Immunotherapy With BCMA CAR-T Cells in Treating Patients With BCMA Positive Relapsed or Refractory Multiple Myeloma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Immunotherapy With BCMA CAR-T Cells in Treating Patients With BCMA Positive Relapsed or Refractory Multiple Myeloma (NCT03338972), a non-randomized phase 1 study. The primary outcome is Dose-limiting Toxicities (DLT) Rate.

2. Clinical Question

This is a safety and dose-finding question, rather than a randomized comparison of treatment against a control. The registry record says the study examined side effects and the best dose of BCMA CAR-T cells. It also lists secondary outcomes concerning persistence and migration of the transferred cells, objective response rate, progression-free survival, and overall survival. Numerical results for those outcomes are not reported in the registry record.

The record describes chemotherapy before the cell infusion and says it may reduce disease and lower lymphocyte counts, which may help the infused cells survive and expand. That is the stated treatment rationale, not evidence that those biological effects occurred in every participant. The central interpretive question is therefore whether the registry reports dose-limiting toxicity counts by dose level, and how much those counts can establish about safety. The numerical primary endpoint results are not reported in the registry record, so the clinical question cannot be answered from the posted numerical results.

3. Trial Design

This was a phase I study sponsored by Fred Hutchinson Cancer Center. The registry record describes a single-group model, non-randomized allocation, and no masking. Enrollment is listed as 28. The study status is completed; its start date is 2017-11-29 and its primary completion date is 2021-05-03.

The treatment was described at four dose levels. Across the groups, patients underwent leukapheresis, received cyclophosphamide and fludarabine on days -4 to -2, and then received BCMA-specific CAR-expressing T lymphocytes by intravenous infusion on day 0. The record gives an infusion duration of 20-30 minutes. It states that no patients received more than one CAR T cell infusion, so the dose-limiting toxicity assessment period was 28 days after the first and only infusion for all patients.

The intervention descriptions also mention the possibility of a second cell dose, but the primary outcome description clarifies that no patient received more than one infusion. The registry record does not report the dose quantities for the four levels in the information. Nor does it report a randomized allocation process or a concurrent control group. Consequently, comparisons between dose levels are not randomized comparisons, and differences in the observed groups cannot be interpreted as if treatment assignment created balanced control groups.

The planned enrollment and the registry's recorded enrollment should not be mistaken for the number contributing to the primary endpoint: the size of the DLT-evaluable analysis set is not reported in the registry record. The stated primary outcome was a count of participants with a dose-limiting toxicity in each arm. The registry record does not include a numerical count for that endpoint or an analysis entry. Although response, survival, cell persistence, and migration outcomes are listed, their numerical results are not reported in the registry record.

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 Dose-limiting Toxicities (DLT) Rate, measured over Up to 28 days after CAR T cell infusion.

The primary endpoint is the dose-limiting toxicity rate, expressed as a count of participants who experienced a dose-limiting toxicity. The registry specifies that the count is to be summarized for each arm using the DLT-evaluable analysis set. Its assessment window is up to 28 days after CAR T cell infusion. The record further states that no patients received more than one infusion, so the window applied after the first and only infusion.

In a phase I dose-finding study, dose-limiting toxicity is used to characterize short-term tolerability at different dose levels. In general, this kind of endpoint can help investigators assess whether treatment-related toxicities arise within a prespecified observation period as dose levels are explored. It is not, by itself, a measure of longer-term safety, tumor response, or survival.

The distinction between a count and a rate matters. The endpoint description says results are reported as counts; interpreting those counts as rates would require the relevant denominator for each DLT-evaluable group. Those denominators and the numerical DLT counts are not reported in the registry record. The adverse-event figures elsewhere in the record do not substitute for the primary DLT endpoint: the registry does not state that the serious or other adverse-event categories are identical to dose-limiting toxicities.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The central statistical feature of this study is its phase I, non-randomized, dose-level design. General explanation: early-phase dose-finding studies commonly focus on treatment tolerability and toxicity while exploring dose levels. Such a design differs from a randomized trial intended to estimate a treatment effect against a control. In this study, the registry identifies four dose levels but no randomized control group.

What does a count endpoint say?

The primary outcome is defined as the count of participants in each arm who experienced a dose-limiting toxicity. A count is a direct summary of how many participants met an outcome definition. By itself, it does not show the probability of toxicity unless the number of participants evaluated in that group is also known. The registry says the DLT-evaluable analysis set is the relevant population, but does not report its group sizes or the primary counts. Thus, neither a group-specific rate nor a confidence interval for that endpoint can be described from the registry record.

Why does the assessment window matter?

The DLT timeframe is up to 28 days after CAR T cell infusion. A defined observation window helps specify which events are included in the endpoint. It also sets a limit on what the endpoint can describe: it concerns DLT assessment during that stated period, not every possible later safety outcome. The record says no patients received more than one infusion, making the assessment period 28 days after the first and only infusion for all patients.

What can group comparisons establish?

General explanation: randomization aims to make treatment groups comparable, on average, with respect to known and unknown characteristics. Without randomization, a difference between groups may reflect patient or treatment differences beyond the dose level itself. The record labels allocation non-randomized and the model single-group. Consequently, the four dose-level groups should not be treated as randomized treatment-versus-control arms. Descriptive comparisons can show what was recorded in each group, but cannot by themselves isolate a causal effect of dose.

How should uncertainty be considered?

General explanation: a confidence interval describes the range of estimates compatible with the observed data under the statistical model used. Sparse outcomes or small groups can yield wide intervals, indicating substantial uncertainty. No DLT confidence intervals or numerical DLT estimates are reported in the registry record, so their precision cannot be assessed. The enrollment figure does not resolve this issue, because the DLT-evaluable group sizes are not reported.

What is the role of the sample-size illustration?

The sample-size planning illustration is described as based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It states that the effect to detect is a specified fraction of the observed effect; time-to-event calculations count total events, while other calculations express participants per arm. General explanation: this kind of calculation explores the sample size that a hypothetical design might require under its assumptions. It is not a report of the actual study's power, and it does not change the non-randomized design. The registry record does not report the study's own sample-size justification, and the illustration should not be read as the trial's original design plan.

The registry lists zero analysis entries. Detailed statistical procedures, including any model used for outcome estimation, adjustment methods, handling of missing data, and any planned interim analyses, are not reported in the registry record. Those details should not be inferred from the endpoint labels or the fact that the study is marked completed. The numerical primary outcome results are also not reported, so recalculation from posted summary statistics is not possible.

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("Treatment (Chemotherapy, BCMA CAR-T Cells) at Dose", "Treatment (Chemotherapy, BCMA CAR-T Cells) at Dose", "Treatment (Chemotherapy, BCMA CAR-T Cells) at Dose", "Treatment (Chemotherapy, BCMA CAR-T Cells) at Dose")
n      <- c(7, 8, 7, 3)
events <- c(0, 0, 1, 0)
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  Treatment (Chemotherapy, BCMA CAR-T Cells) at Dose  7  0  0.0  0.0  41.0  0.0  35.4  0.3  36.9
ARM  Treatment (Chemotherapy, BCMA CAR-T Cells) at Dose  8  0  0.0  0.0  36.9  0.0  32.4  0.3  33.6
ARM  Treatment (Chemotherapy, BCMA CAR-T Cells) at Dose  7  1  14.3  0.4  57.9  2.6  51.3  3.2  52.7
ARM  Treatment (Chemotherapy, BCMA CAR-T Cells) at Dose  3  0  0.0  0.0  70.8  0.0  56.1  0.6  60.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists several secondary outcomes alongside the primary DLT endpoint: duration of persistence of adoptively transferred BCMA CAR-T cells, detectable migration to the primary disease site (bone marrow) at day 28, objective response rate, progression-free survival, and overall survival. It also reports seven outcome measures in total. When a study evaluates multiple outcomes, the chance of at least one apparently notable finding can increase if each is tested separately. General explanation: statistical methods for handling multiple comparisons can address this concern, but the registry record does not report whether any multiplicity adjustment was planned or used.

The record lists zero analysis entries. It does not report a complete statistical analysis plan, the order or hierarchy of secondary outcome analyses, or whether any outcomes were exploratory. Numerical results for the listed outcomes are not reported in the registry record, so it is not possible to assess consistency across endpoints or whether any claims were based on prespecified analyses.

The primary endpoint is described for the DLT-evaluable analysis set, but the size and definition of that set beyond its name are not reported in the registry record. The record does not describe how missing endpoint observations, withdrawals, or participants without evaluable follow-up were handled. It also does not state whether analyses used intention-to-treat or other analysis populations for the secondary outcomes. The enrollment figure should not be assumed to equal the number analyzed for every outcome.

These omissions matter because the analysis population and handling of missing observations affect what a result represents. Without reported denominators and analysis methods, the primary endpoint cannot be reconstructed and completeness of follow-up cannot be assessed. No missing-data method, multiplicity procedure, interim analysis, or statistical adjustment should be presumed.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: fever (62.5%), febrile neutropenia (42.9%), neutropenic fever (33.3%), cytokine release syndrome (14.3%), lung infection (14.3%).

The registry reports adverse-event figures separately for the four dose-level groups. For serious adverse events, the listed affected and at-risk counts are 5 of 7 at dose level 1, 8 of 8 at dose level 2, 5 of 7 at dose level 3, and 3 of 3 at dose level 4. For other adverse events, the corresponding figures are 7 of 7, 8 of 8, 7 of 7, and 3 of 3. These are descriptive group-level counts, not randomized comparisons.

Deaths are listed as 4 at dose level 1, 3 at dose level 2, 0 at dose level 3, and 0 at dose level 4. The registry record does not provide additional detail about timing, cause, attribution, or the relationship of deaths to treatment. The most frequently listed serious terms include FEVER at 62.5%, FEBRILE NEUTROPENIA at 42.9%, NEUTROPENIC FEVER at 33.3%, CYTOKINE RELEASE SYNDROME at 14.3%, LUNG INFECTION at 14.3%, and ACUTE KIDNEY INJURY at 14.3%.

These adverse-event summaries are not the primary DLT results. The record does not report the DLT counts or state that the adverse-event categories map directly to the DLT definition. It also does not report the event-collection period or definitions for the serious and other categories in the information. Interpret the figures as reported safety counts and terms, not as proof of causation or as a complete account of risk.

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

The registry record establishes that a phase I study of BCMA CAR-T cells in recurrent or refractory multiple myeloma was completed and organized treatment across four dose levels. It describes chemotherapy before infusion, a short-window primary safety endpoint, and several secondary outcomes concerning cell behavior, response, and survival. The adverse-event summaries also document events and deaths in the dose-level groups.

What the registry record does not establish from the posted numerical results is the primary endpoint result. The DLT count for each dose level is not reported, and neither are the DLT-evaluable group sizes. It is therefore not possible to quantify the observed DLT rate or its precision, or to identify a dose level with a particular DLT profile from this record. Numerical results for the secondary outcomes are also not reported.

The adverse-event figures can be described as recorded counts, but they should not be conflated with DLT. The registry does not say that every serious adverse event was dose-limiting, nor that every DLT would be classified as a serious adverse event. Likewise, the number of deaths in a group does not on its own establish the cause of death or a causal relationship to treatment.

General explanation: a completed study status means the trial is recorded as completed; it does not itself provide an estimate of treatment effect or resolve uncertainty about safety. The non-randomized design is appropriate to describe as a dose-level study, but does not support the same causal interpretation as randomized comparison with a control. The posted record is therefore informative about the study question, treatment sequence, endpoints, and some adverse-event summaries, while leaving the primary numerical safety result and several analysis details unreported.

14. Why This Trial Matters Statistically

This trial is statistically notable because it asks a dose-finding safety question in a phase I setting, where the observation of toxicity across dose levels is central to interpreting the study. Its primary outcome is explicitly defined as a participant count within a 28-day period after infusion. That definition helps identify what the intended endpoint represents, even though the numerical DLT findings are not reported in the registry record.

The four dose-level groups also illustrate why design context is essential. Non-randomized allocation means the groups are not like-for-like control arms. A descriptive difference across groups could not, by itself, be attributed to dose, because the record does not establish that group characteristics were balanced or that other influences were controlled. This is especially important when group sizes and endpoint denominators are not reported.

The record also distinguishes, at least in its outcome structure, the DLT endpoint from secondary measures of response, survival, and cellular persistence or migration. These outcomes address different questions and should not be treated as interchangeable evidence. The presence of named outcomes does not mean that numerical results or an analysis plan are available; those are not reported in the registry record.

Finally, the adverse-event summaries make clear why safety information needs careful interpretation: group counts, event categories, the primary toxicity definition, and follow-up windows each describe different aspects of safety. The registry offers some descriptive adverse-event figures but not the primary endpoint counts. Statistically, that gap limits how far readers can go from describing recorded events to assessing the study's stated dose-limiting toxicity question.

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 registry record does not report numerical results for the primary DLT endpoint. It also does not report the size of the DLT-evaluable analysis set in each dose-level group, so the stated participant counts cannot be converted to rates or used to assess precision. The number of enrolled participants is not a substitute for endpoint-specific denominators.

The study was non-randomized and single-group, with dose-level groups rather than a randomized control group. As a result, between-group differences would be descriptive and could not establish a causal effect of dose. The record does not provide information about baseline group comparability or adjustment for potential confounders.

The registry lists secondary outcomes but does not report their numerical results in the record. It also does not report detailed statistical methods, missing-data handling, multiplicity procedures, interim analyses, or the study's own sample-size justification. The exact dose quantities for the four dose levels are not reported in the record.

Safety interpretation is limited because the adverse-event categories and the primary DLT outcome are not described as equivalent. Additional detail about event definitions, attribution, timing, and follow-up for the adverse-event summaries is not reported in the registry record. Although deaths are counted by group, cause and treatment relationship are not described. These limitations prevent a full characterization of the primary safety endpoint, the comparative performance of dose levels, and the longer-term clinical outcomes.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Immunotherapy With BCMA CAR-T Cells in Treating Patients With BCMA Positive Relapsed or Refractory Multiple Myeloma — NCT03338972.
• Registry record last updated 2023-09-08; status last verified 2023-08.
• Results first posted 2022-08-05.
• 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

This completed phase I study evaluated autologous BCMA-specific CAR-expressing CD4+ and CD8+ T lymphocytes in patients with BCMA-positive recurrent or refractory multiple myeloma. It used non-randomized allocation, a single-group model, and four dose-level groups. Treatment included leukapheresis, cyclophosphamide and fludarabine before cell infusion, and one CAR T cell infusion per patient.

The primary endpoint was the count of participants with a dose-limiting toxicity within up to 28 days after infusion, assessed in the DLT-evaluable analysis set. Numerical DLT results and the analysis-set group sizes are not reported in the registry record. The record includes descriptive serious and other adverse-event counts and deaths by dose level, and lists secondary outcomes for cell persistence, migration, response, and survival. Numerical results for those secondary outcomes are not reported in the registry record.