550 research outputs found

    Maximum Likelihood Estimation in Gaussian Chain Graph Models under the Alternative Markov Property

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    The AMP Markov property is a recently proposed alternative Markov property for chain graphs. In the case of continuous variables with a joint multivariate Gaussian distribution, it is the AMP rather than the earlier introduced LWF Markov property that is coherent with data-generation by natural block-recursive regressions. In this paper, we show that maximum likelihood estimates in Gaussian AMP chain graph models can be obtained by combining generalized least squares and iterative proportional fitting to an iterative algorithm. In an appendix, we give useful convergence results for iterative partial maximization algorithms that apply in particular to the described algorithm.Comment: 15 pages, article will appear in Scandinavian Journal of Statistic

    Time to diagnosis and mortality in colorectal cancer: a cohort study in primary care

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    PublishedJournal ArticleResearch Support, Non-U.S. Gov'tBACKGROUND: The relationship between the diagnostic interval and mortality from colorectal cancer (CRC) is unclear. This association was examined by taking account of important confounding factors at the time of first presentation of symptoms in primary care. METHODS: A total of 268 patients with CRC were included in a prospective, population-based study in a Danish county. The diagnostic interval was defined as the time from first presentation of symptoms until diagnosis. We analysed patients separately according to the general practitioner's interpretation of symptoms. Logistic regression was used to estimate 3-year mortality odds ratios as a function of the diagnostic interval using restricted cubic splines and adjusting for tumour site, comorbidity, age, and sex. RESULTS: In patients presenting with symptoms suggestive of cancer or any other serious illness, the risk of dying within 3 years decreased with diagnostic intervals up to 5 weeks and then increased (P=0.002). In patients presenting with vague symptoms, the association was reverse, although not statistically significant. CONCLUSION: Detecting cancer in primary care is two sided: aimed at expediting ill patients while preventing healthy people from going to hospital. This likely explains the counterintuitive findings; but it does not explain the increasing mortality with longer diagnostic intervals. Thus, this study provides evidence for the hypothesis that the length of the diagnostic interval affects mortality in CRC patients.The study was supported by grants from the Danish Cancer Society, the Novo Nordic Foundation, the Danish Graduate School in Public Health Science, and Aarhus University

    Trajectories of quality of life, life satisfaction, and psychological adjustment after prostate cancer

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    To describe trajectories of health-related quality of life (QoL), life satisfaction, and psychological adjustment for men with prostate cancer over the medium to long term and identify predictors of poorer outcomes using growth mixture models.One-thousand sixty-four (82.4% response) men diagnosed with prostate cancer were recruited close to diagnosis and assessed over a 72-month (6-year) period with self-report assessment of health-related QoL, life satisfaction, cancer-related distress, and prostate specific antigen anxiety. Urinary, bowel, and sexual function were also assessed using validated questionnaires.Poorer physical QOL was predicted by older age, lower education, lower income, comorbidities, and receiving hormone therapy. Lower life satisfaction was related to younger age, lower income, not being partnered, and comorbidities. Poorer psychological trajectories were predicted by younger age, lower income, comorbidities, and receiving radical prostatectomy or brachytherapy. Better urinary, bowel, and sexual function were related to better global outcomes over time. Anxiety about prostate specific antigen testing was rare.Distinct trajectories exist for medium- to long-term QoL, life satisfaction, and psychological adjustment after prostate cancer; with age and socioeconomic deprivation playing a differential role in men's survivorship profile and the impact of functional status on outcomes increasing over time. These results reinforce the need for an appraisal of men's life course in addition to treatment side effects when planning survivorship care after cancer.Suzanne K. Chambers, Shu Kay Ng, Peter Baade, Joanne F. Aitken, Melissa K. Hyde, Gary Wittert, Mark Frydenberg, Jeff Dun

    Knowledge, attitudes and experience associated with testing for prostate cancer: a comparison between male doctors and men in the community

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    Background: Debate about testing for prostate cancer using prostate-specific antigen (PSA) and digital rectal examination (DRE) continues. The evidence of benefit from screening for prostate cancer using PSA tests is inconclusive, and it is unclear how PSA can be used most effectively in the detection of prostate cancer. Given the lack of consensus, it is important that consumers understand the issues in a way that will permit them to decide whether or not to have a test and, if symptomatic, how their condition is managed.Aims: To compare prostate cancer knowledge, attitudes and testing experiences reported by male doctors and men in the community, despite the lack of evidence of a benefit.Methods : The primary method for ascertaining the attitudes of male doctors (MD) was a telephone survey, with some doctors electing to complete a written survey. Each MD was selected, at random, from a register of male practitioners aged &ge; 49 years of age. A total of 266 MD participated in the survey. The community sample (CS) was accessed using a telephone survey. Five hundred male Victorian residents aged &ge; 49 years of age participated in the study.Results:Knowledge &minus; Overall, 55% of the CS indicated &shy;correctly that prostate disease is sometimes cancer, compared to 83% of MD.Attitudes &minus; Fifty-five per cent of MD believed men should be tested for prostate disease at least every 2 years, compared to 68% of men in the CS.Testing experience &minus; Forty-five per cent of MD had been tested for prostate cancer in the past, and 92% of those tests were reported as negative. In the CS, 56% had been tested for prostate cancer in the past, and 78% of the results were reported as negative. The &shy;significant independent predictors of having had a prostate test among MD were: (i) age (&ge; 60 years; odds ratio (OR): 1.59; 95% confidence intervals (CI): 1.30&minus;1.88) and (ii) positive attitudes towards regular testing for prostate cancer (OR: 2.27; 95% CI: 1.98&minus;2.56). The significant independent predictors for the CS were: (i) age (&ge; 60 years; OR: 1.65; 95% CI: 1.40&minus;1.89), (ii) being married (OR: 1.30; 95% CI: 1.00&minus;1.60), (iii) knowledge that prostate disease was sometimes cancer (OR: 1.46; 95% CI: 1.26&minus;1.66) and (iv) positive attitudes towards regular testing for prostate cancer (OR: 2.12; 95% CI: 1.90&minus;2.34).Conclusions: The results highlight that testing for prostate cancer is widespread in the community and in the medical profession. Further research should be undertaken to identify how to help men make fully informed decisions about prostate cancer testing.<br /

    Experiences of Australian men diagnosed with advanced prostate cancer: A qualitative study

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    Š Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted. Objective To explore men's lived experience of advanced prostate cancer (PCa) and preferences for support. Design Cross-sectional qualitative study applying open-ended surveys and interviews conducted between June and November 2016. Interviews audio-recorded and transcribed verbatim and analysed from an interpretive phenomenological perspective. Setting Australia, nation-wide. Participants 39 men diagnosed with advanced PCa (metastatic or castration-resistant biochemical progression) were surveyed with 28 men subsequently completing a semistructured in depth telephone interview. Results Thematic analysis of interviews identified two organising themes: lived experience and supportive care. Lived experience included six superordinate themes: regret about late diagnosis and treatment decisions, being discounted in the health system, fear/uncertainty about the future, acceptance of their situation, masculinity and treatment effects. Supportive care included five superordinate themes: communication, care coordination, accessible care, shared experience/peer support and involvement of their partner/family. Conclusions Life course and the health and social context of PCa influence men's experiences of advanced disease. Multimodal interventions integrating peer support and specialist nurses are needed that more closely articulate with men's expressed needs

    New Challenges in Psycho-Oncology Research III: A systematic review of psychological interventions for prostate cancer survivors and their partners: clinical and research implications

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    Abstract not availableSuzanne K. Chambers, Melissa K. Hyde, David P. Smith, Suzanne Hughes, Susan Yuill, Sam Egger, Dianne L. O'Connell, Kevin Stein, Mark Frydenberg, Gary Wittert, Jeff Dun

    Bayesian Networks for Max-linear Models

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    We study Bayesian networks based on max-linear structural equations as introduced in Gissibl and Kl\"uppelberg [16] and provide a summary of their independence properties. In particular we emphasize that distributions for such networks are generally not faithful to the independence model determined by their associated directed acyclic graph. In addition, we consider some of the basic issues of estimation and discuss generalized maximum likelihood estimation of the coefficients, using the concept of a generalized likelihood ratio for non-dominated families as introduced by Kiefer and Wolfowitz [21]. Finally we argue that the structure of a minimal network asymptotically can be identified completely from observational data.Comment: 18 page

    Can exercise delay transition to active therapy in men with low-grade prostate cancer? A multicentre randomised controlled trial

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    Š Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted. Introduction Active surveillance is a strategy for managing low-risk, localised prostate cancer, where men are observed with serial prostate-specific antigen assessments to identify signs of disease progression. Currently, there are no strategies to support active surveillance compliance nor are there interventions that can prevent or slow disease progression, ultimately delaying transition to active treatment before it is clinically required. Recently, we proposed that exercise may have a therapeutic potential in delaying the need for active treatment in men on active surveillance. Methods and analysis A single-blinded, two arm, multicentre randomised controlled trial will be undertaken with 168 patients randomly allocated in a ratio of 1:1 to exercise or usual care. Exercise will consist of supervised resistance and aerobic exercise performed three times per week for the first 6 months in an exercise clinical setting, and during months 7-12, a progressive stepped down approach will be used with men transitioning to once a week supervised training. Thereafter, for months 13 to 36, the men will self-manage their exercise programme. The primary endpoint will be the time until the patients begin active therapy. Secondary endpoints include disease progression (prostate specific antigen), body composition and muscle density, quality of life, distress and anxiety and an economic analysis will be performed. Measurements will be undertaken at 6 and 12 months (postintervention) and at 24 and 36 months follow-up. The primary outcome (time to initiation of curative therapy) will be analysed using Cox proportional hazards regression. Outcomes measured repeatedly will be analysed using mixed effects models to examine between-group differences. Data will be analysed using an intention-to-treat approach. Ethics and dissemination Outcomes from the study will be published in peer-reviewed academic journals and presented in scientific, consumer and clinical meetings. Trial registration number ACTRN12618000225213
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