Podcast
Questions and Answers
Were patients randomized in the study groups?
Were patients randomized in the study groups?
- No, randomization was not conducted due to missing data.
- Yes, participants were randomly assigned using computer generated block randomization. (correct)
- Yes, patients were randomized but not allocated to groups properly.
- No, patients were assigned to groups based on their preferences.
Was group allocation concealed during the study?
Was group allocation concealed during the study?
- Yes, it was clearly stated how allocation was concealed.
- No, all patients were aware of their group allocation.
- No, there is no mention of how randomization allocation sequence was concealed. (correct)
- Yes, allocation was concealed using participant codes.
Were the patient groups similar with respect to known prognostic variables after randomization?
Were the patient groups similar with respect to known prognostic variables after randomization?
- No, groups were formed based on varying prognostic factors.
- No, there is no information provided on baseline characteristics or balance. (correct)
- Yes, baseline characteristics were provided and found to be balanced.
- Yes, the groups were similar based on patient histories.
What can be inferred about the randomization process?
What can be inferred about the randomization process?
Which statement is true about the information provided regarding group allocation?
Which statement is true about the information provided regarding group allocation?
What was one of the reasons for the lack of prognostic balance at the end of the study?
What was one of the reasons for the lack of prognostic balance at the end of the study?
Which analysis method was not completed as the study progressed?
Which analysis method was not completed as the study progressed?
What did the study reveal about statistical significance of treatment effects?
What did the study reveal about statistical significance of treatment effects?
What was the reported reduction in the incidence of cancer for the vitamin D and calcium group compared to placebo?
What was the reported reduction in the incidence of cancer for the vitamin D and calcium group compared to placebo?
Which statement is true about the confidence intervals presented in the study?
Which statement is true about the confidence intervals presented in the study?
What was a noted issue regarding follow-up in the study?
What was a noted issue regarding follow-up in the study?
What was the absolute risk reduction for the calcium vitamin D group in the study?
What was the absolute risk reduction for the calcium vitamin D group in the study?
What was the relative risk reduction for the calcium only group compared to placebo?
What was the relative risk reduction for the calcium only group compared to placebo?
What does it indicate if the confidence intervals for the treatment effect are very wide?
What does it indicate if the confidence intervals for the treatment effect are very wide?
Which of the following P values indicates a statistically significant result?
Which of the following P values indicates a statistically significant result?
What is the significance of a 3.1% absolute risk reduction in the calcium only group?
What is the significance of a 3.1% absolute risk reduction in the calcium only group?
What statistical value was reported for the calcium vitamin D group's treatment effect?
What statistical value was reported for the calcium vitamin D group's treatment effect?
What was concluded regarding the blinding of the trial participants?
What was concluded regarding the blinding of the trial participants?
What percentage of participants completed follow-up in the study?
What percentage of participants completed follow-up in the study?
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Study Notes
Randomization and Group Allocation
- Participants were randomly assigned to one of three intervention groups using computer-generated block randomization.
- There is no mention of how the randomization allocation sequence was concealed from those enrolling patients, raising concerns about potential bias.
- Insufficient information is provided regarding the balance of known prognostic variables between groups after randomization, indicating uncertainty about the effectiveness of the randomization process.
Prognostic Variables
- No data is available on baseline characteristics of the groups, which prevents an assessment of similarity regarding known prognostic variables post-randomization.
- Lack of transparency in randomization and allocation concealment casts doubt on the reliability of the study findings.
Study Design and Analysis
- Over 5% of participants were lost to follow-up, potentially affecting study results.
- No differential losses to follow-up mentioned, which is critical for assessment.
- Only 1179 participants included in results for years 1-4; 1085 for years 2-4, indicating inadequate intention-to-treat (ITT) analysis.
- The trial was not stopped early, but significant losses to follow-up led to imbalances between groups.
Outcome Measures
- While large statistically significant reductions noted, clinical relevance is questionable.
- Statistically significant effect observed only for calcium and vitamin D compared to placebo.
- No conclusive evidence that calcium alone improves cancer outcomes.
Treatment Effects
- 60% statistically significant reduction in cancer incidence for vitamin D and calcium group compared to placebo.
- Wide confidence intervals (80% to 17% reduction) raise questions about clinical significance.
- Calcium only group showed a 47% relative risk reduction compared to placebo but was not statistically significant.
- Absolute risk reduction of 4% for calcium + vitamin D group; 3.1% for calcium only group, suggesting relevance to patients.
Precision of Estimates
- Estimates of treatment effect were imprecise with large confidence intervals.
- Confidence interval for calcium and vitamin D group: 0.2 to 0.82, P=0.013.
- Confidence interval for calcium only group: 0.27 to 1.03, P=0.063, indicating poor precision and lack of statistical significance.
Validity of Results
- Random assignment to intervention groups was conducted but concealment of allocation was not detailed.
- No information provided on whether groups were balanced post-randomization.
- Insufficient data on baseline characteristics raises concerns about prognostic balance.
Blinding and Follow-up
- Potential blinding of patients occurred due to placebos, but no clarity on blinding of staff or analysts.
- Follow-up completed for only 87% of participants, leading to questions about the reliability of results.
- Prognostic balance likely not maintained as the study progressed.
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