A Randomized Phase 2 Pharmacokinetic Trial of Chemotherapy With or Without Panitumumab in Patients With Metastatic and/or Recurrent Squamous Cell Carcinoma of the Head and Neck: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Randomized Phase 2 Pharmacokinetic Trial of Chemotherapy With or Without Panitumumab in Patients With Metastatic and/or Recurrent Squamous Cell Carcinoma of the Head and Neck (NCT00756444), a randomized phase 2 study. The primary outcome is Area Under the Curve (AUC) of Total Plasma Cisplatin-derived Platinum Levels With and Without the Presence of Panitumumab.

2. Clinical Question

The registry describes a pharmacokinetic question: whether panitumumab affects the measured exposure to cisplatin-derived platinum. AUC, or area under the concentration curve, summarizes concentration measurements over time. In this trial, the AUC was derived from measurements taken at 0.5, 1, 2, 3, 4, 6 and 24 hours following the start of the cycle 2 cisplatin infusion. The reported endpoint concerns total plasma cisplatin-derived platinum, rather than a clinical response or survival outcome.

The trial record describes cisplatin and 5-FU in both groups, with panitumumab added in one group. The comparison therefore addresses the relationship between adding panitumumab and the measured cisplatin-derived platinum exposure under the study conditions. The primary outcome summaries include 23 participants in the panitumumab plus chemotherapy group and 16 in the chemotherapy-alone group. Those outcome counts are distinct from the enrollment total and from the safety populations reported in the record.

3. Trial Design

The registry identifies this as a randomized phase 2 study with no masking. It records enrollment of 67 participants and reports results for two groups: panitumumab plus chemotherapy and chemotherapy alone. Both groups received cisplatin and 5-FU, while only the first group received panitumumab. The registry record describes the study as a pharmacokinetic trial and notes that it began as a pharmacokinetic sub-study before becoming a stand-alone phase 2 study after an amendment.

The main objective was to estimate the effect of panitumumab on the pharmacokinetics of cisplatin and 5-FU. The registry explanation says cycle 2 was chosen for pharmacokinetic sampling because panitumumab was expected to be at steady state at that point after dosing every 3 weeks. This rationale describes the intended timing of the measurements; it does not establish what the observed concentrations mean outside the trial.

For the primary endpoint, the registry defines the analysis population as participants who received at least 2 cycles of assigned treatment and had sufficient plasma collection to derive AUC. The posted group sizes for that endpoint are 23 and 16. Safety summaries use different at-risk populations: 33 participants in the panitumumab plus chemotherapy group and 34 in the chemotherapy-alone group. These are distinct denominators for distinct summaries and should not be treated as interchangeable.

The registry reports the trial status as completed and gives the enrollment as 67. It does not report the original target sample size or the rationale used to choose it. Details of sequence generation, concealment of allocation, treatment adherence, and the exact operational definition of the pharmacokinetic analysis population are not reported in the registry record. The record labels the study randomized and unmasked, but does not provide further procedural detail in these areas.

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.

Before assignment: Patients were screened at 15 sites to determine eligibility. Using an IVRS, eligible subjects were randomized to panitumumab plus cisplatin and 5-FU or cisplatin and 5-FU alone. It was estimated that approximately 45 subjects would be needed to obtain 30 evaluable subjects. More than 45 subjects were needed and 67 total subjects were enrolled.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Subjects who receive at least 2 cycles of assigned treatment and who have sufficient plasma collection to derive AUC

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 Area Under the Curve (AUC) of Total Plasma Cisplatin-derived Platinum Levels With and Without the Presence of Panitumumab, measured over Levels measured at 0.5, 1, 2, 3, 4, 6 and 24 hours following start of cycle 2 cisplatin infusion.

The primary endpoint is the area under the concentration curve for total plasma cisplatin-derived platinum, measured in ng*hr/mL. AUC is a summary of concentration over time: rather than describing only one blood measurement, it incorporates the measured concentrations across the sampling period. The registry defines the endpoint as the area under the curve from time 0 to the last measurable concentration.

For this endpoint, blood samples were scheduled at 0.5, 1, 2, 3, 4, 6 and 24 hours following the start of the cycle 2 cisplatin infusion. The measure was estimated in the group receiving cisplatin with panitumumab and in the group receiving cisplatin without panitumumab. The record states that measurements were taken during cycle 2 to assess cisplatin and 5-FU pharmacokinetics when panitumumab was expected to be at steady state.

As a pharmacokinetic measure, AUC is used to describe drug-related exposure over a sampling interval. It does not by itself establish a difference in tumor outcomes, symptom outcomes, or survival. The endpoint population also required at least 2 treatment cycles and sufficient plasma collection to derive an AUC, so its group summaries apply to participants meeting those requirements rather than automatically to everyone enrolled.

7. Results Posted in the Registry

• Chemotherapy Alone: mean 62,300 versus 58,000 on control; difference 4,300 (95% CI -2,036 to 10,636), standardized effect d = 0.44; z-test p = 0.183.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: each participant with usable samples contributes a numerical AUC value in ng*hr/mL. The registry reports group means and standard deviations, then a comparison of the group means. These summaries describe the distribution of measured AUC values and the estimated difference between groups.

What does a mean represent?

A mean is the arithmetic average of participant-level measurements in a group. It provides a measure of the group’s central value, but it does not show how tightly individual values cluster or whether the distribution is symmetric. A mean can be affected by unusually high or low observations. The registry reports a mean of 58,000 ng*hr/mL for panitumumab plus chemotherapy and 62,300 ng*hr/mL for chemotherapy alone.

The standard deviation describes the spread of individual measurements around the group mean. The reported standard deviations are 9,530 ng*hr/mL and 10,200 ng*hr/mL. A standard deviation is not the same as a standard error: the standard deviation characterizes participant-to-participant variability, while the standard error characterizes uncertainty in an estimated mean. The registry does not report a separate model-based analysis of individual AUC values.

How is the mean difference read?

The comparison is oriented as chemotherapy alone minus panitumumab plus chemotherapy. Its estimate of 4,300 ng*hr/mL therefore indicates that the observed mean was numerically higher in the chemotherapy-alone group. The sign depends on the stated order of subtraction; reversing the group order would reverse the sign without changing the underlying comparison. This is an unadjusted summary-statistic contrast, rather than a reported covariate-adjusted treatment effect.

A confidence interval expresses uncertainty around an estimate under the assumptions of the statistical procedure used. The 95% interval for the difference runs from -2,036 to 10,640 ng*hr/mL. Because it spans zero, values consistent with the data include a mean difference in either direction as well as no mean difference. A confidence interval is not a range containing a specified proportion of individual participant AUC values; it concerns the estimated group contrast.

What does the p-value tell the reader?

The p-value is 0.183. In general, a p-value describes how unusual data at least as incompatible with a specified null hypothesis would be if that hypothesis and the test assumptions held. It is not the probability that the null hypothesis is true, and it does not measure the probability that the observed result occurred by chance. The registry record does not report the exact test, its assumptions, or whether any covariates were included in a sponsor analysis. The p-value should therefore be read as posted, without assuming unreported model details.

General statistical context: a non-significant p-value does not demonstrate equivalence. A formal equivalence conclusion requires an equivalence margin and an analysis designed to evaluate that margin; such a margin or analysis is not reported in the registry record. The confidence interval is useful because it shows the range of values compatible with the comparison, while also making clear that the estimate is not very precise.

Why can variation matter?

When participant measurements vary substantially, a group mean can be estimated less precisely, especially when the analysis includes relatively few participants. General explanation: if data are more dispersed than a simple model expects, over-dispersion can make standard errors too small and confidence intervals too narrow unless the analysis accounts for it. The registry reports standard deviations but does not report a distributional assessment, a variance model, or a robustness analysis. There is therefore no basis in the record to claim that these particular AUC data were over-dispersed or that a specific correction was used.

General explanation: normal-based methods often summarize a continuous outcome using means and standard deviations, but their accuracy can depend on the distribution and on the sample size. The record does not describe the distribution of individual AUC values or report medians, quantiles, transformations, or diagnostic checks. Those omissions limit assessment of whether the assumptions behind any mean-based inferential procedure were appropriate.

Which participants are represented?

The primary endpoint population required at least 2 cycles of assigned treatment and enough plasma collection to derive AUC. The recorded endpoint counts are 23 and 16. The reasons that other enrolled participants were not included in those endpoint summaries, and the treatment of partial or missing sample collections, are not reported in the registry record. General explanation: restricting an analysis to participants with adequate measurements can affect how representative the analyzed group is, particularly if measurement availability is related to participant characteristics or outcome values. The record does not provide enough information to assess that possibility.

The displayed planning calculations are separate from the trial’s observed comparison. They use the observed effect as a planning reference, assume a two-sided significance level of 0.05, equal allocation, and a normal approximation, and consider specified fractions of the observed effect. These are planning illustrations, not a report of the original trial’s design justification. The trial’s own sample-size assumptions, inferential test details, and any prespecified analysis plan are not reported in the registry record.

10. Confidence Intervals and Precision

The estimated mean difference is 4,300 ng*hr/mL, with a 95% confidence interval from -2,036 to 10,640 ng*hr/mL. The interval includes zero and extends to values on both sides of zero. This means the posted data do not pin down the direction of the underlying mean difference with high precision. They remain compatible with a lower mean in the chemotherapy-alone group, little or no difference, or a higher mean in that group, within the limits of the interval.

The confidence interval is wide relative to the point estimate, so the estimate allows a range of possible differences rather than establishing a narrowly determined effect. That uncertainty is important alongside the p-value of 0.183. The interval is not a statement that 95% of individual AUC values fall between its limits; it concerns uncertainty in the between-group mean difference.

The primary outcome counts were 23 for panitumumab plus chemotherapy and 16 for chemotherapy alone. The group standard deviations were 9,530 ng*hr/mL and 10,200 ng*hr/mL. Together, the modest endpoint counts and the observed variability provide context for the uncertainty in the contrast. The registry does not report the method used to construct the confidence interval, so the assumptions and any adjustment associated with its calculation are not reported in the registry record.

Precision is distinct from clinical importance. The interval describes statistical uncertainty in this pharmacokinetic comparison; the registry does not give a threshold for a clinically important AUC difference. The interval therefore cannot establish whether values near either limit would matter clinically. Nor does a confidence interval that includes zero establish that the groups are equivalent.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures express participants per arm, not total events. They are illustrations based on the observed mean difference, rather than the original trial’s design calculation. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The planning exercise considers detecting 100%, 75%, or 50% of the observed effect.

For planning for 100% of the observed effect, the estimates are 82 participants per arm for 80% power and 110 participants per arm for 90% power. For planning for 75% of the observed effect, they are 146 participants per arm for 80% power and 195 participants per arm for 90% power. For planning for 50% of the observed effect, they are 327 participants per arm for 80% power and 438 participants per arm for 90% power.

In plain terms, the 80% power column describes the number of participants per arm estimated to give an 80% chance of detecting the specified effect under the planning assumptions, if that effect is present. The 90% column uses a higher chance of detection and consequently gives a larger planned number for each effect scenario. Smaller effects need more participants to distinguish them from random variation under the same assumptions.

These are planning illustrations, not observed power. The registry record does not report the original trial’s sample-size justification or the assumptions used to choose its enrollment target. The displayed estimates should not be read as a retrospective assessment of whether the completed trial was adequately powered for its original objective.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 4300.000; pooled standard deviation σ = 9807.140.
2. n = 2 × (1.96 + 0.842)² × 9807.140² / 4300.000² = 81.7, rounded up to 82 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 4300                      # observed difference in means
sigma <- 9807.13998037117                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(756444)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 82 (80% power), 110 (90% power)
 75% of observed effect: n per arm = 146 (80% power), 195 (90% power)
 50% of observed effect: n per arm = 327 (80% power), 438 (90% power)
power.t.test: 82.6 
Simulated power at n = 82 per arm: 0.801 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry reports one primary outcome measure and indicates no posted secondary results. It also records no posted analyses. Thus, the AUC comparison is the only reported outcome result available for interpretation in this record. The registry record does not describe a hierarchy of hypotheses, a multiplicity adjustment, or a prespecified strategy for controlling the chance of false-positive findings across multiple tests.

The record provides group means, standard deviations, a mean difference, a confidence interval, and a p-value. It does not report the exact inferential test, a statistical analysis plan, covariate adjustment, handling of outliers, or a method for checking model assumptions. These details are not reported in the registry record, so it is not possible to determine whether the posted comparison matches a prespecified sponsor analysis or whether other analyses were conducted.

The endpoint population required participants to complete at least 2 cycles of assigned treatment and to have sufficient plasma collection for AUC estimation. The endpoint counts are 23 and 16, while the safety at-risk populations are 33 and 34. The record does not explain the exclusions between enrollment, safety summaries, and the endpoint analysis. Reasons for unavailable measurements, the amount or pattern of missing pharmacokinetic data, and any imputation or sensitivity analyses are not reported in the registry record.

General explanation: missing outcome measurements can affect an estimate if the probability of having a usable measurement is related to the outcome or to participant characteristics. A complete-case analysis and an analysis using imputation can rely on different assumptions. The registry record does not state which missing-data approach was used beyond defining the endpoint population by the availability of sufficient plasma collection.

The registry does not report interim analyses, stopping rules, or any adjustment related to interim testing. It also does not report a formal equivalence or noninferiority margin. Absence of these details in the record should not be taken to mean that no such procedures existed; their status is not reported in the registry record.

14. 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: cerebrovascular accident (6.1%), tumour haemorrhage (5.9%), neutropenia (3.0%), thrombocytopenia (3.0%), dysphagia (3.0%).

The serious adverse event summaries use an at-risk population of 33 participants for panitumumab plus chemotherapy and 34 for chemotherapy alone. Serious adverse events were reported for 11 participants in the panitumumab group and 8 in the chemotherapy-alone group. The total serious adverse event count is 19 among 67 participants. These are participant counts, not a comparison adjusted for follow-up time or other factors.

The registry lists cerebrovascular accident at 6.1%, tumour haemorrhage at 5.9%, and neutropenia, thrombocytopenia, dysphagia, and vomiting at 3.0% each among the top serious terms. The record does not provide additional detail in this summary about event timing, duration, severity grading, recurrence, or attribution. Death counts are not reported in the registry record.

Other adverse events affected 33 of 33 participants in the panitumumab group and 33 of 34 participants in the chemotherapy-alone group. These are separate from the serious adverse event counts and should not be combined with them. The summaries are descriptive; the registry record does not report a comparative statistical analysis for safety outcomes. The counts alone do not establish that treatment caused an event or that the groups differ in risk.

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

The posted primary result answers a narrow pharmacokinetic question: it compares mean total plasma cisplatin-derived platinum AUC during cycle 2 between the two treatment groups among participants with the required treatment and sample data. The observed means were 58,000 ng*hr/mL with panitumumab plus chemotherapy and 62,300 ng*hr/mL with chemotherapy alone. The estimated difference, defined as chemotherapy alone minus panitumumab plus chemotherapy, was 4,300 ng*hr/mL.

The confidence interval from -2,036 to 10,640 ng*hr/mL includes zero, and the p-value is 0.183. These statistics do not establish that the groups have the same mean AUC, and they do not establish a definitive difference. They describe an estimate with uncertainty, including plausible values in either direction. The registry record does not report an equivalence margin or a formal equivalence analysis.

The result does not answer whether adding panitumumab changes cancer control, survival, symptoms, or quality of life. The posted primary endpoint measures drug-related exposure, not a clinical outcome. It also does not determine whether a possible difference in cisplatin-derived platinum exposure would have clinical consequences. Such conclusions would require evidence beyond this endpoint and these posted results.

The safety summaries provide counts of participants with serious and other adverse events, but do not include a reported comparative statistical analysis. They should be interpreted separately from the pharmacokinetic comparison. The record also does not provide enough detail to evaluate event attribution, time at risk, or missing safety information beyond the reported counts.

The most defensible reading is therefore limited: in the endpoint population, the mean AUC was numerically higher in the chemotherapy-alone group, while the uncertainty around the estimated difference remained substantial. The result is informative about the measured pharmacokinetic endpoint under the recorded study conditions, but it should not be extended to unreported outcomes or treated as proof of equality, benefit, or harm.

16. Why This Trial Matters Statistically

This trial illustrates how a randomized treatment comparison can focus on pharmacokinetics rather than a clinical endpoint. Its question concerns whether adding panitumumab is associated with a change in cisplatin-derived platinum exposure, measured through AUC during cycle 2. Separating that question from cancer outcomes is important: an exposure measure is not itself evidence about tumor response, survival, or quality of life.

The result also shows why an estimate should be read together with its uncertainty. The observed mean difference is 4,300 ng*hr/mL, but the 95% confidence interval ranges from -2,036 to 10,640 ng*hr/mL. The interval crosses zero, and the p-value is 0.183. Neither statistic supports a simple claim that the groups are identical, and neither establishes a clear difference. The data allow a broad range of possible mean contrasts.

Another useful statistical lesson is that participant counts depend on the outcome being summarized. Enrollment was 67, the safety groups included 33 and 34 participants, and the primary endpoint summaries included 23 and 16. Reading those denominators in context prevents an overall trial count from being mistaken for the number contributing to every analysis.

Finally, the registry record illustrates the limits of public result summaries. It does not report the exact inferential procedure, detailed missing-data handling, the original sample-size rationale, or multiplicity procedures. Such omissions constrain independent evaluation of assumptions and analysis choices. Statistical interpretation therefore requires attention not only to the point estimate and p-value, but also to the endpoint population, precision, and what the record does not document.

17. 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 primary endpoint analysis includes 23 participants in the panitumumab plus chemotherapy group and 16 in the chemotherapy-alone group, whereas the safety at-risk groups include 33 and 34. The registry record does not explain why these populations differ or identify the reasons participants lacked a usable AUC. This limits assessment of whether the endpoint population represents everyone enrolled or whether availability of pharmacokinetic samples could have affected the comparison.

The registry reports means and standard deviations but not individual-level distributions, medians, or diagnostic checks. It does not describe the inferential test used to produce the confidence interval and p-value, nor does it report whether the analysis adjusted for baseline or other covariates. The statistical analysis plan, treatment of outliers, and sensitivity analyses are not reported in the registry record.

The record gives the sampling schedule and the endpoint definition but does not provide the actual concentration-time data or detailed information about measurements below assay limits, sample collection deviations, or handling of incomplete profiles. It also does not report an equivalence margin, so the absence of a statistically significant difference cannot be interpreted as evidence of equivalence.

The posted safety information is limited to counts and selected serious adverse event terms. Deaths, event timing, exposure-adjusted rates, and a comparative safety analysis are not reported in the registry record. These limitations make the safety summaries descriptive rather than a complete comparative assessment.

The planning illustrations are based on the observed effect and stated assumptions, not the original trial design. The record does not report the trial’s original sample-size justification, interim analyses, or multiplicity plan. These omissions limit evaluation of how the study was designed to support its primary inference.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: A Randomized Phase 2 Pharmacokinetic Trial of Chemotherapy With or Without Panitumumab in Patients With Metastatic and/or Recurrent Squamous Cell Carcinoma of the Head and Neck — NCT00756444.
• Registry record last updated 2018-11-15; status last verified 2018-10.
• Results first posted 2013-12-13.
• 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.

21. Record Summary

The registry describes a completed randomized phase 2 pharmacokinetic trial in metastatic and/or recurrent squamous cell carcinoma of the head and neck. The comparison was cisplatin and 5-FU with or without panitumumab, with no masking reported. Enrollment was 67.

The primary endpoint was total plasma cisplatin-derived platinum AUC during cycle 2. Mean AUC was 58,000 ng*hr/mL in the panitumumab-plus-chemotherapy group and 62,300 ng*hr/mL in the chemotherapy-alone group. The estimated mean difference was 4,300 ng*hr/mL, with a 95% confidence interval from -2,036 to 10,640 ng*hr/mL and p = 0.183.

The endpoint summaries included 23 and 16 participants; safety summaries used at-risk groups of 33 and 34. The registry does not report posted secondary results or detailed analysis methods, missing-data procedures, or the original sample-size justification.