This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record.
1. Trial at a Glance
NRG-GY017 was a randomized, parallel, open-label phase 1 treatment study involving 40 participants with node-positive stage IB2, II, IIIB, or IVA cervical cancer. The study evaluated atezolizumab before and/or with chemoradiotherapy, with immune response defined through T-cell receptor beta clonal expansion in peripheral blood.
| Feature | NRG-GY017 |
|---|---|
| Phase | Phase 1 |
| Status | Completed |
| Population | Patients with node-positive stage IB2, II, IIIB, or IVA cervical cancer |
| Conditions | Cervical adenocarcinoma; cervical adenosquamous carcinoma; cervical squamous cell carcinoma; stage IB2, II, IIA, IIA1, IIA2, IIB, IIIB, or IVA cervical cancer according to AJCC v8 |
| Design | Randomized, parallel, open-label |
| Allocation | Randomized |
| Primary purpose | Treatment |
| Number of arms | 2 |
| Enrollment | 40 |
| Lead sponsor | National Cancer Institute (NCI) |
| Sponsor type | NIH |
| ClinicalTrials.gov | NCT03738228 |
2. Clinical Question
The registry describes NRG-GY017 as a study of atezolizumab before and/or with chemoradiotherapy in patients with node-positive cervical cancer. The principal statistical question is therefore centered on whether the randomized study groups differ in the specified measure of immune response after exposure to atezolizumab in the context of the study treatment strategy.
Population
Patients with cervical adenocarcinoma, cervical adenosquamous carcinoma, or cervical squamous cell carcinoma meeting the registry's node-positive stage criteria: IB2, II, IIIB, or IVA, with additional stage II subcategories listed in the record.
Intervention framework
Atezolizumab was studied in conjunction with a treatment program that included radiation therapy, brachytherapy, and cisplatin.
Comparator structure
The study used 2 randomized parallel arms. The registry describes the study as evaluating atezolizumab before and/or with chemoradiotherapy.
Primary question
How does the specified immune response, measured through total TCRB clonal expansion, compare across the randomized study groups at the prespecified assessment windows?
3. Trial Design
Study interventions
The registry lists four interventions: atezolizumab, brachytherapy, cisplatin, and radiation therapy. The record describes the overall study as evaluating atezolizumab before and/or with chemoradiotherapy. The registry information available here does not provide additional arm-specific dosing or scheduling details.
4. Trial Population and Statistical Context
The enrolled population consisted of 40 participants. Because this was a phase 1 randomized study, the sample size is modest for between-group statistical estimation. A small randomized sample can be useful for characterizing an experimental biological signal, but estimates from such a study are generally less precise than estimates from a substantially larger confirmatory trial.
| Population feature | Registry information |
|---|---|
| Total enrollment | 40 |
| Study arms | 2 |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None |
| Primary purpose | Treatment |
| Study phase | Phase 1 |
Randomization is statistically important even in a small phase 1 study because it creates a defined comparison between study groups. However, randomization does not make a small sample statistically equivalent to a large one: uncertainty around estimated treatment differences can remain substantial.
5. Primary Endpoint
| Endpoint | Registry definition | Time frame |
|---|---|---|
| Immune Response | The immune response is measured by total T cell receptor beta (TCRB) clonal expansion in peripheral blood at day 21 from baseline using Adaptive Biotechnologies' immunoSEQ platform. The registry states that a higher number of total TCR clonal expansion indicates better immune response. | Arm A: 42 days from the first dose of Atezolizumab Arm B: 21 days from the first dose of Atezolizumab |
How the endpoint is constructed
The endpoint is based on total TCRB clonal expansion measured in peripheral blood. The registry describes the measurement using the immunoSEQ platform and anchors the immune-response assessment to day 21 from baseline.
The registry also gives different overall time frames for the two randomized groups: 42 days from the first dose of atezolizumab for Arm A and 21 days from the first dose for Arm B. Those different windows are important when interpreting the comparison because timing is part of the endpoint definition.
The registry explicitly states that a higher number of total TCR clonal expansion indicates a better immune response. The endpoint is therefore directional: larger measured expansion corresponds to a more favorable immune-response interpretation under the registry definition.
6. Planned Analysis
For a continuous laboratory-based immune-response endpoint such as total TCRB clonal expansion, a typical randomized comparison would begin by describing the distribution within each arm and then estimating the between-arm difference. If the endpoint were analyzed as a continuous change from baseline, a model such as an ANCOVA could compare treatment groups while adjusting for the baseline measurement. Alternatively, a two-sample comparison of changes could be used when its assumptions are appropriate.
The most important issue is that the statistical scale must match the endpoint actually analyzed. If clonal-expansion measurements are strongly skewed, a transformation such as the logarithm may be considered before modeling. If the distribution remains unsuitable for a standard parametric model, a rank-based comparison could be considered. These are general statistical approaches for this type of endpoint; the registry information does not identify which of them was used for the posted results.
Baseline adjustment
When a continuous biological measurement is available both before and after treatment, baseline adjustment can improve precision by accounting for differences in starting values. An ANCOVA framework would typically model the follow-up measurement as a function of treatment group and baseline measurement.
This equation describes a common analysis framework for a continuous randomized endpoint. It is an educational representation of a possible analysis, not a claim that this exact model was specified or used in the registry.
Effect estimate
For this endpoint, the treatment contrast could be expressed as an adjusted mean difference, an unadjusted mean or median difference, or another prespecified scale depending on the distribution and statistical analysis plan. The choice of effect measure matters because it determines how the magnitude of an immune-response difference is communicated.
7. Statistical Methods Explained
Why does randomization matter for an immune-response endpoint?
Randomization creates the comparison between the two study groups before the outcome is observed. In principle, this reduces systematic allocation differences as an explanation for a later difference in TCRB clonal expansion. With only 40 enrolled participants, however, randomization cannot guarantee that every baseline characteristic is numerically balanced.
Why is a continuous endpoint different from a survival endpoint?
Total TCRB clonal expansion is a laboratory measurement rather than a time-to-event outcome such as death or progression. Kaplan-Meier curves and Cox proportional-hazards models are therefore not the natural primary tools for the endpoint as it is defined in the registry. The central comparison is the distribution of the immune-response measurement between randomized groups.
Why might baseline adjustment be useful?
Suppose two patients begin with very different levels of TCRB activity. Comparing only their follow-up values can mix treatment effects with pre-existing differences. An analysis that incorporates baseline measurements can separate the treatment-group comparison from variation that was already present before treatment.
What does a higher total TCR clonal expansion mean?
According to the registry definition, a higher number of total TCR clonal expansion indicates a better immune response. This is a statement about the biological endpoint, not a direct statement that a patient lived longer, had better tumor control, or experienced a particular clinical outcome.
Why do the different assessment windows matter?
The registry specifies 42 days from the first dose of atezolizumab for Arm A and 21 days from the first dose for Arm B. A comparison between groups therefore has to respect the prespecified timing. Measurements obtained at different treatment intervals can represent different biological stages, so the timing cannot simply be ignored when interpreting the result.
Why does a small phase 1 sample require caution?
With 40 enrolled participants, random variation can have a substantial effect on estimated between-group differences. Confidence intervals, when available from a formal analysis, are therefore especially important because they communicate the precision of the estimated effect rather than only whether a hypothesis test crossed a threshold.
8. Statistical Interpretation of the Primary Endpoint
A comparison of total TCRB clonal expansion can describe whether the randomized study groups differed in the specified laboratory measure of immune response. The registry explicitly defines greater total TCR clonal expansion as indicating better immune response.
A higher immune-response measurement is not itself a measure of overall survival, progression-free survival, tumor response, or cure. Those are distinct clinical outcomes and cannot be substituted for the TCRB endpoint.
If the analysis reports a difference in TCRB clonal expansion, the numerical scale should be interpreted in the units of the underlying laboratory measurement. A statistically detectable difference and a clinically meaningful difference are not automatically the same thing.
If a formal analysis reports a p-value, that value would address evidence against a specified null hypothesis under the statistical model. It would not tell the reader how large the immune-response difference is. The effect estimate and its confidence interval provide the information about magnitude and precision.
9. Analysis Population and Missing Data Considerations
The registry identifies the enrollment of 40 participants but does not provide an analysis-population definition for the primary immune-response endpoint in the information summarized here. That distinction matters because a randomized analysis, an evaluable-patient analysis, and an analysis restricted to participants with usable laboratory measurements can produce different denominators and different uncertainty.
Laboratory endpoints can also be affected by missing specimens or measurements that fail quality-control requirements. The statistical consequence depends on why measurements are missing and how the prespecified analysis handles them. The registry information does not specify an imputation method for the immune-response endpoint.
Randomized population
Randomization establishes the original comparison between the 2 study arms.
Endpoint-evaluable population
A laboratory endpoint may require an available and valid TCRB measurement. The registry information does not define a separate evaluable population here.
Missing measurements
The registry information does not specify an imputation strategy for missing TCRB measurements.
Interpretation
The denominator used in any formal analysis should therefore be read together with the endpoint definition and analysis population.
10. Safety Results
The registry reports serious adverse events by arm using affected participants over participants at risk. The reported counts are:
| Arm | Participants with serious adverse events | Participants at risk |
|---|---|---|
| Arm A | 6 | 19 |
| Arm B | 7 | 17 |
The reported denominators for serious adverse events are 19 in Arm A and 17 in Arm B. They do not equal the overall enrollment of 40, so the safety result should be interpreted using the registry's stated at-risk denominators rather than substituting the total enrollment.
The registry reports 6 affected participants among 19 at risk in Arm A and 7 among 17 at risk in Arm B. These are counts of participants with serious adverse events, not counts of individual adverse-event episodes. They also should not be interpreted as evidence of a difference in overall safety without considering the underlying exposure, event definitions, follow-up, and statistical analysis.
11. Timing and Longitudinal Structure
Study start
The registry lists January 7, 2019 as the study start date.
Immune-response assessment
The endpoint is anchored to day 21 from baseline for the TCRB clonal-expansion measurement, with the registry specifying 42 days from the first dose of atezolizumab for Arm A and 21 days for Arm B.
Primary completion
The registry lists May 1, 2022 as the primary completion date.
Completed
The ClinicalTrials.gov record identifies the study status as completed.
12. Design Features That Affect Statistical Interpretation
Randomized parallel design
The study was randomized and parallel, so each participant was assigned to one of two study arms rather than being repeatedly assigned to both treatment strategies. This provides a direct between-group framework for the primary immune-response comparison.
Open-label treatment
Masking was listed as none. For a laboratory endpoint such as TCRB clonal expansion, the lack of masking may be less consequential than it would be for a subjective clinical assessment, but it remains a design characteristic that should be recorded when interpreting the trial as a whole.
Phase 1 context
The phase 1 designation places the study in an early clinical-development setting. Statistical interpretation should therefore emphasize estimation, biological signal characterization, uncertainty, and the relationship between the immune endpoint and later clinical-development questions rather than treating the study as equivalent to a large confirmatory efficacy trial.
No reported non-inferiority framework
The registry information does not identify a non-inferiority hypothesis or margin. The primary endpoint is an immune-response measure rather than a registry-defined non-inferiority outcome.
No reported crossover design
The registry information does not identify crossover between randomized study arms. The design is described as parallel.
No reported factorial design
The registry identifies 2 randomized parallel arms and does not describe a factorial allocation structure.
No reported Bayesian analysis
The registry information does not identify a Bayesian statistical method for the primary endpoint.
Multiplicity
The registry identifies one registered primary endpoint: immune response. No additional primary endpoints or multiplicity-adjustment strategy are identified in the information summarized here.
13. A Statistical Framework for TCRB Clonal Expansion
Total TCRB clonal expansion is a quantitative biological measurement. The first statistical task is to characterize its distribution. That includes examining central tendency, variability, and the presence of unusually large or small observations. These steps matter because immune-repertoire measurements can behave differently from approximately symmetric clinical laboratory variables.
Location
The mean or median describes the typical level of clonal expansion, depending on the distribution and prespecified analysis.
Variation
Standard deviation, interquartile range, or another dispersion measure describes how heterogeneous the measurements are within an arm.
Between-arm effect
A treatment contrast quantifies how the immune-response distributions differ between randomized groups.
Precision
A confidence interval communicates the statistical uncertainty surrounding the estimated treatment contrast.
Difference versus ratio
Two common effect scales for quantitative outcomes are a difference and a ratio. A difference preserves the original measurement scale. A ratio instead expresses one group's value relative to another group's value. Which scale is most informative depends on the biological interpretation and the prespecified statistical model.
For skewed biological measurements, a logarithmic transformation can make a ratio interpretation especially natural because differences on the log scale correspond to multiplicative differences on the original scale. The registry information does not specify that such a transformation was used.
14. Why This Trial Matters Statistically
NRG-GY017 is a useful statistical teaching case because it links randomized trial methodology to a biological endpoint that is different from the time-to-event outcomes commonly seen in oncology trials. The central challenge is not simply whether the two arms differ numerically, but how to define, measure, compare, and interpret a quantitative immune-response endpoint within a small randomized phase 1 design.
| Statistical concept | How it appears in NRG-GY017 |
|---|---|
| Randomization | Participants were randomized to 2 parallel study arms. |
| Continuous endpoint | Immune response is measured using total TCRB clonal expansion. |
| Baseline timing | The endpoint is defined around day 21 from baseline. |
| Unequal assessment windows | The registry specifies 42 days from the first atezolizumab dose for Arm A and 21 days for Arm B. |
| Laboratory measurement | TCRB clonal expansion is measured in peripheral blood using the immunoSEQ platform. |
| Small randomized sample | Total enrollment was 40 participants. |
| Safety denominator | Serious adverse events are reported as affected participants over participants at risk by arm. |
| Open-label design | Masking was listed as none. |
| Phase 1 development | The trial is registered as phase 1. |
15. Important Limitations and Interpretation Issues
- Small sample size: total enrollment was 40, so estimates of between-arm differences can be statistically imprecise.
- Laboratory endpoint: immune response is measured through TCRB clonal expansion rather than a direct clinical outcome such as survival or tumor response.
- Different timing by arm: the registry specifies different overall time frames from the first atezolizumab dose for Arm A and Arm B, which must be considered when interpreting the comparison.
- Analysis population: the registry information does not identify a separate primary-endpoint analysis population beyond the enrolled randomized study structure.
- Missing data: the registry information does not specify an imputation method for missing immune-response measurements.
- Effect measure: the registry defines the endpoint but does not identify the statistical effect measure, model, confidence-interval method, or hypothesis-test procedure used for the posted results.
- Biological versus clinical outcomes: higher TCR clonal expansion is defined as better immune response, but the endpoint itself does not establish a clinical survival or tumor-control benefit.
- Open-label design: masking was absent, although the primary endpoint is a laboratory-based measurement.
- Safety denominators: serious adverse events are reported using arm-specific at-risk denominators of 19 and 17 rather than the total enrollment of 40.
16. What a Complete Statistical Report Would Need to Show
For a quantitative primary endpoint such as total TCRB clonal expansion, a statistically complete results presentation would ideally identify the analysis population, the number of observations contributing to the endpoint, the distribution within each randomized arm, the treatment contrast, its confidence interval, and the hypothesis-testing framework if one was prespecified.
| Component | Why it matters |
|---|---|
| Analysis denominator | Defines which participants contributed to the primary endpoint analysis. |
| Arm-specific distribution | Shows the magnitude and variability of immune-response measurements. |
| Effect estimate | Quantifies the between-arm difference on the chosen statistical scale. |
| Confidence interval | Communicates precision around the estimated effect. |
| P-value, if prespecified | Addresses evidence against a specified null hypothesis; it is not a measure of effect size. |
| Analysis model | Allows readers to understand how baseline values, distributional assumptions, and other covariates were handled. |
| Missing-data handling | Shows how incomplete laboratory measurements were incorporated into the analysis. |
These elements are particularly important in a small phase 1 randomized study. A numerical difference between groups is only one part of the statistical story; the uncertainty around that difference and the population from which it was estimated are equally important.
17. Statistical Concepts in This Trial
18. Sources
- ClinicalTrials.gov: NRG-GY017 — NCT03738228.
- PubMed: PubMed record associated with NRG-GY017.
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19. Record Summary
NRG-GY017 is a completed randomized phase 1 study with 40 enrolled participants and 2 parallel, open-label arms. The registry describes atezolizumab before and/or with chemoradiotherapy in patients with node-positive cervical cancer and identifies immune response as the registered primary endpoint. That endpoint is defined through total TCRB clonal expansion in peripheral blood, measured using the immunoSEQ platform, with the registry specifying day 21 from baseline as the measurement point and different overall time frames from the first atezolizumab dose for the two arms.
Statistically, the study illustrates the distinction between a randomized comparison and the interpretation of a quantitative biological endpoint. The appropriate analysis must account for the endpoint's measurement scale, baseline values, variability, assessment timing, analysis population, and missing observations. The registry reports serious adverse events by arm as 6 of 19 participants in Arm A and 7 of 17 participants in Arm B, providing a separate safety perspective from the immune-response endpoint.