Loss of Grip Strength, BMI, and Adjuvant Endocrine Therapy Breast Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Loss of Grip Strength, BMI, and Adjuvant Endocrine Therapy Breast Cancer (NCT01896050), a registered phase not stated study. The primary outcome is Effect of Change in Body Mass Index on Change in Grip Strength With Aromatase Inhibitor Therapy.

2. Clinical Question

The study also describes a comparison of medication groups for change in grip strength and an assessment of whether baseline body mass index was associated with discontinuation of aromatase inhibitor therapy within the first 12 months. These are distinct questions: a relationship between changing BMI and changing grip strength is not the same as a difference between medication groups, nor is it the same as an association with discontinuation.

The registry describes patient-reported symptoms as part of the study and gives arthralgia and obesity among the conditions of interest. However, the record does not supply symptom estimates or results for the secondary questions. The primary question should therefore be read as the study’s intended assessment, rather than as evidence for a particular direction or size of association.

3. Trial Design

This was a prospective longitudinal study of women with early-stage breast cancer beginning adjuvant endocrine therapy. The registry lists enrollment of 115 and identifies the study as completed. The study began in 2009-09, with primary completion in 2014-08. The sponsor was the University of Michigan Rogel Cancer Center.

Participants started either an aromatase inhibitor or tamoxifen. The aromatase inhibitor group included anastrozole, letrozole, or exemestane. The registry describes the arms by the medication participants started; it does not say that treatment was randomly assigned. It explicitly notes that allocation was not stated and that the arms are not a like-for-like control comparison. Consequently, differences between these groups should not automatically be interpreted as effects caused by the medications. Characteristics that influenced treatment choice or differed between participants could also contribute to observed differences, and the registry record does not report an adjustment strategy.

The principal assessment concerned change over time. The primary outcome description concerns BMI change between baseline and 12 months, in relation to grip-strength change during endocrine therapy. The outcome population included participants who completed a full 12 months of treatment and had grip-strength data at both baseline and 12 months. Participants who changed from one aromatase inhibitor to another could remain eligible for this population. The description also indicates that participants who discontinued treatment before completing the period were not part of the stated primary population, although the remainder of that exclusion wording is incomplete in the registry record.

The brief study description says self-reported symptoms were to be collected. The registry lists three outcome measures and four analyses, but does not provide enough detail to identify every model, analysis population, or reported estimate. The full protocol, detailed statistical analysis plan, and rationale for the enrollment target are not reported in the registry record.

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.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: These data only include patients who completed a full 12 months of treatment with either an aromatase inhibitor or tamoxifen and had grip strength data at both baseline and 12 months. Patients could have switched from one aromatase inhibitor to another. Those patients who discontinued treatment prior to the 12 month period were excluded.

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.

6. Primary Endpoint

The registry lists the primary outcome as Effect of Change in Body Mass Index on Change in Grip Strength With Aromatase Inhibitor Therapy, measured over baseline and 12 months.

The primary outcome is framed as the association between change in BMI and change in grip strength during aromatase inhibitor therapy. The stated timeframe is baseline and 12 months. BMI is expressed in kg/m^2, and the registry identifies the measure as a mean with standard deviation. The description specifies BMI change between baseline and 12 months; it does not give numerical grip-strength values, a grip-strength unit, or a numerical estimate of the relationship between the changes.

Grip strength is a measurable physical-function outcome, while BMI describes body size relative to height. Tracking both across treatment can help characterize whether changes in one measure tend to accompany changes in the other in the population being assessed. This is a general explanation of why paired measurements may be informative; it does not establish that the measures are associated in this study.

Using measurements at baseline and 12 months focuses the question on change over a defined observation period. It also means that the stated primary population depends on having measurements at both times and completing a full 12 months of treatment. Participants without the required follow-up measurements do not contribute to that described population, so the result, if reported, would apply most directly to those meeting these requirements. The registry record does not report the number of participants included in the primary outcome analysis or the amount of missing measurement data.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

For a continuous outcome such as grip strength, a mean describes the central value in a group, while a standard deviation describes how spread out individual measurements are around that mean. These summaries answer different questions: a mean is about the group’s average, whereas a standard deviation describes variation among participants. Neither alone expresses uncertainty in the estimated mean or association. The registry identifies a mean and standard deviation for the primary outcome, but does not give the actual summaries.

What does change over time mean?

A longitudinal assessment observes participants at more than one time and compares measurements across those times. In this study, the stated primary timeframe is baseline and 12 months. A change score represents the difference between a participant’s later and earlier measurements; an analysis can then summarize those changes or assess whether changes in one measure are associated with changes in another. This is a general description of change-score methods, not a claim about the specific model used in this study. The registry does not report whether the analysis used individual change scores, a repeated-measures model, covariate adjustment, or another approach.

Change-score analyses depend on having measurements at the relevant times. The primary outcome description limits the population to participants who completed a full 12 months of therapy and had grip-strength data at baseline and 12 months. This defines the population described for that outcome, but does not reveal the number analyzed or whether other analyses used different populations. The record does not state how missing BMI or symptom data were handled.

How should an association be read?

An association describes how two measured quantities vary together. It does not, on its own, show that a change in one quantity caused a change in the other. In this study, the primary question concerns BMI change and grip-strength change during aromatase inhibitor therapy. A numerical association, if reported, would need to be considered alongside its uncertainty, the measurement process, and the characteristics of the analyzed participants. The registry record does not report the association estimate or an uncertainty interval.

A confidence interval is a statistical range intended to convey uncertainty around an estimate under the assumptions of the analysis. A narrower interval generally indicates greater precision than a wider interval, while an interval that includes values representing no association may be compatible with a range of interpretations. This is general statistical explanation. No confidence interval for the primary association is reported in the registry record, so its precision cannot be assessed.

A p-value, when used, summarizes how compatible the observed data are with a specified null hypothesis under the statistical model. It does not measure the probability that the null hypothesis is true, nor does it indicate whether a difference is important in practice. The registry record does not report primary or secondary p-values, and the analysis plan does not state whether or how hypothesis tests were used.

Why does over-dispersion matter?

Over-dispersion is a general issue for count outcomes: the observed variability is greater than a model’s assumptions would predict. If ignored, uncertainty estimates from an unsuitable model can be too small, making results appear more precise than they are. It is not possible to determine from the registry record whether over-dispersion was relevant to any analysis. The primary endpoint is a continuous measure, and the record does not report count-model methods.

What do the planning illustrations represent?

The registry describes sample-size planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. The illustration is described as targeting a stated fraction of the observed effect. For non-time-to-event outcomes, the planning quantity is participants per arm for 80% power or another stated power target; time-to-event planning uses a total event count. No resulting planning values are reported in the registry record. These calculations are planning illustrations, not observed power and not evidence that the study was designed around those assumptions. The trial’s own sample-size justification is not reported in the registry record.

Observed power is not a useful substitute for an estimate and its confidence interval: it is calculated from the observed effect and does not provide an independent measure of evidential strength. General statistical interpretation should focus on the estimate, its uncertainty, the analysis population, and the design. Those outcome-specific quantities are not reported in the registry record.

What limits a treatment-group comparison?

The registry identifies the study as prospective but does not state random allocation. It also warns that the treatment arms are not a like-for-like control comparison. General statistical reasoning distinguishes a descriptive comparison from a causal treatment effect. Random allocation, when used and properly implemented, helps balance measured and unmeasured baseline factors on average. In a nonrandomized study, statistical adjustment may address measured differences, but cannot necessarily address unmeasured differences. The registry record does not report an adjustment model or the variables included in one.

Medication switching is permitted within the described aromatase inhibitor population. The registry does not explain how switching was represented in analyses beyond noting that participants could switch between aromatase inhibitors. The effect of any such analytic choices on estimates cannot be determined. A complete interpretation would require the analysis method, sample size for each outcome, estimate, uncertainty, and details of missing-data handling; these are not reported in the registry record.

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("AI Therapy", "Tamoxifen")
n   <- c(71, 18)
m   <- c(-0.15, 2.44)
sp  <- c(5.7, 6.11)
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  AI Therapy  71  -0.150  5.700  -1.499  1.199
CARM  Tamoxifen  18  2.440  6.110  -0.598  5.478

11. Multiplicity, Missing Data and Analysis Populations

The record lists three outcome measures and four analyses, including a primary question about BMI change and grip-strength change, a medication-group assessment of grip-strength change, and an assessment of baseline BMI in relation to discontinuation of aromatase inhibitor therapy within the first 12 months. It does not report how many hypotheses were tested, whether outcomes were assigned a testing hierarchy, or whether any adjustment for multiple comparisons was used. The statistical plan for multiplicity is not reported in the registry record.

General statistical explanation: when several outcomes or comparisons are examined, the chance of at least one apparently notable result can increase if each is assessed separately without a plan to account for the collection of tests. This does not mean that every analysis requires the same adjustment; the appropriate approach depends on the study aims and analysis plan. Since that plan is not reported, the registry entries do not establish how multiplicity was addressed.

The primary outcome population requires a full 12 months of treatment and grip-strength data at baseline and 12 months. The count meeting those conditions, the amount of missing data, and the reasons for missingness are not reported in the registry record. The record also does not explain whether participants who discontinued treatment were excluded from other outcomes, included under different definitions, or followed for any additional assessments.

General statistical explanation: complete-case analysis can be difficult to interpret if inclusion depends on participant characteristics or outcomes. Missing-data methods rely on assumptions, and those assumptions should be stated alongside the analysis. The registry record does not report whether imputation, sensitivity analyses, or other missing-data methods were used. The analysis population for each secondary outcome and any interim analyses are also not reported in the registry record.

12. Safety Results

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

Other (non-serious) adverse events

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

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: death (1.1%).

The registry lists serious adverse-event counts of 1 among 93 participants at risk in the AI Therapy group and 0 among 22 participants at risk in the Tamoxifen group. It lists other adverse-event counts of 37 among 93 at risk in the AI Therapy group and 2 among 22 at risk in the Tamoxifen group. The record identifies death at 1.1% as the top serious term.

These entries should be read as descriptive registry counts. The record does not report whether events were considered related to treatment, how events were collected or classified, or whether counts refer to participants with events or event occurrences under a particular reporting convention. The exact meaning of the other-event category is not explained in the record.

The arms differ in size and are not described as a like-for-like control comparison. The raw counts therefore should not be treated as a direct estimate of comparative risk or as proof that treatment caused or prevented an event. No uncertainty estimates or adjusted safety comparisons are reported in the registry record. The serious-event entries are separate from the primary question about BMI and grip-strength change.

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

The registry record establishes that a prospective study was conducted to examine grip strength over time in women starting adjuvant endocrine therapy, with attention to BMI and medication group. It identifies the intended primary question and describes a population with measurements at baseline and 12 months. It also records enrollment of 115 and a completed study status.

The record does not give the primary outcome estimate, the grip-strength summaries, or an uncertainty interval. It therefore does not establish the direction, size, or precision of any relationship between BMI change and grip-strength change. The secondary outcome entries likewise do not include numerical results. The study question should not be mistaken for a reported finding.

Even with numerical results, a relationship between two changes would not by itself establish that one caused the other. The medication arms also cannot be interpreted as a randomized treatment comparison on the information in the record: allocation is not stated, and the registry cautions that the arms are not like-for-like controls. Participant differences and treatment selection could influence observed comparisons.

The requirement for completing a full 12 months and having grip-strength measurements at both assessment times narrows the described primary analysis population. Results from such a group, if available, would not automatically describe everyone who began treatment. The registry does not provide the number included in the analysis or the details needed to assess missing follow-up.

Accordingly, the posted record supports a description of the research aim, treatment groups, follow-up timeframe, and selected adverse-event counts. It does not support a conclusion about the magnitude or certainty of the primary association, a causal effect of treatment, or comparative safety. Those interpretations require outcome estimates and methodological details that are not reported in the registry record.

14. Why This Trial Matters Statistically

This study raises a useful statistical distinction between describing change and explaining change. Measuring grip strength and BMI at baseline and 12 months allows a longitudinal question about whether the measures change together. That question differs from asking whether the medication groups have different average changes, and both differ from asking whether baseline BMI is associated with treatment discontinuation. Keeping these estimands separate helps avoid treating related outcomes as interchangeable.

The record also illustrates why study design matters as much as the numerical outcome. Participants began either an aromatase inhibitor or tamoxifen, but allocation is not stated and the groups are explicitly not described as like-for-like controls. A difference between groups in a nonrandomized comparison is descriptive unless the design and analysis provide a basis for stronger causal interpretation. The record does not provide the adjustment details needed to evaluate that basis.

Follow-up requirements matter too. The primary outcome population requires treatment completion and paired grip-strength data. This can make the analysis population different from the full group that began therapy. Reporting the number analyzed and the reasons for missing follow-up would help readers judge how representative the estimate might be, but those details are not reported in the registry record.

Finally, a study objective is not a result. The registry identifies a question with potential relevance to physical function and BMI, but does not report the estimate or its uncertainty. Statistical interpretation depends on those values, the method used, the population analyzed, and the handling of missing data and multiple outcomes. Without them, the most accurate account is a description of the design and the limits of what the posted record can establish.

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.

The registry record does not report the numerical primary outcome results, including the estimated relationship between BMI change and grip-strength change. It also omits confidence intervals, p-values, and the group summaries needed to assess direction, magnitude, and precision. Results for the listed secondary outcomes are likewise not reported in the registry record.

The treatment allocation method is not stated. The registry cautions that the arms are not a like-for-like control comparison, limiting interpretation of any between-arm contrast as a treatment effect. The record does not report baseline characteristics by arm, statistical adjustment variables, or an analysis plan that would clarify how differences between participants were addressed.

The primary outcome population is restricted to participants who completed a full 12 months and had grip-strength data at baseline and 12 months. The number meeting these criteria, the number with missing data, and the reasons for missingness are not reported. The outcome description’s wording about participants who discontinued treatment is incomplete, which limits clarity about exclusions. The record allows switching between aromatase inhibitors but does not explain the analysis treatment of switching in detail.

The registry lists enrollment of 115 but does not provide analysis-specific sample sizes. The study’s sample-size justification, detailed statistical analysis plan, multiplicity approach, and any interim analyses are not reported in the registry record. Adverse-event attribution and collection details are also absent. These reporting gaps prevent a full assessment of precision, selection into analysis, and the robustness of any comparison.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Loss of Grip Strength, BMI, and Adjuvant Endocrine Therapy Breast Cancer — NCT01896050.
• Registry record last updated 2016-06-28; status last verified 2016-05.
• Results first posted 2016-05-12.
• 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

NCT01896050 is a completed prospective study sponsored by the University of Michigan Rogel Cancer Center. The registry lists enrollment of 115, a start date of 2009-09, and primary completion in 2014-08. It concerns women with early-stage breast cancer beginning aromatase inhibitor therapy or tamoxifen.

The primary question addresses change in BMI in relation to change in grip strength during aromatase inhibitor therapy, with a baseline-to-12-month timeframe. The described primary population completed a full 12 months of treatment and had grip-strength data at both times. The registry does not report the numerical primary or secondary outcome estimates, analysis-specific sample sizes, or key statistical methods needed to assess those results.

The registry reports serious and other adverse-event counts by treatment group, but does not provide enough detail to interpret them as comparative treatment effects. Allocation was not stated, and the groups are not described as like-for-like controls.