Application of a non-parametric non-mixture cure rate model for analyzing the survival of patients with colorectal cancer in Iran / 한국역학회지

OBJECTIVES: Colorectal cancer (CRC) patients are considered to have been cured when the mortality rate of individuals with the disease returns to the same level as expected in the general population. This study aimed to assess the impact of various risk factors on the cure fraction of CRC patients using a real dataset of Iranian CRC patients with a non-mixture non-parametric cure model.METHODS: This study was conducted on the medical records of 512 patients who were definitively diagnosed with CRC at Taleghani Hospital, Tehran, Iran from 2001 to 2007. A non-mixture non-parametric cure rate model was applied to the data after using stepwise selection to identify the risk factors of CRC.RESULTS: For non-cured cases, the mean survival time was 1,243.83 days (95% confidence interval [CI], 1,174.65 to 1,313.00) and the median survival time was 1,493.00 days (95% CI, 1,398.67 to 1,587.33). The 1- and 3-year survival rates were 92.9% (95% CI, 91.0 to 95.0) and 73.4% (95% CI, 68.0 to 79.0), respectively. Pathologic stage T1 of the primary tumor (estimate=0.58; p=0.013), a poorly differentiated tumor (estimate=1.17; p<0.001), a body mass index (BMI) between 18.6 and 24.9 kg/m2 (estimate=−0.60; p=0.04), and a BMI between 25.0 and 29.9 kg/m2 (estimate=−1.43; p<0.001) had significant impacts on the cure fraction of CRC in the multivariate analysis. The proportion of cured patients was 64.1% (95% CI, 56.7 to 72.4).CONCLUSIONS: This study found that the pathologic stage of the primary tumor, tumor grade, and BMI were potential risk factors that had an impact on the cure fraction. A non-mixture non-parametric cure rate model provides a flexible framework for accurately determining the impact of risk factors on the long-term survival of patients with CRC.

Application of a non-parametric non-mixture cure rate model for analyzing the survival of patients with colorectal cancer in Iran / 한국역학회지

OBJECTIVES: Colorectal cancer (CRC) patients are considered to have been cured when the mortality rate of individuals with the disease returns to the same level as expected in the general population. This study aimed to assess the impact of various risk factors on the cure fraction of CRC patients using a real dataset of Iranian CRC patients with a non-mixture non-parametric cure model. METHODS: This study was conducted on the medical records of 512 patients who were definitively diagnosed with CRC at Taleghani Hospital, Tehran, Iran from 2001 to 2007. A non-mixture non-parametric cure rate model was applied to the data after using stepwise selection to identify the risk factors of CRC. RESULTS: For non-cured cases, the mean survival time was 1,243.83 days (95% confidence interval [CI], 1,174.65 to 1,313.00) and the median survival time was 1,493.00 days (95% CI, 1,398.67 to 1,587.33). The 1- and 3-year survival rates were 92.9% (95% CI, 91.0 to 95.0) and 73.4% (95% CI, 68.0 to 79.0), respectively. Pathologic stage T1 of the primary tumor (estimate=0.58; p=0.013), a poorly differentiated tumor (estimate=1.17; p<0.001), a body mass index (BMI) between 18.6 and 24.9 kg/m2 (estimate=−0.60; p=0.04), and a BMI between 25.0 and 29.9 kg/m2 (estimate=−1.43; p<0.001) had significant impacts on the cure fraction of CRC in the multivariate analysis. The proportion of cured patients was 64.1% (95% CI, 56.7 to 72.4). CONCLUSIONS: This study found that the pathologic stage of the primary tumor, tumor grade, and BMI were potential risk factors that had an impact on the cure fraction. A non-mixture non-parametric cure rate model provides a flexible framework for accurately determining the impact of risk factors on the long-term survival of patients with CRC.

Application of a non-parametric non-mixture cure rate model for analyzing the survival of patients with colorectal cancer in Iran / 한국역학회지

OBJECTIVES@#Colorectal cancer (CRC) patients are considered to have been cured when the mortality rate of individuals with the disease returns to the same level as expected in the general population. This study aimed to assess the impact of various risk factors on the cure fraction of CRC patients using a real dataset of Iranian CRC patients with a non-mixture non-parametric cure model.@*METHODS@#This study was conducted on the medical records of 512 patients who were definitively diagnosed with CRC at Taleghani Hospital, Tehran, Iran from 2001 to 2007. A non-mixture non-parametric cure rate model was applied to the data after using stepwise selection to identify the risk factors of CRC.@*RESULTS@#For non-cured cases, the mean survival time was 1,243.83 days (95% confidence interval [CI], 1,174.65 to 1,313.00) and the median survival time was 1,493.00 days (95% CI, 1,398.67 to 1,587.33). The 1- and 3-year survival rates were 92.9% (95% CI, 91.0 to 95.0) and 73.4% (95% CI, 68.0 to 79.0), respectively. Pathologic stage T1 of the primary tumor (estimate=0.58; p=0.013), a poorly differentiated tumor (estimate=1.17; p<0.001), a body mass index (BMI) between 18.6 and 24.9 kg/m2 (estimate=−0.60; p=0.04), and a BMI between 25.0 and 29.9 kg/m2 (estimate=−1.43; p<0.001) had significant impacts on the cure fraction of CRC in the multivariate analysis. The proportion of cured patients was 64.1% (95% CI, 56.7 to 72.4).@*CONCLUSIONS@#This study found that the pathologic stage of the primary tumor, tumor grade, and BMI were potential risk factors that had an impact on the cure fraction. A non-mixture non-parametric cure rate model provides a flexible framework for accurately determining the impact of risk factors on the long-term survival of patients with CRC.

Evaluation of prognostic factors effect on survival time in patients with colorectal cancer, based on weibull competing-risks model

Aim: The aim of this study was to assess the association between survival of patients with colorectal cancer and prognostic factors in a competing risk parametric model using Weibull distribution

Background: The prognosis of colorectal cancer is relatively good in terms of survival time. In many prognostic studies, patients may be exposed to several types of competing events. These different causes of death are called competing risks

Methods: Data was recorded from 372 patients with colorectal cancer who registered in the Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences [Tehran, Iran] from 2004 to 2015 in a retrospective study. Analysis was performed using competing risks model and Weibull distribution. Software used for data analysis was R, and significance level was regarded as 0.05

Results: The result indicated that, at the end of follow-up, 111 [29.8%] deaths were from colorectal cancer and 14 [3.8%] deaths were due to other diseases. The average body mass index [BMI] was 24.61[SD 3.98]. The mean survival time for a patient in 372 was 62.05[SD 48.78] month with median equals to 48 months. According to competing-risks method, only stageIII [HR, 1.69; 95% CI, 1.246-2.315], stageIV[HR, 4.51; 95% CI,2.91-6.99 ] and BMI[HR, 0.96; 95% CI, 0.96-0.975] have a significant efect on patient's survival time

Conclusion: This study indicated pathologic stage[III,IV] and BMI as the prognosis, using a Weibull model with competing risks analysis, while other models without the competing events lead to significant predictors which may be due to over-estimation

[Prevalence of Helicobacter pylori and intestinal metaplasia in consecutive gastritis patients; over the period of 7 years]

Helicobacter pylori [H. pylori] is the cause of most cases of peptic ulcers and gastric cancers and cause some of the most important cause of stomach cancer and lymphoma. The objective of this study was to evaluate the time trend of Helicobacter pylori prevalence and presence of intestinal Metaplasia over the period of 7 years in gastritis Iranian patients

Materials and Methods: In this cross-section study data related to H. pylori and intestinal Metaplasia [IM] among 14,860 consecutive gastritis patients, who referred to the gastrointestinal department of Tehran's Taleghani Hospital in Iran, was examined across the sex and age group

Results: The overall prevalence rate among patient with H. pylori infection was 83.5% [12406/14860] and 11,394 [84.1%] of them were related to the gastritis. The prevalence rate of H. pylori among patient with gastritis significantly higher [p<0.05] compared to patients without gastritis. In addition, the prevalence decreased with age while the presence of intestinal metaplasia increased with age [p<0.05]

Conclusion: The results of this study showed that the prevalence of H. pylori infection in Iranian population has declined in recent years; nevertheless it seems to be highly prevalent in Iran. We also find a significant positive relationship between H. pylori infection and IM with gastritis. There is no association between sex and infection but in contrast with the most studies its prevalence decreased with age

Burden of gastrointestinal cancers and problem of the incomplete information; how to make up the data?

Cancer registration is an important source for measuring the burden of cancer in a population. In practice, however, quite frequently incorrect patients are registered or data items can be inaccurately recorded or not recorded at all. Also the process or quality of these registrations varies among countries. In this paper, we briefly discussed some statistical techniques including; Mortality and Incidence Analysis Model [MIAMOD], Prevalence and Incidence Analysis Model [PIAMOD], Bayesian Inference and Capture-recapture methods, which provide tools to re-correct the incomplete or misclassified cancer statistics with regards to gastrointestinal cancers

Years of life lost due to gastric cancer is increased after Bayesian correcting for misclassification in Iranian population

Aim: To estimate the change in years of life lost [YLL] due to gastric cancer mortality after correcting formisclassification in registering causes of death using the Bayesian method

Background: For evaluating the health status of a country and determining priority of risk factors, some epidemiologicindicators are needed. Due to premature death, YLL is one of the most widely used indicators. To have an exact estimate ofYLL, an accurate death registry data is needed, but the Iranian death registry is subject to misclassification error

Material and methods: Gastric cancer mortality data from 2006 to 2010 for Iran were extracted from national deathstatistics. The rate of misclassification in registered causes of deaths was estimated, using Bayesian method for eachyear. Then YLL of gastric cancer is estimated for different age-sex categories before and after implementing Bayesianmethod

Results: Using Bayesian method, the estimated misclassification rate for gastric cancer in cancer without label group were 5%,3%, 3%, 7% and 7% respectively from 2006 to 2010. Estimated Years of life lost due to gastric cancer before correctingmisclassification were respectively 111684.93, 114957.31, 112391.93, 112250.53 and 113300.92 person-years for years 2006to 2010. After correcting misclassification, the total YLL of gastric cancer increased to 1535.19, 921.11, 908.39, 2566.39 and2507.00 person-years, respectively from 2006 to 2010

Conclusion: If health policy makers ignore the existence of misclassification in registered causes of death, they mayunderestimate the burden of some causes of death and overestimate some others

Evaluation of parametric models by the prediction error in colorectal cancer survival analysis

The aim of this study is to determine the factors influencing predicted survival time for patients with colorectal cancer [CRC] using parametric models and select the best model by predicting error's technique. Survival models are statistical techniques to estimate or predict the overall time up to specific events. Prediction is important in medical science and the accuracy of prediction is determined by a measurement, generally based on loss functions, called prediction error. A total of 600 colorectal cancer patients who admitted to the Cancer Registry Center of Gastroenterology and Liver Disease Research Center, Taleghani Hospital, Tehran, were followed at least for 5 years and have completed selected information for this study. Body Mass Index [BMI], Sex, family history of CRC, tumor site, stage of disease and histology of tumor included in the analysis. The survival time was compared by the Log-rank test and multivariate analysis was carried out using parametric models including Log normal, Weibull and Log logistic regression. For selecting the best model, the prediction error by apparent loss was used. Log rank test showed a better survival for females, BMI more than 25, patients with early stage at diagnosis and patients with colon tumor site. Prediction error by apparent loss was estimated and indicated that Weibull model was the best one for multivariate analysis. BMI and Stage were independent prognostic factors, according to Weibull model. In this study, according to prediction error Weibull regression showed a better fit. Prediction error would be a criterion to select the best model with the ability to make predictions of prognostic factors in survival analysis

Burden of gastrointestinal cancer in Asia; an overview

The cancers in the digestive system including gastric cancer, colorectal cancer, liver cancer, esophageal cancer and pancreatic cancer are one of the most common cancers in Asia. The burden of GI cancer is increasing in Asia because of aging, growth of the population and the risk factors including smoking, obesity, changing lifestyle and high prevalence of H pylori, HBV and HCV. In most Asian countries, cancer control programs or early detection and treatment services are limited despite this increase. There are many people in the developing countries inside Asia who have no health insurance and many of them are too poor to go for screening tests, early detection or medical treatments. Therefore, it is important for the health organizations and governments in each country to recognize these groups and reduce the incidence and mortality of gastrointestinal cancers, using simple and economic screening test, vaccination and changing risk factors such as smoking, diet and lifestyle by education programs

[ Comparision of Iranian Physician and nurses attitudes towards do- not- resusciate Ordersdian]

Background and Aim: Decision making process about Do- Not-Resusciate [DNR] order is unique, since, it is the only treatment decision that should be taken in advance. Most physicians and nurses are not sure whether and when to make a decision about DNR order and its moral aspects. The current study is performed to compare and investigate nurses and physicians attitude about DNR order for patients in their final phases of life

Materials and Methods: In this descriptive-comparative study, 152 physicians and 152 nurses have been studied. The sampling method was stratified sampling. The data gathering tools were a demographical questionnaire and a attitude questionnaire about DNR order

Results: The nurses and physicians in this research with averages of 3.25 for nurses and 3.22 for physicians, had a positive attitude about DNR order. But there was no significant difference between the attitude average score of the physicians and nurses about DNR order [p>0.5]. Nurses and physicians with experience of participating in implementation of cardiopulmonary resuscitation and DNR order, had more positive attitude toward DNR order

Conclusions: The findings suggest that there is no difference between the physician's and nurse's view about DNR order. Although there is a significant relationship between former experience of participating in implementation of cardiopulmonary resuscitation and DNR order with positive attitude about DNR order

Recurrence and five -year survival in Colorectal Cancer patients after surgery

Background: Colorectal cancer [CRC] is a common malignancyworldwide and its outcome is most closely related to the extent of disease at presentation. Early diagnosis of an asymptomatic recurrence increases the likelihood of a complete surgical resection

Objectives: The aim of this study was to evaluate the incidence of colorectal cancer recurrence and survival rate within 5 years, after surgery

Patients and Methods: During the 9-year period since 21[st] Mar, 2004 to 20th Mar, 2013, patients whose primary colorectal cancer were resected in Taleghani hospital, Tehran, Iran were selected in a historical cohort. The necessary data such as demographic, age, gender, family history of CRC, site and size of tumor, stage of tumor, operation details, histological results, treatment method, histopathologic, etc. were collected. Then the recurrence and survival of colorectal cancer within 5 years after operation and their risk factors were evaluated. P value less than 0.05 were considered significant. All analysis was done using SPSS software

Results: A total of 107 patients underwent resection for colorectal cancer during the study period, with mean age of 53.50 +/- 12.68 years [range 24 - 76 years], survival rate of 73.8% [rectum 70.0% and colon 75.9%], and mean survival time of 142.17 +/- 21.60 month. The recurrence rate of CRC patients, during five years after surgery was 5.7%. Regional lymph nodes, Distance metastasis and Adjuvant therapy were significant prognosis factors of survival after surgery

Conclusions: The rate of recurrence in Iranian patients was low, which could be due to improvement of exactness and expertise of surgeons or better adjuvant therapy. The significant association between survival and adjuvant therapy clarifies this finding. Early diagnosis and primary detection could increase the rate of survival

[Prevalence of celiac disease and toxoplasmosis during pregnancy]

Celiac disease [CD] is an autoimmune disorder characterized by gluten sensitivity in genetically susceptible individuals. There is no previous report on CD and Toxoplasma gondii infection and no previous assessments with regard to the association of these conditions on pregnancy. The aim of this study was to estimate the prevalence of undiagnosed CD and T.gondii in the pregnant women. In this descriptive study, during the period of January-July 2007, 496 pregnant women with mean age of 26 +/- 5 years [SD 4.11] and mean pregnancy duration 5.2 months were referred to reproduction section of rural and urban health care centers in Lorestan province. They underwent a total IgA test and antihuman IgA class antitissue transglutaminase [tTGA] antibodies for detection of CD. Those with IgA deficiency were tested with IgG tTG. Also IgG and IgM-Toxoplasma level were measured for detection of total antibody against T.gondii. Of 496 pregnant women, 13 [2.6%] had a positive CD serology for tTGA [95% CI: 1.2%-4.3%]. 154/496 patients had IgG positive test and 35/154 patients had IgM positive for T.gondii indicating acute stage of T.gondii infection. It is well established that CD and T.gondii infection are both associated with a high incidence of unfavorable outcomes in pregnancy. Our data suggest that CD may predispose to the development of T.gondii infection

Leukemia cancer mortality trend in Iran, from 1995 to 2004

Cancer is the third most common cause of death in Iran, the leukemia cancer is one of the most important causes of cancer mortality. Regarding cancer mortality, data would be important to monitor the program screening effects, earlier diagnosis, demographic data and other prognostic factors. The aim of this study was mortality rates evaluating, then leukemia cancer trends among the Iranian population within almost a period of a decade, i.e. from 1995 to 2004. National death Statistic Reported by Ministry of Health and Medical Education [MOH and ME] from 1995 to 2004, stratified by age group, sex, and cause of death, have included in this study. Leukemia cancer has expressed as the annual mortality rates/100,000, in general, and/or per gender, and age group. The general mortality rate of leukemia cancer has slightly increased within the mentioned study period, from 0.44 to 2.54, then leukemia cancer mortality has often seen in men more than women. The mortality rate of leukemia has significantly increased throughout Iran. Associated risk factors with leukemia have headmost identified for their prevention and control. So, future studies to reveal leukemia risk factors among the Iranian population would be crucial in order to control its burden

Sample size calculation in medical studies

Optimum sample size is an essential component of any research. The main purpose of the sample size calculation is to determine the number of samples needed to detect significant changes in clinical parameters, treatment effects or associations after data gathering. It is not uncommon for studies to be underpowered and thereby fail to detect the existing treatment effects due to inadequate sample size. In this paper, we explain briefly the basic principles of sample size calculations in medical studies

Study on association between H-ras gene polymorphism and gastric adenocarcinoma risk

The aim of this study was to investigate relation between H-ras T81C polymorphism and some of the important risk factors in gastric adenocarcinoma [GA]. GA is one of the leading causes of cancer death in most countries. RAS gene is an important member in the PI3K-AKT signaling and the single nucleotide polymorphism at H-rasc DNA position 81 has been demonstrated has an important role in tumor genesis. In this study, we carried out single-nucleotide polymorphism analysis in an Iranian population. A total of 100 patients with gastric adenocarcinoma and 100 controls were examined for the presence of T81C H-ras polymorphism using PCR- RFLP assay. Statistical analysis revealed no relationship significant between TT, TC, CC and risk of GA, but, there was a poorly relation between male patient with C-carrier genotype and increasing risk of GA [P=0.07]. Also, we investigate effect of four important risk factors for GA. There was a statistically significant difference between increasing of age and susceptibility for GA [OR-1.106, 95%CI=1.073-1.139, P<0.001]. We observed a statistically significant between smoking and T81C polymorphism C-carrier genotypes [ORX3.98, 95%CI=1.831-8.68, P<0.001] as this individual had three-time risk for GA. We did not show a significant association between three main genotypes and H. pylori infection for risk of GA. These results suggested that there is no relationship between T81C-HRAS polymorphism and gastric cancer risk in Iranian patients. But, gender [male in our study] and the other risk factor described above have an important role in developing of GA

Estimation of average diagnosis and treatment costs of hepatitis C

the objective of this study was to estimate the average cost of diagnosis and treatment of hepatitis C among patients based on their treatment regime, during the one course of treatment and six-month after stopping that. Hepatitis C virus [HCV] infection is a major cause of liver-related morbidity and mortality worldwide and a major public health problem. All data for this cross-sectional study were collected from medical records of 200 patients with hepatitis C, who referred to a private gastroenterology clinic between years 2005 through 2009. Information related to the 200 patients was extracted from their medical records and finally, 77 patients of them, who their treatment was not interfering with any other disease entered in this study. Therefore diagnosis and treatment costs of these patients were calculated. Attributable costs were reported as purchasing power parity dollars [PPP$]. Mean costs of diagnosis and treatment in one course of treatment and six month after that with standard interferon plus ribavirin [INF-RBV] exceeds 3,850 PPP$ and for patients who treated with peg-interferon plus ribavirin [PEG-RIBV] was 16,494 PPP$. Also in both types of treatment, medication cost was found to be a dominant cost component. Hepatitis C represents a very important and potentially costly disease to managed care organizations. Patients with this disease require expensive drug therapies and consume significant health care resources

How to control confounding effects by statistical analysis

A Confounder is a variable whose presence affects the variables being studied so that the results do not reflect the actual relationship. There are various ways to exclude or control confounding variables including Randomization, Restriction and Matching. But all these methods are applicable at the time of study design. When experimental designs are premature, impractical, or impossible, researchers must rely on statistical methods to adjust for potentially confounding effects. These Statistical models [especially regression models] are flexible to eliminate the effects of confounders

History of upper gastrointestinal cancers in relatives: a community-based estimate

The present study aimed to evaluate the prevalence of positive family history of these cancers in a large population-based sample of Tehran province, capital of Iran. Upper gastrointestinal [UGI] cancers [gastric and esophagus cancer] constitute a major health problem worldwide. A family history of cancer can increase the risk for developing cancer and recognized as one of the most important risk factors in predicting personal cancer risk. This study designed as a cross-sectional survey in general population [2006-2007] of Tehran province. Totally 7,300 persons [age>= 20 years] sampled by random sampling on the basis of the list of postal, of whom 6,700 persons agreed to participate [response rate 92%]. Respondents were asked if any first-degree [FDR] or second-degree [SDR] relatives had gastric or esophageal cancer. Totally, 6,453 respondents [48% male] entered to the study. The mean age of responders with positive FH was significantly higher than those with negative FH [P<0.05]. In total, 341 respondents [5.3%] reporting a history of UGI cancers in their relatives, 134[2.1%] in FDRs, and 207[3.2%] in SDRs. Our findings showed that the reported prevalence of FH of UGI cancers was relatively low and varied by specific respondent characteristics such as age and sex. However, the estimates of prevalence presented here are likely to be conservative compared with actual prevalence because of self-reported data gathering

Epidemiological features of gastro-esophageal reflux disease in Iran based on general population

The aim of this study was to evaluate the epidemiology of GERD base on population study in Tehran providence. Gastro-esophageal reflux disease [GERD] is a common and chronic problem. Recent reports from developing counties indicate increment in the incidence and prevalence of the disease over the past. This study was a cross-sectional household survey conducted from May 2006 to December 2007 in Tehran province, Iran. Participants completed a valid gastro-esophageal reflux Questionnaire. The questionnaire included personal and family characteristics such as age, gender, and educational status. In addition, interviewers asked them regarding 10 GI symptoms. Altogether 18180 individuals participated in this cross-sectional study. The mean +/- SD age of participant was 38.7 +/- 17.1 and 9072 [49.9%] were women. The prevalence of GERD was 8.85 [8.43-9.26]. There was significant relationship between age, sex, marital and educational status with GERD. GERD symptoms were more common in women, older people, individuals with low education and married people. There was overlap between GERD, irritable bowel syndrome [IBS] and uninvestigated dyspepsia [UD]. According to our finding although the prevalence of GERD in our population is less than other studies, this prevalence is increasing in recent years