Epidemiology - identifying the causes and preventability of cancer?

Criteria for the evaluation of large cohort studies: an application to the nurses' health study

Evaluating the success of major funding programs from the National Institutes of Health (NIH) remains a vexing challenge. We propose a set of criteria to evaluate epidemiological studies that fit within the discovery, development, and delivery paradigm introduced by the NIH. We apply these criteria to the Nurses' Health Study (NHS), a large epidemiological cohort study initiated in the 1970s to evaluate the associations between oral contraceptives and risk of breast cancer and between diet and other lifestyle factors and risk of cancer overall. Our evaluation suggests that the NHS has led to important changes in health practice, and it underscores the need to develop metrics that are suitable to the evaluation of large epidemiological cohort studies.

Do stress-related psychosocial factors contribute to cancer incidence and survival?

A substantial body of research has investigated the associations between stress-related psychosocial factors and cancer outcomes. Previous narrative reviews have been inconclusive. In this Review, we evaluated longitudinal associations between stress and cancer using meta-analytic methods. The results of 165 studies indicate that stress-related psychosocial factors are associated with higher cancer incidence in initially healthy populations (P = 0.005); in addition, poorer survival in patients with diagnosed cancer was noted in 330 studies (P <0.001), and higher cancer mortality was seen in 53 studies (P <0.001). Subgroup meta-analyses demonstrate that stressful life experiences are related to poorer cancer survival and higher mortality but not to an increased incidence. Stress-prone personality or unfavorable coping styles and negative emotional responses or poor quality of life were related to higher cancer incidence, poorer cancer survival and higher cancer mortality. Site-specific analyses indicate that psychosocial factors are associated with a higher incidence of lung cancer and poorer survival in patients with breast, lung, head and neck, hepatobiliary, and lymphoid or hematopoietic cancers. These analyses suggest that stress-related psychosocial factors have an adverse effect on cancer incidence and survival, although there is evidence of publication bias and results should be interpreted with caution.

Prostate cancer: genes, environment, immunity and the use of immunotherapy

Prostate cancer remains the most prevalent noncutaneous cancer, leading to almost 30,000 deaths every year in men in the United States. A large body of knowledge emphasizes a strong influence of epidemiological factors such as lifestyle, environment and diet, on the development of prostate cancer. Although risk reduction of prostate cancer has been somewhat successful, effective prevention is still lacking. Immunotherapeutic approaches, although moderately complicated, remain promising in an effort to control the progression and development of the disease. Taken together, the parameters of epidemiological studies and immunotherapeutic regimens might eventually be the most effective and preventive approach for prostate cancer. This review highlights some of the events associated with the development and prevention of prostate cancer.

What can we learn from the population incidence of cancer? Armitage and Doll revisited

Most cancers occur with the same characteristic pattern of incidence. The simplicity of this pattern is in contrast to the perceived complexity of carcinogenesis. Therefore, age-onset statistics represent a tempting set of data and have provoked many bold but often misguided conclusions concerning the physiopathological mechanisms of cancer. Half a century has passed since the original multistage theory of Armitage and Doll. Although their basic notion of a healthy cell becoming malignant in several rate-limiting steps is still accepted, prevailing wisdom about the nature and number of these steps has never settled into a consensus. Why have we been unable to elucidate the quantitative dependence of cancer incidence on the molecular processes that feature in its aetiology? In this review we aim to provide answers for this question.

Extrapulmonary effects of chronic obstructive pulmonary disease on physical activity: a cross-sectional study

RATIONALE

Physical activity is reduced in patients with chronic obstructive pulmonary disease (COPD). COPD has a systemic component that includes significant extrapulmonary effects that may contribute to its severity in individual patients.

OBJECTIVES

To investigate the association of extrapulmonary effects of the disease and its comorbidities with reduced physical activity in patients with COPD.

METHODS

In a cross-sectional study, 170 outpatients with COPD (GOLD [Global Initiative for Chronic Obstructive Lung Disease] stages I-IV; BODE [body mass index, airway obstruction, dyspnea, and exercise capacity] score 0-10) underwent a series of tests. Physical activity was assessed over 5 to 6 consecutive days by using a multisensor accelerometer armband that records steps per day and the physical activity level (total daily energy expenditure divided by whole-night sleeping energy expenditure). Cardiovascular status was assessed by echocardiography, vascular Doppler sonography, and levels of N-terminal pro-B-type natriuretic peptide. Mental status, metabolic/muscular status, systemic inflammation, and anemia were assessed by Beck Depression Inventory, bioelectrical impedance analysis, handgrip strength, high-sensitivity C-reactive protein/fibrinogen, and hemoglobin, respectively.

MEASUREMENTS AND MAIN RESULTS

In a multivariate linear regression analysis using either steps per day or physical activity level as a dependent variable, the extrapulmonary parameters that were associated with reduced physical activity in patients with COPD independently of GOLD stages or BODE score were N-terminal pro-B-type natriuretic peptide levels, echocardiographically measured left ventricular diastolic function, and systemic inflammation.

CONCLUSIONS

Higher values of systemic inflammation and left cardiac dysfunction are associated with reduced physical activity in patients with COPD.

Hypoxia and cancer

A major feature of solid tumours is hypoxia, decreased availability of oxygen, which increases patient treatment resistance and favours tumour progression. How hypoxic conditions are generated in tumour tissues and how cells respond to hypoxia are essential questions in understanding tumour progression and metastasis. Massive tumour-cell proliferation distances cells from the vasculature, leading to a deficiency in the local environment of blood carrying oxygen and nutrients. Such hypoxic conditions induce a molecular response, in both normal and neoplastic cells, that drives the activation of a key transcription factor; the hypoxia-inducible factor. This transcription factor regulates a large panel of genes that are exploited by tumour cells for survival, resistance to treatment and escape from a nutrient-deprived environment. Although now recognized as a major contributor to cancer progression and to treatment failure, the precise role of hypoxia signalling in cancer and in prognosis still needs to be further defined. It is hoped that a better understanding of the mechanisms implicated will lead to alternative and more efficient therapeutic approaches.

Cancer epidemiology: study designs and data analysis

Among the scientific interests of cancer epidemiology is the identification of both environmental and genetic factors associated with cancer development. Observational designs requiring sophisticated methodology are applied to control for potential confounding factors. The enormous biotechnological potential developed in the last two decades has allowed the integration of a plethora of new biomarkers in epidemiological studies to better define the exposure and "neoclassic" outcomes, as well as incorporating genetic susceptibility factors in both classical and new epidemiological designs. The integration of scopes, objectives, data and tools coming from different disciplines also benefits epidemiology, thus evolving into "systems epidemiology". In this manuscript, we review the basic concepts of study designs and data analysis and introduce readers to the more innovative aspects that are now being applied in epidemiological studies.

Lung cancer risk prediction: a tool for early detection

Although 45% of men and 39% of women will be diagnosed with cancer in their lifetime, it is difficult to predict which individuals will be affected. For some cancers, substantial progress in individual risk estimation has already been made. However, relatively few models have been developed to predict lung cancer risk beyond effects of age and smoking. This paper reviews published models for lung cancer risk prediction, discusses their potential contribution to clinical and research settings and suggests improvements to the risk modeling strategy for lung cancer. The sensitivity and specificity of existing cancer risk models is less than optimal. Improvement in individual risk prediction is important for selection of individuals for prevention or early detection interventions. In addition to smoking, factors related to occupational exposure, personal medical history and family history of cancer can add to the predictive power. A good risk prediction model is one that can identify a small fraction of the population in which a large proportion of the disease cases will occur. In the future, genetic and other biological markers are likely to be useful, although they will require rigorous evaluation. Validation is essential to establish the predictive effect and for ongoing monitoring of the model's continued relevance.

Cohort studies of etiology and survival after cancer: the unique needs for uninterrupted funding

The existing prospective cohorts are providing key data that are guiding public health and clinical practice in many different areas. The existing cohorts can also provide the biological specimens and data to address genetic determinant of cancer now, rather than in a decade, and at far less cost than that proposed for a new national U.S. cohort. Review and funding mechanisms are needed to avoid disruption in follow-up and the associated damage to existing cohorts.

The balance between heritable and environmental aetiology of human disease

The Human Genome Project and the ensuing International HapMap Project were largely motivated by human health issues. But the distance from a DNA sequence variation to a novel disease gene is considerable; for complex diseases, closing this gap hinges on the premise that they arise mainly from heritable causes. Using cancer as an example of complex disease, we examine the scientific evidence for the hypothesis that human diseases result from interactions between genetic variants and the environment.