No abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. American Statistical Association is collaborating with JSTOR to digitize, preserve and extend access to Journal of the American Statistical Association.We study Bayesian models and methods for analysing network traffic counts in problems of inference about the traffic intensity between directed pairs of origins and destinations in networks. This is a class of problems very recently discussed by Vardi in a 1996 JASA article and is of interest in both communication and transportation network studies. The current article develops the theoretical framework of variants of the origin-destination flow problem and introduces Bayesian approaches to analysis and inference. In the first, the so-called fixed routing problem, traffic or messages pass between nodes in a network, with each message originating at a specific source node, and ultimately moving through the network to a predetermined destination node. All nodes are candidate origin and destination points. The framework assumes no travel time complications, considering only the number of messages passing between pairs of nodes in a specified time interval. The route count, or route flow, problem is to infer the set of actual number of messages passed between each directed origin-destination pair in the time interval, based on the observed counts flowing between all directed pairs of adjacent nodes. Based on some development of the theoretical structure of the problem and assumptions about prior distributional forms, we develop posterior distributions for inference on actual origin-destination counts and associated flow rates. This involves iterative simulation methods, or Markov chain Monte Carlo (MCMC), that combine Metropolis-Hastings steps within an overall Gibbs sampling framework. We discuss issues of convergence and related practical matters, and illustrate the approach in a network previously studied in Vardi's article. We explore both methodological and applied aspects much further in a concrete problem of a road network in North Carolina, studied in transportation flow assessment contexts by civil engineers. This investigation generates critical insight into limitations of statistical analysis, and particularly of non-Bayesian approaches, due to inherent structural features of the problem. A truly Bayesian approach, imposing partial stochastic constraints through informed prior distributions, offers a way of resolving these problems and is consistent with prevailing trends in updating traffic flow intensities in this field. Following this, we explore a second version of the problem that introduces elements of uncertainty about routes taken by individual messages in terms of Markov selection of outgoing links for messages at ...

(2014) Safety and efficacy of aerobic training in operable breast cancer patients receiving neoadjuvant chemotherapy: A phase II randomized trial, Acta Oncologica, 53:1, 65-74,

BACKGROUND. A feasibility study examining the effects of supervised aerobic exercise training on cardiopulmonary and quality of life (QOL) endpoints among postsurgical nonsmall cell lung cancer (NSCLC) patients was conducted. METHODS. Using a single‐group design, 20 patients with stage I‐IIIB NSCLC performed 3 aerobic cycle ergometry sessions per week at 60% to 100% of peak workload for 14 weeks. Peak oxygen consumption (VO2peak) was assessed using an incremental exercise test. QOL and fatigue were assessed using the Functional Assessment of Cancer Therapy–Lung (FACT‐L) scale. RESULTS. Nineteen patients completed the study. Intention‐to‐treat analysis indicated that VO2peak increased 1.1 mL/kg−1/min−1 (95% confidence interval [CI], −0.3‐2.5; P = .109) and peak workload increased 9 W (95% CI, 3‐14; P = .003), whereas FACT‐L increased 10 points (95% CI, −1‐22; P = .071) and fatigue decreased 7 points (95% CI; −1 to −17; P = .029) from baseline to postintervention. Per protocol analyses indicated greater improvements in cardiopulmonary and QOL endpoints among patients not receiving adjuvant chemotherapy. CONCLUSIONS. This pilot study provided proof of principle that supervised aerobic training is safe and feasible for postsurgical NSCLC patients. Aerobic exercise training is also associated with significant improvements in QOL and select cardiopulmonary endpoints, particularly among patients not receiving chemotherapy. Larger randomized trials are warranted. Cancer 2008. © 2008 American Cancer Society.

Background To investigate the prognostic importance of functional capacity and exercise behavior in patients with metastatic non-small cell lung cancer (NSCLC). Patients and methods Using a prospective design, 118 consecutive participants with histologically confirmed metastatic (inoperable) NSCLC and Eastern Cooperative Oncology group (ECOG) 0–3 completed a six-minute walk test to assess functional capacity and questionnaire that assessed self-reported exercise behavior. Cox proportional models were used to estimate the risk of all-cause mortality according to six-minute walk distance (6MWD) (<358.5 m, 358.5–450 m, ≥450 m) and exercise behavior (MET-hrs wk−1) categories with adjustment for important covariates. Results Median follow-up was 26.6 months; 77 deaths were reported during this period. Functional capacity was an independent predictor of survival (Ptrend = 0.003) and added incremental prognostic value beyond that provided by PS plus other traditional markers of prognosis (Ptrend = 0.025). Compared with patients achieving a 6MWD <358.5 m, the adjusted hazard ratio (HR) for all-cause mortality was 0.61 (95% CI, 0.34–1.07) for a 6MWD of 358.5–450 m, and 0.48 (95% CI, 0.24–0.93) for a 6MWD >450 m. In unadjusted analysis, there was a borderline significant effect of exercise behavior on survival (p = 0.052). Median survival was 12.89 months (95% CI, 9.11–21.05 months) for those reporting <9 MET-hrs wk−1 compared with 25.63 months (95% CI, 11.28 to ∞ months) for those reporting ≥9 MET-hrs wk−1. Conclusions Functional capacity is a strong independent predictor of survival in advanced NSCLC that adds to the prediction of survival beyond traditional risk factors. This parameter may improve risk stratification and prognostication in NSCLC.

Aerobic exercise training (AET) is an effective adjunct therapy to attenuate the adverse side-effects of adjuvant chemotherapy in women with early breast cancer. Whether AET interacts with the antitumor efficacy of chemotherapy has received scant attention. We carried out a pilot study to explore the effects of AET in combination with neoadjuvant doxorubicin–cyclophosphamide (AC+AET), relative to AC alone, on: (i) host physiology [exercise capacity (VO2 peak), brachial artery flow-mediated dilation (BA-FMD)], (ii) host-related circulating factors [circulating endothelial progenitor cells (CEP) cytokines and angiogenic factors (CAF)], and (iii) tumor phenotype [tumor blood flow (15O–water PET), tissue markers (hypoxia and proliferation), and gene expression] in 20 women with operable breast cancer. AET consisted of three supervised cycle ergometry sessions/week at 60% to 100% of VO2 peak, 30 to 45 min/session, for 12 weeks. There was significant time × group interactions for VO2 peak and BA-FMD, favoring the AC+AET group (P < 0.001 and P = 0.07, respectively). These changes were accompanied by significant time × group interactions in CEPs and select CAFs [placenta growth factor, interleukin (IL)-1β, and IL-2], also favoring the AC+AET group (P < 0.05). 15O–water positron emission tomography (PET) imaging revealed a 38%decrease in tumor blood flow in the AC+AET group. There were no differences in any tumor tissue markers (P > 0.05). Whole-genome microarray tumor analysis revealed significant differential modulation of 57 pathways (P < 0.01), including many that converge on NF-κB. Data from this exploratory study provide initial evidence that AET can modulate several host- and tumor-related pathways during standard chemotherapy. The biologic and clinical implications remain to be determined.

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A B S T R A C T PurposeIdentifying strong markers of prognosis are critical to optimize treatment and survival outcomes in patients with malignant recurrent glioma. We investigated the prognostic significance of exercise behavior and functional capacity in this population. Patients and MethodsUsing a prospective design, 243 patients with WHO grades 3 to 4 recurrent malignant glioma and Karnofsky performance status (KPS) Ն 70 completed a self-administered questionnaire that assessed exercise behavior and performed a 6-minute walk test (6MWT) to assess functional capacity. Cox proportional models were used to estimate the risk of all-cause mortality according to 6MWT distance (6MWD; Ͻ 390 meters, 390-489 meters, Ͼ 489 meters) and exercise behavior (metabolic equivalent [MET] -h/wk) adjusted for KPS and other important clinical factors. ResultsMedian follow-up was 27.43 months. During this period, 149 deaths were recorded (61% of the total sample). Exercise behavior was an independent predictor of survival (P ϭ .0081). Median survival was 13.03 months for patients reporting Ͻ 9 MET-h/wk relative to 21.84 months for those reporting Ն 9 MET-h/wk. Exercise behavior added incremental prognostic value beyond that provided by KPS, age, sex, grade, and number of prior progressions (P Ͻ .001). Compared with patients reporting Ͻ 9 MET-h/wk, the adjusted hazard ratio for mortality was 0.64 (95% CI, 0.46 to 0.91) for patients reporting Ն 9 MET-h/wk. Functional capacity was not an independent predictor of prognosis. ConclusionExercise behavior is a strong independent predictor of survival that provides incremental prognostic value to KPS as well as traditional markers of prognosis in malignant recurrent glioma.