This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Lung Volume Reduction Coil Treatment in Patients With Emphysema (RENEW) Study (NCT01608490), a randomized na study. The primary outcome is Meters: 6 Minute Walk Test - Change From Baseline to 12 Months Follow up.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01608490 |
| Phase | NA |
| Condition | Emphysema |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 315 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Boston Scientific Corporation |
| Results posted | Yes |
2. Clinical Question
Population
Patients with emphysema who were analyzed at 12 months. The registry record lists an enrollment of 315 and describes the study as multicenter. The primary outcome population is defined as patients analyzed at 12 months; further details about eligibility for that analysis are not reported in the registry record.
Intervention
The RePneu Lung Volume Reduction Coil System, an implantable device delivered through a fiber-optic bronchoscope. The device description identifies sterile Nitinol coils and a sterile, disposable, single-use delivery system.
Comparator
Standard medical care. The control group did not undergo bronchoscopy for coil placement. The registry description also says the control group did not receive prophylactic antibiotics or steroids before and after treatment visits or chest x-rays in connection with those visits.
Primary question
How did the change in six-minute walk test distance from baseline through 12 months compare between the coil-system and standard-medical-care groups? The primary outcome is described as mean absolute change, with the median used if the data were skewed. The posted result identifies the parameter as a median and reports a value for each group.
3. Trial Design
RENEW was a randomized, parallel-group study of the RePneu Lung Volume Reduction Coil System and standard medical care in patients with emphysema. The registry record lists an enrollment of 315, a start date of 2012-10, primary completion in 2015-12, and a status of terminated. The phase is listed as NA. The sponsor is Boston Scientific Corporation.
The brief study description calls the study multicenter and assessor-blinded. The registry's masking field is listed as none. Those descriptions appear together in the record, but further information explaining the masking procedures is not reported in the registry record. The allocation is listed as randomized, and the model as parallel. Details about the randomization sequence, allocation concealment, stratification, or implementation are not reported in the registry record.
The intervention was an implantable coil system delivered through a fiber-optic bronchoscope. The control group received standard medical care and did not undergo bronchoscopy for coil placement. The control-arm description also distinguishes the groups in relation to prophylactic antibiotics or steroids and chest x-rays around treatment visits. The registry describes visit frequency for the control group as similar to that of the study group, although the corresponding description is truncated in the record.
The primary outcome was change in six-minute walk test distance from baseline through 12 months. The stated outcome population was patients analyzed at 12 months. The registry also lists secondary outcomes concerning FEV1, the St. George's Respiratory Questionnaire, and a six-minute walk test responder analysis. The posted results include two secondary endpoints; values for the FEV1 endpoint are not reported in the registry record. The reason the study was terminated is 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
| Stage | RePneu Lung Volume Reduction Coil System | Control Arm is Standard Medical Care |
|---|---|---|
| STARTED | 158 | 157 |
| COMPLETED | 141 | 142 |
| NOT COMPLETED | 17 | 15 |
Analysis population for the primary outcome, as defined in the registry: Patients who were analyzed at 12 months.
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.
| Characteristic | Unit | RePneu Lung Volume Reduction Coil System | Control Arm is Standard Medical Care | Total |
|---|---|---|---|---|
| Participants analysed | 158 | 157 | 315 | |
| Age, Continuous | years | 63.4 (SD 8.05) | 64.3 (SD 7.76) | 63.9 (SD 7.9) |
| Sex: Female, Male: Female | Participants | 86 | 79 | 165 |
| Sex: Female, Male: Male | Participants | 72 | 78 | 150 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 1 | 2 | 3 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 157 | 155 | 312 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
6. Primary Endpoint
The registry lists the primary outcome as Meters: 6 Minute Walk Test - Change From Baseline to 12 Months Follow up, measured over baseline through 12 months follow up.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | meters |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is change from baseline in distance covered during the six-minute walk test, assessed at 12 months. The test measures the distance a participant can walk over a fixed testing period and is used as a functional measure of walking capacity. In this study, the endpoint compares the change in walking distance between the coil-system group and the standard-medical-care group.
The registry describes the outcome as mean absolute change, with the median used if the data were skewed. The posted parameter is median, and the dispersion is identified as inter-quartile range. The group values are 10.3 meters for the coil-system group and -7.6 meters for the control group. The posted lower and upper values are -33.0 and 45.0 meters for the coil-system group, and -40.0 and 26.0 meters for the control group. The registry identifies the analysis population as patients analyzed at 12 months.
Change from baseline provides a way to express how an outcome shifted during follow-up rather than describing only a follow-up measurement. A median summarizes the middle of the observed change values and is less influenced by unusually large or small values than a mean. The inter-quartile range describes the spread of the central part of the distribution. These are general statistical interpretations; the registry does not report further detail about the distribution of individual results or the clinical threshold used to define a meaningful change.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
For the primary six-minute walk test outcome, the posted median change was 10.3 meters in the RePneu coil-system group and -7.6 meters in the standard-medical-care group, measured from baseline through 12 months. The registry identifies the outcome as median change and gives inter-quartile ranges. The posted lower and upper values are -33.0 and 45.0 meters in the coil-system group and -40.0 and 26.0 meters in the control group. These summaries describe the observed distributions; they do not establish how any individual participant changed.
The group summaries point in different directions: the coil-system group's median change is positive, while the control group's is negative. The posted ranges extend across both negative and positive values in each group. They therefore indicate variation in observed change within both groups. A group median does not mean every participant experienced a change equal to that value, and the overlap of the reported ranges should not be treated as a formal test of the between-group contrast.
The registry does not post a primary between-group estimate, confidence interval, or p-value for this endpoint. It also does not post a mean difference or another adjusted comparison for the primary outcome. Values for a two-arm comparison are marked as missing or not estimable for this endpoint. Accordingly, the group summaries alone do not quantify the uncertainty around a primary treatment contrast or provide a reported inferential test. The reason a comparison is absent is not reported in the registry record.
The analysis population is described as patients analyzed at 12 months, rather than all randomized participants. The number included in each posted primary outcome group is listed as 158.0 and 157.0. Further information about missing 12-month measurements, exclusions, or how the analysis population was formed is not reported in the registry record. This limits assessment of whether the posted values represent all randomized participants or a subset with outcome data.
The findings describe the registry's posted results for this endpoint and follow-up. They should be read alongside the trial's design and reporting limitations, including the absence of a primary between-group estimate and the lack of detail about missing data and analysis procedures. The registry status is terminated, but the reason for termination is not reported. These results, on their own, do not settle questions about the effect of the device or the experience of individual participants.
9. Statistical Methods Explained
The primary endpoint is a change score: each participant's follow-up walking distance is considered relative to that participant's baseline distance, and the group-level summary is reported at 12 months. Change scores can make the focus of a comparison explicit: the question is about change during follow-up, not just the absolute walking distance at one visit. The registry specifies median change for the posted primary result and identifies inter-quartile range as its dispersion measure.
What does a median summarize?
As a general statistical concept, the median is the central value when observations are ordered. Half of the observations lie on either side of the median, subject to ties. It can be useful when a distribution is skewed or contains extreme observations, because individual extremes generally have less influence on the median than on the mean. The registry's endpoint description says the median would be used if results were skewed, and the posted parameter is median. The record does not report a distributional assessment or explain the choice in further detail.
The inter-quartile range describes the central spread of a distribution, from the lower quartile to the upper quartile. The primary result lists lower and upper values for each group, but does not provide a primary confidence interval or a test of the between-group difference. A spread of individual observations and a confidence interval for a group estimate answer different questions: the former describes variation in participant-level results, while the latter describes uncertainty in an estimated quantity. The registry labels the primary dispersion as inter-quartile range, so the posted bounds should be read in that context rather than as a confidence interval.
What would a between-group estimate add?
A direct comparison would estimate how the outcome differs between randomized groups and quantify uncertainty around that estimate. For a mean comparison, that might be expressed as a mean difference; for a median-based analysis, another suitable contrast and method would be needed. The registry marks the primary two-arm comparison as unavailable or not estimable and does not report a primary p-value or confidence interval. Thus, the posted group summaries do not supply the inferential comparison needed to assess the precision of a primary contrast. The method intended for a primary between-group analysis is not reported in the registry record.
How should the secondary estimates be read?
The posted secondary results include a continuous SGRQ outcome and a binary six-minute walk test responder outcome. Their comparisons are recalculated, unadjusted summaries from the posted group statistics. For the SGRQ outcome, the reported group means are -8.1 and 0.8, with standard errors of 1.08 and 1.05. The recalculated mean difference is -8.9, with a 95% confidence interval from -11.85 to -5.948 and an unadjusted p-value of <0.001. For the responder analysis, the posted counts are 60 and 41. The recalculated risk difference is 0.119, with a 95% confidence interval from 0.016 to 0.221 and an unadjusted p-value of 0.024. These are unadjusted recalculations; no corresponding reported analyses are listed in the registry.
A confidence interval gives a range of values compatible with the estimate under the assumptions of the statistical method. In general, a narrower interval indicates greater precision, while a wider interval indicates greater uncertainty. A p-value is a measure of how unusual data at least as incompatible with a null hypothesis would be if that hypothesis and the model assumptions held. It is not the probability that the null hypothesis is true, nor does it measure the size or importance of an effect. These are general interpretations and do not replace an analysis plan specific to this trial.
Why are planning figures not observed power?
The registry includes planning illustrations based on fractions of the observed secondary effects. These illustrations use a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation. They are calculations based on observed effects, not the trial's own design justification, and they are not observed power. The sample-size justification and the trial's design assumptions are not reported in the registry record. Planning numbers should be understood as illustrations of what a future design might require under the stated assumptions, not as evidence about the probability that this completed trial detected an effect.
For outcomes with extra variability beyond what a simple model assumes, general statistical methods may need to account for over-dispersion. Over-dispersion means that observed variation is greater than a model's expected variation; ignoring it can make uncertainty appear too small. The posted binary comparison is a simple unadjusted recalculation, and the registry does not report whether an over-dispersion adjustment, covariate adjustment, or other model was used in a sponsor analysis. No sponsor-reported analyses are listed for the posted secondary endpoints.
10. Multiplicity, Missing Data and Analysis Populations
The registry record does not report a statistical analysis plan, a testing hierarchy, or a procedure for controlling multiplicity. It lists several secondary outcomes, while the posted numeric results include two secondary endpoints and no reported analyses. When multiple outcomes are tested, interpreting each p-value as though it were the sole planned test can overstate the strength of evidence. This is a general statistical issue; the record does not state whether any multiplicity adjustment was planned or applied.
The primary endpoint is described as change in six-minute walk test distance among patients analyzed at 12 months. The posted group sizes are 158.0 and 157.0. The record does not explain whether participants without 12-month measurements were excluded, how missing outcomes were handled, or whether any imputation or sensitivity analysis was conducted. The number of participants randomized to each arm is not separately stated in the posted outcome data, and the relationship between enrollment and the analyzed populations is not described in sufficient detail to evaluate attrition.
It is also not reported whether the primary analysis followed an intention-to-treat principle, a per-protocol approach, or another population definition. The record does not explain how protocol deviations, treatment discontinuation, or participants with incomplete follow-up were handled. These omissions matter because analysis choices can affect both the estimated group contrast and its uncertainty, especially when missingness differs between groups or relates to outcomes.
The registry lists zero posted analyses, and the secondary comparisons are recalculated, unadjusted comparisons from posted summary statistics. The primary comparison is marked unavailable or not estimable. Details about prespecified models, covariate adjustment, assumptions, interim analyses, or sample-size justification are not reported in the registry record. Without these details, the posted numbers cannot be matched to a complete inferential framework or checked against a documented analysis plan.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| RePneu Lung Volume Reduction Coil System | 78 | 155 | 50.3% |
| Control Arm is Standard Medical Care | 44 | 157 | 28.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| RePneu Lung Volume Reduction Coil System | 10 of 155 |
| Control Arm is Standard Medical Care | 8 of 157 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| RePneu Lung Volume Reduction Coil System | 155 of 155 |
| Control Arm is Standard Medical Care | 142 of 157 |
Most frequent serious adverse event terms
| Event term | Organ system | RePneu Lung Volume Reduction Coil System | Control Arm is Standard Medical Care |
|---|---|---|---|
| Chronic obstructive pulmonary disease | Respiratory, thoracic and mediastinal disorders | 43 of 155 | 32 of 157 |
| Pneumonia | Infections and infestations | 31 of 155 | 8 of 157 |
| Pneumothorax | Respiratory, thoracic and mediastinal disorders | 15 of 155 | 1 of 157 |
| Bronchitis | Infections and infestations | 5 of 155 | 2 of 157 |
| Dyspnoea | Respiratory, thoracic and mediastinal disorders | 5 of 155 | 1 of 157 |
| Respiratory failure | Respiratory, thoracic and mediastinal disorders | 5 of 155 | 1 of 157 |
| Medical device complication | General disorders | 5 of 155 | 0 of 157 |
| Acute respiratory failure | Respiratory, thoracic and mediastinal disorders | 3 of 155 | 1 of 157 |
| Haemoptysis | Respiratory, thoracic and mediastinal disorders | 4 of 155 | 0 of 157 |
| Bronchopulmonary aspergillosis | Infections and infestations | 3 of 155 | 0 of 157 |
Most frequent non-serious adverse event terms
| Event term | Organ system | RePneu Lung Volume Reduction Coil System | Control Arm is Standard Medical Care |
|---|---|---|---|
| Chronic obstructive pulmonary disease | Respiratory, thoracic and mediastinal disorders | 108 of 155 | 91 of 157 |
| Haemoptysis | Respiratory, thoracic and mediastinal disorders | 91 of 155 | 0 of 157 |
| Pneumonia | Infections and infestations | 36 of 155 | 12 of 157 |
| Bronchitis | Infections and infestations | 21 of 155 | 25 of 157 |
| Dyspnoea | Respiratory, thoracic and mediastinal disorders | 33 of 155 | 12 of 157 |
| Cough | Respiratory, thoracic and mediastinal disorders | 28 of 155 | 3 of 157 |
| Chest discomfort | General disorders | 20 of 155 | 1 of 157 |
| Non-cardiac chest pain | General disorders | 21 of 155 | 0 of 157 |
| Pneumothorax | Respiratory, thoracic and mediastinal disorders | 18 of 155 | 1 of 157 |
| Upper respiratory tract infection | Infections and infestations | 9 of 155 | 9 of 157 |
Serious events with the highest arm-level rate: chronic obstructive pulmonary disease (27.7%), pneumonia (20.0%), pneumothorax (9.7%), medical device complication (3.2%), bronchitis (3.2%).
The registry reports serious adverse events in both groups. In the coil-system group, 78 participants were affected among 155 at risk; in the standard-medical-care group, 44 were affected among 157 at risk. The registry also reports other adverse events in 155 participants among 155 at risk in the coil-system group and 142 among 157 at risk in the control group. Deaths are listed as 10 and 8, respectively. These are posted counts, not adjusted comparisons, and the record does not provide a statistical comparison or further detail on exposure time.
The serious adverse event terms listed most often include chronic obstructive pulmonary disease at 27.7%, pneumonia at 20.0%, pneumothorax at 9.7%, medical device complication at 3.2%, bronchitis at 3.2%, and dyspnoea at 3.2%. The registry does not describe the event-term percentages' denominator in the posted information, so they should be read as listed rather than converted into participant counts or compared with the group-level affected counts.
Adverse event totals do not by themselves establish causation. The record does not provide event timing, severity distributions beyond the serious-event category, exposure-adjusted rates, or details about attribution and collection procedures. Counts also do not account for differences in follow-up or time at risk. These safety figures describe what the registry posts; they do not establish whether a particular event was caused by the device or by another factor.
12. What the Result Does, and Does Not, Mean
The posted primary summaries describe median changes in six-minute walk test distance at 12 months for the coil-system and standard-medical-care groups. They show a positive median change in one group and a negative median change in the other, while the reported lower and upper values span both negative and positive changes in each group. This is a description of the group data, not a complete estimate of the treatment contrast.
The registry does not report a primary between-group estimate, confidence interval, or p-value. Therefore, the posted primary summaries do not quantify the precision of a primary contrast or provide a formal test of that contrast. The absence of a primary comparison does not establish that groups were the same; it means that the registry record does not report the estimate needed to evaluate the difference directly.
The secondary comparisons are unadjusted recalculations from summary statistics. Their estimates and p-values can be informative as exploratory descriptions, but they are not equivalent to analyses reported under a documented trial analysis plan. There is no reported multiplicity adjustment, and the record does not describe missing-data handling or a prespecified hierarchy for secondary endpoints. Those limitations reduce the certainty with which secondary findings can be interpreted.
The registry status is terminated, but the reason for termination is not reported in the registry record. Termination alone does not explain why the study stopped or what consequences it had for enrollment, follow-up, or analysis. The posted enrollment and outcome group sizes do not establish the full flow of participants through the trial.
These findings do not show how every participant experienced treatment, establish causation for an individual adverse event, or resolve all questions about effectiveness and safety. They describe registry-level summaries with important gaps in inferential reporting. Conclusions should remain tied to those posted summaries and their uncertainty, rather than extending beyond the information recorded.
13. Why This Trial Matters Statistically
RENEW illustrates why a clinical trial's group summaries and its between-group estimate are not interchangeable. The primary outcome is central to the trial question, yet the record provides median change summaries and inter-quartile ranges without a primary contrast, confidence interval, or p-value. Readers can see the direction and spread of the posted group values, but cannot use those summaries alone to assess the precision of a direct comparison.
The endpoint also illustrates the importance of matching a statistical summary to the data. The registry specifies median change and inter-quartile range, rather than a mean and standard deviation. These summaries characterize the center and spread differently. A suitable comparison should reflect the outcome's distribution and the analysis plan; the specific primary comparison method is not reported in the registry record.
The secondary results show another important distinction: a recalculated unadjusted estimate is not the same as a sponsor-reported analysis. The posted secondary comparisons provide estimates and uncertainty calculations from summary statistics, but the registry lists no reported analyses. They should therefore be interpreted with care, particularly when multiple secondary outcomes are listed and the record does not document how they were prioritized or whether multiplicity was addressed.
Finally, the record makes the analysis population and data completeness consequential. The primary outcome applies to patients analyzed at 12 months, but missing-data methods, participant flow, and the definition of the analysis set are not reported. Such details are necessary for judging how well an outcome analysis represents the randomized groups. The trial is a useful example of how transparent reporting of estimates, uncertainty, populations, and analysis procedures determines what readers can infer from registry results.
14. 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.
A major trial-specific limitation is the missing primary between-group comparison. The registry posts group medians and inter-quartile ranges for the six-minute walk test, but marks the two-arm comparison as unavailable or not estimable. No primary confidence interval or p-value is posted, and the reason for the missing comparison is not reported in the registry record. This leaves the principal question less directly addressed than the group summaries might suggest.
The record defines the primary outcome population as patients analyzed at 12 months, but does not report how that population was assembled. Although group sizes are posted for the endpoint, the registry does not describe missing follow-up, exclusions, or the handling of incomplete data. This limits assessment of potential attrition bias and prevents a clear account of how the analyzed populations relate to randomization.
There is limited information about analysis procedures. A statistical analysis plan, the primary comparison method, covariate adjustments, interim analyses, and sample-size justification are not reported in the registry record. The registry lists several secondary outcomes, but does not report a multiplicity procedure or a hierarchy governing their interpretation. The secondary comparisons are recalculated and unadjusted, and reported analyses are not listed.
The record's study descriptions also leave some design details unclear. It calls the study assessor-blinded in the brief summary while the masking field is listed as none; further explanation is not reported. The reason for termination is also not reported. Finally, the adverse-event summaries lack detail about event timing, attribution, and exposure-adjusted rates. These gaps constrain interpretation without changing the posted values themselves.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Lung Volume Reduction Coil Treatment in Patients With Emphysema (RENEW) Study — NCT01608490.
- Registry record last updated 2021-07-19; status last verified 2021-07.
- Results first posted 2017-06-27.
- 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.
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18. Record Summary
RENEW was a randomized, parallel-group study of the RePneu Lung Volume Reduction Coil System versus standard medical care in patients with emphysema. The registry lists enrollment of 315, a start date of 2012-10, primary completion in 2015-12, and status as terminated. The primary outcome was change in six-minute walk test distance from baseline through 12 months among patients analyzed at 12 months.
The posted primary group summaries are medians with inter-quartile ranges, but no primary between-group estimate or inferential test is reported. Two secondary comparisons are available as unadjusted recalculations from posted summary statistics; the registry lists no reported analyses. Missing-data methods, multiplicity procedures, the reason for termination, and the sample-size justification are not reported in the registry record.