This page separates reported trial results from statistical interpretation. Numerical results are restricted to the ClinicalTrials.gov record. This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. View the official registry record.
1. Trial at a Glance
NETTER-1 was a randomized, parallel-group, open-label phase 3 treatment trial evaluating 177Lu-DOTA0-Tyr3-Octreotate against Octreotide LAR in patients with inoperable, progressive, somatostatin receptor positive midgut carcinoid tumours.
| Feature | NETTER-1 |
|---|---|
| Phase | Phase 3 |
| Condition | Carcinoid Tumor of the Small Bowel; Neuroendocrine Tumour |
| Population | Patients with inoperable, progressive, somatostatin receptor positive midgut carcinoid tumours |
| Design | Randomized, parallel-group, open-label |
| Allocation | Randomized |
| Primary endpoint | Progression Free Survival (PFS) |
| Primary endpoint type | Time-to-event |
| Primary hypothesis | Superiority |
| Enrollment | 231 |
| Lead sponsor | Advanced Accelerator Applications |
| ClinicalTrials.gov | NCT01578239 |
2. Clinical Question
The central statistical question was whether treatment with 177Lu-DOTA0-Tyr3-Octreotate differed from Octreotide LAR with respect to progression-free survival in patients with inoperable, progressive, somatostatin receptor positive midgut carcinoid tumours.
Population
Patients with inoperable, progressive, somatostatin receptor positive midgut carcinoid tumours.
Intervention
177Lu-DOTA0-Tyr3-Octreotate.
Comparator
Octreotide LAR.
Primary question
Does 177Lu-DOTA0-Tyr3-Octreotate produce a different time-to-progression-or-death experience from Octreotide LAR under a superiority hypothesis?
3. Trial Design
177Lu-DOTA0-Tyr3-Octreotate
- Drug intervention.
- Compared with Octreotide LAR.
- Included in the primary PFS comparison.
Octreotide LAR
- Drug comparator.
- Compared with 177Lu-DOTA0-Tyr3-Octreotate.
- Included in the primary PFS comparison.
4. Trial Timeline
Trial start
The registry records the start of NETTER-1 on 06 Sep 2012.
Primary completion
The registry records primary completion on 31 Jul 2015.
Registry status
the ClinicalTrials.gov record in the ClinicalTrials.gov record identifies the study status as COMPLETED.
5. Endpoints
| Endpoint | Registry definition / time frame | Type |
|---|---|---|
| Progression Free Survival (PFS) | From date of randomization until date of radiographic progression or date of death from any cause, whichever comes first until Primary Analysis cutoff date reached on 24July2015, assessed up to approximately 34 months | Time-to-event |
| Overall Survival (OS) | From date of randomization until date of death from any cause up to final safety cut-off date reached on 18Jan2021 | Time-to-event |
| Rate of Overall Survival (OS) | 12 months, 24 months, 36 months, 48 months, 60 months | Time-to-event |
| Time to Tumour Progression (TTP) | From date of randomization until date of progression or date of death from any cause, whichever comes first until Primary Analysis | Time-to-event |
| Objective Response Rate (ORR) | From date of randomization until date of progression or date of death from any cause, whichever comes first until Primary Analysis | Binary |
The ClinicalTrials.gov record identifies one registered primary endpoint: PFS. The other posted statistical analyses are secondary endpoints. This distinction matters because the primary endpoint defines the central confirmatory comparison specified in the registry, while secondary analyses provide additional evidence about survival, tumour progression, and response.
Primary endpoint definition
The registry defines PFS as the time from randomization to documented centrally assessed disease progression, as evaluated by the Independent Review Committee (IRC), or death due to any cause. If a participant had no centrally assessed progression and had not died at the time of the primary endpoint analysis, the participant was regarded as censored in the context of a time-to-event analysis.
6. Analysis Populations
| Analysis population | Role in the reported analysis |
|---|---|
| Full Analysis Set (FAS) | Used for the posted PFS, OS, OS-rate, TTP, and ORR statistical analyses. |
| ORR population qualification | For ORR, only participants with available post-baseline CT scans were considered. |
The use of the Full Analysis Set for the reported efficacy comparisons is important when interpreting the treatment effect. It anchors the main time-to-event analyses to the randomized study population represented by the FAS rather than redefining the comparison solely around participants who remained on treatment.
ORR has an additional qualification: only participants with available post-baseline CT scans were considered. That makes its analysis population conceptually different from the time-to-event analyses, even though the registry identifies the FAS as the underlying analysis population.
7. Primary Result: Progression Free Survival
PFS was the registered primary endpoint. The posted analysis compared 177Lu-DOTA0-Tyr3-Octreotate with Octreotide LAR using a log-rank test in the Full Analysis Set. The reported hazard ratio was estimated from the corresponding Cox model.
Hazard ratio for progression-free survival
95% CI: 0.108–0.289 · P < 0.0001
Hazard ratio expressed as 177Lu-DOTA0-Tyr3-Octreotate / Octreotide LAR.
| Primary endpoint | Analysis population | Method | Effect estimate | 95% CI | P-value |
|---|---|---|---|---|---|
| Progression Free Survival (PFS) | Full Analysis Set (FAS) | Log-rank test; HR estimated from corresponding Cox model | HR 0.177 | 0.108–0.289 | <0.0001 |
The reported hazard ratio of 0.177 means that, under the corresponding Cox model and with 177Lu-DOTA0-Tyr3-Octreotate as the numerator treatment, the estimated instantaneous rate of the PFS event was about 17.7% of the corresponding rate in the Octreotide LAR group. Expressed as a relative reduction in the estimated hazard, this corresponds to approximately a 82.3% lower estimated hazard.
The hazard ratio does not mean that 82.3% of patients avoided progression or death, nor does it mean that every individual patient experienced an 82.3% reduction in personal risk. A hazard ratio is a relative, model-based time-to-event measure.
The 95% confidence interval of 0.108–0.289 describes uncertainty around the estimated hazard ratio under the statistical model and sampling framework. It does not describe the range of treatment effects among individual patients.
The P-value of <0.0001 addresses the evidence against the relevant null hypothesis under the reported testing framework. It is not a measure of the size of the treatment effect. The magnitude of the effect is described by the hazard ratio, while its statistical precision is described by the confidence interval.
Because this is a Cox-model hazard ratio, its interpretation also depends on the model's assumptions, including the proportional-hazards framework. A single HR summarizes the relative event-rate experience across the analyzed time period; it is not itself a complete description of the underlying survival curves.
8. Secondary Result: Overall Survival
Overall Survival was analyzed from randomization until death from any cause up to the final safety cut-off date reached on 18Jan2021. The analysis used the Full Analysis Set and a log-rank test, with a hazard ratio as the reported effect measure.
Hazard ratio for overall survival
95% CI: 0.60–1.17 · P = 0.3039
177Lu-DOTA0-Tyr3-Octreotate vs Octreotide LAR.
| Secondary endpoint | Analysis population | Method | Effect estimate | 95% CI | P-value |
|---|---|---|---|---|---|
| Overall Survival (OS) | Full Analysis Set (FAS) | Log-rank test | HR 0.84 | 0.60–1.17 | 0.3039 |
An OS hazard ratio of 0.84 indicates an estimated hazard of death in the 177Lu-DOTA0-Tyr3-Octreotate group that was approximately 84% of that in the Octreotide LAR group under the reported Cox-model framework. In relative terms, the point estimate corresponds to approximately a 16% lower estimated hazard of death.
That point estimate should not be interpreted as a 16% reduction in the probability of death for an individual patient. Hazard ratios describe relative instantaneous event rates, not absolute survival probabilities.
The 95% CI of 0.60–1.17 is relatively broad compared with the point estimate and includes 1.00. The interval therefore communicates substantial uncertainty around the estimated relative hazard. It should be considered alongside the reported P-value of 0.3039.
The P-value does not tell us how clinically important an HR of 0.84 is. It describes the statistical evidence under the specified hypothesis-testing framework. The effect estimate and confidence interval provide the more direct information about magnitude and precision.
OS is also a downstream endpoint that can reflect the entire subsequent clinical course after randomization. The ClinicalTrials.gov record does not provide a detailed account of subsequent therapies or crossover, so those factors should not be inferred from the reported OS estimate.
9. Secondary Result: Rate of Overall Survival
The registry separately lists the Rate of Overall Survival (OS) at 12, 24, 36, 48, and 60 months as a secondary time-to-event outcome. Its posted statistical analysis uses the Full Analysis Set, a log-rank test, and a hazard ratio as the effect measure.
| Endpoint | Time points | Analysis population | Effect measure | Estimate | 95% CI | P-value |
|---|---|---|---|---|---|---|
| Rate of Overall Survival (OS) | 12, 24, 36, 48, 60 months | Full Analysis Set (FAS) | Hazard ratio | 0.84 | 0.60–1.17 | 0.3039 |
10. Secondary Result: Time to Tumour Progression
Time to Tumour Progression was analyzed from randomization until progression or death from any cause, whichever came first, until Primary Analysis. The Full Analysis Set was used, with a log-rank test and hazard ratio.
Hazard ratio for time to tumour progression
95% CI: 0.077–0.242 · P < 0.0001
177Lu-DOTA0-Tyr3-Octreotate vs Octreotide LAR.
| Secondary endpoint | Analysis population | Method | Effect estimate | 95% CI | P-value |
|---|---|---|---|---|---|
| Time to Tumour Progression (TTP) | Full Analysis Set (FAS) | Log-rank test | HR 0.137 | 0.077–0.242 | <0.0001 |
The reported HR of 0.137 means that the estimated instantaneous rate of the TTP event was about 13.7% of the corresponding rate in the Octreotide LAR group under the reported model. The point estimate therefore corresponds to approximately a 86.3% lower estimated hazard.
Again, this is not an 86.3% probability of preventing progression, and it is not a statement that every patient experiences the same relative reduction. It is a population-level model-based relative effect.
The 95% CI of 0.077–0.242 indicates the uncertainty around the HR estimate. Its location entirely below 1.00 is consistent with the reported superiority result and the P-value of <0.0001.
The P-value provides evidence concerning the statistical hypothesis being tested; it does not quantify the magnitude of the treatment effect. The HR and its confidence interval are needed to describe magnitude and precision.
Because TTP is a time-to-event endpoint, censoring and the assumptions underlying the hazard-ratio model remain relevant. The ClinicalTrials.gov record does not provide individual event and censoring histories, so no independent reconstruction of the survival function is attempted here.
11. Secondary Result: Objective Response Rate
Objective Response Rate was analyzed as a binary endpoint. The Full Analysis Set was identified as the analysis population, with the additional qualification that only participants with available post-baseline CT scans were considered. The registry reports a Fisher exact test for comparison between the two treatment groups.
Fisher exact test for objective response rate
Superiority hypothesis · Full Analysis Set, with available post-baseline CT scans considered.
| Secondary endpoint | Endpoint type | Analysis population | Method | Reported result |
|---|---|---|---|---|
| Objective Response Rate (ORR) | Binary | Full Analysis Set (FAS); only participants with available post-baseline CT scans considered | Fisher exact test | P = 0.0141 |
The Fisher exact test evaluates the evidence for a difference in the binary response distribution between the randomized treatment groups under the reported superiority framework.
The reported P-value of 0.0141 is evidence about the statistical comparison, but it is not an effect-size measure. Without reported response counts or response percentages in the ClinicalTrials.gov record, the magnitude of the difference in ORR cannot be calculated or reconstructed here.
The analysis population also deserves attention. The registry states that only participants with available post-baseline CT scans were considered. That restriction means the reported ORR analysis should not be interpreted as if every enrolled participant necessarily contributed an observed response assessment.
Fisher's exact test is particularly appropriate for a 2-by-2 categorical comparison when exact inference is desired. It does not, however, supply the missing clinical quantities by itself: response rates, an absolute risk difference, and a confidence interval would be needed to describe the size and precision of the response difference.
12. Statistical Methodology
Log-rank test
The registry identifies the log-rank test as the reported method for the PFS, OS, OS-rate, and TTP analyses. The log-rank framework compares the experience of two groups across event times rather than reducing a time-to-event endpoint to a single fixed follow-up point.
The test uses information from observed event times while allowing participants who have not experienced the event at their last assessment to contribute information through censoring.
Hazard ratio
The registry reports a hazard ratio for the time-to-event comparisons. For PFS, the analysis notes explicitly state that the HR is expressed as 177Lu-DOTA0-Tyr3-Octreotate / Octreotide LAR and is estimated from the corresponding Cox model.
An HR below 1 indicates a lower estimated instantaneous event rate in the numerator group under the fitted model. An HR above 1 indicates a higher estimated instantaneous event rate.
Fisher exact test
ORR was treated as a binary endpoint and analyzed using Fisher's exact test. Rather than relying on a large-sample approximation, Fisher's test evaluates the observed 2-by-2 treatment-by-response table under an exact framework.
Intention-to-treat analysis
The statistical-analysis records identify intention-to-treat analysis as an associated concept for the posted analyses, while the analysis population is specifically listed as the Full Analysis Set. The key principle is that randomized treatment assignment remains the basis for the primary treatment comparison rather than selectively redefining treatment groups according to outcomes observed after randomization.
Censoring in time-to-event analysis
The PFS definition explicitly describes censoring for participants who had no centrally assessed progression and had not died at the time of the primary endpoint analysis. Censoring allows such participants to contribute follow-up information without treating the absence of an observed event as if it were an observed event-free lifetime.
13. Statistical Methods Explained
Why was a log-rank test used for PFS?
PFS is a time-to-event endpoint. Some participants experience progression or death during follow-up, while others may remain without the event when their observation ends. A log-rank test is designed for comparing two groups while incorporating the timing of events and right-censored observations. It therefore matches the structure of the registered PFS endpoint better than a simple comparison of proportions at one arbitrary time point.
What does an HR of 0.177 mean?
The PFS HR of 0.177 is a relative measure of the estimated event rate, with 177Lu-DOTA0-Tyr3-Octreotate in the numerator. Under the reported Cox model, the estimated instantaneous PFS-event rate was approximately 17.7% of the corresponding rate in the Octreotide LAR group. It does not mean that exactly 17.7% of participants progressed, nor that each patient experienced the same relative reduction.
Why is the confidence interval important?
A point estimate such as HR 0.177 is only one estimate from the observed trial data. The 95% CI of 0.108–0.289 gives a range describing statistical uncertainty around that estimate under the model and sampling framework. A confidence interval is therefore essential for understanding precision; the P-value alone cannot provide that information.
Why does the P-value not measure effect size?
The P-value addresses how compatible the observed data are with a specified null hypothesis under the testing framework. It does not directly state how large the treatment difference is. For example, P < 0.0001 accompanies the PFS HR of 0.177, but the effect size is conveyed by the HR and its confidence interval, not by the P-value.
Why was Fisher's exact test used for ORR?
ORR is a binary endpoint: participants are classified according to whether they meet the response definition. Fisher's exact test provides an exact comparison of the resulting categorical data between the treatment groups.
Why does the open-label design matter?
The registry identifies the trial as having no masking. Knowledge of treatment assignment can potentially influence subjective aspects of treatment delivery, follow-up, or assessment. For PFS, the registry definition specifies centrally assessed progression evaluated by an Independent Review Committee, which provides an important methodological safeguard, although the ClinicalTrials.gov record does not quantify the effect of the open-label design.
Why is the analysis population important?
The posted analyses use the Full Analysis Set. This matters because changing the analysis population can change the treatment comparison. ORR has an additional restriction to participants with available post-baseline CT scans, so its result should not be interpreted as though it necessarily represents an observed response assessment for every participant in the overall enrollment.
14. Safety Results
The ClinicalTrials.gov record reports serious adverse events by treatment arm. These are reported as affected participants over participants at risk.
| Safety measure | 177Lu-DOTA0-Tyr3-Octreotate | Octreotide LAR |
|---|---|---|
| Serious adverse events | 40/111 | 31/112 |
The denominators are important: the registry reports 40 of 111 for 177Lu-DOTA0-Tyr3-Octreotate and 31 of 112 for Octreotide LAR. These figures should not be replaced with a newly calculated percentage when the instruction for this page is to preserve reported numbers exactly.
15. Primary Endpoint Statistical Story
Endpoint
PFS was the single registered primary endpoint and was defined as time from randomization to radiographic progression or death from any cause, whichever came first.
Population
The reported primary analysis used the Full Analysis Set.
Test
The registry reports a log-rank test for the primary comparison.
Effect measure
The reported HR was 0.177, with a two-sided 95% CI of 0.108–0.289 and P < 0.0001.
This structure illustrates an important distinction in clinical-trial statistics: the test and the effect measure answer different questions. The log-rank test addresses evidence for a difference in time-to-event experience, while the hazard ratio describes the estimated relative event rate. The confidence interval then quantifies uncertainty around that effect estimate.
16. Comparing the Reported Time-to-Event Effects
| Endpoint | Role | HR | 95% CI | P-value | Method |
|---|---|---|---|---|---|
| Progression Free Survival | Primary | 0.177 | 0.108–0.289 | <0.0001 | Log-rank; Cox HR |
| Overall Survival | Secondary | 0.84 | 0.60–1.17 | 0.3039 | Log-rank |
| Rate of Overall Survival | Secondary | 0.84 | 0.60–1.17 | 0.3039 | Log-rank |
| Time to Tumour Progression | Secondary | 0.137 | 0.077–0.242 | <0.0001 | Log-rank |
The table demonstrates why endpoint definitions matter. PFS and TTP both concern disease progression within a time-to-event framework, while OS concerns death from any cause. Their hazard ratios should therefore not be treated as interchangeable measures of the same outcome.
17. Multiplicity and Hypothesis Testing
The ClinicalTrials.gov record identifies one primary endpoint and multiple secondary endpoint analyses. The primary hypothesis type is superiority. The ClinicalTrials.gov record does not provide an alpha-allocation scheme, multiplicity-adjustment procedure, sequential-testing hierarchy, or interim-analysis plan.
| Analysis | Registry role | Reported testing framework |
|---|---|---|
| Progression Free Survival | Primary endpoint | Superiority; log-rank test |
| Overall Survival | Secondary endpoint | Superiority; log-rank test |
| Rate of Overall Survival | Secondary endpoint | Superiority; log-rank test |
| Time to Tumour Progression | Secondary endpoint | Superiority; log-rank test |
| Objective Response Rate | Secondary endpoint | Superiority; Fisher exact test |
Because the ClinicalTrials.gov record does not state how type I error was allocated across endpoints or whether any formal multiplicity adjustment was used, the secondary P-values should not be assigned an error-control procedure that is not documented in the ClinicalTrials.gov record.
18. What the PFS Hazard Ratio Does — and Does Not — Mean
The PFS HR of 0.177 means that the estimated instantaneous rate of the PFS event under the corresponding Cox model was approximately 17.7% of the rate in the Octreotide LAR group.
It does not mean that 17.7% of participants progressed, that 82.3% of participants were progression-free, or that each individual patient experienced an identical 82.3% reduction in risk.
The 95% CI of 0.108–0.289 describes uncertainty around the HR estimate. It does not describe a range of individual patient outcomes.
The reported P < 0.0001 indicates strong statistical evidence under the specified superiority testing framework. It is not itself a measure of effect magnitude or clinical importance.
19. Limitations
- Registry-level information: this analysis is constrained to the ClinicalTrials.gov record. It does not add unreported baseline characteristics, event counts, medians, subgroup results, or other numerical outcomes.
- Open-label design: the registry identifies no masking, so treatment assignment was not concealed from participants and investigators. The primary PFS definition nevertheless specifies centrally assessed progression evaluated by an Independent Review Committee.
- Hazard-ratio assumptions: Cox-model HRs are model-based and should not be treated as complete descriptions of survival distributions. Their usual interpretation relies on an appropriate proportional-hazards framework.
- Missing individual-level information: individual event and censoring times are not provided, so independent Kaplan-Meier reconstruction is not possible from the ClinicalTrials.gov record.
- ORR analysis population: only participants with available post-baseline CT scans were considered for the posted ORR analysis. The ClinicalTrials.gov record does not provide the corresponding response counts.
- Secondary-endpoint multiplicity: the ClinicalTrials.gov record does not specify an alpha-allocation or multiplicity-adjustment procedure across the secondary analyses.
- Safety detail: serious adverse events are reported by affected participants and participants at risk, but the ClinicalTrials.gov record does not provide event-level descriptions or statistical comparisons.
- Endpoint distinctions: PFS, TTP, OS, and OS rate represent different clinical quantities and should not be treated as interchangeable measures.
20. Why This Trial Matters Statistically
NETTER-1 is a useful teaching case because it connects randomization, time-to-event endpoints, censoring, log-rank testing, Cox-model hazard ratios, exact categorical testing, and analysis-population definitions within one phase 3 comparison.
| Concept | How it appears in NETTER-1 |
|---|---|
| Randomization | The study is classified as randomized with a parallel design. |
| Time-to-event analysis | PFS is the registered primary endpoint; OS and TTP are also time-to-event endpoints. |
| Log-rank test | Reported for PFS, OS, OS rate, and TTP. |
| Hazard ratio | Used to quantify the relative time-to-event effect for the posted survival analyses. |
| Confidence interval | Reported for the PFS, OS, OS-rate, and TTP hazard ratios. |
| Fisher exact test | Used for the binary ORR comparison. |
| Full Analysis Set | Used for the posted statistical analyses. |
| Intention-to-treat principle | Identified as an associated analysis concept in the posted analyses. |
| Censoring | Explicitly incorporated into the PFS definition for participants without a documented progression or death at the primary endpoint analysis. |
| Open-label design | The registry reports no masking. |
| Endpoint hierarchy | One primary PFS endpoint is distinguished from multiple secondary endpoints. |
The strongest statistical lesson is that a clinical trial result is not adequately summarized by a single P-value. The PFS analysis combines a prespecified endpoint, a defined event process, a randomized comparison, a log-rank test, a model-based hazard ratio, and a confidence interval. Each component answers a different part of the statistical question.
21. Interpreting the Five Posted Statistical Analyses Together
PFS
The primary analysis reports HR 0.177 (95% CI 0.108–0.289; P < 0.0001), providing the central time-to-event result of the trial.
OS
The secondary OS analysis reports HR 0.84 (95% CI 0.60–1.17; P = 0.3039).
TTP
The secondary TTP analysis reports HR 0.137 (95% CI 0.077–0.242; P < 0.0001).
ORR
The secondary binary endpoint analysis reports Fisher exact P = 0.0141, without response counts in the ClinicalTrials.gov record.
These results illustrate why statistical interpretation should preserve endpoint-specific context. The PFS and TTP estimates are hazard ratios for time-to-event outcomes. ORR is a binary outcome analyzed with Fisher's exact test. OS is another time-to-event outcome but has a different event definition. The numbers therefore describe different dimensions of treatment effect rather than repeated measurements of one quantity.
22. Related Tutorials
Learn more about the methods used in this trial:
23. Related Statistical Calculators
24. Sources
- ClinicalTrials.gov: NCT01578239 — NETTER-1.
- PubMed: PMID 34793718.
- PubMed: PMID 32123969.
- PubMed: PMID 29878866.
- PubMed: PMID 28076709.
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25. Record Summary
NETTER-1 provides a compact example of how a randomized phase 3 clinical trial can generate several complementary statistical analyses. The registered primary endpoint was PFS, a time-to-event outcome analyzed with a log-rank test and expressed through a Cox-model hazard ratio of 0.177 with a two-sided 95% confidence interval of 0.108–0.289 and P < 0.0001. Secondary analyses included OS, rate of OS, TTP, and ORR, with the latter evaluated using Fisher's exact test.
The most important statistical distinction is between evidence of a difference and magnitude of an effect. Log-rank and Fisher exact tests provide hypothesis-test results, while hazard ratios and their confidence intervals describe the estimated relative effect and its precision. For ORR, the ClinicalTrials.gov record provides the Fisher exact P-value but not the response counts, so no response-rate difference is inferred.
The trial also illustrates why endpoint definitions and analysis populations matter. PFS incorporates radiographic progression or death and specifies censoring for participants without an event at the primary analysis. OS measures death from any cause. TTP is another progression-related time-to-event endpoint. ORR is binary and is restricted to participants with available post-baseline CT scans in the posted analysis. Treating these endpoints as interchangeable would obscure the statistical questions each one addresses.