Population-based Study Of Incident Cases Research Articles

A Modified Cure Rate Model Based on a Piecewise Distribution with Application to Lobular Carcinoma Data

A novel cure rate model is introduced by considering, for the number of concurrent causes, the modified power series distribution and, for the time to event, the recently proposed power piecewise exponential distribution. This model includes a wide variety of cure rate models, such as binomial, Poisson, negative binomial, Haight, Borel, logarithmic, and restricted generalized Poisson. Some characteristics of the model are examined, and the estimation of parameters is performed using the Expectation–Maximization algorithm. A simulation study is presented to evaluate the performance of the estimators in finite samples. Finally, an application in a real medical dataset from a population-based study of incident cases of lobular carcinoma diagnosed in the state of São Paulo, Brazil, illustrates the advantages of the proposed model compared to other common cure rate models in the literature, particularly regarding the underestimation of the cure rate in other proposals and the improved precision in estimating the cure rate of our proposal.

Cure rate models for heterogeneous competing causes.

Cure rate models have been widely studied to analyze time-to-event data with a cured fraction of patients. In this type of model, the number of concurrent causes is assumed to be a random variable. However, in practice, it is natural to admit that the distribution of the number of competing causes is different from individual to individual. Our proposal is to assume that the number of competing causes belongs to a class of a finite mixture of competing causes distributions. We assume the number of malignant cells follow a mixture of two power series distributions and suppose that the time to the event of interest follows a Weibull distribution. We consider the proportion of the cured number of competing causes depending on covariates, allowing direct modeling of the cure rate. The proposed model includes several well-known models as special cases and defines many new special models. An expectation-maximization algorithm is proposed for parameter estimation, where the expectation step involves the computation of the expected number of concurrent causes for each individual. A Monte Carlo simulation is performed to assess the behavior of the estimation method. In order to show the potential for the practice of our model, we apply it to the real medical data set from a population-based study of incident cases of cutaneous melanoma diagnosed in the state of São Paulo, Brazil, illustrating that the model proposed can outperform traditional models in terms of model fitting.

A general class of promotion time cure rate models with a new biological interpretation.

Over the last decades, the challenges in survival models have been changing considerably and full probabilistic modeling is crucial in many medical applications. Motivated from a new biological interpretation of cancer metastasis, we introduce a general method for obtaining more flexible cure rate models. The proposal model extended the promotion time cure rate model. Furthermore, it includes several well-known models as special cases and defines many new special models. We derive several properties of the hazard function for the proposed model and establish mathematical relationships with the promotion time cure rate model. We consider a frequentist approach to perform inferences, and the maximum likelihood method is employed to estimate the model parameters. Simulation studies are conducted to evaluate its performance with a discussion of the obtained results. A real dataset from population-based study of incident cases of melanoma diagnosed in the state of São Paulo, Brazil, is discussed in detail.

Weighted Lindley frailty model: estimation and application to lung cancer data.

In this paper, we propose a novel frailty model for modeling unobserved heterogeneity present in survival data. Our model is derived by using a weighted Lindley distribution as the frailty distribution. The respective frailty distribution has a simple Laplace transform function which is useful to obtain marginal survival and hazard functions. We assume hazard functions of the Weibull and Gompertz distributions as the baseline hazard functions. A classical inference procedure based on the maximum likelihood method is presented. Extensive simulation studies are further performed to verify the behavior of maximum likelihood estimators under different proportions of right-censoring and to assess the performance of the likelihood ratio test to detect unobserved heterogeneity in different sample sizes. Finally, to demonstrate the applicability of the proposed model, we use it to analyze a medical dataset from a population-based study of incident cases of lung cancer diagnosed in the state of São Paulo, Brazil.

The Negative Binomial Beta Prime Regression Model with Cure Rate: Application with a Melanoma Dataset

This paper introduces a cure rate survival model by assuming that the time to the event of interest follows a beta prime (BP) distribution and that the number of competing causes of the event of interest follows a negative binomial distribution. The proposed model provides a novel alternative to the existing cure rate regression models due to its flexibility, as the BP model can exhibit greater levels of skewness and kurtosis than these of the gamma and inverse Gaussian distributions. Moreover, the hazard rate function of this model can have an upside-down bathtub or an increasing shape. We approach both parameter estimation and local influence based on likelihood methods. In special, three perturbation schemes are considered for local influence. Numerical evaluation of the proposed model is performed by Monte Carlo simulations. In order to illustrate the potential for practice of our model, we apply it to the real medical dataset from a population-based study of incident cases of melanoma diagnosed in the state of Sao Paulo, Brazil.

Long-term frailty modeling using a non-proportional hazards model: Application with a melanoma dataset.

The semiparametric Cox regression model is often fitted in the modeling of survival data. One of its main advantages is the ease of interpretation, as long as the hazards rates for two individuals do not vary over time. In practice the proportionality assumption of the hazards may not be true in some situations. In addition, in several survival data is common a proportion of units not susceptible to the event of interest, even if, accompanied by a sufficiently large time, which is so-called immune, "cured," or not susceptible to the event of interest. In this context, several cure rate models are available to deal with in the long term. Here, we consider the generalized time-dependent logistic (GTDL) model with a power variance function (PVF) frailty term introduced in the hazard function to control for unobservable heterogeneity in patient populations. It allows for non-proportional hazards, as well as survival data with long-term survivors. Parameter estimation was performed using the maximum likelihood method, and Monte Carlo simulation was conducted to evaluate the performance of the models. Its practice relevance is illustrated in a real medical dataset from a population-based study of incident cases of melanoma diagnosed in the state of São Paulo, Brazil.

Sa1881 Long Term Outcomes and Predictors of Disabling Disease and Bowel Damage During Crohn's Disease: A Population-Based Study of Incident Cases Diagnosed Between 1994 and 1997

Sa1881 Long Term Outcomes and Predictors of Disabling Disease and Bowel Damage During Crohn's Disease: A Population-Based Study of Incident Cases Diagnosed Between 1994 and 1997

Distinctive Features of Melanoma and Its Management in Elderly Patients

Life expectancy is increasing in most developed countries, and elderly people have the highest incidence of melanoma. To identify characteristics of melanoma and its management in the elderly compared with younger patients. Retrospective population-based study of incident cases of primary melanoma in 1621 patients with stage I or II melanoma in 2004 and 2008. Questionnaires administered to physicians and a survey of cancer registries and pathology laboratories were used to obtain data. The study was conducted in 5 regions in northeastern France. Characteristics of patients and tumors, circumstances of diagnosis, and further management in older patients (≥70 years, 487 patients [30.0%]) compared with younger ones (<70 years, 1134 [70.0%]). Older patients had more frequent melanomas of the head and neck (29.4% vs 8.7%; P < .001) and of the nodular, lentigo maligna, or acral lentiginous histologic subtypes. They had thicker and more frequently ulcerated tumors, categorized as T3 or T4 in 36.7% of cases vs 20.1% in younger patients. Diagnosis of melanoma occurred more frequently in a general practice setting and less frequently in direct consultation with a dermatologist or regular screening for skin cancer. Time to definitive excision was longer in older patients, and 16.8% of them compared with 5.0% of the younger population had insufficient excision margins (P < .001). A sentinel lymph node biopsy was performed in 23.3% of the older patients with melanoma thicker than 1 mm vs 41.4% in the younger patients (P < .001). Adjuvant therapy was less frequently started in older patients and was prematurely stopped in a higher proportion of that population. Age-related variations are observed at every step of melanoma management. The most important concerns are access of elderly people to settings for early diagnosis and excision with appropriate margins.

The impact of socio-economic circumstances on overall and grade-specific prostate cancer incidence: a population-based study

Background:If the observed increasing incidence of prostate cancer and higher incidence in more affluent men are due to differences in diagnostic sensitivity, an excess of asymptomatic low-grade tumours might be expected.Methods:We conducted a descriptive population-based study of incident cases of prostate cancer (International Classification of Diseases version 10 codes for prostate cancer) in the West of Scotland, using the Scottish Cancer Registry data from 1991 to 2007. Socio-economic circumstances were measured using the Carstairs score, and disease grade measured using the Gleason score. Deprivation-specific European age-standardised incidence rates were calculated, and joinpoint regression analysis were used to identify significant changes in trends over time.Results:A total of 15 519 incident cases of prostate cancer were diagnosed. Incidence increased by 70% from 44 to 75 per 100 000 cases between 1991 and 2007, an average annual growth of 3.6%. Men aged <65 years experienced the largest increase in incidence. A widening socio-economic deprivation gap in incidence appeared from 1998 onwards in low-grade disease only. From 2003 to 2007, the deprivation gap (affluent to deprived) was 40.3 per 100 000 cases (P<0.001; trend), with rates 37% lower among the most deprived compared with the most affluent. This deprivation gap represents an estimated 1764 cases of prostate cancer over a 5-year period.Conclusion:Prostate cancer incidence continues to increase; an increase in low-grade disease in affluent men may suggest that prostate-specific antigen testing is responsible, but it does not explain the overall increases in all grades of disease.

The relation between cognition and motor dysfunction in drug‐naive newly diagnosed patients with Parkinson's disease

Recent studies have reported cognitive decline to be common in the early phase of Parkinson's disease. Imaging data connect working memory and executive functioning to the dopamine system. It has also been suggested that bradykinesia is the clinical manifestation most closely related to the nigrostriatal lesion. Exploring the relationship between motor dysfunction and cognition can help us find shared or overlapping systems serving different functions. This relationship has been sparsely investigated in population-based studies of untreated Parkinson's disease. The aim of the present study was to investigate the association between motor signs and cognitive performance in the early stages of Parkinson's disease before the intake of dopaminergic medication. Patients were identified in a population-based study of incident cases with idiopathic parkinsonism. Patients with the postural instability and gait disturbances phenotype were compared with patients with the tremor-dominant phenotype on demographics and cognitive measures. Associations between cognitive and motor scores were investigated, with age, education, and sex controlled for. Bradykinesia was associated with working memory and mental flexibility, whereas axial signs were associated with episodic memory and visuospatial functioning. No significant differences in the neuropsychological variables were found between the postural instability and gait disturbances phenotype and the tremor phenotype. Our results indicate a shared system for slow movement and inflexible thinking that may be controlled by a dopaminergic network different from dopaminergic networks involved in tremor and/or rigidity. The association between axial signs and memory and visuospatial function may point to overlapping systems or pathologies related to these abilities.

The Role of Circumstances of Diagnosis and Access to Dermatological Care in Early Diagnosis of Cutaneous Melanoma

To describe circumstances of the diagnosis and access to dermatological care for patients with cutaneous melanoma (CM) and to investigate factors associated with early detection. Retrospective population-based study of incident cases of invasive CM in 2004, using questionnaires to physicians and a survey of cancer registries and pathology laboratories. Five regions in northeastern France. Six hundred fifty-two patients who were referred to dermatologists by general practitioners (group 1) or by other specialists (group 2), who directly consulted a dermatologist for CM (group 3), or who were diagnosed as having CM during a prospective follow-up of nevi (group 4) or when consulting a dermatologist for other diseases (group 5). Characteristics of patients, tumors, and patients' residence in each group, including the geographical concentration of dermatologists. We performed multivariate analysis of these factors to determine association with Breslow thickness. Age, tumor location, Breslow thickness, ulceration, histological type, and geographical concentration of dermatologists significantly differed among groups. Patients consulting dermatologists directly formed the largest group (45.1%). Those referred by general practitioners (26.1%) were the oldest and had the highest frequency of thick (>3 mm), nodular, and/or ulcerated CM. Patients from groups 4 (8.4%) and 5 (14.1%) had the thinnest CMs. Ulcerated and/or thick tumors were absent in group 4. In multivariate analysis, histological types superficial spreading melanoma and lentigo maligna melanoma, younger age, high concentration of dermatologists, and detection by dermatologists were significantly associated with thinner CMs. Easy access of patients to dermatologists, information campaigns targeting elderly people, and education of general practitioners are complementary approaches to improving early detection.

Survival in Alzheimer disease: A multiethnic, population-based study of incident cases

In the article “Survival in Alzheimer disease: A multiethnic, population-based study of incident cases” …

Early and midlife exposure to anesthesia and age of onset of Alzheimer's disease.

Patients with Alzheimer's disease (AD) who have a late onset of dementia may represent a subgroup of AD that has a unique multifactorial/genetic profile. It was hypothesized in the present study that if external factors interact with a biological or genetic susceptibility in at least some subsets of patients with AD, these factors may accelerate the manifestation of the disease. The cumulative exposure to different types of general and major regional anesthetics prior to the onset of dementia was calculated in a population-based study of incident cases of AD residing in Rochester, MN, for more than 40 years preceding the onset of dementia (N = 252). Correlational analysis revealed that age of onset was inversely related to cumulative exposure to general and spinal anesthesia before the age of 50, whereas there was no, or an expected positive, correlation for anesthetic exposure after 50 years. These findings may suggest that the manifestation of dementia in AD patients may be related to exposure to external factors at an earlier age.