Evaluating the Shared Decision Making Process Scale in Cancer Screening Decisions: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluating the Shared Decision Making Process Scale in Cancer Screening Decisions (NCT04601272), a registered phase not stated study. The primary outcome is Shared Decision Making Process Measure.

2. Clinical Question

This is a measurement-performance study, not a trial comparing the clinical effects of screening strategies. Its central focus is the scale used to describe the decision-making process. The secondary outcomes named in the registry include another shared decision making questionnaire, decisional conflict, decision regret, treatment choice, an adapted preference scale, and knowledge. The record does not provide numerical results for these measures or explain how their findings relate to the primary measure.

3. Trial Design

The registry classifies the study as retrospective and observational. Its stated purpose is to evaluate the performance of the Shared Decision Making Process scale among patients who received a decision aid about whether to screen for cancer. The behavioral intervention is called a decision aid. The record does not describe a randomized assignment, and allocation is not stated. The cancer-specific groups are therefore not a randomized set of comparison arms and should not be read as a controlled contrast.

The record identifies breast, colon, and prostate screening groups, with eligibility descriptions tied to age, sex, and no prior diagnosis of the relevant cancer. The brief summary also names lung cancer screening, but no lung screening group appears among the listed arm descriptions. The record does not explain this difference. It reports enrollment of 240 and identifies Massachusetts General Hospital as the sponsor. The study is marked completed, with a start date of 2020-09-29 and a primary completion date of 2021-04-16.

The primary outcome is the Shared Decision Making Process Measure at the baseline survey. The primary population is described as participants with enough information to calculate a score; the registry also states that 233/233 patients answered the question. The record lists six named secondary outcomes: the 9-item Shared Decision Making Questionnaire, Decisional Conflict Tool (SURE), Single-Item Measure of Decision Regret, Treatment Choice, Adapted Controlled Preference Scale, and Knowledge. It states that there are 7 outcome measures, but the additional measure is not identified in the registry record.

The record does not report a detailed statistical analysis plan, a sample-size justification for the study design, or an account of follow-up procedures. The planning assumptions associated with sample-size illustrations are not a description of how participants were assigned or how the observational groups were formed. Because the listed groups are defined by screening topic, their characteristics and results cannot automatically be treated as directly comparable.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: Eligible patients were English speaking and fell within the appropriate age range for considering cancer screening for the clinical topic. Colon cancer group were patients between 45 and 75 years old; breast cancer group were women between 35 and 55 years old; prostate cancer group were men between 45 and 74 years old.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: participants who provided enough information to calculate a shared decision making process score (primary outcome of interest). 233/233 patients provided an answer to this question.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: Participants who received a decision aid for breast/colon/prostate cancer within the last 2 years. Participants provided enough information to calculate the shared decision making process score (primary outcome of interest)

6. Primary Endpoint

The registry lists the primary outcome as Shared Decision Making Process Measure, measured over Baseline survey.

The primary endpoint is the Shared Decision Making Process Measure, a short patient-reported survey intended to measure the amount of shared decision making in an interaction. Its score ranges from 0-4, with higher values indicating a better shared decision making process outcome. The registry identifies the unit as a score on a scale and specifies the mean as the summary measure, with standard deviation as the measure of dispersion. The timeframe is the baseline survey.

A patient-reported measure can capture a participant's account of a decision process that may not be fully represented by clinical outcomes alone. In general, a scale can help describe whether participants perceive that relevant decision-making elements were part of an interaction. The registry's stated purpose is to evaluate the performance of this scale in cancer screening decisions. That purpose concerns measurement, rather than whether screening itself is beneficial or whether one screening choice is preferable.

The registry record does not report the observed mean score or standard deviation. It also does not provide an estimate of measurement reliability, validity, or the scale's performance across the cancer-specific groups. The stated score range and direction explain how the measure is intended to be read, but they do not establish how participants scored or how well the measure performed in this study.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary outcome as a continuous score and specifies the mean and standard deviation as its summary statistics. The score ranges from 0-4, and higher values are described as indicating a better shared decision making process outcome. No observed mean or standard deviation is reported in the registry record. The statistical concepts below explain how these summaries are generally used; they do not fill in missing study results.

What does a mean describe?

In general, the mean is a measure of the center of a set of scores. It gives a compact description of the average score in the group being summarized. For a patient-reported scale, the mean can describe the overall level of reported experience in the analyzed population. It does not show how scores are distributed around that average, whether participants had similar experiences, or whether there were distinct patterns among subgroups. Those questions require additional descriptive information and, where appropriate, analyses specified for that purpose.

The interpretation of a mean also depends on which participants contribute scores and how the scale is constructed. Here, the registry defines the primary population as participants with enough information to calculate the score and states that 233/233 patients answered the question. It does not describe additional scoring rules, handling of partially completed items, or the distribution of responses. Those details are not reported in the registry record.

What does a standard deviation describe?

In general, the standard deviation describes how spread out individual observations are around their mean. A smaller standard deviation indicates that observed values tend to be closer to the mean, while a larger one indicates more spread. It is a description of variation among observations, not a measure of uncertainty in the estimated mean. The registry names standard deviation as the dispersion measure but reports no numerical value for it.

A mean without a measure of spread provides limited information about how participants' scores vary. Conversely, a standard deviation does not indicate whether a difference between groups is statistically distinguishable from chance. That question ordinarily requires an estimate of the difference, its uncertainty, and an analysis appropriate to the design. The registry record does not report such a comparison for the primary endpoint.

How should a confidence interval be understood?

In general, a confidence interval expresses the uncertainty around an estimate under a statistical procedure and its assumptions. For a mean, it can convey a range of values compatible with the observed data and method. Its width depends on factors such as variability, the amount of available information, and the analysis used. A confidence interval is not a guarantee that the true value lies within its endpoints, and it does not replace consideration of study design or measurement quality. No confidence interval for the primary score is reported in the registry record.

Why does the study design matter?

This registry describes a retrospective observational study, not a randomized comparison. In general, random assignment can support causal comparisons by helping balance factors between assigned groups, while observational comparisons may reflect differences that existed before the measured outcome. In this study, the listed groups concern different cancer screening topics and have different eligibility descriptions. They are not presented as a decision-aid group and a no-decision-aid control group. A contrast among these topic groups would therefore need to account for the study question and design and could not automatically be interpreted as an effect of the decision aid.

The record does not state an allocation procedure or a statistical model. It also does not report adjustments for participant characteristics. Any explanation of how confounding was addressed, or of whether a particular analysis was prespecified, would be speculation. These elements are not reported in the registry record.

What do the planning assumptions mean?

The registry describes sample-size illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. These are assumptions for planning illustrations, not a description of the study's own design. The registry record does not provide the observed effect or the resulting participant counts in the registry record reported for this analysis, so no planning count can be interpreted.

In general, a sample-size calculation asks how much information may be needed to detect an effect of a chosen size under specified assumptions. An illustration based on an observed effect is conditional on that effect and on the calculation's assumptions. It is not an observed result and should not be called observed power. Because the study is observational and the cancer-topic groups are not like-for-like randomized arms, the equal-allocation assumption in a planning illustration should not be mistaken for actual allocation in this study.

The registry also notes that time-to-event illustrations use a total number of events, whereas other illustrations use participants per arm. The primary endpoint in this record is a continuous score, not a time-to-event outcome. General distinctions between these calculation types do not provide evidence about the study's observed endpoint or its precision.

What can be inferred from the analysis listing?

The registry lists 0 analyses. That entry does not provide an estimate, test, or model for the primary score. The record also gives no p-value or confidence interval for the listed secondary outcomes. Without those results, there is no basis to describe statistical significance, the direction or size of an association, or the precision of an effect. Statistical significance, even when reported, would not by itself establish that a measure is useful or that a decision aid changes the quality of decisions; those interpretations depend on the study question, design, and measurement evidence.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Breast Cancer Screening", "Colon Cancer Screening", "Prostate Cancer Screening")
n   <- c(71, 86, 76)
m   <- c(1.05, 1.2, 2.1)
sp  <- c(1.07, 1.1, 0.9)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Breast Cancer Screening  71  1.050  1.070  0.797  1.303
CARM  Colon Cancer Screening  86  1.200  1.100  0.964  1.436
CARM  Prostate Cancer Screening  76  2.100  0.900  1.894  2.306

11. Multiplicity, Missing Data and Analysis Populations

The registry identifies a primary outcome and lists several secondary outcomes, but it does not report an analysis plan or results for these measures. The primary measure is the Shared Decision Making Process Measure. Named secondary outcomes are the 9-item Shared Decision Making Questionnaire, Decisional Conflict Tool (SURE), Single-Item Measure of Decision Regret, Treatment Choice, Adapted Controlled Preference Scale, and Knowledge. The record states that there are 7 outcome measures, while only six secondary measures are named; the additional measure is not identified in the registry record.

Multiplicity arises in general when several outcomes or statistical tests are examined. The more tests conducted, the greater the chance that at least one will appear notable by chance if each is interpreted separately. Statistical plans can address this issue by defining a primary outcome, limiting confirmatory tests, or adjusting how evidence is assessed. The registry record does not report whether any multiplicity strategy was planned or used. With 0 analyses listed, the posted record does not permit a review of how multiple outcomes were tested or interpreted.

For the primary outcome, the registry states that 233/233 patients answered the question and describes the analysis population as participants with enough information to calculate a score. This response information does not describe missingness in secondary outcomes, other items, or any unreported analyses. The record does not explain how incomplete questionnaires or unavailable measurements were handled, whether any participants were excluded from particular outcome analyses, or whether missing-data methods were used. Those details are not reported in the registry record.

Overall enrollment is 240, while the primary outcome population is reported as 233/233. The record does not give a participant flow explanation connecting these figures. It would be inappropriate to infer why the counts differ or to assume that all other outcome measures have the same response pattern. No analysis population beyond the stated primary population is described.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry lists serious adverse event information separately for the breast, colon, and prostate cancer screening groups. The number at risk is 71 for breast screening, 86 for colon screening, and 76 for prostate screening. For each group, the number affected by serious adverse events is 0, and deaths are listed as 0. The record lists no serious adverse event terms.

These entries are descriptive counts in the registry. They do not establish that the risk of a serious adverse event is absent. In general, observing no events in a group does not rule out events that could occur in a larger population or under different observation conditions. Interpretation also depends on what events were collected, how they were defined, and for how long participants were monitored. The registry record does not describe those details.

The listed figures should not be treated as a comparison of decision aid exposure against a control condition. The study is described as retrospective and observational, and the screening-topic groups are not like-for-like control arms. The record does not report a safety analysis plan or inferential comparison. These counts therefore describe what was recorded for the groups, not a causal safety effect or a guarantee of safety.

13. What the Result Does, and Does Not, Mean

The registry record establishes that the study was designed to evaluate the Shared Decision Making Process Measure among patients who had received a decision aid about cancer screening. It describes the scale's score range and direction, the baseline survey timeframe, the cancer-specific group eligibility descriptions, and the primary outcome response information. These registry entries help define the measurement question and the study population as recorded.

The record does not report the primary mean or standard deviation, or a confidence interval or test for the score. It therefore does not show the observed level of shared decision making or the precision of an estimate. Nor does it provide numerical findings on the named secondary measures. The study's stated aim should not be confused with evidence that the measure performed well: the numerical and analytic results needed to assess performance are not reported in the registry record.

This record also does not establish whether receiving a decision aid changes participants' decision-making experiences. There is no described no-aid control group, random allocation is not stated, and the listed groups are organized by screening topic. Even if numerical differences between topics were available, the design would not automatically support a causal interpretation. The record likewise does not compare screening choices or establish the clinical consequences of choosing to screen or not screen.

In general, an outcome measure can help researchers describe an experience, but its usefulness depends on evidence about how it behaves and what its scores mean. Such evidence may include reliability, validity, relationships with related measures, and performance across relevant populations. The registry lists related secondary outcomes but reports no analyses linking them to the primary scale. Their presence alone cannot establish these properties.

The responsible conclusion is narrow: the registry documents a completed observational study with a defined patient-reported primary measure and specified cancer screening groups, but it does not report the numerical results or analyses needed to judge the measure's performance. This is a limitation of what can be concluded from the registry record, not evidence that the study found a particular favorable or unfavorable result.

14. Why This Trial Matters Statistically

Patient-reported measures can make the decision process itself an object of study, rather than focusing only on the choice made or a later clinical outcome. For research on shared decision making, a clearly described scale can offer a consistent way to characterize participants' experiences across different screening decisions. This study's stated focus on the performance of the Shared Decision Making Process Measure therefore addresses a statistical and measurement question relevant to how such experiences may be evaluated.

The registry identifies a 0-4 score, indicates that higher values represent a better process outcome, and names the mean and standard deviation as planned descriptive summaries. It also records that 233/233 patients answered the primary outcome question. These details make the intended measure and response population more concrete. However, a scale's definition and response count are not substitutes for reporting its observed distribution, uncertainty, and relationship with other measures.

The study also illustrates why design labels matter when interpreting group-based data. Breast, colon, and prostate screening decisions involve different eligibility descriptions, and the record does not describe random assignment or a like-for-like control group. Distinguishing descriptive comparisons from causal comparisons is central to sound interpretation. A measure may be studied across several decision contexts without those contexts serving as interchangeable experimental arms.

The statistical contribution that can be assessed from this record is limited because no numerical analyses are listed. The record does not show whether the measure's scores align with related constructs, distinguish among experiences, or behave consistently across the listed screening topics. Reporting those analyses would be needed to assess the stated measurement objective. The study's topic is statistically important, but the registry entry alone leaves the central empirical question unanswered.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

Several limitations specific to this registry record constrain interpretation. First, it does not report the primary outcome mean, standard deviation, confidence interval, or inferential analysis. It therefore gives no numerical account of the observed scale scores or their precision. Although the primary question response is reported as 233/233, response information alone cannot show the distribution of scores or whether the measure distinguished among participants' experiences.

Second, the record reports 0 analyses. It does not provide the methods or results needed to assess the scale's performance, including any relationship between the primary measure and the named secondary outcomes. Reliability, validity, and comparisons across screening topics are not reported in the registry record. The stated purpose of evaluating performance cannot, by itself, establish that the measure performed adequately.

Third, the study is described as retrospective and observational. Allocation is not stated, and the registry explicitly does not characterize the listed groups as a like-for-like control comparison. The groups concern different cancer decisions and have differing eligibility descriptions. Comparisons between them, if conducted, could reflect differences in participants or decision contexts rather than a difference caused by a decision aid.

Fourth, the brief summary mentions lung cancer screening, but the listed arm descriptions cover breast, colon, and prostate screening. The record does not explain this mismatch. It also states that there are 7 outcome measures while naming six secondary measures. The additional measure is not identified in the registry record.

Finally, the record does not describe questionnaire scoring details, missing-data handling beyond the primary response statement, participant flow, follow-up duration for safety reporting, or a multiplicity strategy. These gaps limit assessment of the analysis populations and the scope of any conclusions. They should not be filled by assumptions about the study protocol or its results.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Evaluating the Shared Decision Making Process Scale in Cancer Screening Decisions — NCT04601272.
• Registry record last updated 2023-03-30; status last verified 2022-06.
• Results first posted 2023-03-30.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT04601272 is a completed retrospective observational study sponsored by Massachusetts General Hospital. It evaluated the performance of the Shared Decision Making Process Measure among patients who had received a decision aid about cancer screening. The registry lists breast, colon, and prostate screening groups; the brief summary also mentions lung screening, but no lung group description is listed.

The primary endpoint is a patient-reported score ranging from 0-4, with higher scores indicating a better shared decision making process outcome. The registry labels the timeframe as the baseline survey and identifies the mean and standard deviation as summary measures. It reports 240 enrolled and states that 233/233 patients answered the primary outcome question. The record lists 0 analyses and does not report numerical primary or secondary outcome results.

Allocation is not stated, and the groups are not described as a like-for-like control comparison. The record lists 0 affected by serious adverse events and 0 deaths in each of the three described groups. These are descriptive registry entries and do not establish a causal comparison or absence of risk.