Multi-institutional competing risks analysis of distant brain failure and salvage patterns after upfront radiosurgery without whole brain radiotherapy for brain metastasis

Background

In this study, we use a competing risks analysis to assess factors predictive of early-salvage whole brain radiotherapy (WBRT) and early death after upfront stereotactic radiosurgery (SRS) alone for brain metastases in an attempt to identify populations that benefit less from upfront SRS.

Patients and methods

Patients from eight academic centers were treated with SRS for brain metastasis. Competing risks analysis was carried out for distant brain failure (DBF) versus death prior to DBF as well as for salvage SRS versus salvage WBRT versus death prior to salvage. Linear regression was used to determine predictors of the number of brain metastases at initial DBF (nDBF).

Results

A total of 2657 patients were treated with upfront SRS alone. Multivariate analysis (MVA) identified an increased hazard of DBF associated with increasing number of brain metastases (P < 0.001), lowest SRS dose received (P < 0.001), and melanoma histology (P < 0.001), while there was a decreased hazard of DBF associated with increasing age (P < 0.001), KPS < 70 (P < 0.001), and progressive systemic disease (P = 0.004). MVA for first salvage SRS versus WBRT versus death prior to salvage revealed an increased hazard of first salvage WBRT seen with increasing number of brain metastases (P < 0.001) and a decreased hazard with widespread systemic disease (P = 0.002) and increasing age (P < 0.001). Variables associated with nDBF included age (P = 0.02), systemic disease status (P = 0.03), melanoma histology (P = 0.05), and initial number of brain metastases (P < 0.001).

Conclusions

Patients with a higher initial number of brain metastases were more likely to experience DBF, have a higher nDBF, and receive early-salvage WBRT, while patients who were older, had lower KPS, or had more systemic disease were more likely to experience death prior to DBF or salvage WBRT.

Constraining the p-Mode-g-Mode Tidal Instability with GW170817

We analyze the impact of a proposed tidal instability coupling p modes and g modes within neutron stars on GW170817. This nonresonant instability transfers energy from the orbit of the binary to internal modes of the stars, accelerating the gravitational-wave driven inspiral. We model the impact of this instability on the phasing of the gravitational wave signal using three parameters per star: an overall amplitude, a saturation frequency, and a spectral index. Incorporating these additional parameters, we compute the Bayes factor (lnB_{!pg}^{pg}) comparing our p-g model to a standard one. We find that the observed signal is consistent with waveform models that neglect p-g effects, with lnB_{!pg}^{pg}=0.03_{-0.58}^{+0.70} (maximum a posteriori and 90% credible region). By injecting simulated signals that do not include p-g effects and recovering them with the p-g model, we show that there is a ≃50% probability of obtaining similar lnB_{!pg}^{pg} even when p-g effects are absent. We find that the p-g amplitude for 1.4  M_{⊙} neutron stars is constrained to less than a few tenths of the theoretical maximum, with maxima a posteriori near one-tenth this maximum and p-g saturation frequency ∼70  Hz. This suggests that there are less than a few hundred excited modes, assuming they all saturate by wave breaking. For comparison, theoretical upper bounds suggest ≲10^{3} modes saturate by wave breaking. Thus, the measured constraints only rule out extreme values of the p-g parameters. They also imply that the instability dissipates ≲10^{51}  erg over the entire inspiral, i.e., less than a few percent of the energy radiated as gravitational waves.

Worry about Performance: Unravelling the Relationship between 'Doing More' and 'Doing Better'

OBJECTIVE

Recent studies have described worry about caregiver performance (WaP) as a distinct dimension of caregiver burden. We aimed to explore care recipient and caregiver characteristics between the concordant and discordant WaP groups in a population of caregivers of older adults with cognitive impairment. The secondary objective is to explore if there are differences between high and low WaP subsets in the 'doing more' and 'doing better' groups.

DESIGN, SETTING AND PARTICIPANTS

This is a retrospective study of 936 dyads of community-dwelling older adults with cognitive complaints and their primary family caregiver from a hospital in Singapore.

MEASUREMENTS

We performed descriptive and inferential statistics of the characteristics of caregivers and patients. We categorized caregiver-patient dyads into four groups, namely concordant (high vs low WaP) and discordant ('doing more' vs 'doing better') groups. For both concordant and discordant groups, we further defined low and high WaP subgroups using tertile cutoffs.

RESULTS

The concordant low WaP group is predicted by the spousal relationship (p<.001) and care recipients with fewer neuropsychiatric symptoms (p<.001). There is no significant difference between the discordant groups, which were predominantly the adult children. Further analysis of subgroups found that in the 'doing better' group, there were more spouses in the high as compared to low WaP subgroups, with the reverse true in the 'doing more' group. In the 'doing more' group, caregivers with high WaP also had higher total ZBI (p<0.05) with higher factors (F1, F2 and F3) scores (p<0.05). They also endorsed higher NPI-Q scores (p=0.045) particularly in the domain of depression / dysphoria (p=0.034). These differences are not seen in the 'doing better' group.

CONCLUSION

Our study suggests an association with caregiver characteristics (adult child) and disruptive behavior in the 'do more' high WaP discordant group. Delineating into the high and low WaP subgroups can help us identify the 'do more' high WaP subgroup that merits further attention and early intervention.

Frontal Assessment Battery in Early Cognitive Impairment: Psychometric Property and Factor Structure

BACKGROUND

The Frontal Assessment Battery (FAB) is a reliable and valid bedside tool for testing executive function in dementia. Given the increasing interest in utility of FAB as a screening tool in early cognitive impairment (ECI), there is a surprising lack of studies evaluating its psychometric property and factor structure, nor the influence of factors such as age, education and gender, in ECI.

OBJECTIVES

This study aims to investigate the psychometric properties and factor structure of FAB in older adults with ECI, as well as the influence of age, gender and education.

DESIGN, SETTING AND PARTICIPANTS

This is a retrospective, observational cross-sectional study with 300 community dwelling, predominantly Chinese older adults (14 normal, 130 mild cognitive impairment (MCI), and 156 mild dementia) who presented to Memory Clinic from January 2011 to December 2013. Measurements and Analysis: We collected data on demographic, cognitive, functional and behavioral evaluation. To examine the psychometric properties of FAB, we examined the concurrent, convergent, and discriminant validity; internal consistency by Cronbach's alpha; and factor structure by exploratory factor analysis. The influence of age, education and gender was examined using unadjusted and adjusted correlational analyses with CDR-SOB. We performed analysis for the whole group and for MCI subgroup.

RESULTS

FAB total score decreases significantly from normal to dementia group attesting to concurrent validity. It correlated significantly with digit span backwards and Chinese Mini Mental State Examination (r=0.38 and 0.47 respectively, p<0.01) and poorly with Neuropsychiatric Inventory-Questionnaire and depression (r=0.004 and -0.02 respectively), supporting its convergent and discriminant validity. Factor analysis yielded a single-factor solution for FAB with fair Internal consistency (alpha=0.610). FAB is relatively unaffected by age, gender and education level. These good psychometric properties extend to MCI, albeit with greater influence by education level. FAB items of conceptualization and mental flexibility have good discriminatory ability between MCI and normal subjects.

CONCLUSION

FAB has good concurrent, convergent and discriminant validity with fair internal consistency in ECI that is premised on a one-factor structure. It is relatively unaffected by age, gender or education. Taken together, FAB is a useful bedside screening tool for executive function in ECI.

Search for Subsolar-Mass Ultracompact Binaries in Advanced LIGO's First Observing Run

We present the first Advanced LIGO and Advanced Virgo search for ultracompact binary systems with component masses between 0.2  M_{⊙}-1.0  M_{⊙} using data taken between September 12, 2015 and January 19, 2016. We find no viable gravitational wave candidates. Our null result constrains the coalescence rate of monochromatic (delta function) distributions of nonspinning (0.2  M_{⊙}, 0.2  M_{⊙}) ultracompact binaries to be less than 1.0×10^{6}  Gpc^{-3}  yr^{-1} and the coalescence rate of a similar distribution of (1.0  M_{⊙}, 1.0  M_{⊙}) ultracompact binaries to be less than 1.9×10^{4}  Gpc^{-3}  yr^{-1} (at 90% confidence). Neither black holes nor neutron stars are expected to form below ∼1  M_{⊙} through conventional stellar evolution, though it has been proposed that similarly low mass black holes could be formed primordially through density fluctuations in the early Universe and contribute to the dark matter density. The interpretation of our constraints in the primordial black hole dark matter paradigm is highly model dependent; however, under a particular primordial black hole binary formation scenario we constrain monochromatic primordial black hole populations of 0.2  M_{⊙} to be less than 33% of the total dark matter density and monochromatic populations of 1.0  M_{⊙} to be less than 5% of the dark matter density. The latter strengthens the presently placed bounds from microlensing surveys of massive compact halo objects (MACHOs) provided by the MACHO and EROS Collaborations.

GW170817: Measurements of Neutron Star Radii and Equation of State

On 17 August 2017, the LIGO and Virgo observatories made the first direct detection of gravitational waves from the coalescence of a neutron star binary system. The detection of this gravitational-wave signal, GW170817, offers a novel opportunity to directly probe the properties of matter at the extreme conditions found in the interior of these stars. The initial, minimal-assumption analysis of the LIGO and Virgo data placed constraints on the tidal effects of the coalescing bodies, which were then translated to constraints on neutron star radii. Here, we expand upon previous analyses by working under the hypothesis that both bodies were neutron stars that are described by the same equation of state and have spins within the range observed in Galactic binary neutron stars. Our analysis employs two methods: the use of equation-of-state-insensitive relations between various macroscopic properties of the neutron stars and the use of an efficient parametrization of the defining function p(ρ) of the equation of state itself. From the LIGO and Virgo data alone and the first method, we measure the two neutron star radii as R_{1}=10.8_{-1.7}^{+2.0}  km for the heavier star and R_{2}=10.7_{-1.5}^{+2.1}  km for the lighter star at the 90% credible level. If we additionally require that the equation of state supports neutron stars with masses larger than 1.97  M_{⊙} as required from electromagnetic observations and employ the equation-of-state parametrization, we further constrain R_{1}=11.9_{-1.4}^{+1.4}  km and R_{2}=11.9_{-1.4}^{+1.4}  km at the 90% credible level. Finally, we obtain constraints on p(ρ) at supranuclear densities, with pressure at twice nuclear saturation density measured at 3.5_{-1.7}^{+2.7}×10^{34}  dyn cm^{-2} at the 90% level.

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω_{0}^{T}<5.58×10^{-8}, Ω_{0}^{V}<6.35×10^{-8}, and Ω_{0}^{S}<1.08×10^{-7} at a reference frequency f_{0}=25  Hz.

GW170817: Implications for the Stochastic Gravitational-Wave Background from Compact Binary Coalescences

The LIGO Scientific and Virgo Collaborations have announced the event GW170817, the first detection of gravitational waves from the coalescence of two neutron stars. The merger rate of binary neutron stars estimated from this event suggests that distant, unresolvable binary neutron stars create a significant astrophysical stochastic gravitational-wave background. The binary neutron star component will add to the contribution from binary black holes, increasing the amplitude of the total astrophysical background relative to previous expectations. In the Advanced LIGO-Virgo frequency band most sensitive to stochastic backgrounds (near 25 Hz), we predict a total astrophysical background with amplitude Ω_{GW}(f=25  Hz)=1.8_{-1.3}^{+2.7}×10^{-9} with 90% confidence, compared with Ω_{GW}(f=25  Hz)=1.1_{-0.7}^{+1.2}×10^{-9} from binary black holes alone. Assuming the most probable rate for compact binary mergers, we find that the total background may be detectable with a signal-to-noise-ratio of 3 after 40 months of total observation time, based on the expected timeline for Advanced LIGO and Virgo to reach their design sensitivity.

First Search for Nontensorial Gravitational Waves from Known Pulsars

We present results from the first directed search for nontensorial gravitational waves. While general relativity allows for tensorial (plus and cross) modes only, a generic metric theory may, in principle, predict waves with up to six different polarizations. This analysis is sensitive to continuous signals of scalar, vector, or tensor polarizations, and does not rely on any specific theory of gravity. After searching data from the first observation run of the advanced LIGO detectors for signals at twice the rotational frequency of 200 known pulsars, we find no evidence of gravitational waves of any polarization. We report the first upper limits for scalar and vector strains, finding values comparable in magnitude to previously published limits for tensor strain. Our results may be translated into constraints on specific alternative theories of gravity.