This page separates reported trial results from statistical interpretation. The ClinicalTrials.gov record reports that results were posted for the primary safety endpoint, but no formal statistical analyses were posted to ClinicalTrials.gov.
1. Trial at a Glance
SAIL was a phase 1, sequential, unmasked treatment study of sirolimus and hydroxychloroquine in women with lymphangioleiomyomatosis. The registry describes one treatment arm and two hydroxychloroquine dose levels: 200 mg and 400 mg.
| Feature | SAIL |
|---|---|
| Phase | Phase 1 |
| Condition | Lymphangioleiomyomatosis |
| Design model | Sequential |
| Masking | None |
| Primary purpose | Treatment |
| Enrollment | 14 |
| Number of arms | 1 |
| Interventions | Sirolimus and hydroxychloroquine 200 mg; sirolimus and hydroxychloroquine 400 mg |
| Lead sponsor | Brigham and Women's Hospital |
| Sponsor type | Other |
| Status | Completed |
| ClinicalTrials.gov | NCT01687179 |
2. Clinical Question
The central question was whether combination therapy with sirolimus and hydroxychloroquine could be administered safely in patients with lymphangioleiomyomatosis over the registry-defined 48-week assessment period.
Population
Women with lymphangioleiomyomatosis. The total enrollment was 14.
Intervention
Combination therapy with sirolimus and hydroxychloroquine, evaluated at hydroxychloroquine doses of 200 mg and 400 mg.
Comparator
The registry does not identify a separate comparator arm. It records one study arm in a sequential design.
Primary question
What adverse events and serious adverse events occurred during combination therapy over 48 weeks?
3. Trial Design
Sequential dose evaluation
The combination was evaluated with hydroxychloroquine at two dose levels, 200 mg and 400 mg. Because the registry identifies the design as sequential and the number of arms as 1, these dose levels should not be interpreted as two independently randomized treatment groups.
That distinction is important statistically. In a randomized parallel-group comparison, differences between arms can be interpreted within the framework created by random allocation. A sequential dose study has a different purpose: safety observations accumulate as participants are evaluated under the study's sequence. The registry does not report a randomized control group.
4. Endpoints
| Endpoint | Registry definition | Time frame |
|---|---|---|
| Safety of Combination Therapy With Sirolimus and Hydroxychloroquine in LAM Patients | Safety was assessed based on the adverse events and serious adverse events that occurred in these patients when they were on this combination therapy. Percentage of adverse events in each system at a dose was calculated from the total adverse events at that dose. Subjects were closely monitored and adverse events were classified and graded according to the Common Terminology Criteria for Adverse Events (CTCAE) Version 4.0. | 48 weeks |
The endpoint is therefore fundamentally a safety endpoint rather than a comparative efficacy endpoint. The registry's description emphasizes both the occurrence of adverse events and serious adverse events and the classification of adverse events by system and dose.
5. Analysis Population and Dose-Level Interpretation
The registry reports total enrollment of 14 and one registered study arm. The serious-adverse-event information is reported separately for the two hydroxychloroquine dose levels.
| Safety group reported by the registry | Serious adverse events affected | At risk |
|---|---|---|
| Sirolimus and hydroxychloroquine 200 mg | 0 | 3 |
| Sirolimus and hydroxychloroquine 400 mg | 1 | 10 |
6. Statistical Methodology
Descriptive safety analysis
The primary endpoint is a safety assessment based on adverse events and serious adverse events. For an endpoint of this type, the principal statistical task is descriptive: count events, classify them according to the prespecified terminology, and summarize their occurrence within the relevant treatment or dose group.
The registry explicitly describes calculating the percentage of adverse events in each system at a dose from the total adverse events at that dose.
CTCAE classification and grading
The registry states that adverse events were classified and graded according to the Common Terminology Criteria for Adverse Events, Version 4.0. This provides a standardized framework for describing the severity and clinical category of adverse events rather than reducing safety to a single overall event count.
Serious adverse events
Serious adverse events are presented as affected participants divided by participants at risk for each reported dose level. The registry reports 0/3 for the 200 mg group and 1/10 for the 400 mg group.
No formal inferential analysis posted
The registry reports that results were posted for the primary safety endpoint, but it does not contain posted statistical analyses. Consequently, the available results are descriptive safety counts rather than estimates accompanied by formal confidence intervals or hypothesis tests.
7. Planned Analysis
The registry defines the primary endpoint as the safety of combination therapy with sirolimus and hydroxychloroquine in LAM patients over 48 weeks. Safety is assessed through adverse events and serious adverse events occurring while patients are on combination therapy.
The registry further specifies that adverse events are classified and graded according to CTCAE Version 4.0 and that the percentage of adverse events in each system at a dose is calculated from the total adverse events at that dose.
| Statistical component | How the endpoint is typically evaluated |
|---|---|
| Adverse-event occurrence | Count participants or events experiencing adverse events during the defined safety period. |
| Serious adverse events | Summarize the number of affected participants and the number at risk within the relevant safety group. |
| System-level adverse events | Classify events by the relevant body-system category and describe their frequency within the dose level. |
| Severity | Use the CTCAE grading framework specified by the registry. |
| Dose-level description | Describe safety findings separately for the 200 mg and 400 mg hydroxychloroquine dose levels rather than treating the sequential study as a randomized comparison. |
8. Posted Safety Results
The registry reports serious adverse events by the two dose levels used in the sequential study. These are the principal numerical safety results available in the record.
Serious adverse events at 200 mg
Sirolimus and hydroxychloroquine 200 mg: 0 affected participants among 3 at risk.
Serious adverse events at 400 mg
Sirolimus and hydroxychloroquine 400 mg: 1 affected participant among 10 at risk.
| Dose level | Affected / at risk | Descriptive reading |
|---|---|---|
| 200 mg | 0 / 3 | No serious adverse event was reported among the 3 participants at risk in this registry safety summary. |
| 400 mg | 1 / 10 | One serious adverse event was reported among the 10 participants at risk in this registry safety summary. |
The 0/3 result means that no affected participant was reported among the 3 participants at risk in the registry's 200 mg safety summary. It does not establish that the treatment has zero risk of serious adverse events. With only 3 participants in the denominator, an observed count of zero provides very limited information about the underlying event rate.
The 1/10 result means that one affected participant was reported among 10 participants at risk in the registry's 400 mg safety summary. It does not establish that the higher dose caused that event, nor does it establish that the event rate at 400 mg is higher than at 200 mg.
There is no randomized comparison here, and the dose groups arise within a sequential design. The two observed counts therefore should not be interpreted as an estimate of a causal dose-response relationship.
No confidence interval or p-value was posted for these safety results. A confidence interval would describe statistical uncertainty around an estimated event probability; a p-value would address a specified hypothesis. Neither would substitute for clinical review of the individual adverse events and their CTCAE classifications.
9. Why a Zero Count Is Not the Same as Zero Risk
A particularly important statistical lesson from the 200 mg safety result is that an observed zero is a statement about the observed sample, not proof that the underlying probability is zero.
When no event is observed, the observed proportion is zero. Statistical uncertainty remains because only a small number of participants were observed.
For the 200 mg group, the registry reports 0 events among 3 participants at risk. If the underlying serious-adverse-event probability were nonzero, it would still be possible to observe zero events in a sample of this size. The absence of an observed event therefore should not be converted into a claim of established safety.
The same principle applies to the 400 mg result. One event among 10 participants provides direct evidence that a serious adverse event occurred in the observed safety population, but it does not by itself identify the cause of that event or establish a stable population-level event probability.
10. Comparing the Two Dose Levels Carefully
The presence of two dose-level safety summaries naturally invites comparison, but the design determines what such a comparison can legitimately show.
What can be described
The registry reports 0/3 serious adverse events at 200 mg and 1/10 at 400 mg. These are descriptive observations within the reported safety groups.
What cannot be established from these counts
The counts alone do not establish that the 400 mg dose has a higher serious-adverse-event risk or that the observed event was caused by the dose.
Why design matters
The study is registered as sequential with one arm, rather than as a randomized comparison between two independent treatment groups.
Why sample size matters
The reported denominators are 3 and 10. Such small safety populations produce substantial uncertainty around any underlying event-rate estimate.
For a randomized trial, a between-group safety comparison can be anchored to random allocation. In this study, the sequential design changes the interpretation: the dose levels are part of the study sequence rather than two randomized arms.
11. Statistical Methods Explained
Why is this primarily a descriptive analysis?
Safety endpoints in an early-phase study are commonly summarized by counts, frequencies, severity categories, and clinically meaningful event classifications. The SAIL registry specifically describes calculating percentages of adverse events within systems at each dose and grading events with CTCAE Version 4.0. Those are descriptive rather than model-based procedures.
What does 0/3 mean?
It means that zero participants were reported as affected by a serious adverse event among the 3 participants at risk in the 200 mg safety summary. It does not mean that the probability of a serious adverse event is zero.
What does 1/10 mean?
It means that one participant was reported as affected by a serious adverse event among the 10 participants at risk in the 400 mg safety summary. The count is an observed safety finding, not a causal estimate.
Why shouldn't 0/3 and 1/10 be treated as a formal dose comparison?
The registry identifies the study as sequential and records one arm. Without random allocation between dose groups, the difference in observed event counts cannot be attributed to hydroxychloroquine dose alone. Sequence, participant characteristics, exposure, and other factors could also matter.
Why does CTCAE grading matter?
A raw count of adverse events does not convey the severity or clinical category of an event. CTCAE Version 4.0 provides the standardized classification and grading framework specified by the registry, allowing safety findings to be described in a consistent clinical vocabulary.
Why are confidence intervals useful even when no formal analysis is posted?
Confidence intervals can communicate the uncertainty associated with an estimated event probability. In a very small safety study, the interval can be wide, reinforcing the point that an observed proportion is not necessarily a precise estimate of the underlying population risk. The registry does not post confidence intervals for the reported serious-adverse-event counts.
12. Interpreting the 48-Week Safety Endpoint
The registry specifies a 48-week time frame for the primary safety endpoint. This time frame defines the period over which adverse events and serious adverse events are assessed for the primary endpoint.
Time frame is an important part of a safety estimand. A statement such as "no serious adverse events were observed" has meaning only when the population, exposure period, and event definition are specified. Here, the registry identifies combination therapy, the LAM population, CTCAE-based classification, and a 48-week time frame.
| Element | Registry specification |
|---|---|
| Population | LAM patients |
| Exposure | Combination therapy with sirolimus and hydroxychloroquine |
| Safety events | Adverse events and serious adverse events |
| Classification | CTCAE Version 4.0 |
| Time frame | 48 weeks |
| Dose-level reporting | 200 mg and 400 mg hydroxychloroquine |
13. Serious Adverse Events and Denominators
Safety statistics are highly dependent on their denominators. The registry's serious-adverse-event field gives both the number affected and the number at risk, which is preferable to reporting only an event count.
The visual difference should not be mistaken for a statistically established dose effect. The denominators are small, the study is sequential, and the registry does not provide an inferential comparison between the two dose levels.
14. What the Registry Does and Does Not Establish
| Question | What the registry establishes |
|---|---|
| Was the study completed? | Yes. The status is listed as completed. |
| Was it phase 1? | Yes. |
| Was there a randomized comparator arm? | The registry lists one arm and a sequential design; it does not identify a separate comparator arm. |
| Was masking used? | No. |
| What was the primary endpoint? | Safety of combination therapy with sirolimus and hydroxychloroquine in LAM patients over 48 weeks. |
| How were adverse events classified? | According to CTCAE Version 4.0. |
| Were results posted? | Yes. |
| Were formal statistical analyses posted? | No. |
| What serious adverse-event counts are reported? | 0/3 at 200 mg and 1/10 at 400 mg. |
15. Limitations
- Small enrollment: the study enrolled 14 participants, so rare safety events can easily remain unobserved.
- Sequential design: the registry identifies one study arm and a sequential design rather than a randomized comparison of the two dose levels.
- No comparator arm: there is no separate control group in the registered design against which adverse-event rates can be compared.
- Small dose-level denominators: the serious-adverse-event summaries use denominators of 3 and 10, limiting precision.
- Denominator accounting: the two reported serious-adverse-event denominators total 13, whereas enrollment is 14; the registry information shown does not explain the relationship of the remaining enrolled participant to these specific safety denominators.
- Descriptive results: no formal statistical analyses, confidence intervals, or p-values are posted for the reported safety endpoint.
- Safety interpretation: the occurrence or absence of an event cannot by itself establish causality.
- Time frame: the primary safety endpoint is defined over 48 weeks; observations outside that time frame are not represented by this endpoint definition.
16. Why This Trial Matters Statistically
SAIL is a useful teaching case because it illustrates a different statistical problem from the large randomized efficacy trials that dominate clinical-trial reporting. Here, the central task is not estimating a treatment hazard ratio or comparing survival curves. It is understanding how safety evidence should be summarized when the study is small, sequential, unmasked, and without a randomized comparator.
| Concept | How it appears in SAIL |
|---|---|
| Phase 1 design | The study is classified as phase 1. |
| Sequential design | The registry identifies a sequential design with one arm. |
| Safety endpoint | The primary endpoint evaluates adverse events and serious adverse events over 48 weeks. |
| Descriptive statistics | The registry describes calculating percentages of adverse events by system at a dose. |
| Standardized adverse-event terminology | Events were classified and graded according to CTCAE Version 4.0. |
| Small denominators | Serious-adverse-event summaries use 3 and 10 participants at risk. |
| Zero-event interpretation | 0/3 illustrates why absence of observed events is not proof of zero underlying risk. |
| Non-randomized dose interpretation | Differences between sequential dose levels should not be interpreted as randomized treatment effects. |
17. Safety Evidence: Counts, Rates, and Causality
Three different questions are often conflated in safety reporting: Did an event occur?, How frequently did it occur?, and Was it caused by the treatment? The SAIL registry's serious-adverse-event field directly addresses the first question and supplies the denominator needed for a descriptive frequency calculation. It does not, from these counts alone, answer the causality question.
This distinction is particularly important in a single-arm study. Without a concurrent comparator group, an observed adverse event cannot readily be separated into treatment-associated risk versus the background occurrence of events in the underlying patient population.
Event occurrence
One serious adverse event is reported among 10 participants at risk at the 400 mg dose.
Event frequency
The registry supplies affected and at-risk counts, allowing the safety observation to be expressed descriptively.
Causality
The numerical count alone does not establish that an event was caused by hydroxychloroquine, sirolimus, or their combination.
Comparative safety
A randomized comparator is not identified in the registry design, so a conventional randomized safety contrast is not available.
18. Statistical Interpretation of Small Safety Studies
Early-phase safety studies are often intentionally small because their objectives differ from those of confirmatory efficacy trials. The statistical consequence is that estimates of uncommon event probabilities are inherently imprecise.
For example, observing no serious adverse events among 3 participants is compatible with many possible underlying risks. The sample simply contains too few observations to distinguish a very low probability from a materially larger probability with confidence. Similarly, one event among 10 participants provides a direct observation of an event but remains a very uncertain basis for estimating a stable population rate.
The appropriate emphasis is therefore on what was observed, among whom, at which dose level, and over what time frame. The counts should not be transformed into stronger claims about population-level safety than the study design and sample size can support.
19. Clinical Interpretation vs Statistical Interpretation
Statistical interpretation
The registry reports descriptive serious-adverse-event counts of 0/3 at 200 mg and 1/10 at 400 mg. No formal statistical analysis was posted, and the dose levels were studied sequentially rather than as randomized comparator groups.
Clinical interpretation
The safety findings should be considered in the context of the observed adverse events, their CTCAE classifications and grades, the treatment exposure, and the small number of participants represented in each reported safety denominator.
20. A Practical Framework for Reading the SAIL Safety Result
| Step | Question to ask | SAIL application |
|---|---|---|
| 1 | What is the endpoint? | Safety of combination therapy over 48 weeks. |
| 2 | What population is being described? | LAM patients enrolled in the phase 1 study. |
| 3 | What is the denominator? | The registry reports 3 at risk at 200 mg and 10 at risk at 400 mg for serious adverse events. |
| 4 | What was observed? | 0 affected at 200 mg and 1 affected at 400 mg. |
| 5 | Is there randomization? | The registry identifies one arm and a sequential design. |
| 6 | Is there formal uncertainty reported? | No confidence intervals or p-values are posted in the statistical-analysis field. |
| 7 | What terminology standard was used? | CTCAE Version 4.0. |
21. Study Timeline
SAIL begins
The registry lists September 2012 as the study start date.
Two hydroxychloroquine dose levels
The registered intervention includes sirolimus with hydroxychloroquine 200 mg and sirolimus with hydroxychloroquine 400 mg in a sequential, single-arm design.
Safety assessment
The primary endpoint evaluates adverse events and serious adverse events during combination therapy over 48 weeks.
Study completion period
The registry lists August 2015 as the primary completion date.
22. What a Strong Safety Analysis Should Report
The SAIL record illustrates why a safety table is more informative when it preserves the structure of the underlying observation. A useful safety analysis identifies the treatment or dose level, number at risk, number affected, event classification, severity, and relevant observation period.
| Reporting element | Why it matters |
|---|---|
| Dose level | Safety observations are reported separately for 200 mg and 400 mg hydroxychloroquine. |
| Participants at risk | Provides the denominator needed to understand the scale of the observation. |
| Participants affected | Identifies how many participants experienced the reported serious adverse event. |
| Adverse-event system | The registry specifies system-level percentage calculations for adverse events. |
| CTCAE classification and grade | Provides standardized clinical characterization of adverse events. |
| Time frame | Places the safety findings within the 48-week primary endpoint period. |
A safety analysis is therefore more than a single percentage. The denominator, event definition, severity framework, exposure, and observation period all affect interpretation.
23. Important Statistical Takeaways
A zero observed event count in a small sample does not establish that the underlying event probability is zero.
An observed event among 10 participants does not establish that the dose caused the event or that its risk is higher than at another dose.
The registered sequential, single-arm structure limits direct causal comparison between the two dose-level safety summaries.
24. Sources
- ClinicalTrials.gov: SAIL (NCT01687179).
- PubMed record: PubMed 31299246.
- PubMed record: PubMed 30144422.
- PubMed record: PubMed 28192114.
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Clinical trial statistics become easier to interpret when study design, endpoints, denominators, uncertainty, and analysis populations are considered together.
25. Record Summary
SAIL provides a compact example of how statistical reasoning changes when the primary objective is safety in an early-phase, sequential study rather than confirmatory efficacy in a randomized trial. The registry describes a phase 1 study with one arm, no masking, 14 enrolled participants, and two hydroxychloroquine dose levels used with sirolimus. The primary endpoint is safety over 48 weeks, assessed through adverse events and serious adverse events with CTCAE Version 4.0 classification and grading.
The posted serious-adverse-event results are 0/3 at 200 mg and 1/10 at 400 mg. Those observations are useful descriptive safety information, but their small denominators and sequential design place clear limits on comparative inference. In particular, the absence of an observed event in 3 participants is not evidence of zero underlying risk, and the single event among 10 participants does not by itself establish a causal dose effect.
The statistical lesson is straightforward but important: safety counts must be interpreted through their denominators, study design, event definitions, severity classifications, and observation period. For SAIL, those elements are more informative than a formal p-value would be, especially because no formal statistical analyses were posted to the registry.