Study of Gemcitabine, Carboplatin, and Panitumumab (GCaP) as Neoadjuvant Chemotherapy in Patients With Muscle-Invasive Bladder Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study of Gemcitabine, Carboplatin, and Panitumumab (GCaP) as Neoadjuvant Chemotherapy in Patients With Muscle-Invasive Bladder Cancer (NCT01916109), a na phase 2 study. The primary outcome is Pathologic Complete Response Rate (<pT0).

2. Clinical Question

The clinical question concerns tumor and lymph-node findings after preoperative treatment, assessed from the final cystectomy specimen. The registry lists the primary outcome as “Pathologic Complete Response Rate (<pT0)” and gives a timeframe of 1 year. Its description specifies absence of carcinoma (pT0 disease) and absence of microscopic lymph node metastases (N0).

Because the study has one treatment group, it can describe outcomes among participants treated with GCaP, but it cannot make a like-for-like comparison with a control group. The stated purpose is to investigate whether the combination can shrink the tumor before surgery. The record does not report a response count or response rate, so the clinical question cannot be answered from the posted outcome information. Nor does the record establish how any observed response would compare with a different treatment approach.

3. Trial Design

This is a phase 2 study of gemcitabine, carboplatin, and panitumumab as neoadjuvant chemotherapy for muscle-invasive bladder cancer. The registry lists a single-group model, no masking, and allocation marked NA. Enrollment is 4. The study status is terminated. Its recorded start is 2013-08, and primary completion is recorded as 2015-07.

The intervention group is named Gemcitabine, Carboplatin, and Panitumumab (GCaP). The arm description states that patients will receive four cycles administered every 21 days. Panitumumab is described as intravenous at a dose of 9mg/kg on day 1; gemcitabine as intravenous at 1,000 mg/m2 on days 1 and 8; and carboplatin as intravenous at AUC 4.5 on day 1. Radical cystectomy is listed as a procedure. The arm-description text ends mid-sentence, so additional details are not reported in the registry record.

The design is not randomized and has no control arm listed. Accordingly, any outcome information from this group would describe participants receiving the combination, rather than estimate a treatment contrast against another regimen or usual care. The registry record does not report a reason for termination, a protocol-specific sample-size justification, or details of study conduct beyond the listed design and arm description. It also does not report how many participants completed treatment or underwent cystectomy.

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

Reasons for not completing this period:

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.

6. Primary Endpoint

The registry lists the primary outcome as Pathologic Complete Response Rate (<pT0), measured over 1 year.

The primary endpoint is titled “Pathologic Complete Response Rate (<pT0).” It is measured in participants, with the registry giving a timeframe of 1 year. The accompanying definition requires absence of carcinoma, described as pT0 disease, and absence of microscopic lymph node metastases, described as N0, on the final cystectomy specimen. Thus, the endpoint uses pathology findings after surgery to characterize whether residual cancer is identified in the specified specimen.

A pathologic endpoint is used in this setting because it assesses disease findings in tissue removed at surgery after neoadjuvant treatment. The combined definition matters: the stated response requires both the primary-tumor finding and the lymph-node finding. A tumor finding alone would not meet the full definition as written.

The record gives no observed number of participants meeting this definition, no response rate, and no uncertainty interval. The denominator used for an analysis is also not reported in the registry record. Enrollment of 4 is not automatically the endpoint denominator: the record does not state whether all enrolled participants had an evaluable cystectomy specimen or how missing specimens would be handled.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a single-group design estimate?

In general, a single-group study can describe the frequency of an outcome among participants who receive the study intervention and are assessed. For a binary endpoint such as meeting or not meeting a pathologic response definition, the analysis would ordinarily depend on a numerator and a denominator. The numerator is the number meeting the definition; the denominator is the number included under the analysis rules. The registry record does not report either value for the primary outcome. Enrollment of 4 does not establish the endpoint denominator or imply that every participant had an evaluable specimen.

Without a comparator group, there is no direct between-group contrast. The study’s single-group structure cannot answer how outcomes would differ under another regimen. General statistical adjustment cannot create a randomized comparison when none is part of the listed design. The record identifies the model as single-group and allocation as NA, and it lists no control arm.

How should precision be understood?

In general, a confidence interval expresses the range of values compatible with the data and a stated statistical procedure. It helps distinguish a point estimate from the uncertainty around that estimate. No confidence interval for the primary endpoint is reported in the registry record, and no result is posted from which to assess precision. With a small enrollment, estimates of binary outcomes can be especially sensitive to the outcome status of individual participants; that is a general statistical consideration, not a reported result for this study.

Likewise, a p-value would address compatibility with a specified null hypothesis under a specified analysis. The registry record does not report a primary analysis, a null hypothesis, or a p-value. It would therefore be inappropriate to infer statistical significance or lack of significance from the outcome listing alone.

What do the analysis counts indicate?

The registry record lists one outcome measure and zero analyses. An outcome measure identifies what the study intended to assess; it is not itself evidence that an analysis result was posted. Since there is no posted primary result, the registry entries do not establish the observed response count, the estimated response rate, or its uncertainty. An analysis plan specifying the statistical method for this endpoint is not reported in the registry record.

How do planning illustrations differ from observed results?

In general, sample-size planning asks how many participants would be needed under assumptions about an effect, variability, significance level, allocation, and analysis method. The stated planning assumptions describe a two-arm illustration with equal allocation, a two-sided significance level of 0.05, and a normal approximation; the effect to detect is expressed as a fraction of an observed effect. Such an illustration is distinct from this study’s single-group design and is not an observed outcome or an analysis of the enrolled participants. Sample-size illustrations are planning aids, not observed power. The registry record does not report the study’s own sample-size justification, and the primary outcome results needed to assess any effect are not posted.

For a binary endpoint, methods may differ in how they form intervals or test hypotheses, particularly when counts are small. General choices can include exact or approximate procedures, but the statistical method used for the primary endpoint is not reported in the registry record. No method should be attributed to the study without that information.

Why do outcome definitions and denominators matter?

The endpoint definition combines primary-tumor pathology and lymph-node status. An analysis needs a consistent rule for classifying participants against both components. It also needs to specify what happens when a specimen is unavailable or a required assessment is missing. Neither such missing-outcome handling nor the analysis population is reported in the registry record. These details affect interpretation because excluding participants with unavailable pathology can produce a different estimate from counting them as nonresponders or handling them through another prespecified approach.

In general, missing data should be described rather than silently treated as a particular outcome. The record does not state how many participants had missing endpoint data, whether any were unevaluable, or whether all enrolled participants were included in an analysis. Consequently, no assumptions about completeness or the denominator are warranted.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Gemcitabine, Carboplatin, and Panitumumab (GCaP)")
n      <- c(3)
events <- c(3)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Gemcitabine, Carboplatin, and Panitumumab (GCaP)  3  3  100.0  29.2  100.0  43.9  100.0  39.8  99.4

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome measure and zero analyses. It does not report a multiplicity strategy, such as how inference would be handled across multiple endpoints or repeated analyses. With only one listed outcome measure, the record still does not establish whether additional analyses were planned in a protocol or how they would be handled. The analysis plan is not reported in the registry record.

Missing-data handling is also not reported. In particular, the record does not state what would happen if a participant lacked a final cystectomy specimen or if the specimen could not be classified using both pT0 and N0 criteria. The number of participants with complete endpoint data is not reported in the registry record. Enrollment of 4 should therefore not be treated as the confirmed denominator for the response measure.

The analysis population is not reported in the registry record. There is no statement about whether an analysis would include all enrolled participants, only those who received treatment, or only those with evaluable pathology. The record also does not report participant flow through treatment and surgery. These omissions prevent assessment of exclusions, attrition, and the relationship between the enrolled group and any analyzed group.

Because no primary analysis is posted, there are no reported estimates on which to assess multiplicity, missingness, or sensitivity to analysis-population choices. These are uncertainties about what the registry record reports; they do not establish that any particular data problem occurred.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: wound dehiscence (25.0%).

The adverse-event entries list one participant affected by a serious adverse event among 4 at risk, and 2 participants affected by other adverse events among 4 at risk. Wound dehiscence appears among the top serious adverse-event terms, with 25.0% listed. These values describe the group named Gemcitabine, Carboplatin, and Panitumumab (GCaP).

The serious and other adverse-event categories are presented separately. The record does not state whether participants affected in one category also appear in the other, so the counts should not be added or treated as distinct participants. It also does not report event-level detail such as timing, duration, severity grading, or whether events were considered related to treatment. Deaths are not reported in the registry record.

These counts do not provide a comparison with another regimen, because the study is single-group. They are descriptive entries for the enrolled group, not a comparative estimate of risk. The record does not report a full safety analysis or explain how adverse events were collected.

13. What the Result Does, and Does Not, Mean

The registry record establishes that a phase 2, single-group study evaluated a planned neoadjuvant combination of gemcitabine, carboplatin, and panitumumab for muscle-invasive bladder cancer, with radical cystectomy listed as a procedure. It identifies pathologic complete response as the primary outcome and defines it using pT0 disease and N0 status on the final cystectomy specimen. It also reports enrollment of 4 and selected adverse-event counts.

The record does not establish how many participants met the primary response definition. It gives no response rate, confidence interval, or primary analysis result. It therefore cannot show the magnitude or precision of any response estimate. The absence of an analysis in the registry record should not be mistaken for a zero response or for proof that the endpoint was not assessed; the posted information simply does not report an outcome analysis.

The design also does not support a controlled treatment comparison. With no comparator group, the study cannot estimate a difference in response between GCaP and another approach from the listed design. The result, even if a single-group estimate were posted, would describe this group rather than establish a comparative treatment effect.

The safety entries provide limited descriptive counts, not a complete safety profile. Their interpretation is constrained by the small enrolled group, absent event-level details, and lack of a comparator. No conclusion about relative safety follows from these entries.

In short, the record is informative about the study question, treatment plan, endpoint definition, and some event counts, but it does not report the primary clinical outcome. The statistical evidence needed to characterize response and its uncertainty is not reported in the registry record.

14. Why This Trial Matters Statistically

This trial matters statistically because its design and posted results illustrate the distinction between a planned endpoint and an analyzed endpoint. The registry names a specific pathology-based primary outcome, but lists zero analyses and does not report an outcome value. A clearly defined endpoint is necessary for interpretation, yet it cannot substitute for the observed numerator, denominator, and uncertainty estimate.

The single-group design also clarifies the limits of descriptive evidence. A study can document what was observed among participants receiving a regimen, but a control group is needed for a direct comparison within the trial. The record lists no comparator, so readers should not interpret the intended question about tumor shrinkage as a comparative estimate of benefit.

Enrollment of 4 makes transparent reporting of participant flow and endpoint evaluability especially important. The record does not give the number with an available cystectomy specimen or the endpoint analysis population. Without those details, even a response count would need a clearly stated denominator to be interpretable.

Finally, the registry shows why safety counts and efficacy outcomes should be kept distinct. The listed adverse-event figures describe selected events in the group, while the primary response result is not reported. Neither the design nor the posted entries support conclusions beyond these descriptive details. The key statistical lesson is that an outcome definition, study design, and reported analysis each contribute different information; one cannot stand in for another.

15. 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 principal trial-specific limitation is the absence of a posted primary endpoint analysis. Although the record identifies the response measure and its definition, it does not report the number meeting the definition, the denominator, an estimate, or an uncertainty interval. The recorded enrollment is 4, but the number with evaluable pathology is not reported in the registry record.

The study is single-group and has no listed comparator. Any findings from the group could not provide a direct randomized or controlled contrast with another treatment. The record lists no masking and marks allocation as NA; it does not report additional design features that would alter this interpretation.

The study status is terminated, but the reason for termination is not reported in the registry record. Participant flow, treatment completion, surgery completion, and reasons for any missing endpoint data are also not reported. The analysis population, missing-data approach, multiplicity handling, and statistical method for the primary endpoint are not reported in the registry record.

Safety reporting is limited to the listed group counts and top serious term. Event timing, duration, grading details, relatedness, and the handling of overlapping categories are not reported. Deaths are not reported in the registry record. The arm description is incomplete, ending mid-sentence, so further treatment details cannot be established from that entry.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Study of Gemcitabine, Carboplatin, and Panitumumab (GCaP) as Neoadjuvant Chemotherapy in Patients With Muscle-Invasive Bladder Cancer — NCT01916109.
• Registry record last updated 2016-02-12; status last verified 2016-01.
• Results first posted 2016-02-12.
• 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.

19. Record Summary

The registry record describes a phase 2, single-group, unmasked study of gemcitabine, carboplatin, and panitumumab as neoadjuvant chemotherapy for muscle-invasive bladder cancer. Enrollment is 4; status is terminated. The recorded start is 2013-08 and primary completion is 2015-07.

The primary outcome is pathologic complete response, defined as pT0 disease with N0 status on the final cystectomy specimen, with a timeframe of 1 year. The record lists one outcome measure and zero analyses, and does not report a response result or its denominator. It also lists one participant with a serious adverse event, 2 with other adverse events, and wound dehiscence at 25.0% among top serious terms. The reason for termination, analysis plan, missing-data approach, and primary efficacy findings are not reported in the registry record.