Estudo de alterações estruturais cerebrais em pacientes com esquizofrenia crônica e de primeiro episódio através de imagens por ressonância magnética com morfometria baseada no voxel

Introdução: Embora alterações estruturais cerebrais na esquizofrenia venham sendo repetidamente demonstradas em estudos de ressonância magnética (RM), ainda permanece incerto se tais alterações são estáticas ou progressivas. Enquanto estudos longitudinais são tradicionalmente utilizados na avaliação da questão da progressão, estudos transversais de neuroimagem comparando diretamente pacientes com esquizofrenia crônica e de primeiro episódio a controles saudáveis têm sido bastante raros até o presente. Com o recente interesse em meganálises combinando dados multicêntricos de RM visando-se a maior poder estatístico, o presente estudo multicêntrico de morfometria baseada no voxel (VBM) foi realizado para avaliar os padrões de alterações estruturais cerebrais segundo os diferentes estágios da doença, bem como para avaliar quais (se alguma) dessas alterações se correlacionariam especificamente a moderadores clínicos potenciais, tais como exposição cumulativa a antipsicóticos, tempo de doença e gravidade da doença. Métodos: Selecionou-se uma ampla amostra de pacientes com esquizofrenia (161, sendo 99 crônicos e 62 de primeiro episódio) e controles (151) a partir de quatro estudos prévios de RM (1,5T) realizados na mesma região do Brasil. O processamento e análise das imagens foi realizado usando-se o software Statistical Parametric Mapping (SPM8) com emprego do algoritmo DARTEL (diffeomorphic anatomical registration through exponentiated Lie algebra). Os efeitos de grupo sobre os volumes regionais de substância cinzenta (SC) foram analisados através de comparações voxel-a-voxel por análises de covariância em modelos lineares gerais, inserindo-se, em todas as análises, o volume total de SC, protocolo do scanner, idade e sexo como variáveis de confusão. Por fim, foram realizadas análises de correlação entre os aludidos moderadores clínicos potenciais e os volumes cerebrais globais e regionais. Resultados: Os pacientes com esquizofrenia de primeiro episódio apresentaram reduções volumétricas sutis em comparação aos controles, em um circuito neural circunscrito e identificável apenas em análises SVC (small volume correction) [p < 0.05, com correção family-wise error (FWE)], incluindo a ínsula, estruturas têmporo-límbicas e corpo estriado. Os pacientes crônicos, por outro lado, apresentaram um padrão de alterações extensas comparativamente aos controles, envolvendo os córtices frontais orbitais, superiores e inferiores bilateralmente, córtex frontal médio direito, ambos os córtices cingulados anteriores, ambas as ínsulas, e os córtices temporais superior e médio direitos (p < 0.05, análises whole-brain com correção FWE). Foram encontradas correlações negativas significantes entre exposição cumulativa a antipsicóticos e volumes globais de SC e substância branca nos pacientes com esquizofrenia, embora as correlações com reduções regionais não tenham sido significantes. Detectaram-se, ainda, correlações negativas significantes entre tempo de doença e volumes regionais relativos da ínsula esquerda, córtex cingulado anterior direito e córtices pré-frontais dorsolaterais nas análises SVC para os grupos conjuntos (esquizofrenia crônica e de primeiro episódio). Conclusão: Os achados supracitados indicam que: a) as alterações estruturais associadas com o diagnóstico de esquizofrenia são mais disseminadas na forma crônica em comparação à de primeiro episódio; b) reduções volumétricas regionais em áreas específicas do cérebro podem variar em função do tempo de doença; c) a exposição cumulativa a antipsicóticos associou-se a alterações volumétricas globais, e não regionais

Double-strand break repair gene polymorphisms and risk of breast or ovarian cancer

Deficiencies in DNA repair have been hypothesized to increase cancer risk and excess cancer incidence is a feature of inherited diseases caused by defects in DNA damage recognition and repair. We investigated, using a case-control design, whether the double-strand break repair gene polymorphisms RAD51 5' untranslated region -135 G > C, XRCC2 R188H G > A, and XRCC3 T241M C > T were associated with risk of breast or ovarian cancer in Australian women. Sample sets included 1,456 breast cancer cases and 793 age-matched controls ages under 60 years of age, 549 incident ovarian cancer cases, and 335 controls of similar age distribution. For the total sample and the subsample of Caucasian women, there were no significant differences in genotype distribution between breast cancer cases and controls or between ovarian cancer cases and combined control groups. The crude odds ratios (OR) and 95% confidence intervals (95% CI) associated with the RAD51 GC/CC genotype frequency was OR, 1.10; 95% CI, 0.80-1.41 for breast cancer and OR, 1.22; 95% CI, 0.92-1.62 for ovarian cancer. Similarly, there were no increased risks associated with the XRCC2 GA/AA genotype (OR, 0.98; 95% CI, 0.76-1.26 for breast cancer and OR, 0.93; 95% CI, 0.69-1.25 for ovarian cancer) or the XRCC3 CT/TT genotype (OR, 0.92; 95% Cl, 0.77-1.10 for breast cancer and OR, 0.87; 95% CI, 0.71-1.08 for ovarian cancer). Results were little changed after adjustment for age and other measured risk factors. Although there was little statistical power to detect modest increases in risk for the homozygote variant genotypes, particularly for the rare RAD51 and XRCC2 variants, the data suggest that none of these variants play a major role in the etiology of breast or ovarian cancer.

Comparative phylogeographic summary statistics for testing simultaneous vicariance

Testing for simultaneous vicariance across comparative phylogeographic data sets is a notoriously difficult problem hindered by mutational variance, the coalescent variance, and variability across pairs of sister taxa in parameters that affect genetic divergence. We simulate vicariance to characterize the behaviour of several commonly used summary statistics across a range of divergence times, and to characterize this behaviour in comparative phylogeographic datasets having multiple taxon-pairs. We found Tajima's D to be relatively uncorrelated with other summary statistics across divergence times, and using simple hypothesis testing of simultaneous vicariance given variable population sizes, we counter-intuitively found that the variance across taxon pairs in Nei and Li's net nucleotide divergence (pi(net)), a common measure of population divergence, is often inferior to using the variance in Tajima's D across taxon pairs as a test statistic to distinguish ancient simultaneous vicariance from variable vicariance histories. The opposite and more intuitive pattern is found for testing more recent simultaneous vicariance, and overall we found that depending on the timing of vicariance, one of these two test statistics can achieve high statistical power for rejecting simultaneous vicariance, given a reasonable number of intron loci (> 5 loci, 400 bp) and a range of conditions. These results suggest that components of these two composite summary statistics should be used in future simulation-based methods which can simultaneously use a pool of summary statistics to test comparative the phylogeographic hypotheses we consider here.

Should managed populations be monitored every year?

We often need to estimate the size of wild populations to determine the appropriate management action, for example, to set a harvest quota. Monitoring is usually planned under the assumption that it must be carried out at fixed intervals in time, typically annually, before the harvest quota is set. However, monitoring can be very expensive, and we should weigh the cost of monitoring against the improvement that it makes in decision making. A less costly alternative to monitoring annually is to predict the population size using a population model and information from previous surveys. In this paper, the problem of monitoring frequency is posed within a decision-theory framework. We discover that a monitoring regime that varies according to the state of the system call outperform fixed-interval monitoring This idea is illustrated using data for a red kangaroo (Macropits rufus) population in South Australia. Whether or not one should monitor in a given year is dependent on the estimated population density in the previous year, the uncertainty in that population estimate, and past rainfall. We discover that monitoring is-important when a model-based prediction of population density is very uncertain. This may occur if monitoring has not taken place for several years, or if rainfall has been above average. Monitoring is also important when prior information suggests that the population is near a critical threshold in population abundance. However, monitoring is less important when the optimal management action would not be altered by new information.

Small-scale randomized controlled trials need more powerful methods of mediational analysis than the Baron-Kenny method

Objective: To devise more-effective physical activity interventions, the mediating mechanisms yielding behavioral change need to be identified. The Baron-Kenny method is most commonly used. but has low statistical power and May not identify mechanisms of behavioral change in small-to-medium size Studies. More powerful statistical tests are available, Study Design and Setting: Inactive adults (N = 52) were randomized to either a print or a print-plus-telephone intervention. Walking and exercise-related social support Were assessed at baseline, after file intervention, and 4 weeks later. The Baron-Kenny and three alternative methods of mediational analysis (Freedman-Schatzkin; MacKinnon et al.: bootstrap method) were used to examine the effects of social support on initial behavior change and maintenance. Results: A significant mediational effect of social support on initial behavior change was indicated by the MacKinnon et al., bootstrap. and. marginally. Freedman-Schatzkin methods, but not by the Baron-Kenny method. No significant mediational effecl of social support on maintenance of walking was found. Conclusions: Methodologically rigorous intervention studies to identify mediators of change in physical activity are costly and labor intensive, and may not be feasible with large samples. The Use of statistically powerful tests of mediational effects in small-scale studies can inform the development of more effective interventions. (C) 2006 Elsevier Inc. All rights reserved.

Presence-absence versus abundance data for monitoring threatened species

Effective detection of population trend is crucial for managing threatened species. Little theory exists, however, to assist managers in choosing the most cost-effective monitoring techniques for diagnosing trend. We present a framework for determining the optimal monitoring strategy by simulating a manager collecting data on a declining species, the Chestnut-rumped Hylacola (Hylacola pyrrhopygia parkeri), to determine whether the species should be listed under the IUCN (World Conservation Union) Red List. We compared the efficiencies of two strategies for detecting trend, abundance, and presence-absence surveys, underfinancial constraints. One might expect the abundance surveys to be superior under all circumstances because more information is collected at each site. Nevertheless, the presence-absence data can be collected at more sites because the surveyor is not obliged to spend a fixed amount of time at each site. The optimal strategy for monitoring was very dependent on the budget available. Under some circumstances, presence-absence surveys outperformed abundance surveys for diagnosing the IUCN Red List categories cost-effectively. Abundance surveys were best if the species was expected to be recorded more than 16 times/year; otherwise, presence-absence surveys were best. The relationship between the strategies we investigated is likely to be relevant for many comparisons of presence-absence or abundance data. Managers of any cryptic or low-density species who hope to maximize their success of estimating trend should find an application for our results.

GESTÃO DO CONHECIMENTO: UM ESTUDO SOBRE A RELAÇÃO ENTRE A LIDERANÇA TRANSFORMACIONAL, A CONVERSÃO DO CONHECIMENTO E A EFICÁCIA ORGANIZACIONAL

Este estudo teve como objetivo principal analisar a relação entre a Liderança Transformacional, a Conversão do Conhecimento e a Eficácia Organizacional. Foram considerados como pressupostos teóricos conceitos consolidados sobre os temas desta relação, além de recentes pesquisas já realizadas em outros países e contextos organizacionais. Com base nisto identificou-se potencial estudo de um modelo que relacionasse estes três conceitos. Para tal considera-se que as organizações que buscam atingir Vantagem Competitiva e incorporam a Knowledge-Based View possam conquistar diferenciação frente a seus concorrentes. Nesse contexto o conhecimento ganha maior destaque e papel protagonista nestas organizações. Dessa forma criar conhecimento através de seus colaboradores, passa a ser um dos desafios dessas organizações ao passo que sugere melhoria de seus indicadores Econômicos, Sociais, Sistêmicos e Políticos, o que se define por Eficácia Organizacional. Portanto os modos de conversão do conhecimento nas organizações, demonstram relevância, uma vez que se cria e se converte conhecimentos através da interação entre o conhecimento existente de seus colaboradores. Essa conversão do conhecimento ou modelo SECI possui quatro modos que são a Socialização, Externalização, Combinação e Internalização. Nessa perspectiva a liderança nas organizações apresenta-se como um elemento capaz de influenciar seus colaboradores, propiciando maior dinâmica ao modelo SECI de conversão do conhecimento. Se identifica então na liderança do tipo Transformacional, características que possam influenciar colaboradores e entende-se que esta relação entre a Liderança Transformacional e a Conversão do Conhecimento possa ter influência positiva nos indicadores da Eficácia Organizacional. Dessa forma esta pesquisa buscou analisar um modelo que explorasse essa relação entre a liderança do tipo Transformacional, a Conversão do Conhecimento (SECI) e a Eficácia Organizacional. Esta pesquisa teve o caráter quantitativo com coleta de dados através do método survey, obtendo um total de 230 respondentes válidos de diferentes organizações. O instrumento de coleta de dados foi composto por afirmativas relativas ao modelo de relação pesquisado com um total de 44 itens. O perfil de respondentes concentrou-se entre 30 e 39 anos de idade, com a predominância de organizações privadas e de departamentos de TI/Telecom, Docência e Recursos Humanos respectivamente. O tratamento dos dados foi através da Análise Fatorial Exploratória e Modelagem de Equações Estruturais via Partial Least Square Path Modeling (PLS-PM). Como resultado da análise desta pesquisa, as hipóteses puderam ser confirmadas, concluindo que a Liderança Transformacional apresenta influência positiva nos modos de Conversão do Conhecimento e que; a Conversão do Conhecimento influencia positivamente na Eficácia Organizacional. Ainda, concluiu-se que a percepção entre os respondentes não apresenta resultado diferente sobre o modelo desta pesquisa entre quem possui ou não função de liderança.

Raising the bar for systematic conservation planning

Mathematical methods in systematic conservation planning (SCP) represent a significant step toward cost-effective, transparent allocation of resources for biodiversity conservation. However, research demonstrates important consequences of uncertainties in SCP. Current research often relies on simplified case studies with unknown forms and amounts of uncertainty and low statistical power for generalizing results. Consequently, conservation managers have little evidence for the true performance of conservation planning methods in their own complex, uncertain applications. SCP needs to build evidence for predictive models of error and robustness to multiple, simultaneous uncertainties across a wide range of problems of known complexity. Only then can we determine true performance rather than how a method appears to perform on data with unknown uncertainty.

Habits and attitudes towards retinoscopy and the relative accuracy of dedicated and combined retinoscopes

The studies presented in this thesis were carried out because of a lack of previous research with respect to (a) the habits and attitudes towards retinoscopy and (b) the relative accuracy of dedicated retinoscopes compared to combined types in which changing the bulb allows use in spot or streak mode. An online British survey received responses from 298 optometrists. Decision tree analyses revealed that optometrists working in multiple practices tended to rely less on retinoscopy than those in the independent sector. Only half of the respondents used dynamic retinoscopy. The majority, however, agreed that retinoscopy was an important test. The University attended also influenced the type of retinoscope used and the use of autorefractors. Combined retinoscopes were used most by the more recently qualified optometrists and few agreed that combined retinoscopes were less accurate. A trial indicated that combined and dedicated retinoscopes were equally accurate. Here, 4 optometrists (2 using spot and 2 using streak retinoscopes) tested one eye of 6 patients using combined and dedicated retinoscopes. This trial also demonstrated the utility of the relatively unknown ’15 degrees of freedom’ rule that exploits replication in factorial ANOVA designs to achieve sufficient statistical power when recruitment is limited. An opportunistic international survey explored the use of retinoscopy by 468 practitioners (134 ophthalmologists, 334 optometrists) attending contact related courses. Decision tree analyses found (a) no differences in the habits of optometrists and ophthalmologists, (b) differences in the reliance on retinoscopy and use of dynamic techniques across the participating countries and (c) some evidence that younger practitioners were using static and dynamic retinoscopy least often. In conclusion, this study has revealed infrequent use of static and dynamic retinoscopy by some optometrists, which may be the only means of determining refractive error and evaluating accommodation in patients with communication difficulties.

The effect of ocular nutritional supplements on macular pigment optical density

This thesis describes the investigation of the effects of ocular supplements with different levels of nutrients on the macular pigment optical density (MPOD) in participants with healthy eyes. Abstract A review of the literature highlighted that ocular supplements are produced in various combinations of nutrients and concentrations. The ideal concentrations of nutrients such as lutein (L) have not been established. It was unclear whether different stages of eye disease require different concentrations of key nutrients, leading to the design of this study. The primary aim was to determine the effects of ocular supplements with different concentrations of nutrients on the MPOD of healthy participants. The secondary aim was to determine L and zeaxanthin (Z) intake at the start and end of the study through completion of food diaries. The primary study was split into two experiments. Experiment 1 was an exploratory study to determine sample size and experiment 2 the main study. Statistical power was calculated and a sample size of 38 was specified. Block stratification for age, gender and smoking habit was applied and from 101 volunteers 42 completed the study, 31 with both sets of food diaries. Four confounders were accounted for in the design of the study; gender, smoking habit, age and diet. Further factors that could affect comparability of results between studies were identified during the study and were not monitored; ethnicity, gastro-intestinal health, alcohol intake, body mass index and genetics. Comparisons were made between the sample population and the Sheffield general population according to recent demographic results in the public domain. Food diaries were analysed and shown to have no statistical difference when comparing baseline to final results. The average L and Z intake for the 31 participants who returned both sets of food diaries was initially 1.96mg and 1.51mg for the final food diaries. The effect of the two ocular supplements with different levels of xanthophyll (6mg lutein/zeaxanthin and 10mg lutein only) on MPOD was not significantly different over a four-month period.

Determinants of local government pension funding: Empirical evidence from Florida

The financial community is well aware that continued underfunding of state and local government pension plans poses many public policy and fiduciary management concerns. However, a well-defined theoretical rationale has not been developed to explain why and how public sector pension plans underfund. This study uses three methods: a survey of national pension experts, an incomplete covariance panel method, and field interviews.^ A survey of national public sector pension experts was conducted to provide a conceptual framework by which underfunding could be evaluated. Experts suggest that plan design, fiscal stress, and political culture factors impact underfunding. However, experts do not agree with previous research findings that unions actively pursue underfunding to secure current wage increases.^ Within the conceptual framework and determinants identified by experts, several empirical regularities are documented for the first time. Analysis of 173 local government pension plans, observed from 1987 to 1992, was conducted. Findings indicate that underfunding occurs in plans that have lower retirement ages, increased costs due to benefit enhancements, when the sponsor faces current year operating deficits, or when a local government relies heavily on inelastic revenue sources. Results also suggest that elected officials artificially inflate interest rate assumptions to reduce current pension costs, consequently shifting these costs to future generations. In concurrence with some experts there is no data to support the assumption that highly unionized employees secure more funding than less unionized employees.^ Empirical results provide satisfactory but not overwhelming statistical power, and only minor predictive capacity. To further explore why underfunding occurs, field interviews were carried out with 62 local government officials. Practitioners indicated that perceived fiscal stress, the willingness of policymakers to advance funding, bargaining strategies used by union officials, apathy by employees and retirees, pension board composition, and the level of influence by internal pension experts has an impact on funding outcomes.^ A pension funding process model was posited by triangulating the expert survey, empirical findings, and field survey results. The funding process model should help shape and refine our theoretical knowledge of state and local government pension underfunding in the future. ^

Tree Mortality following Prescribed Fire and a Storm Surge Event in Slash Pine (Pinus elliottii var. densa) Forests in the Florida Keys, USA

In fire-dependent forests, managers are interested in predicting the consequences of prescribed burning on postfire tree mortality. We examined the effects of prescribed fire on tree mortality in Florida Keys pine forests, using a factorial design with understory type, season, and year of burn as factors. We also used logistic regression to model the effects of burn season, fire severity, and tree dimensions on individual tree mortality. Despite limited statistical power due to problems in carrying out the full suite of planned experimental burns, associations with tree and fire variables were observed. Post-fire pine tree mortality was negatively correlated with tree size and positively correlated with char height and percent crown scorch. Unlike post-fire mortality, tree mortality associated with storm surge from Hurricane Wilma was greater in the large size classes. Due to their influence on population structure and fuel dynamics, the size-selective mortality patterns following fire and storm surge have practical importance for using fire as a management tool in Florida Keys pinelands in the future, particularly when the threats to their continued existence from tropical storms and sea level rise are expected to increase.

Assessment of the Spatial and Temporal Distribution of Functional Connectivity in Resting-State BOLD fMRI

Recent research into resting-state functional magnetic resonance imaging (fMRI) has shown that the brain is very active during rest. This thesis work utilizes blood oxygenation level dependent (BOLD) signals to investigate the spatial and temporal functional network information found within resting-state data, and aims to investigate the feasibility of extracting functional connectivity networks using different methods as well as the dynamic variability within some of the methods. Furthermore, this work looks into producing valid networks using a sparsely-sampled sub-set of the original data.

In this work we utilize four main methods: independent component analysis (ICA), principal component analysis (PCA), correlation, and a point-processing technique. Each method comes with unique assumptions, as well as strengths and limitations into exploring how the resting state components interact in space and time.

Correlation is perhaps the simplest technique. Using this technique, resting-state patterns can be identified based on how similar the time profile is to a seed region’s time profile. However, this method requires a seed region and can only identify one resting state network at a time. This simple correlation technique is able to reproduce the resting state network using subject data from one subject’s scan session as well as with 16 subjects.

Independent component analysis, the second technique, has established software programs that can be used to implement this technique. ICA can extract multiple components from a data set in a single analysis. The disadvantage is that the resting state networks it produces are all independent of each other, making the assumption that the spatial pattern of functional connectivity is the same across all the time points. ICA is successfully able to reproduce resting state connectivity patterns for both one subject and a 16 subject concatenated data set.

Using principal component analysis, the dimensionality of the data is compressed to find the directions in which the variance of the data is most significant. This method utilizes the same basic matrix math as ICA with a few important differences that will be outlined later in this text. Using this method, sometimes different functional connectivity patterns are identifiable but with a large amount of noise and variability.

To begin to investigate the dynamics of the functional connectivity, the correlation technique is used to compare the first and second halves of a scan session. Minor differences are discernable between the correlation results of the scan session halves. Further, a sliding window technique is implemented to study the correlation coefficients through different sizes of correlation windows throughout time. From this technique it is apparent that the correlation level with the seed region is not static throughout the scan length.

The last method introduced, a point processing method, is one of the more novel techniques because it does not require analysis of the continuous time points. Here, network information is extracted based on brief occurrences of high or low amplitude signals within a seed region. Because point processing utilizes less time points from the data, the statistical power of the results is lower. There are also larger variations in DMN patterns between subjects. In addition to boosted computational efficiency, the benefit of using a point-process method is that the patterns produced for different seed regions do not have to be independent of one another.

This work compares four unique methods of identifying functional connectivity patterns. ICA is a technique that is currently used by many scientists studying functional connectivity patterns. The PCA technique is not optimal for the level of noise and the distribution of the data sets. The correlation technique is simple and obtains good results, however a seed region is needed and the method assumes that the DMN regions is correlated throughout the entire scan. Looking at the more dynamic aspects of correlation changing patterns of correlation were evident. The last point-processing method produces a promising results of identifying functional connectivity networks using only low and high amplitude BOLD signals.

Inter-site and inter-scanner diffusion MRI data harmonization.

We propose a novel method to harmonize diffusion MRI data acquired from multiple sites and scanners, which is imperative for joint analysis of the data to significantly increase sample size and statistical power of neuroimaging studies. Our method incorporates the following main novelties: i) we take into account the scanner-dependent spatial variability of the diffusion signal in different parts of the brain; ii) our method is independent of compartmental modeling of diffusion (e.g., tensor, and intra/extra cellular compartments) and the acquired signal itself is corrected for scanner related differences; and iii) inter-subject variability as measured by the coefficient of variation is maintained at each site. We represent the signal in a basis of spherical harmonics and compute several rotation invariant spherical harmonic features to estimate a region and tissue specific linear mapping between the signal from different sites (and scanners). We validate our method on diffusion data acquired from seven different sites (including two GE, three Philips, and two Siemens scanners) on a group of age-matched healthy subjects. Since the extracted rotation invariant spherical harmonic features depend on the accuracy of the brain parcellation provided by Freesurfer, we propose a feature based refinement of the original parcellation such that it better characterizes the anatomy and provides robust linear mappings to harmonize the dMRI data. We demonstrate the efficacy of our method by statistically comparing diffusion measures such as fractional anisotropy, mean diffusivity and generalized fractional anisotropy across multiple sites before and after data harmonization. We also show results using tract-based spatial statistics before and after harmonization for independent validation of the proposed methodology. Our experimental results demonstrate that, for nearly identical acquisition protocol across sites, scanner-specific differences can be accurately removed using the proposed method.

Acceptance of relapse fears in breast cancer patients: effects of an act-based abridged intervention

Objective: Relapse fear is a common psychological scar in cancer survivors. The aim of this study is to assess the effects of an abridged version of Acceptance and Commitment Therapy (ACT) in breast cancer patients.Method: An open trial was developed with 12 non-metastatic breast cancer patients assigned to 2 conditions, ACT and waiting list. Interventions were applied in just one session and focused on the acceptance of relapse fears through a ‘defusion’ exercise. Interference and intensity of fear measured through subjective scales were collected after each intervention and again 3 months later. Distress, hypochondria and ‘anxious preocupation’ were also evaluated through standardized questionnaires.Results: The analysis revealed that ‘defusion’ contributed to decrease the interference of the fear of recurrence, and these changes were maintained three months after intervention in most subjects. 87% of participants showed clinically significant decreases in interference at follow-up sessions whereas no patient in the waiting list showed such changes. Statistical analysis revealed that the changes in interference were significant when comparing pre, post and follow-up treatment, and also when comparing ACT and waiting list groups. Changes in intensity of fear, distress, anxious preoccupation and hypochondria were also observed.Conclusions: Exposure through ‘defusion’ techniques might be considered a useful option for treatment of persistent fears in cancer patients. This study provides evidence for therapies focusing on psychological acceptance in cancer patients through short, simple and feasible therapeutic methods.