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 Testing the PD-1 Inhibitor Pembrolizumab as Maintenance Therapy After Initial Chemotherapy in Metastatic Bladder Cancer (NCT02500121), a randomized phase 2 study. The primary outcome is Progression-free Survival (PFS).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02500121 |
| Phase | Phase 2 |
| Condition | Urothelial Carcinoma, Bladder Cancer |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 108 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Matthew Galsky |
| Results posted | Yes |
2. Clinical Question
Population
The trial enrolled patients with metastatic urothelial cancer who had achieved at least stable disease after first-line chemotherapy. The primary endpoint description concerns patients randomized in this setting. The results therefore address this selected post-chemotherapy population, not all people with urothelial or bladder cancer. The registry record reports enrollment of 108 participants. One participant assigned to placebo was excluded from the primary analysis because the participant received pembrolizumab rather than placebo during the initial several cycles.
Intervention
The experimental strategy was maintenance pembrolizumab, described as 200mg intravenously every 3 weeks. Treatment could continue for up to 24 months in the absence of prohibitive toxicities or disease progression. This was maintenance treatment following initial chemotherapy, rather than a comparison of pembrolizumab with chemotherapy as first-line treatment.
Comparator
The control strategy was placebo using commercially available normal saline, with no active placebo drug mixed into the saline. The registry describes treatment in both arms as continuing, absent prohibitive toxicities or disease progression, for up to 24 months. The trial used a randomized, parallel-group design and is described as double-blinded; the masking field also labels it quadruple-masked.
Primary question
The primary endpoint was progression-free survival, measured from randomization until death or disease progression, whichever occurred first, using immune-related RECIST. The statistical question is whether the observed time-to-event experience differed between the maintenance pembrolizumab and placebo groups. The posted primary results give median progression-free survival and 95% confidence intervals for each arm, but the registry record does not report a comparative hazard ratio or a sponsor-reported test for this endpoint. The medians describe each group; by themselves, they do not quantify the uncertainty in an arm-to-arm effect estimate.
3. Trial Design
This was a randomized, parallel-group phase II study of maintenance pembrolizumab versus placebo after first-line chemotherapy in patients with metastatic urothelial cancer. Participants had to have achieved at least stable disease on their initial chemotherapy to enter the maintenance comparison. The registry record reports enrollment of 108 participants and a completed study. Its masking information describes the trial as double-blinded and also records quadruple masking, without specifying which roles were included in that label.
Participants were assigned to placebo or pembrolizumab. The experimental arm received pembrolizumab 200mg intravenously every 3 weeks. The control arm received normal saline as placebo, without an active drug mixed into it. In either arm, study treatment was to continue for up to 24 months unless disease progression or prohibitive toxicity intervened. These details define the treatment strategies being compared; they do not establish how treatment was actually continued for each participant.
The primary outcome was progression-free survival, assessed after a median follow-up time of 12.9 months. Its analysis included 52 participants in the placebo arm and 55 in the pembrolizumab arm. The registry explains that one participant randomized to placebo was excluded because pembrolizumab was received instead of placebo during the initial several cycles. The posted results therefore do not use all 108 enrolled participants in the primary endpoint analysis, and the stated reason for that exclusion should be kept in view when interpreting the estimates.
The registry lists secondary outcomes covering six-month progression-free survival, safety and tolerability, objective response, response after progression on placebo, and median overall survival. A detailed comparative analysis is not reported for these outcomes in the registry record. The study is phase II, but its sample-size justification, planned statistical analyses, and any interim-analysis procedures are not reported in the registry record. They should not be inferred from the enrollment total or from the observed endpoint results.
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 | Control Arm A | Experimental Arm B |
|---|---|---|
| STARTED | 53 | 55 |
| Crossover to Pembrolizumab | 27 | 0 |
| COMPLETED | 26 | 29 |
| NOT COMPLETED | 27 | 26 |
Reasons for not completing this period:
| Reason | Control Arm A | Experimental Arm B |
|---|---|---|
| Lost to Follow-up | 0 | 1 |
| Withdrawal by Subject | 1 | 1 |
| Death | 26 | 24 |
Analysis population for the primary outcome, as defined in the registry: One patient randomly assigned to placebo was excluded from the analysis because of inconsistent receipt of pembrolizumab rather than placebo during the initial several cycles of study treatment.
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.
Population: One patient randomly assigned to placebo was excluded from the analysis because of inconsistent receipt of pembrolizumab rather than placebo during the initial several cycles of study treatment.
| Characteristic | Unit | Control Arm A | Experimental Arm B | Total |
|---|---|---|---|---|
| Participants analysed | 52 | 55 | 107 | |
| Age, Continuous | years | 65 (44 to 87) | 68 (41 to 83) | 66 (41 to 87) |
| Sex: Female, Male: Female | Participants | 10 | 16 | 26 |
| Sex: Female, Male: Male | Participants | 42 | 39 | 81 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 2 | 0 | 2 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 3 | 4 | 7 |
| Race (NIH/OMB): White | Participants | 46 | 50 | 96 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 1 | 1 | 2 |
| Region of Enrollment: United States | participants | 52 | 55 | 107 |
| Presence of Visceral Metastatic Disease at time of Initiation of First Line Chemotherapy | Participants | 32 | 39 | 71 |
| ECOG Performance Score: ECOG 0 | Participants | 23 | 22 | 45 |
| ECOG Performance Score: ECOG 1 | Participants | 29 | 33 | 62 |
| Cycles of First-Line Chemotherapy | cycles | 6 (4 to 6) | 6 (4 to 6) | 6 (4 to 6) |
| Best Response to First Line Chemotherapy: Complete Response/Partial Response | Participants | 36 | 40 | 76 |
| Best Response to First Line Chemotherapy: Stable Disease | Participants | 16 | 15 | 31 |
| Cisplatin based First Line Chemotherapy | Participants | 40 | 40 | 80 |
6. Primary Endpoint
The registry lists the primary outcome as Progression-free Survival (PFS), measured over Calculated after a median follow-up time of 12.9 months.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | 95% Confidence Interval |
| Unit | months |
| Endpoint classification | Time-to-Event Analysis |
Progression-free survival measures the time from randomization until the first of two events: disease progression or death. The trial assessed progression using immune-related RECIST, with progression defined using RECIST v1.0 criteria. The description includes a 20% increase in the sum of the longest diameters of target lesions, a measurable increase in a non-target lesion, or the appearance of new lesions. The endpoint therefore combines radiographic disease change and death into a time-to-event outcome.
General statistical context: time-to-event endpoints are useful when the timing of an event matters and participants may have different lengths of follow-up. A median time-to-event value is the point by which half of the endpoint distribution has experienced the event, under the analysis method used. It is not the average duration of benefit, nor does it describe every participant's course. The registry reports median progression-free survival and 95% confidence intervals for each arm, but does not report a comparative hazard ratio or a sponsor-reported statistical test for the primary endpoint.
The endpoint is clinically and statistically distinct from response rate. A participant can have disease control without a response that meets the objective response definition, and progression-free survival also reflects the timing of progression or death. The posted median values summarize the observed time-to-event distributions; the confidence intervals indicate that these estimates are uncertain, particularly when read as summaries of a phase II study with finite follow-up.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted median progression-free survival was 3.0 months in the placebo arm, with a 95% confidence interval from 2.7 to 5.5 months. In the pembrolizumab arm, the median was 5.4 months, with a 95% confidence interval from 3.1 to 7.3 months. Thus, the observed arm-specific median was higher in the pembrolizumab group. The confidence intervals are broad and overlap; they communicate uncertainty around each median and do not, by themselves, determine whether the arms differ statistically.
The key limitation for a direct comparative interpretation is that the registry record does not report a primary-endpoint hazard ratio, a confidence interval for an arm-to-arm effect, or a sponsor-reported test. A comparison of two medians is not a substitute for such an analysis. Nor can the presence or degree of overlap between separate confidence intervals be treated as a formal test of the difference. The posted results support describing the two group-specific medians, but they do not supply a complete inferential comparison of progression-free survival between randomized groups.
The primary analysis included 52 participants in the placebo arm and 55 in the pembrolizumab arm. One participant randomized to placebo was excluded because pembrolizumab was received instead of placebo during the initial several cycles. The registry does not explain whether or how that participant was included in any other analysis. This treatment-receipt issue matters because the analysis population is not simply all randomized participants, and the registry record does not report a broader analysis-population definition or sensitivity analysis.
The median follow-up time was 12.9 months. Follow-up is relevant because time-to-event estimates depend on the time at which participants are observed and on how censoring is handled. The registry description gives the follow-up summary but does not report the censoring rules, numbers at risk over time, or the statistical method used to estimate the medians and confidence intervals. Those details cannot be assumed from the endpoint label alone.
The objective response outcome has posted arm-level counts, and a simple unadjusted recalculation gives p = 0.088. This is not a sponsor-reported analysis; the registry lists no reported analyses for that outcome. It should therefore be read as an exploratory calculation rather than definitive evidence. The primary endpoint and the response outcome measure different aspects of disease course, and neither result should be used to make claims about outcomes that were not reported. Overall, the primary record is descriptive at the arm level, with limited comparative inference available.
9. Statistical Methods Explained
What a median time-to-event result means. Progression-free survival is a time-to-event endpoint: each participant is followed from randomization until progression or death, whichever comes first. General statistical context: a median time-to-event estimate summarizes the point at which the estimated event-free experience reaches its midpoint. It does not mean that every participant had an event at that time, and it is not the mean time without progression. A median also does not summarize the entire pattern of events or account on its own for how the two groups compare across follow-up.
The registry reports a median for each arm and a 95% confidence interval for each median. A confidence interval describes uncertainty in an estimate under the statistical procedure used. In general, a narrower interval indicates greater precision and a wider interval indicates less precision. The intervals are 2.7 to 5.5 months for placebo and 3.1 to 7.3 months for pembrolizumab. The registry record does not describe the procedure used to calculate them, so a particular estimation method should not be attributed to the trial.
Why an arm-to-arm estimate matters. Separate arm-specific medians are descriptive. A comparative time-to-event analysis commonly reports an effect measure that directly contrasts the groups, with a confidence interval and an inferential test where appropriate. The registry does not report a primary-endpoint hazard ratio, its confidence interval, or a primary-endpoint p-value. As a result, readers cannot use the posted median estimates alone to quantify the relative difference in progression-free survival or its statistical precision. General statistical context: comparing whether two separate confidence intervals overlap is not equivalent to testing the difference between the groups.
How the endpoint was defined. The primary endpoint ran from randomization to death or progression, whichever occurred first, using immune-related RECIST. The definition refers to RECIST v1.0, including a 20% increase in the sum of the longest diameters of target lesions, a measurable increase in a non-target lesion, or new lesions. These criteria describe what counted as progression in the endpoint. The registry record does not provide further detail on independent review, assessment procedures, or how disagreements in disease assessment were handled.
Analysis population and follow-up. The endpoint results are based on 52 placebo-assigned participants and 55 pembrolizumab-assigned participants. One participant randomized to placebo was excluded from the analysis after receiving pembrolizumab rather than placebo during the initial several cycles. The record gives this explanation but does not report an intention-to-treat analysis, a per-protocol definition, a sensitivity analysis, or the treatment of that participant in other outcomes. The median follow-up was 12.9 months. The registry record does not report censoring rules, follow-up completeness, or the numbers at risk at specific times.
Secondary comparisons. The posted objective response results include counts for each arm, but no sponsor-reported analysis is listed. A simple unadjusted recalculation gives p = 0.088. General statistical context: an unadjusted p-value addresses a single comparison under its assumptions and does not account for examining multiple outcomes. It also does not communicate the size and precision of an effect by itself. The registry record does not describe a multiplicity strategy or a prespecified hierarchy for secondary outcomes, so the unadjusted result should be treated cautiously and as exploratory.
Planning illustrations. The sample-size illustrations use the observed effect as a starting point, equal allocation between two arms, a two-sided significance level of 0.05, and a normal approximation. They show participants per arm for 80% power and participants per arm for 90% power when planning for 100%, 75%, or 50% of the observed effect. The resulting illustrations are 113 and 151 participants per arm for planning for 100% of the observed effect; 185 and 246 for planning for 75% of the observed effect; and 375 and 501 for planning for 50% of the observed effect. These are planning illustrations based on the observed response effect, not the trial's own sample-size justification. They are not observed power, and they do not establish that the trial was designed around the effect observed in the posted data. The registry record does not report the trial's sample-size assumptions or justification.
General statistical context: a planning calculation describes the approximate sample size that a new study might require under chosen assumptions. The assumptions include the effect size to detect, allocation, significance level, and calculation method. If the true effect is smaller than the effect used for planning, a larger sample may be needed to achieve the same target power. Here, the illustrations deliberately vary the fraction of the observed effect, but they do not resolve whether those assumptions match the original trial design. The trial's planned power, target effect, and original calculation method are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The record does not describe how the study handled multiple outcomes or multiple statistical tests. It lists a primary progression-free survival endpoint and several secondary outcomes, including six-month progression-free survival, safety, objective response, response after progression on placebo, and overall survival. The registry record does not report a prespecified testing hierarchy, an adjustment for multiplicity, or a distinction between confirmatory and exploratory analyses. Without such details, unadjusted secondary results should not be interpreted as if they were protected against the increased chance of false-positive findings that can arise when multiple comparisons are examined.
The primary endpoint results are reported as arm-specific medians with confidence intervals. A comparative hazard ratio, confidence interval for a between-arm effect, and sponsor-reported primary test are not reported in the registry record. The registry also lists no reported analyses for the objective response outcome. The unadjusted recalculation is therefore a separate descriptive aid, not a replacement for a prespecified sponsor analysis.
Missing-data and analysis-population procedures are also not described in detail. The record states that one participant randomized to placebo was excluded from the primary analysis because pembrolizumab was received instead of placebo during the initial several cycles. It does not report whether that participant was included in another analysis, how other treatment deviations were handled, or whether any sensitivity analyses were performed. The record does not state how missing disease assessments or incomplete follow-up were handled, or how censoring was defined for progression-free survival.
These omissions do not prove that no such procedures existed; they mean that they are not reported in the registry record. Without the analysis plan and missing-data details, readers cannot verify whether the posted analyses followed a prespecified strategy or judge how alternative choices might affect the estimates. The appropriate interpretation is therefore bounded by the information actually reported: the endpoint definitions, arm-level estimates, the stated exclusion, and the available outcome summaries.
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 |
|---|---|---|---|
| Arm A | 10 | 53 | 18.9% |
| Arm B | 25 | 55 | 45.5% |
| Crossover | 6 | 27 | 22.2% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Arm A | 12 of 53 |
| Arm B | 24 of 55 |
| Crossover | 14 of 27 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Arm A | 50 of 53 |
| Arm B | 51 of 55 |
| Crossover | 24 of 27 |
Most frequent serious adverse event terms
| Event term | Organ system | Arm A | Arm B | Crossover |
|---|---|---|---|---|
| DYSPNEA | Respiratory, thoracic and mediastinal disorders | 1 of 53 | 2 of 55 | 0 of 27 |
| LUNG INFECTION | Infections and infestations | 0 of 53 | 2 of 55 | 1 of 27 |
| SEPSIS | Infections and infestations | 0 of 53 | 3 of 55 | 0 of 27 |
| URINARY TRACT INFECTION | Infections and infestations | 0 of 53 | 3 of 55 | 0 of 27 |
| ABDOMINAL PAIN | Gastrointestinal disorders | 1 of 53 | 0 of 55 | 1 of 27 |
| CONSTIPATION | Gastrointestinal disorders | 1 of 53 | 0 of 55 | 1 of 27 |
| NEOPLASMS BENIGN, MALIGNANT AND UNSPECIFIED (INCL CYSTS AND POLYPS) | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 2 of 53 | 0 of 55 | 0 of 27 |
| PNEUMONITIS | Respiratory, thoracic and mediastinal disorders | 1 of 53 | 1 of 55 | 0 of 27 |
| THROMBOEMBOLIC EVENT | Vascular disorders | 1 of 53 | 1 of 55 | 0 of 27 |
| WOUND COMPLICATION | Injury, poisoning and procedural complications | 1 of 53 | 0 of 55 | 1 of 27 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Arm A | Arm B | Crossover |
|---|---|---|---|---|
| FATIGUE | General disorders | 20 of 53 | 21 of 55 | 7 of 27 |
| ANEMIA | Blood and lymphatic system disorders | 19 of 53 | 17 of 55 | 7 of 27 |
| DIARRHEA | Gastrointestinal disorders | 10 of 53 | 20 of 55 | 5 of 27 |
| CREATININE INCREASED | Investigations | 13 of 53 | 16 of 55 | 5 of 27 |
| COUGH | Respiratory, thoracic and mediastinal disorders | 8 of 53 | 15 of 55 | 7 of 27 |
| CONSTIPATION | Gastrointestinal disorders | 11 of 53 | 13 of 55 | 3 of 27 |
| LYMPHOCYTE COUNT DECREASED | Investigations | 8 of 53 | 17 of 55 | 2 of 27 |
| HYPERGLYCEMIA | Metabolism and nutrition disorders | 8 of 53 | 11 of 55 | 7 of 27 |
| HYPERTENSION | Vascular disorders | 11 of 53 | 9 of 55 | 5 of 27 |
| DYSPNEA | Respiratory, thoracic and mediastinal disorders | 5 of 53 | 14 of 55 | 5 of 27 |
Serious events with the highest arm-level rate: sepsis (5.5%), urinary tract infection (5.5%), neoplasms benign, malignant and unspecified (incl cysts and polyps) (3.8%), abdominal pain (3.7%), constipation (3.7%).
The registry's safety summary reports serious adverse events for 10 of 53 participants in Arm A, 25 of 55 in Arm B, and 6 of 27 in the crossover group. Other adverse events are reported for 50 of 53, 51 of 55, and 24 of 27 participants, respectively. The summary also records 12 deaths in Arm A, 24 in Arm B, and 14 in the crossover group. These are event counts within the groups identified in the safety record; they are not, by themselves, adjusted comparisons between randomized arms.
The crossover group is distinct from the original randomized comparison. Its participants should not be combined with, or treated as interchangeable with, either original arm for a causal comparison. The registry record does not provide a comparative safety analysis, definitions and grading details for each category, or explanations of how the death counts relate to adverse-event attribution. Serious adverse events, other adverse events, and deaths are separate summary categories and should not be assumed to be mutually exclusive.
General statistical context: safety counts are most interpretable alongside clear definitions, observation periods, severity and attribution criteria, and an analysis population. The registry lists several serious-event terms, but these descriptive summaries do not establish that a treatment caused an event or that groups differ after accounting for follow-up and other factors.
12. What the Result Does, and Does Not, Mean
The primary result describes median progression-free survival in the two randomized groups among the participants included in the reported analysis. The pembrolizumab arm had a higher observed median than the placebo arm, while the confidence intervals show uncertainty around both estimates. The record does not provide a comparative primary-endpoint estimate or test, so the medians do not establish the magnitude or statistical precision of a between-arm effect.
This distinction matters because an observed difference in group summaries is not equivalent to a definitive conclusion about treatment effect. General statistical context: randomization supports a fair comparison when groups are analyzed according to an appropriate prespecified approach, but interpretation also depends on the analysis population, endpoint measurement, follow-up, missing data, and the planned statistical analysis. Here, one placebo-assigned participant was excluded from the primary analysis after receiving pembrolizumab, and the record does not report a sensitivity analysis or broader analysis-population strategy.
The findings concern a specific setting: maintenance treatment after first-line chemotherapy in metastatic urothelial cancer among patients who achieved at least stable disease. They should not be generalized automatically to people who have not received that initial treatment, whose disease did not achieve at least stable disease, or to other clinical settings. The registry identifies this as a phase II trial, but its sample-size justification and planned statistical framework are not reported.
The available secondary results add limited context. The objective response outcome has arm-level results and an unadjusted recalculation, while detailed results for several other listed secondary outcomes are not reported in the registry record. An unadjusted secondary finding does not replace a primary-endpoint analysis and carries less weight when the multiplicity plan is not reported. None of these statistics alone establishes an individual outcome or provides medical advice.
13. Why This Trial Matters Statistically
This trial illustrates why an endpoint estimate and a treatment comparison are not the same thing. The registry reports a median progression-free survival for each randomized arm, together with a confidence interval for each median. Those values allow readers to describe the observed time-to-event summaries, but a direct comparative estimate is needed to quantify the contrast and its uncertainty. The absence of a reported primary hazard ratio or test leaves an important inferential gap.
It also illustrates how analysis populations affect interpretation. The registry reports 108 participants enrolled, but the primary endpoint analysis includes 52 placebo-assigned and 55 pembrolizumab-assigned participants. The stated exclusion of one participant because the received treatment differed from the assignment is relevant to assessing how randomization was carried through into analysis. Without a reported intention-to-treat result or sensitivity analysis, the robustness of the posted primary estimates cannot be evaluated from the registry record alone.
The secondary-outcome record offers another statistical lesson. A secondary endpoint can describe a different dimension of the trial, yet an unadjusted comparison is not automatically confirmatory, particularly when a multiplicity plan is not reported. Likewise, planning illustrations based on an observed effect are not evidence that the original trial was adequately powered for that effect. They are not observed power and do not reveal the trial's original design assumptions.
These issues are common in interpreting clinical-trial records: distinguish descriptive results from comparative inference, separate planned design information from post hoc illustration, and identify which analysis populations and procedures are documented. That approach keeps conclusions aligned with the precision and scope of the reported evidence.
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.
Several limitations specific to this record constrain interpretation. First, the primary results are arm-specific medians and confidence intervals, without a reported comparative hazard ratio, confidence interval for the between-arm effect, or sponsor-reported test. This prevents a direct assessment of the primary comparison from the posted record. The median follow-up time is 12.9 months, but the registry does not report numbers at risk over time, censoring details, or follow-up completeness.
Second, the primary analysis excluded one participant randomized to placebo because pembrolizumab was received instead of placebo during the initial several cycles. The reason is stated, but the record does not report the result of an analysis retaining all randomized participants or a sensitivity analysis addressing this deviation. The reported primary endpoint counts also do not account for all 108 enrolled participants, and the registry does not give a full account of analysis populations for each outcome.
Third, the registry record does not report the original sample-size justification, planned statistical analysis, missing-data procedures, interim analyses, or multiplicity strategy. Their absence in the record should not be interpreted as proof that none existed, but it prevents readers from assessing those design and analysis choices. The planning illustrations based on observed response results do not fill this gap.
Finally, detailed results are not reported for several listed secondary outcomes, including six-month progression-free survival, response after progression on placebo, and median overall survival. The safety summary includes a crossover group as well as the original arms, but does not supply a comparative safety analysis or enough detail to interpret event attribution. These reporting limits mean the posted findings offer a partial statistical account rather than a complete evaluation of every registered outcome.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Testing the PD-1 Inhibitor Pembrolizumab as Maintenance Therapy After Initial Chemotherapy in Metastatic Bladder Cancer — NCT02500121.
- Registry record last updated 2022-09-30; status last verified 2022-09.
- Results first posted 2022-09-30.
- 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
The registry describes a completed, randomized, parallel-group phase II study of maintenance pembrolizumab versus placebo after first-line chemotherapy in metastatic urothelial cancer. Participants had achieved at least stable disease on chemotherapy. Pembrolizumab was administered at 200mg intravenously every 3 weeks, and treatment in either arm could continue for up to 24 months in the absence of prohibitive toxicity or progression.
The primary endpoint was progression-free survival from randomization to death or progression, assessed using immune-related RECIST. After a median follow-up time of 12.9 months, the reported median was 3.0 months for placebo and 5.4 months for pembrolizumab, with 95% confidence intervals of 2.7 to 5.5 months and 3.1 to 7.3 months, respectively. One placebo-assigned participant was excluded from the primary analysis after receiving pembrolizumab.
The registry lists several secondary outcomes, but detailed results and comparative analyses are not reported for all of them. The primary comparative analysis, sample-size justification, multiplicity approach, and several missing-data procedures are not reported in the registry record. The available results therefore support descriptive interpretation while leaving important inferential and design questions unresolved.