Epidemiologic Research Assingment Help With Solution

Epidemiologic Research Assingment Help With Solution

A. Design of study/Collection of Data
 
a. Objectives
 
i. What was the objective of the study
To assess the further effects of continuing tamoxifen to 10 years instead of stopping at 5 years.
 
ii. What was the rationale for the study (i.e., what distinguishing it from prior research in this area; why did the authors think this relationship was worth studying?)
 
Previous trials have shown that, for women with ERpositiveearly breast cancer, 5 years of adjuvant tamoxifensubstantially reduces recurrence rates throughout the first 10 years after diagnosis and substantially reducesbreast cancer mortality throughout the first 15 years. Thus, the effects of 5 years of treatment with tamoxifenon annual rates of mortality persist for at least a decade
after treatment ends. Because of this carryover benefit after only 5 years of tamoxifen, it was already recognized when ATLAS began that there could well be littleadditional benefit during the first few years of additionaltreatment, even if worthwhile benefit would emerge later.With an average of 7•6 woman-years of further follow-upafter entry at 5 years, the findings thus far availableconform with these expectations. ATLAS has now shownthat, compared with stopping after only 5 years oftamoxifen, continuing for another 5 years (to 10 years)provides further protection against recurrence and breastcancer mortality, particularly after reaching 10 years.
 
b. Study base (i.e., what is the underlying population from which subjects were selected)? Be as specific as you can.
 
In the worldwide Adjuvant Tamoxifen: Longer Against Shorter (ATLAS) trial, 12894 women with earlybreast cancer who had completed 5 years of treatment with tamoxifen were randomly allocated to continue tamoxifento 10 years or stop at 5 years (open control). Allocation (1:1) was by central computer, using minimisation. After entry(between 1996 and 2005), yearly follow-up forms recorded any recurrence, second cancer, hospital admission, ordeath.
 
c. Study design
 
i. What type of study was conducted?
 
ii. Describe the process of subject selection (e.g., what subjects were chosen from the study base to form the study population? How were cases/exposed subject selected? Controls/unexposed subjects?)
 
iii. What was the sample size? Ratio of comparison groups?
The type of study conducted was Randomized Control trial. The process of subject selectionthe study used was by reporting effects on breast cancer outcomes among the 6846 women with ER-positive disease, and side-effects among all women (with positive, negative, or unknown ER status). Among women with ER-positive disease, allocation to continue tamoxifen reduced the risk of breast cancer recurrence (617 recurrences in 3428 women allocated to continue vs 711 in 3418 controls, p=0•002), reduced breastcancer mortality (331 deaths vs 397 deaths, p=0•01), and reduced overall mortality (639 deaths vs 722 deaths, p=0•01).

 
d. Outcome/Disease
i. What was the primary outcome/disease of interest?
ii. How was it measured?
iii. How was it operationalized?
 
The primary outcome isreduces the breast cancer mortality rate throughout the first 15 years after diagnosis. how, in ER-positive disease,10 years of treatment compares with 5 years of tamoxifen in terms of main effects on recurrence and breast cancer mortality, and how the specific side-effects of 10 years and 5 years of tamoxifen differ.
 
e. Exposure
i. What was the primary exposure of interest?
ii. How was it measured?
iii. How was it operationalized?
The primary exposure are women with oestrogen receptor (ER)-positive early breast cancer, treatment with tamoxifen for5 years .The study protocol’s stated that 20,000 women would need to berandomised. Entry to the study was stopped in 2005(with 12,894 patients, including 6846 with ER-positivedisease). The study used data for all patients with ER-positive, ERnegative,or ER-untested disease to assess side effects.The data for patients with ER-negative or ER-untesteddisease cannot contribute directly to assessment ofeffects in ER-positive disease. The study was operationalized
 
f. Potential confounders/effect modifiers
 
i. What provisions were made in the DESIGN of the study to minimize and/or measure the influence of external factors (e.g., restriction during subject selection, collection of information on other factors (PCFs)?
 
ii. Should the authors have considered the effect of other variables not included in the study? If you think so, justify why.
 
B. Analysis of Data
a. Measure of association
i. What measure of association was reported in this study?
ii. Was this measure appropriate for this study design?
 
b. Confounding/effect modification
i. What methods were used in the data analysis to control for confounding (e.g., multivariate regression analysis, stratification)? Were these sufficient?
ii. What methods were used in the data analysis to evaluate effect modification (e.g., stratification, test for interaction)? Were these sufficient?
 
C. Interpretation of Data
a. What was the major result of the study? Include information on direction and magnitude of association for most important finding.
 
b. Selection bias
i. Was subject selection influenced by both exposure and outcome status?
ii. Did method of subject selection differ between comparison groups?
iii. Could the study results have been affected by selection bias? Describe direction, magnitude and likelihood. Be sure to identify which ‘cell’ was inflated.
 
c. Information bias
i. Was collection of data influenced by both exposure and outcome status?
ii. Did the method of collection differ between comparison groups (i.e. exposed vs. unexposed; cases vs. non-cases)?
iii. Could the study results have been affected by information bias? Describe direction, magnitude and likelihood.
 
d. Nondifferential misclassification of exposure
i. Was the exposure of interest measured accurately?
ii. Could the study results have been affected by nondifferential misclassification of exposure bias? Describe direction, magnitude and likelihood.
 
e. Nondifferential misclassification of outcome/disease
i. Was the outcome of interest measured accurately?
ii. Could the study results have been affected by nondifferential misclassification of outcome/disease bias? Describe direction, magnitude and likelihood.
 
f. Generalization
i. To what larger population may the results of this study be generalized (e.eg. the study base, additional groups)? If you include groups beyond the study base, justify why. If you think results could not be applied to certain groups, justify why.
 
g. Study interpretation
i. Was a biologic mechanism for the association proposed?
ii. What is the biggest shortcoming/limitation of this study?
iii. What is the biggest strength of this study?
iv. Based on your responses to the bias/confounding sections, do you think the true association is higher, lower, or the same as the association the authors have observed? Is the difference likely to be substantial? Does it lead you to question the author’s findings and interpretations

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