Alternative for the Cox regression model: using parametric models to analyze the survival of cancer patients

Although the Cox proportional hazard regression is the most popular model for analyzing the prognostic factors on survival of cancer patients, under certain circumstances, parametric models estimate the parameter more efficiently than the Cox model. The aim of this study was to compare the Cox regression model with parametric models in patients with gastric cancer who registered at Taleghani hospital, Tehran, Iran. In a retrospective cohort study, 746 patients with gastric cancer were studied from February 2003 through January 2007. Gender, age at diagnosis, distant metastasis, extent of wall penetration, tumor size, histology type, tumor grade, lymph node metastasis and pathologic stage were selected as prognosis, and entered to the models. Lognormal, Exponential, Gompertz, Weibull, Loglogistic and Gamma regression were performed as parametric models, and Akaike Information Criterion [AIC] were used to compare the efficiency of the models. Based on AIC, Log logistic is an efficient model. Log logistic analysis indicated that wall penetration and presence of pathologic distant metastasis were potential risks for death in full and final model analyses. In the multivariate analysis, all the parametric models fit better than Cox with respect to AIC; and the log logistic regression was the best model among them. Therefore, when the proportional hazard assumption does not hold, these models could be used as an alternative and could lead to acceptable conclusions

Trend analysis of gastric cancer and colorectal cancer mortality in Iran, 1995-2003

Cancer is the third most common cause of death in Iran. Gastric cancer [GC] and colorectal cancer [CRC] are two important causes of mortality due to cancer. With regards to cancer mortality, data are important to monitor the effects of screening program, earlier diagnosis, demographic data and other prognostic factors. The aim of this study was to evaluate the mortality rates and trends from GC and CRC in Iranian population during a period of almost a decade, i.e. from 1995 to 2003. National death Statistic Reported by the Ministry of Health and Medical Education [MOH and ME] from 1995 to 2003, stratified by age group, sex, and cause of death are included in this study. CRC and GC were expressed as the annual mortality rates/100,000, general and/or per gender, and age group. The general mortality rate of CRC slightly increased during the years under study from 0.44 to 2.54 and CRC mortality was higher for older age and male. The general mortality rates of GC showed a sharp increasing from 1.68 to 9.67. In addition to this, GC mortality rate was higher for male than female. Our study indicated remarkable increasing trends in GC and CRC mortality. So developing for a gastric cancer for both primary prevention and early detection programs and manage the delays of diagnosis is recommended to decrease the trend of GC mortality. For CRC, since the rate of CRC screening is very low in Iran, it is recommended that in Iran screening be started as a public program in order to control the mortality and burden of CRC in the future

[Seroepidemiologic study of HAV infection in Tehran province: a population based study]

Hepatitis A is a viral infection which is transmitted via fecal-oral route and its prevalence is directly related to the public health standards. The prevalence rate of this infection is different in different populations. The aim of this study was to determine the prevalence of hepatitis A antibody and assess the need for vaccination against hepatitis A in Tehran Province. This descriptive analytical cross-sectional study was conducted from 2006 to 2007 in Tehran Province. 448 subjects were selected by random cluster sampling. Blood samples were collected and demographic data were recorded in a questionnaire. Anti-HAV antibodies were measured by ELISA competitive method. Chi-square test and student t-test were used for statistical analysis. This study included 287 women and 161 men. Anti-HAV antibody was positive in 405 subjects [90.4%]. There were no significant relationships between HAV seropositivity and different age groups or gender. The results of our study showed a high prevalence of antibody in this region which is compatible with those of WHO results. Our results were similar to those obtained in Zabol City and eastern parts of Golestan Province but were not compatible with the results of the studies from Isfahan and Tabriz. At the present time there is no need for vaccination in this region

Prevalence of positive family history of colorectal cancer in the Iranian general population

Individuals with a positive family history of colorectal cancer have an increased risk of developing this type of cancer. The number of affected relatives and the age at diagnosis are two factors that increase the risk of colorectal cancer. The aim of this study was to assess the prevalence of a positive family history of colorectal cancer in a random sample among the Iranian general population. Five thousand five hundred [5500] subjects' aged>/-20 years were randomly selected by cluster sampling and invited to participate in an interview about the occurrence of colorectal cancer in their first- or second-degree relatives. Of all the responders, 162 [2.9%] subjects reported a positive family history of colorectal cancer; 71 [1.24%] reported having one first-degree relative with colorectal cancer diagnosed before the age of 50; or reported two or more first-degree relatives with colorectal cancer. In addition, 83 [1.51%] and 14 [0.25%] subjects reported having one and two or more second-degree relatives with colorectal cancer respectively. The prevalence of a positive family history of colorectal cancer in Iran is lower than the United States and European countries. Identifying high-risk population for colorectal cancer and encouraging them to participate in surveillance protocols is the first step in targeting preventive measures

Positive association between diabetes mellitus and risk of colorectal cancer

In recent years, many studies employed and found an association between type 2 diabetes mellitus and colorectal cancer. Although increased risk of colorectal cancer in individuals with Non Insulin Dependent Diabetes Mellitus [NIDDM] has been observed in previous studies, limited information is available on the colorectal cancer associated with NIDDM in Iran. The purpose of this study was to define colorectal cancer risk associated with diabetes mellitus. The present study was designed as an unmatched case control study. Cases were 393 patients with histologically confirmed colorectal carcinomas and 393 controls were randomly selected among the healthy participants in a health survey. To control potential confounding factors such as sex, age, smoking habits and Body Mass Index [BMI], multiple logistic regression model was fitted to obtain Odds Ratio of colorectal cancer and the corresponding 95% CIs, according to history of diabetes mellitus. Overall, 86 [10%] cases versus 15 [1.7%] controls gave a history of diabetes mellitus. The corresponding multivariate OR was 6.77 [CI 95%: 3.84- 11.92] indicating that having a positive history of diabetes mellitus increases one's risk of colorectal cancer about six-fold. The risk of colorectal cancer was slightly increased for women [p<0.05]. Current smokers were at a higher CRC risk [OR=2.83, CI95%:2.13-3.76] than never smokers. We found a strong positive association between NIDDM and prevalent colorectal cancer. In summary, these findings provide further indirect epidemiological evidence for the hypothesis that hyperinsulinaemia may be important in the development of colorectal cancer

Global genome methylation status in gastritis lesion in comparison with normal adjacent tissue and its relationship with clinicopathologic findings

To determine the role of global genome methylation in gastritis lesion and its relation with clinicopathologic finding. The study was conducted on 44 gastritis and normal adjacent specimens using a technique composed of restriction enzyme digestion and pyrosequencing known as LUMA [LUminometric Methylation Assay]. At first, DNA extracted from gastritis lesion and normal tissue was digested with HpaII [sensitive to methylation in recognition site] and MspI [insensitive]. These enzymes leave an overhang after cutting which are then filled in a polymerase extension assay with stepwise addition of dNTPs using pyrosequencing. The comparison of the height of picks obtained form both enzymes provides the possibility to evaluate and compare global genome methylation level of normal and gastritis tissues. If the target site is fully methylated, the HpaII/MspI will approach toward zero .If not, this ratio will go around one. In the other conditions the ratio varies between 0-1. According to our findings, gastritis tissue was significantly more hypomethylated [p = 0.04] than the nornal tissue and Global genome methylation had no correlation with sex, age, microsatellite instability [MSI] and gastritis severity. Global DNA hypomethylation occurs in the gastritis lesion. Presumably the process of hypomethylation keeps falling in the next steps leading to gastric cancer