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 De-Escalation Radiotherapy in Patients With Low-Risk HPV-Related Oropharyngeal Squamous Cell Carcinoma (NCT03822897), a na phase 2 study. The primary outcome is Event-free Survival.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03822897 |
| Phase | Phase 2 |
| Condition | Oropharyngeal Cancer |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 103 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Canadian Cancer Trials Group |
| Results posted | Yes |
2. Clinical Question
Population
The trial concerns patients with low-risk HPV-related oropharyngeal squamous cell carcinoma. The registry lists oropharyngeal cancer as the condition. It does not give further eligibility details or describe the population used in an outcome analysis, so details such as the precise clinical criteria defining low risk are not reported in the registry record.
Intervention
The treatment strategy is elective volume-adjusted de-escalation radiotherapy. The registry lists radiation and cisplatin as interventions. The experimental arm description says patients receive one of two treatment options at the treating physician’s discretion, and that both options are treated as part of a unified strategy. The available description does not fully specify those options.
Comparator
There is no randomized comparator arm. This is a non-randomized, single-arm study, with allocation listed as NA and masking listed as none. As a result, the design does not provide a concurrent control group for a like-for-like comparison. The registry’s own note cautions that its arms are not a randomized comparison.
Primary question
The primary outcome asks what proportion of patients remain event-free at 2 years under the trial’s treatment strategy. An event is defined as progression, surgery, non-protocol treatment for the current cancer without documentation of the site of failure, or death from any cause. The registry record states the outcome definition but does not report an observed event-free proportion or its confidence interval.
3. Trial Design
This is a phase II, single-group study of elective volume-adjusted de-escalation radiotherapy in patients with low-risk HPV-related oropharyngeal squamous cell carcinoma. The registry lists the allocation as NA, identifies the model as single group, and records no masking. The sponsor is the Canadian Cancer Trials Group. The listed enrollment is 103.
The experimental arm description characterizes the study as non-randomized. Patients receive one of two treatment options according to treating physician discretion; both options are considered part of a unified treatment strategy and analyzed as a single arm. The description includes only a partial account of the treatment options, so their details are not reported in the registry record. Radiation and cisplatin are listed as interventions.
Because there is no randomized control arm, the study is not designed to estimate a randomized treatment contrast. Its primary outcome is event-free survival, reported as the proportion of patients who remain event-free at 2 years. Secondary outcomes listed in the registry are overall survival, local-regional control, out-of-field regional control, and distant metastasis-free survival. The record lists five outcome measures, but no outcome analyses.
The registry lists the study start as 2019-06-28 and primary completion as 2024-06-25. Its status is active, not recruiting. These administrative details do not establish that the primary analysis has been completed or that results are available. The registry record does not report a detailed protocol, a sample-size justification, an interim analysis plan, or the statistical analysis plan. Those features should not be inferred from the phase or design label.
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 | Experimental Arm |
|---|---|
| STARTED | 103 |
| COMPLETED | 100 |
| NOT COMPLETED | 3 |
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 | Experimental Arm |
|---|---|---|
| Participants analysed | 103 | |
| Age, Continuous | years | 62.8 (56 to 70) |
| Sex: Female, Male: Female | Participants | 18 |
| Sex: Female, Male: Male | Participants | 85 |
| Race and Ethnicity Not Collected | Participants | — |
| ECOG Performance Status: 0 | Participants | 82 |
| ECOG Performance Status: 1 | Participants | 21 |
6. Primary Endpoint
The registry lists the primary outcome as Event-free Survival, measured over 2 years.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | Percentage of patients event-free at 2y |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is event-free survival, expressed as the percentage of patients who remain event-free at 2 years. The event-free interval begins at registration and ends at the first recorded qualifying event. The listed events are progression, surgery, non-protocol radiotherapy, chemotherapy, or biologic therapy for the current cancer diagnosis without documentation of the site of failure, and death from any cause.
This composite endpoint combines events that can indicate disease progression or a change from the planned treatment strategy. Including death from any cause also means that the endpoint is not limited to cancer-related events. The registry’s definition therefore matters when interpreting what an event-free proportion would represent: it summarizes remaining free from any of the specified events, rather than measuring only tumour recurrence or survival.
A proportion at a fixed time point can communicate the share of the analyzed population who have not experienced a qualifying event by that time. A confidence interval, if reported, would describe the statistical uncertainty around that estimate. The registry record gives the endpoint definition and timeframe but does not report the observed proportion, confidence interval, number of events, or analysis population. The extent to which follow-up was complete for this endpoint is also not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The record identifies a clinically defined treatment strategy and a fixed-time primary outcome, but it does not report the primary outcome result. There is therefore no registry-based event-free percentage or confidence interval to interpret. The endpoint description tells readers what would count as an event; it does not establish how often events occurred or how precisely the outcome was estimated.
The single-arm design also limits what an outcome proportion could establish. A proportion observed after treatment would describe outcomes among the analyzed trial participants. Without a randomized comparison group, it would not by itself quantify how outcomes would differ under another treatment strategy. Differences in patient selection, clinical characteristics, follow-up, or other aspects of care could affect comparisons made with results from other studies. Such external comparisons are not equivalent to randomization.
The two physician-selected treatment options are analyzed as one treatment strategy in the registry description. Accordingly, the design does not set out a randomized comparison between those options. The record does not report how many patients received each option or provide option-specific outcome analyses. It would be inappropriate to infer comparative outcomes between the options from this description.
The registry lists 103 as enrollment and gives the study status as active, not recruiting. These registry entries do not supply the number included in a primary endpoint analysis, the amount of follow-up available, or the handling of participants whose outcome status is unknown. The outcome population and missing-data procedures are not reported in the registry record. An enrollment figure should not be treated as the denominator for an endpoint estimate unless the analysis explicitly establishes that relationship.
Safety information is recorded separately from the efficacy endpoint. The serious adverse event summary lists 8 affected among 100 at risk, and names dehydration, nausea, vomiting, oropharyngeal pain, dysphagia, and other gastrointestinal disorders among the leading serious terms with percentages. The record also lists 6 deaths. These safety figures do not supply the missing event-free survival estimate, and the registry does not establish from these summaries whether an adverse event caused a death or was attributed to treatment.
Any planning illustrations should be interpreted as calculations under stated assumptions, not as evidence that the trial had a particular probability of detecting an effect. The planning description refers to a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Those are illustration assumptions, not the design of this single-arm trial. The registry record does not report the trial’s own sample-size justification or power calculation.
9. Statistical Methods Explained
What does a confidence interval communicate?
A confidence interval expresses uncertainty around an estimate. For a fixed-time event-free proportion, the interval would indicate the range of values compatible with the data under the method used to calculate it. A narrower interval generally indicates greater precision, while a wider interval indicates less precision. The interval does not remove limitations in the study design, and it does not make a single-arm estimate a comparison with an alternative treatment.
The registry names a 95% confidence interval as the dispersion measure for the primary outcome, but it does not report the estimate or interval. Consequently, the precision of the primary outcome cannot be assessed from the registry record. The method used to construct the interval is also not reported there. Different methods can behave differently, particularly when event counts or the number remaining under observation are limited, so a numerical interval should be read together with its analysis method and denominator.
What does the event-free endpoint represent?
Event-free survival is a time-to-event concept: it accounts for when a qualifying event occurs after registration, rather than treating all follow-up as if it ended at the same time. The registry describes its reported measure as the proportion event-free at 2 years. To interpret that proportion, readers would need to know how participants with incomplete follow-up were handled and how the estimate was obtained. Those details are not reported in the registry record.
In general, a time-to-event analysis can retain information from participants followed for different lengths of time by accounting for censoring. Censoring occurs when a participant’s event status is no longer observed before the event of interest is recorded. Valid interpretation depends on the analysis method and assumptions about why follow-up ends. The registry’s endpoint definition does not report censoring rules, follow-up completeness, or any assumptions used in an analysis.
The composite definition also requires attention. Progression, surgery, certain non-protocol treatment, and death are not identical clinical events. A combined endpoint counts the first qualifying event under the stated definition, so the overall measure does not show the separate contribution of each event type. The registry does not report component-specific results for the primary endpoint.
Why does the single-arm design matter?
In general, randomization helps make groups comparable on average, including for factors that are not fully measured. This study is described as non-randomized and single-arm, so it does not make that kind of concurrent comparison. Its outcome results, if reported, could describe what happened in the studied group, but attributing a difference in outcome to the treatment strategy would require a suitable comparison and careful consideration of other explanations.
The physician’s discretion in choosing between treatment options adds another reason not to interpret the options as a direct comparison. Treatment selection may reflect clinical circumstances, but the registry record does not describe the basis for those decisions or report option-specific analyses. The two options are instead presented as components of a unified strategy.
How should planning calculations be read?
General sample-size calculations depend on assumptions about the target effect, variability, significance level, allocation, and analysis method. The planning description in the registry refers to a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It states that the effect to detect is a stated fraction of the observed effect. These are planning assumptions, not observed trial outcomes or evidence about the design that was actually used.
The stated allocation assumption between two arms does not describe this trial’s single-arm design. Any calculated sample sizes based on those assumptions are planning illustrations. They are not observed power and do not show that the study could or could not detect a clinically meaningful difference. The trial’s own sample-size justification and statistical plan are not reported in the registry record.
For general context, over-dispersion occurs when observed variability is greater than a model assumes. When present, it can make standard errors too small and confidence intervals too narrow if the model does not account for it. Whether over-dispersion is relevant depends on the outcome and analysis model. The registry record does not specify a model for the primary outcome, so no claim about over-dispersion in this trial can be made.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists five outcome measures: event-free survival as the primary outcome, along with overall survival, local-regional control, out-of-field regional control, and distant metastasis-free survival as secondary outcomes. It records zero analyses. Thus, outcome definitions are present, but analysis results are not reported in the registry record.
In general, testing or emphasizing multiple outcomes can increase the chance of at least one apparently notable result arising by chance. A prespecified hierarchy, adjustment method, or clear distinction between primary and secondary outcomes can help readers understand how multiple results are interpreted. The registry record does not report a multiplicity strategy, an analysis hierarchy beyond identifying the primary outcome, or whether any adjustment was planned. No correction method should be assumed.
The record also does not report missing-data methods, censoring rules, or the amount of missing outcome information. It does not identify the population used for an analysis, such as which enrolled participants would be included or how departures from the planned treatment strategy would be handled. These details are important because the analyzed population and handling of incomplete follow-up can affect outcome estimates. Their absence in the registry record means the analysis population and missing-data approach cannot be evaluated.
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 |
|---|---|---|---|
| Experimental Arm | 8 | 100 | 8.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Experimental Arm | 6 of 100 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Experimental Arm | 100 of 100 |
Most frequent serious adverse event terms
| Event term | Organ system | Experimental Arm |
|---|---|---|
| Dehydration | Metabolism and nutrition disorders | 3 of 100 |
| Nausea | Gastrointestinal disorders | 2 of 100 |
| Vomiting | Gastrointestinal disorders | 2 of 100 |
| Oropharyngeal pain | Respiratory, thoracic and mediastinal disorders | 2 of 100 |
| Dysphagia | Gastrointestinal disorders | 1 of 100 |
| Other gastrointestinal disorders | Gastrointestinal disorders | 1 of 100 |
| Lung infection | Infections and infestations | 1 of 100 |
| Sepsis | Infections and infestations | 1 of 100 |
| Acute kidney injury | Renal and urinary disorders | 1 of 100 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Experimental Arm |
|---|---|---|
| Dry mouth | GASTROINTESTINAL DISORDERS | 94 of 100 |
| Dysgeusia | NERVOUS SYSTEM DISORDERS | 86 of 100 |
| Mucositis oral | GASTROINTESTINAL DISORDERS | 82 of 100 |
| Dermatitis radiation | INJURY, POISONING AND PROCEDURAL COMPLICATIONS | 78 of 100 |
| Fatigue | GENERAL DISORDERS AND ADMINISTRATION SITE CONDITIONS | 52 of 100 |
| Dysphagia | GASTROINTESTINAL DISORDERS | 49 of 100 |
| Constipation | GASTROINTESTINAL DISORDERS | 39 of 100 |
| Nausea | GASTROINTESTINAL DISORDERS | 36 of 100 |
| Other gastrointestinal disorders | GASTROINTESTINAL DISORDERS | 34 of 100 |
| Weight loss | INVESTIGATIONS | 34 of 100 |
Serious events with the highest arm-level rate: dehydration (3.0%), nausea (2.0%), vomiting (2.0%), oropharyngeal pain (2.0%), dysphagia (1.0%).
The serious adverse event summary lists an experimental arm with 100 participants at risk and 8 affected. The leading serious adverse event terms are dehydration (3.0%), nausea (2.0%), vomiting (2.0%), oropharyngeal pain (2.0%), dysphagia (1.0%), and other gastrointestinal disorders (1.0%). The registry also lists 6 deaths.
These figures are descriptive safety information. They do not show whether an event was caused by treatment, how long participants were observed, whether a participant could contribute more than one event, or how events were collected. Those details are not reported in the registry record. The listed term percentages should not be interpreted as comparative risks because this trial has no randomized control group.
The death count appears in the adverse event summary, but the record does not state that these deaths were caused by treatment or identify their relationship to the primary endpoint. Nor does the summary establish whether deaths and the listed serious terms overlap. The serious adverse event figures should therefore be read as reported counts and percentages, not as proof of causation or as a substitute for the missing efficacy analysis.
12. What the Result Does, and Does Not, Mean
The registry record defines a study of a de-escalation radiotherapy strategy and identifies event-free survival at 2 years as its primary outcome. It also describes a physician-selected choice between treatment options that are analyzed together as a single arm. These features allow readers to understand the broad clinical question and how the primary outcome was defined.
The record does not report an event-free survival estimate, its confidence interval, or results for the secondary outcomes. It therefore does not establish the observed frequency of events in the trial population or the precision of any efficacy estimate. The listed enrollment of 103 does not fill that gap: the registry does not report the analysis denominator or endpoint results.
Even if an outcome proportion were available, this single-arm design would describe outcomes in the treated group rather than establish a causal difference from another treatment. There is no randomized comparison, and the registry’s physician-discretion treatment selection is not a basis for comparing the options. The study cannot be interpreted as having demonstrated that the strategy is better, worse, equivalent, or non-inferior to another approach on the basis of this record.
The safety summary provides counts and percentages for serious adverse events and lists deaths, but it does not provide a randomized safety comparison or establish treatment causation. The absence of a registry analysis also means readers cannot use the listed adverse event data to infer the balance between benefits and harms from trial results.
Planning calculations are a separate matter from observed outcomes. Any sample-size illustrations based on assumed effects are not trial results and are not observed power. The registry record does not report the trial’s own design justification, detailed analysis methods, missing-data procedures, or multiplicity approach. Those omissions limit assessment of how any eventual results were planned and analyzed.
13. Why This Trial Matters Statistically
This trial raises a statistical question about how to summarize a treatment strategy when the central aim is to assess a fixed-time outcome in a single group. Event-free survival at 2 years gives a defined target measure, while the composite endpoint makes the exact event definition central to interpretation. The listed events include progression, surgery, certain non-protocol treatment, and death from any cause, so the outcome represents more than tumour recurrence alone.
The design also illustrates the distinction between describing outcomes and estimating comparative effects. A single-arm result can characterize the experience of the analyzed participants, but it does not create a randomized counterfactual. Reader confidence in interpretation therefore depends on the outcome estimate, its precision, follow-up completeness, and any external context, none of which can replace a concurrent randomized comparison.
The physician-selected treatment options underscore why treatment strategy and treatment component are different questions. The registry treats the options as one strategy and does not report option-specific results. That framing can be appropriate to the stated single-arm design, but it does not provide evidence about the relative outcomes of the options.
Finally, the record highlights the distinction between trial conduct, outcome definitions, and statistical results. It contains design and endpoint information, along with safety summaries, but lists no analyses. Without reported estimates and analytic details, neither the magnitude nor the precision of the primary outcome can be assessed from the registry record.
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.
The main limitation for statistical interpretation is the absence of posted outcome analyses. The registry defines event-free survival and lists secondary outcomes, but does not report their estimates, confidence intervals, event counts, or analysis populations. Consequently, the primary outcome’s magnitude and precision cannot be evaluated.
The non-randomized, single-arm design does not provide a concurrent control for estimating a treatment contrast. In addition, the treating physician chooses between two options that are grouped into one strategy. The registry does not report the number receiving each option, the decision criteria, or option-specific outcomes. The design therefore does not support a direct comparison of the options.
The primary endpoint combines multiple kinds of events, but the record does not report results by event component. It also does not describe the analysis method, censoring, follow-up completeness, or handling of missing outcomes. These omissions make it difficult to assess how the stated 2-year proportion would be estimated and how sensitive it might be to incomplete observation.
The record lists enrollment as 103 and status as active, not recruiting, but does not state how many participants contribute to a primary endpoint analysis or whether the planned follow-up is complete. It does not report the trial’s own sample-size justification, interim analysis plan, or detailed statistical plan. Safety summaries do not include enough information to establish event attribution or comparative risk. Each of these limitations concerns information not reported in the registry record, rather than proof that the underlying study did not collect it.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: De-Escalation Radiotherapy in Patients With Low-Risk HPV-Related Oropharyngeal Squamous Cell Carcinoma — NCT03822897.
- Registry record last updated 2026-11-04; status last verified 2026-11.
- Results first posted 2025-09-30.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT03822897 is a phase II, non-randomized, single-arm study sponsored by the Canadian Cancer Trials Group. It evaluates elective volume-adjusted de-escalation radiotherapy in patients with low-risk HPV-related oropharyngeal squamous cell carcinoma. The registry lists radiation and cisplatin as interventions, and describes physician discretion between two treatment options analyzed as one strategy.
The primary outcome is the percentage of patients event-free at 2 years, with events defined to include progression, surgery, certain non-protocol treatment, or death from any cause. Secondary outcomes include overall survival, local-regional control, out-of-field regional control, and distant metastasis-free survival. The listed enrollment is 103; the status is active, not recruiting. The record lists safety summaries but no outcome analyses. Primary results and detailed statistical methods are not reported in the registry record.