle during insertion, accomplishing steering of the needle by rotating the needle shaft. Combining this technique with the observation that a straight trajectory can be accomplished by spinning the needle at a constant rate during insertion, this paper presents a novel technique for proportional control of the curvature of the trajectory via duty-cycled spinning of the needle. In order to accommodate this technique to very soft tissues such as the brain, several custom needle prototypes have also been designed in order to increase the steering versatility of the system by maximizing the attainable curvature. The paper describes the needle-steering system and the needle prototypes, and presents preliminary results from tests in an artificial brain tissue substitute.

BACKGROUND: Hypothalamic hamartomas are associated with precocious puberty and chronic epilepsy characterized by gelastic seizures. The seizure disorder is usually refractory to most antiepileptic drugs. Gamma knife surgery has emerged as an alternative to microsurgical removal or radiofrequency ablation to improve seizure control. We present our experience with radiosurgery in 4 patients afflicted by this disorder. METHODS: Using gamma knife radiosurgery, 4 patients with intractable gelastic seizures and complex epilepsy were managed. Patient age varied from 5 to 29 years. The duration of symptoms was 4-28 years. A conformal radiosurgery plan was designed with a mean of 4.25 isocenters to cover the hamartoma at the 50% isodose line. A mean margin dose of 17.5 Gy was used. The clinical outcome was evaluated with the Engel scale. RESULTS: No complication occurred. After a median follow-up of 22 months, 3 patients had shown some improvement, with 2 attaining Engel class II status. CONCLUSION: Gamma knife surgery is a promising alternative to microsurgical removal for patients with refractory epilepsy caused by hypothalamic hamartomas.