Trial of Topotecan With VX-970 (M6620), an ATR Kinase Inhibitor, in Small Cell Cancers and Extrapulmonary Small Cell Cancers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Trial of Topotecan With VX-970 (M6620), an ATR Kinase Inhibitor, in Small Cell Cancers and Extrapulmonary Small Cell Cancers (NCT02487095), a non-randomized phase 1, phase 2 study. The primary outcome is Ph II: Number of Participants With a Clinical Response.

2. Clinical Question

The study's stated objective was to study the safety and efficacy of the combination in small cell lung cancer. The treatment rationale in the brief description is that chemotherapy damages tumor-cell DNA, while tumor-cell DNA repair may limit chemotherapy's effects; VX-970 was being studied as a way to interfere with that repair. This is the study rationale, not evidence that the combination changed DNA repair or improved response.

The registry lists 62 participants enrolled overall. That total does not identify how many participants contributed to the Phase II primary endpoint or to each cancer cohort. The record notes that 1/26 participants was not evaluable for response in the Phase II DL4 SCLC group, and that the EPSCC cohort was exploratory. Because response results are not reported, the clinical question remains unanswered by the posted endpoint data.

3. Trial Design

This was a Phase I/II study with non-randomized allocation, no masking, and a sequential model. It began on 2015-07-30, had primary completion on 2021-02-24, and is recorded as completed. The National Cancer Institute (NCI) is listed as sponsor. Total enrollment was 62. These record-level features describe how the study was organized; they do not establish the number analyzed for each endpoint.

Phase I evaluated escalating doses of topotecan and VX-970 (M6620). The registry describes the purpose as determining the maximum safe dose of the combination, using a protocol rule under which no more than 1 in 6 people would have an intolerable side effect. The listed Phase I groups vary in topotecan and VX-970 dose and in whether VX-970 was given on day 5 alone or on day 2 and day 5. Dose escalation is not random assignment, so observed differences between dose groups can reflect dose, participant characteristics, timing, or other factors; the record does not provide a randomized basis for attributing such differences to dose.

Phase II used dose level 4, described as the maximum tolerated dose or recommended Phase II dose. The Phase II dose-level group is separated for the clinical-response outcome because EPSCC was an exploratory cohort. The registry's primary endpoint is specifically labeled as a Phase II count of participants with a clinical response. The result for that endpoint is not reported in the registry record.

The brief description specifies 21-day cycles. Topotecan was administered intravenously on days 1 through 5, and VX-970 intravenously on day 5 alone or on day 2 and day 5. Participant monitoring was described as weekly for the first cycle and every 3 weeks thereafter. These are protocol descriptions; the registry record does not report individual adherence, treatment exposure, or how many cycles participants completed.

Because there was no randomized comparator, this design can describe activity and safety observed among participants treated in the study, but it cannot provide a randomized estimate of comparative treatment effect. The record does not report the protocol's sample-size justification, a detailed statistical analysis plan, or whether interim analyses were planned.

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: No participants were treated on Dose Level -1, Topotecan 1mg/m\^2 intravenous (IV) (days 1-5); VX970 (M6620) 105mg/m\^2 IV on day 5.

Phase I Dose Escalation

Dose Expansion

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 Ph II: Number of Participants With a Clinical Response, measured over Every two cycles (each cycle is 21 days) up to approximately 30 months..

The primary endpoint is the Phase II number of participants with a clinical response. It is a count, rather than a time-to-event measure or a continuous measurement. Response was assessed using RECIST, which classifies tumor change using target-lesion measurements and lymph-node criteria. Complete response is defined as disappearance of all target lesions, with pathological lymph nodes reduced to a short axis under 10 mm. Partial response requires at least a 30% decrease in the sum of target-lesion diameters from baseline. Progressive disease requires at least a 20% increase from the smallest sum on study. Stable disease meets neither the partial-response nor progressive-disease threshold.

A response count is used to describe how many participants met the specified response criteria during assessment. It is clinically interpretable as a tally of participants meeting a defined tumor-response classification, but the count alone does not describe response duration, survival, or comparative benefit. Those are distinct outcomes; the registry separately lists progression-free survival, duration of response, and overall survival among secondary outcomes.

The assessment timeframe is every two cycles, with each cycle lasting 21 days, up to approximately 30 months. The record states that 1/26 participants in the Phase II DL4 SCLC group was not evaluable for response. It does not report the number with complete response, partial response, stable disease, progressive disease, or an overall response count. Therefore, the endpoint definition can be explained, but its observed result and precision cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The methods described in the registry include a binary primary outcome represented as a count of participants with an event—in this case, participants with a clinical response. General statistical concepts can clarify how such results are ordinarily read, but the registry record does not report an estimate, confidence interval, or detailed primary-outcome analysis.

What does a count of participants with response tell us?

A count states how many participants met the endpoint definition. For interpretation, that count is ordinarily considered alongside the number of participants assessed, because counts from groups of different sizes are not directly comparable. A response proportion would describe the share meeting the criteria, and a confidence interval would describe uncertainty around an estimate. Neither the response count nor a response proportion or confidence interval is reported in the registry record. The total enrollment of 62 covers the study overall and is not an endpoint-specific denominator.

RECIST supplies operational definitions for response categories. Complete response means disappearance of target lesions, subject to the stated lymph-node criterion. Partial response requires a decrease from baseline in the sum of target-lesion diameters, while progressive disease requires an increase from the smallest sum on study. Stable disease is defined by not meeting either the response or progression threshold. These categories make the assessment rule explicit, but they do not remove measurement variability or provide an outcome result without participant assessments.

Why does the study phase matter?

Phase I dose escalation and Phase II evaluation address different study purposes. The registry describes Phase I as identifying a maximum safe dose, and Phase II as using the maximum tolerated dose or recommended Phase II dose. The clinical-response primary endpoint is labeled Phase II. Combining Phase I and Phase II participants into one response denominator would therefore be inappropriate without an analysis specification supporting that choice; no such specification is reported. The registry also separates the Phase II SCLC group from the exploratory EPSCC cohort for this outcome.

In a sequential dose-escalation study, participants enter dose groups according to the escalation process rather than random assignment. General statistical interpretation should therefore avoid treating dose groups as if they were concurrent randomized arms. Differences between groups may be associated with dose, but they may also reflect cohort composition, timing, or other influences. A non-randomized design does not by itself identify the causal effect of changing the dose.

What is the role of statistical uncertainty?

General: a confidence interval is a range of values compatible with the data and a specified statistical procedure. It helps readers understand the precision of an estimate; a wider interval indicates less precision under that procedure. A point estimate alone, even when reported, does not show how much uncertainty surrounds it. The registry record does not report a confidence interval for the primary clinical-response outcome, so precision cannot be assessed.

General: for a binary outcome, the number of observed events is affected by the size of the group being assessed. Missing or non-evaluable assessments can also affect the denominator and potentially the estimate. The registry identifies 1/26 participants as not evaluable for response in the Phase II DL4 SCLC group, but it does not provide the response count or a complete accounting of endpoint evaluability across all Phase II cohorts. The appropriate handling of non-evaluable participants is not reported in the registry record.

How should planning illustrations be understood?

The statistical planning illustrations use an observed effect as their starting point, apply a two-sided significance level of 0.05, assume equal allocation between two arms, and use a normal approximation. They consider effects expressed as fractions of the observed effect. These are planning assumptions, not a record of the trial's own design or a retrospective measure of how likely the trial was to detect an effect. The record does not report the protocol's sample-size justification, and any planning illustration should not be described as observed power.

General: sample-size calculations estimate how many participants a future study might need under specified assumptions about the effect, variability, allocation, and error rates. When an observed effect is used as the planning basis, the resulting illustration depends on that estimate and can be unstable, particularly when the estimate is imprecise. The illustrations do not replace the missing endpoint result or establish that the completed study was designed with those assumptions.

What can safety counts establish?

Safety summaries count participants affected by recorded events within a group. Counts can describe what was observed, but a participant may experience more than one event, and group counts do not necessarily represent event totals. Seriousness, attribution to treatment, and timing are separate considerations. General: causal assessment requires attention to study design and clinical context; a count alone does not establish that treatment caused an event. In this non-randomized study, these counts do not constitute a randomized comparative safety estimate.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 14 outcome measures, including Phase I and Phase II progression-free survival, duration of response, Phase I overall survival, and laboratory or immune-cell measures. Multiple outcomes can address different questions, but testing many outcomes can increase the chance of at least one apparently notable result if results are interpreted without accounting for multiplicity. General statistical methods for addressing multiplicity include prespecifying a primary outcome, adjusting inference across a family of tests, or treating secondary analyses as exploratory. The registry record does not report whether any multiplicity strategy was planned or used.

The Phase II clinical-response count is identified as the primary outcome. However, the registry record does not report its observed result, an uncertainty interval, or a detailed statistical analysis plan. It also does not report whether other outcomes were formally tested, how missing assessments were handled, or which analysis populations were used. The absence of these details prevents assessment of the analysis choices and how they may affect interpretation.

For the response endpoint, the record notes that 1/26 participants in the Phase II DL4 SCLC group was not evaluable. It does not state how that participant was treated analytically, nor does it provide complete evaluability information for the other Phase II cohort. General: excluding participants with unavailable assessments can change the group represented by an estimate; counting them as nonresponders is a different analysis choice. The registry record does not say which approach was used.

The number enrolled overall is 62, but the record does not provide endpoint-specific analysis populations or enough detail to derive a response denominator. Registered outcomes should therefore not be mistaken for completed analyses. Whether outcome reporting is incomplete, whether analyses exist elsewhere, and whether any missingness was addressed through a planned method are not reported in the registry record.

11. 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: small intestinal obstruction (66.7%), death nos (33.3%), dehydration (33.3%), fever (33.3%), infections and infestations - other, klebsiella bacteremia (33.3%).

The adverse-event summary gives, for each listed group, the number at risk and the number affected for serious adverse events and other adverse events, as well as a death count. In Phase I DL1, 3 of 6 participants were recorded as affected by serious adverse events and 6 of 6 by other adverse events; 5 deaths are listed. In DL2, the corresponding counts are 4 of 6 and 6 of 6, with 6 deaths. In DL3, they are 3 of 3 and 3 of 3, with 3 deaths. In DL4, they are 5 of 6 and 6 of 6, with 5 deaths. For the Phase II DL4 group, the counts are 25 of 41 for serious adverse events and 41 of 41 for other adverse events, with 35 deaths.

These are participant counts within the registry's named groups. The record lists serious-event terms including small intestinal obstruction (66.7%), death NOS (33.3%), dehydration (33.3%), fever (33.3%), Klebsiella bacteremia (33.3%), and nausea (33.3%). The term percentages are reproduced as recorded; the registry summary does not establish that these events were caused by study treatment.

The death counts should not be read as treatment-related deaths without an attribution statement, which is not reported in the registry record. Nor do the group counts permit a randomized safety comparison. They describe events recorded among participants in a sequential, non-randomized study, not a causal contrast between equivalent arms.

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

The registry establishes that a Phase I/II study of topotecan with VX-970 (M6620) was completed, enrolled 62 participants overall, and specified a Phase II clinical-response count as its primary outcome. It also records the response criteria and the assessment schedule. These details show what investigators intended to measure and how response was defined.

The record does not report the number of Phase II participants who achieved clinical response. It therefore does not support a conclusion about the frequency of response, nor does it provide an estimate's precision. The absence of a posted result is not evidence that no participants responded, that all participants responded, or that the treatment had no effect.

The safety counts describe serious and other adverse events and deaths recorded within the listed groups. They are useful as descriptive counts, but they do not establish causation or comparative risk. The study was non-randomized, and its Phase I groups were organized through dose escalation. No randomized control group is reported.

These results should also be kept distinct from the study rationale. The brief description proposes that VX-970 might interfere with tumor-cell DNA repair and thereby affect chemotherapy response. A biological rationale is not a measured clinical-response result. The registry lists other outcomes, including progression-free survival, duration of response, and overall survival, but their numerical results are not reported in the registry record.

Accordingly, the main conclusion supported by the posted information is about the design and reporting: the study assessed a specified response endpoint and recorded safety counts, but the primary response result and its statistical uncertainty are unavailable in the registry record. No conclusion about treatment efficacy or comparative benefit can be drawn from the missing response result.

13. Why This Trial Matters Statistically

This trial is statistically notable for the distinction between a registered endpoint and a reported result. The primary Phase II outcome is clearly defined as a participant count using RECIST, yet the registry record does not report the response count. A precise endpoint definition is important, but it cannot substitute for the observed estimate, its denominator, or an account of uncertainty.

The sequential, non-randomized structure also shapes what comparisons can mean. Phase I dose groups were part of escalation, while Phase II used the maximum tolerated dose or recommended Phase II dose. These groups do not provide a randomized control comparison. Any apparent difference across them would need cautious interpretation because assignment was not randomized and groups may differ in ways beyond dose.

The study also distinguishes SCLC from an exploratory EPSCC cohort for the Phase II response outcome. This highlights why analysis populations and disease subgroups should be explicit: an overall enrollment count does not identify who contributed to a particular outcome. The registry notes one participant not evaluable among 26 in the Phase II DL4 SCLC group but does not provide the full endpoint accounting.

Finally, the safety summary illustrates the difference between descriptive event counts and causal evidence. Counts can document events observed during a study, while attribution and comparisons require additional information and an appropriate design. The record's limitations in response reporting, analysis details, and comparison structure are therefore central to statistical interpretation, not merely technical footnotes.

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 trial-specific limitations affect interpretation of the registry record. First, the primary clinical-response result is not reported. Without the response count, endpoint denominator, and an uncertainty estimate, neither the response frequency nor its precision can be evaluated. The record's note that 1/26 participants in the Phase II DL4 SCLC group was not evaluable identifies an issue for that cohort but does not explain how non-evaluable participants were handled or give comparable accounting for the exploratory EPSCC cohort.

Second, this was a non-randomized, unmasked, sequential study. Phase I dose groups reflect dose escalation rather than random assignment, and the Phase II group has no randomized control arm. Differences between groups cannot be interpreted as controlled treatment effects. The registry record does not report a separate comparator or a randomized estimate.

Third, total enrollment of 62 does not establish the number analyzed for the Phase II endpoint. The record does not report the complete analysis populations, endpoint-specific denominators, or the statistical methods used for the primary result. A protocol sample-size justification, detailed statistical analysis plan, and any planned interim analyses are not reported in the registry record.

Finally, the safety counts do not, by themselves, establish event attribution or comparative risk. The registry lists deaths and serious adverse-event terms, but a treatment-causality assessment is not reported in the record. These limitations concern what can be concluded from registry reporting and study design; they do not establish that unreported analyses or information do not exist elsewhere.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Trial of Topotecan With VX-970 (M6620), an ATR Kinase Inhibitor, in Small Cell Cancers and Extrapulmonary Small Cell Cancers — NCT02487095.
• Registry record last updated 2025-04-13; status last verified 2025-03.
• Results first posted 2022-04-12.
• 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.

18. Record Summary

The registry records a completed, non-randomized, unmasked, sequential Phase I/II study sponsored by the National Cancer Institute (NCI), with 62 participants enrolled. The study evaluated topotecan with VX-970 (M6620) across escalating Phase I dose levels and a Phase II dose described as the maximum tolerated dose or recommended Phase II dose.

The Phase II primary outcome was the number of participants with a clinical response assessed by RECIST every two cycles, up to approximately 30 months. The response criteria are defined in the record, but the observed response result and its precision are not reported in the registry record. The record notes 1/26 participants in the Phase II DL4 SCLC group was not evaluable for response.

Group-level serious and other adverse-event counts and deaths are recorded. The non-randomized design does not support a randomized treatment comparison, and the safety counts alone do not establish causation. The registry lists 14 outcome measures and 0 analyses.