Kidney cancer with brain metastases. Prognostic factors and treatment outcome.

The aim of this study was to study the effectiveness of stereotactic radiosurgery by Gamma Knife in kidney cancer with brain metastases. There were analyzed results in 112 patients with such spread of the disease who received treatment in the Gamma Knife Center, Moscow. The median age of patients was 58 years (range, 33-77 years). Total number of metastatic lesions was 444, and the average number of brain metastases in one patient 4 (from 1 to 30). A single brain metastasis had 28 patients (25 %). Median of total volume of brain metastasis for each patient was 5. 9 cm3 (from 0. 1 to 29,1sm3). Mean marginal dose for metastatic lesion was 22 Gy (from 12 Gy to 26 Gy) and the average value of isodose, on which planning was performed - 64% (from 39% to 99%). The overall survival after radiosurgery was 37,7%, 16,4% and 9,3% for 12, 24 and 36 months, respectively, with a median overall survival of 9,1 months (95% CI = 7,1-11,8). New brain metastases after radiosurgical treatment occurred in 44 (54,3%) patients with a median of 10,1 months. (95% CI = 7-18). Local recurrences after radiosurgical treatment were detected in 19 (17%) patients with a median of 6,6 months (95% CI = 4,0-9,6). The Karnovsky index was >80. Local control was achieved in 96% of metastatic lesions in 87% of patients. Side effects of radiosurgical treatment occurred in 33. 8% of patients (6% radionecrosis and 23. 8% an increase of perifocal edema). Thus stereotactic radiosurgery by Gamma Knife is an effective treatment option for brain metastases in kidney cancer providing a high level of local control of metastatic lesions with minimal neurotoxicity. In a case of distant recurrence reuse of such treatment provides good local control and improves overall survival compared with other methods of treatment.

Inverse free electron lasers and laser wakefield acceleration driven by CO2 lasers.

The staged electron laser acceleration (STELLA) experiment demonstrated staging between two laser-driven devices, high trapping efficiency of microbunches within the accelerating field and narrow energy spread during laser acceleration. These are important for practical laser-driven accelerators. STELLA used inverse free electron lasers, which were chosen primarily for convenience. Nevertheless, the STELLA approach can be applied to other laser acceleration methods, in particular, laser-driven plasma accelerators. STELLA is now conducting experiments on laser wakefield acceleration (LWFA). Two novel LWFA approaches are being investigated. In the first one, called pseudo-resonant LWFA, a laser pulse enters a low-density plasma where nonlinear laser/plasma interactions cause the laser pulse shape to steepen, thereby creating strong wakefields. A witness e-beam pulse probes the wakefields. The second one, called seeded self-modulated LWFA, involves sending a seed e-beam pulse into the plasma to initiate wakefield formation. These wakefields are amplified by a laser pulse following shortly after the seed pulse. A second e-beam pulse (witness) follows the seed pulse to probe the wakefields. These LWFA experiments will also be the first ones driven by a CO(2) laser beam.