Brain metastases in renal cell carcinoma: management with gamma knife radiosurgery.

PURPOSE: The purpose of this study was to evaluate survival and local control of brain metastases in patients with renal cell carcinoma. METHODS AND MATERIALS: From November 1993 through March 1999, 38 radiosurgical treatments using the Leksell gamma knife unit were performed on 22 patients with renal cell carcinoma. The indications for treatment were failure after whole-brain radiation therapy or de novo treatment. All radiosurgical treatments were given on an outpatient basis. The workup included computed tomography and magnetic resonance imaging. The age of the patients ranged from 38 to 80 years (median age, 60 years). The mean minimum tumor dose was 18 Gy, and the mean volume was 3.9 cc. Previous whole-brain radiation therapy was used in 11/22 (50%) patients. Four of 22 patients presented with single metastasis. Thirteen patients were treated once, one patient was treated four times and one patient seven times for new lesions. The number of lesions treated ranged from one to 21. RESULTS: One patient is al ive at 63 months of fol low-up. Twenty-one patients died, with a median survival of 8 months (range, 1-38 months). Eighteen of 21 patients died of nonneurologic causes. Overall local control was 98.5%. One patient developed radiation necrosis. CONCLUSIONS The long-term survival achieved in patients with renal cell carcinoma requires aggressive management, even in the presence of multiple brain metastases. Gamma knife radiosurgery for renal cell carcinoma is an effective noninvasive modality of treatment. It offers high local control rate and improved quality of life and survival.

Gamma knife radiosurgery in the treatment of patients with single and multiple brain metastases from carcinoma of the breast.

PURPOSE: The purpose of the study was to evaluate the results of gamma knife radiosurgery for treatment of brain metastases from carcinoma of the breast. MATERIALS AND METHODS: From December 1993 to July 1998, 68 women with breast carcinoma metastatic to the brain were treated with gamma knife radiosurgery at Miami Neuroscience Center in Coral Gables, Florida. The ages ranged from 25 to 80 years, with a median age of 52 years. Thirty-eight patients had previously received conventional modalities of treatment for brain metastases including whole-brain irradiation. A total of 110 treatments were given to the 68 women to an average of eight tumor sites per patient. Minimum doses ranged from 6 to 25 Gy to the 35% to 85% isodose line, with 95% of the prescribed minimum doses ranging from 15 to 24 Gy. Patients were treated for one to three lesions (n = 26), four to seven lesions (n = 18), and eight or more lesions (n = 24). RESULTS: The median overall actuarial survival for the entire group was 7.8 months. The actuarial survival was 32% at 1 year. The median follow-up was 7.8 months. Overall local control by lesion was 94% (485/518 lesions), and average tumor volume was 3.3 cm3. Twenty-seven (40%) of 68 eligible patients survived 1 year, nine (13%) survived 2 years, and two (3%) survived more than 3 years. Fifty-one of 56 documented deaths (91%) were unrelated to brain metastases. In a subgroup of 15 patients with single brain metastases, the average tumor volume was 16.6 cm3, and local control was 73% (11/15 lesions). The 15 patients who died had a median survival of 7.7 months (range, 3 to 45.7 months). CONCLUSIONS: Gamma knife radiosurgical treatment of patients with brain metastases from carcinoma of the breast has shifted the question of survival to that of systemic control. There was no radiation-induced dementia, and a remarkably low incidence of local failure was seen. Survival has been found to be independent of the number of lesions treated.

Anomalous primary radiation from the Leksell Gamma Knife Unit.

The Leksell Gamma Knife Unit, Type U, utilizes 201 separate 60Co sources intersecting at a common focus for radiosurgical treatment of the brain. It has been generally understood that all primary unattenuated radiation beams are confined within the protective housing during all phases of Gamma Knife operation. We have found that when the unit's shielding door is lowered for treatment, twelve primary beams exit the unit's door opening. Furthermore, in the original Gamma Knife unit design, two of the twelve primary beams failed to be attenuated by either the unit base or the unit wings. This has implications for the design of structural shielding and the protection of personnel during emergency procedures. Engineering modifications to eliminate the problem are discussed.

Models of lung transvascular fluid and protein transport.

Transport theory has been applied to lymph flow (QL), protein lymph to plasma concentration ratios (L/P), and permeability surface area for urea (PSu) in unanesthetized sheep. Three models of the plasma-interstitial barrier have been used: a single pathway fiber matrix model, a continuous cylindrical-pore model with log normal distribution of filtration coefficients, and a cylindrical two-pore model. The fiber matrix model was unable to match measured PSu, QL, and L/P. The continuous-pore model was capable of describing the data, but the fitted median pore size was inconsistent with a continuum theory. The two-pore model described steady-state data and was used in additional model applications. We explored the 90% confidence limits for the fitted structural parameters of the two-pore theory. We found that many sets of model parameters were capable of fitting the available experimental data. We therefore sought combinations of parameters that might characterize the microvascular barrier under baseline and altered permeability situations. One combination that looks promising is the ratio of large-pore to small-pore radius raised to the sixth power and multiplied by the large-pore frequency. This value remains relatively constant following elevations in microvascular pressure, saline infusions, and plasma infusions but increases dramatically after endotoxin infusion.