External Validation of Three Prognostic Scores for Brain Metastasis Velocity in Patients Treated with Intracranial Stereotactic Radiotherapy

BACKGROUND AND INTRODUCTION Brain metastasis velocity (BMV) has been proposed as a prognostic factor for overall survival (OS) in patients with brain metastases (BMs). In this study, we conducted an external validation and comparative assessment of the performance of all three BMV scores. MATERIALS AND METHODS Patients treated with intracranial stereotactic radiotherapy (SRT) for BM at a single center between 2014 and 2018 were identified. Where possible, all three BMV scores were calculated. Log-rank tests and linear, logistic and Cox regression analysis were used for validation and predictor identification of OS. RESULTS For 333 of 384 brain metastasis patients, at least one BMV score could be calculated. In a sub-group of 187 patients, "classic" BMV was validated as categorical (p<0.0001) and continuous variable (HR 1.02; 95% CI 1.02-1.03; p<0.0001). In a sub-group of 284 patients, "initial" BMV was validated as categorical variable (high-risk vs. low-risk; p<0.01), but not as continuous variable (HR 1.02; 95% CI 0.99-1.04; p=0.224). "Volume-based" BMV could not be validated in a sub-group of 104 patients. On multivariable Cox regression analysis, iBMV (HR 1.85; 95% CI 1.01-3.38; p<0.05) and cBMV (HR 2.32; 95% CI 1.15 4.68; p<0.05) were predictors for OS for intermediate-risk patients after first SRT and first DBFs, respectively. cBMV proved to be the dominant predictor for OS for high-risk patients (HR 2.99; 95% CI 1.30-6.91; p<0.05). CONCLUSION This study externally validated cBMV and iBMV as prognostic scores for OS in patients treated with SRT for BMs whereas validation of vBMV was not achieved

Indirect Dark Matter Search with the MAGIC Telescope

The 17m Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) Telescope located on the canary island La Palma has the lowest energy threshold of all existing Cherenkov Telescopes. This makes MAGIC well suited to look for high energy gamma rays coming from e.g. neutralino annihilation in Dark Matter (DM) dominated source candidates like spheroidal dwarf galaxies. So far, DRACO and Willman-I have been observed for several hours each, but no signal was found and the upper limits received look not very encouraging. On the other hand, the AGILE and FERMI satellites might soon detect more promising candi- dates like hypothetical mini-halos or intermediate mass black holes. In such cases, follow up observations with Cherenkov telescopes with their much higher sensitivity above 48 100 GeV will be needed to fully measure the spectra and search for a characteristic energy cutoff. In case of a positive detection of a DM signal, an absolute energy calibration will be crucial. So far, Cherenkov telescopes had to rely fully on Monte Carlo simulations, resulting in a rather large systematic uncertainty. With an improved trigger electronics, MAGIC recently was able to see the cutoff energy of the Crab pulsar. Since this cutoff energy is within reach of FERMI, a cross-calibration of both instruments will soon be possible