This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Phase II Study of PARP Inhibitor Olaparib and IV Ascorbate in Castration Resistant Prostate Cancer (NCT05501548), a na phase 2 study. The primary outcome is PSA50 Response.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05501548 |
| Phase | Phase 2 |
| Condition | Prostate Cancer, Castration-resistant Prostate Cancer |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 4 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins |
| Results posted | Yes |
2. Clinical Question
Population
People with castration-resistant prostate cancer, described in the study summary as having no known DNA repair gene mutations and receiving second or later line of therapy. The primary outcome description refers to metastatic castration-resistant prostate cancer. Further eligibility details are not reported in the registry record.
Intervention
The study evaluated olaparib in combination with high-dose intravenous ascorbate. The regimen description states olaparib 300 mg by mouth, twice daily, and ascorbate 1 g/kg intravenously twice weekly at least 24 hours apart, until objective disease progression, unacceptable toxicities, or withdrawal for other reasons.
Comparator
There was no separate comparator group. The registry describes a single-group study, so the combination was not compared within this trial with olaparib alone, ascorbate alone, or another treatment.
Primary question
The primary question was whether participants experienced a PSA50 response: a decrease in prostate-specific antigen to 50% or less of baseline, confirmed by a second measurement at least 4 weeks apart. The registry says data were not collected for this outcome, so it does not provide an answer to that question.
3. Trial Design
This is a phase II, single-group study of olaparib plus intravenous ascorbate in castration-resistant prostate cancer. The registry lists allocation as not applicable and masking as none. With no separate control group, the design cannot estimate a treatment contrast against a concurrent comparator. It can describe outcomes among participants receiving the combination, but the primary outcome data were not collected according to the registry record.
The study summary frames the combination as second or later line therapy for people with castration-resistant prostate cancer and no known DNA repair gene mutations. The primary outcome description specifies metastatic castration-resistant prostate cancer. Eligibility criteria beyond these descriptions are not reported in the registry record. The recorded regimen was olaparib 300 mg by mouth, twice daily, with ascorbate 1 g/kg intravenously twice weekly at least 24 hours apart. Treatment was described as continuing until objective disease progression, unacceptable toxicities, or participant withdrawal for other reasons.
The registry lists enrollment as 4, a start date of 2023-06-30, primary completion on 2024-10-14, and status as terminated. Those administrative details do not establish why the study ended or whether the intended analysis was completed; the reason for termination is not reported in the registry record. A sample-size justification, recruitment target rationale, interim monitoring plan, and detailed statistical analysis plan are also not reported in the registry record. The study lists secondary outcomes concerning safety and tolerability, PSA doubling time, radiographic and PSA progression-free survival, and overall survival. The registry lists no analyses.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | Olaparib and Vitamin C |
|---|---|
| STARTED | 4 |
| COMPLETED | 4 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Data was not collected for this outcome measure.
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.
| Characteristic | Unit | Olaparib and Vitamin C |
|---|---|---|
| Participants analysed | 4 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 |
| Age, Categorical: >=65 years | Participants | 4 |
| Sex: Female, Male: Female | Participants | 0 |
| Sex: Female, Male: Male | Participants | 4 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 |
| Race (NIH/OMB): White | Participants | 4 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | Participants | 4 |
6. Primary Endpoint
The registry lists the primary outcome as PSA50 Response, measured over up to 5 years.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is PSA50 response. It counts participants with metastatic castration-resistant prostate cancer whose prostate-specific antigen (PSA) decreases to 50% or less of the baseline value. The decrease must be confirmed by a second measurement at least 4 weeks apart. PSA values are described as being measured monthly during the trial, with the outcome timeframe listed as up to 5 years.
In general, a prespecified response threshold turns a continuous laboratory measurement into a clinically interpretable response category. Requiring confirmation can help distinguish a sustained change from a transient measurement fluctuation. The registry does not provide the number meeting the threshold, the number evaluable for response, or an estimated response rate. Instead, it explicitly states that data were not collected for this outcome measure. Therefore, the endpoint definition is available, but the observed response cannot be described from this record.
PSA response is distinct from the listed secondary outcomes. PSA doubling time describes the pace of change in PSA, while progression-free survival and overall survival concern time-to-event outcomes. The registry lists those outcome categories but provides no results for them in the information recorded for this study. Their definitions, analysis populations, and results are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The main interpretive fact is that the registry record says data were not collected for the primary PSA50 response outcome. It therefore supplies no observed response count, response proportion, uncertainty interval, or hypothesis test for the primary question. The absence of an outcome result is not evidence that no participant responded, and it is not evidence that a response occurred. The result is unavailable in the registry record.
The listed enrollment is 4, but that figure alone does not establish how many participants received treatment, completed follow-up, or were evaluable for each outcome. Those analysis details are not reported in the registry record. The adverse-event summary separately gives 4 at risk for the listed group; that safety denominator should not be treated as a response denominator. No connection between enrollment, treatment exposure, and the missing primary outcome data is established by the record.
Even if response data had been recorded, a single-group study would describe outcomes during treatment rather than estimate a controlled difference between treatments. In general, outcomes in a single group can reflect multiple influences, including participant characteristics, disease course, prior treatment, and concurrent care. Without a comparator group, the study design cannot separate those influences from the treatment combination. The record lists allocation as not applicable and masking as none.
The registry status is terminated, with primary completion listed as 2024-10-14. These entries describe the record's administrative status and timing; they do not explain the termination or establish the reason that primary outcome data were not collected. The reason is not reported in the registry record. Nor does the record state whether the planned follow-up ended early, whether participants withdrew, or whether results were analyzed outside the registry.
There are no analyses listed. Consequently, no inferential result, adjusted estimate, confidence interval, or reported significance test can be assessed. A confidence interval, in general, expresses the precision of an estimate under a specified statistical model; none is reported for the primary endpoint. Any sample-size planning illustration is a planning calculation, not observed power and not an outcome result. The evidence available in the registry is thus limited to the endpoint definition, design description, enrollment entry, and safety summary. It does not support a conclusion about the magnitude or precision of PSA50 response.
9. Statistical Methods Explained
What does a single-group design estimate?
The registry describes a single-group study without a comparator. In general, a single-group analysis can estimate or describe outcomes within the group under study, subject to how participants and outcomes are defined and recorded. It cannot directly estimate what would have happened to the same participants under a different treatment. A controlled comparison is needed to estimate a between-treatment contrast without relying on assumptions that are especially difficult to verify from a single group.
That distinction matters for interpreting any response count. A response observed while participants receive olaparib and ascorbate would be an outcome during combination treatment; it would not, by itself, identify the effect attributable to either component or the combination relative to another strategy. In this record, even that descriptive response result is unavailable because the registry states that the primary outcome data were not collected.
How is the primary response defined?
PSA50 is a binary endpoint: a participant either meets the stated response definition or does not, based on PSA relative to baseline and confirmation. In general, binary outcomes can be summarized with a count and a proportion, with uncertainty depending on the number of observed outcomes and the number of participants included in the analysis. The registry provides neither response count nor an analysis denominator, so no such estimate can be interpreted.
The confirmation requirement is part of the outcome definition, not an analysis result. The record describes a second measurement at least 4 weeks after the qualifying decrease and monthly PSA measurement during the trial. It does not report how confirmation was handled if a measurement was missing, how baseline was selected, or how participants without sufficient follow-up were classified. Those details are not reported in the registry record.
What would uncertainty measures mean?
In general, a confidence interval describes a range of values compatible with an estimate under a statistical model and its assumptions. For a response proportion, the interval would communicate uncertainty due to the finite observed sample, but its width and interpretation depend on the observed data and method. No response estimate or confidence interval is reported for this study. A p-value, in general, evaluates how compatible data are with a specified null model; it does not measure the probability that a treatment works. No primary-outcome p-value or test is reported.
The planning assumptions in the record refer to a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They are described as planning assumptions for illustrations, not as the trial's own design. The record also says the target effect for those illustrations is a stated fraction of the observed effect, and that time-to-event illustrations use total events while other illustrations use participants per arm. Since this trial is single-group and the record gives no primary response result or actual illustration values, those assumptions do not constitute an analysis of this study. Planning sample sizes are not observed power.
Why do outcome definitions and denominators matter?
Every endpoint needs a clear population and observation rule. For a response endpoint, the analysis population might be defined by treatment receipt, availability of baseline and follow-up measurements, or another prespecified rule. In general, different rules can change the denominator and affect how missing observations are represented. The registry does not report the analysis population for PSA50 or how missing measurements were handled. It explicitly says data were not collected for the primary outcome, so the record cannot show whether the missingness arose from unavailable measurements, lack of an analysis, or another circumstance.
The listed secondary outcomes include safety and tolerability, PSA doubling time, radiographic progression-free survival, PSA progression-free survival, and overall survival. In general, time-to-event methods account for differing follow-up and censoring, while estimates depend on event definitions and censoring rules. Those detailed definitions, analysis methods, censoring rules, and results are not reported in the registry record. The registry lists no analyses, so no time-to-event estimate or comparison can be evaluated from this record.
What is over-dispersion, and is it relevant?
In general, over-dispersion occurs when variability in count data exceeds what a chosen model assumes. Accounting for it can prevent standard errors from being too small when the model otherwise understates variability. The primary outcome is defined as a response count, but the record reports no response data or model. It does not report a statistical model for the primary outcome, so there is no model-specific over-dispersion assessment to interpret.
More broadly, the registry does not report a sample-size justification, analysis plan, interim analysis plan, or inferential method for the outcomes. Such items should not be inferred from the phase designation, endpoint list, or planning assumptions. Without the analysis details and outcome data, the statistical interpretation is necessarily descriptive of what is recorded and what remains unreported.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary endpoint and several secondary outcome topics, but it does not report a multiplicity strategy. Multiplicity arises in general when several outcomes or tests are examined: the chance of at least one apparently notable finding can increase as the number of tests grows. Statistical plans may address this by defining a hierarchy, adjusting inference, or treating secondary analyses as exploratory. None of those approaches is reported in the registry record, so the status of any secondary result as confirmatory or exploratory cannot be determined.
The record lists no analyses and states that data were not collected for the primary PSA50 outcome. It does not provide an analysis population, a participant flow, or a rule for handling missing primary endpoint measurements. It also does not describe whether missing data were expected, how they would be classified, or whether sensitivity analyses were planned. These details are not reported in the registry record. Missing data should not be interpreted as nonresponse unless a stated analysis rule supports that classification; no such rule is recorded.
Likewise, analysis populations for the secondary outcomes are not reported. The record does not say who was included in the safety summaries or in any time-to-event analysis, nor does it give censoring rules, endpoint adjudication procedures, or a statistical analysis plan. The listed safety denominator is not a substitute for an efficacy analysis population.
Because no analyses are listed, there is no basis in the record to evaluate multiplicity adjustment, prespecification, or the handling of missingness in reported estimates. The absence of those details does not establish that no such procedures were used outside the registry; it means they are not reported in the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Olaparib and Vitamin C | 0 | 4 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Olaparib and Vitamin C | 0 of 4 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Olaparib and Vitamin C | 4 of 4 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Olaparib and Vitamin C |
|---|---|---|
| Nausea | Gastrointestinal disorders | 4 of 4 |
| Fatigue | General disorders | 3 of 4 |
| Constipation | Gastrointestinal disorders | 3 of 4 |
| Dry eye | Eye disorders | 2 of 4 |
| Pain | General disorders | 2 of 4 |
| Bruising | Injury, poisoning and procedural complications | 2 of 4 |
| Anemia | Blood and lymphatic system disorders | 2 of 4 |
| Headache | Nervous system disorders | 1 of 4 |
| Non-cardiac chest pain | General disorders | 1 of 4 |
| Productive cough | Respiratory, thoracic and mediastinal disorders | 1 of 4 |
The registry safety summary lists the Olaparib and Vitamin C group with 4 at risk for serious adverse events and 0 affected; it also lists 0 deaths. These are the recorded serious-event figures for the group. They should be read as counts in the registry summary, not as proof that the regimen is free of serious risks. The record does not give event-level descriptions because no top serious terms are listed.
The same summary lists 4 at risk and 4 affected for “other” adverse events. This is a separate registry category from serious adverse events. The record does not define the “other” category in the information, so it should not be assumed to mean a particular severity grade or type of event. The group summary does not provide event counts by participant, timing, duration, attribution, or resolution.
The study's secondary outcome description refers to safety and tolerability and to grade 3 to 5 toxicities. However, the registry summary does not provide a grade-specific breakdown or detailed safety analysis. Its listed at-risk figures are not evidence about unreported outcomes or follow-up beyond the recorded summary. Given the listed enrollment of 4 and the absence of detailed safety methods, the serious-event counts should be interpreted narrowly as the registry's recorded figures, not as a comprehensive estimate of safety.
12. What the Result Does, and Does Not, Mean
The registry record establishes what the study set out to examine: PSA50 response to olaparib combined with intravenous ascorbate in a single group with castration-resistant prostate cancer. It also records the intended secondary outcome areas and a treatment regimen. But the record explicitly says that data were not collected for the primary outcome. It therefore gives no observed PSA50 result and cannot support a claim about the frequency of response.
The missing primary result should not be read as a zero response, and it should not be taken as evidence of benefit or lack of benefit. The study's single-group design would, even with outcome data, describe outcomes during combination treatment rather than provide a direct comparison with another treatment. The record also does not report the reason for termination or explain why primary endpoint data were not collected, so those circumstances cannot be used to infer an outcome.
The safety summary records no serious adverse events and no deaths in the listed group, while all 4 at risk are recorded as affected for other adverse events. These figures have limited scope: there is no detailed event listing, grade breakdown, or reported safety analysis. They should not be generalized beyond the registry's recorded summary.
In general, estimates from a study require both outcome observations and a clear analysis population, while causal interpretation depends on the design and assumptions. Here, the registry lists no analyses and does not report key analysis details. It cannot establish the size, precision, or comparative effect of the combination. The defensible interpretation is that the study was registered as a phase II single-group investigation, but the registry record does not contain collected primary outcome data from which the central efficacy question can be answered.
13. Why This Trial Matters Statistically
This study illustrates an important distinction between a registered endpoint and an observed endpoint result. A detailed outcome definition can specify a threshold, confirmation rule, measurement schedule, and timeframe; those details support consistent measurement in principle. They do not substitute for recorded observations. The registry's statement that primary outcome data were not collected means that the central response question remains unanswered in this record, regardless of how clearly the outcome was defined.
The design also matters. A single-group study can provide descriptive information about outcomes and safety in the treated group when those data are available. It cannot, without a comparator, isolate the difference that might be associated with treatment relative to another strategy. That limitation is separate from the missing endpoint data: both the design and the absence of recorded primary results constrain interpretation.
Statistically, the record highlights the need to distinguish enrollment from outcome evaluability, and event counts from estimates with known precision. The enrollment entry and safety summary do not establish the denominator for PSA50 response. The registry lists no analyses and does not report an analysis population or missing-data method. Readers therefore cannot determine how a response rate would have been estimated or how uncertainty would have been quantified.
For clinical researchers, the case underscores why complete outcome reporting and transparent analysis methods are essential. For biostatisticians, it shows why the registered endpoint definition, the actual observed data, the analysis population, and the inferential method must be considered separately. Each contributes a different part of the evidence; none can replace the others.
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.
The most direct limitation is that the registry states data were not collected for the primary PSA50 outcome. No response count, response estimate, or uncertainty measure is available. The record lists no analyses, and it does not report analysis populations or missing-data handling for primary or secondary outcomes.
The single-group design has no concurrent comparator. Accordingly, it cannot estimate a within-trial contrast between the combination and another treatment. Masking is listed as none, and allocation is listed as not applicable. The registry does not report procedures for outcome assessment or any steps to address potential measurement or assessment bias.
Although enrollment is listed as 4, the record does not give participant flow, treatment exposure, follow-up completeness, or evaluability by outcome. The listed safety denominator does not resolve those gaps for efficacy. The safety summary is brief and does not identify serious event terms or provide details on event grade, timing, attribution, or duration.
The registry gives a terminated status and a primary completion date, but it does not report the reason for termination. It also does not report a sample-size justification, detailed statistical analysis plan, multiplicity approach, interim analyses, or time-to-event methods. The stated planning assumptions are not a substitute for those study-specific details. These limitations mean that the available record supports description of the design and selected safety counts, but not an efficacy estimate or a comprehensive assessment of study conduct.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Phase II Study of PARP Inhibitor Olaparib and IV Ascorbate in Castration Resistant Prostate Cancer — NCT05501548.
- Registry record last updated 2025-01-29; status last verified 2025-01.
- Results first posted 2025-01-29.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry describes a phase II, single-group study of olaparib and intravenous ascorbate for castration-resistant prostate cancer. The regimen is listed as olaparib 300 mg by mouth, twice daily, with ascorbate 1 g/kg intravenously twice weekly at least 24 hours apart. The primary endpoint is PSA50 response, defined by a decrease to 50% or less of baseline confirmed by a second measurement at least 4 weeks apart.
Enrollment is listed as 4. The record gives a start date of 2023-06-30, primary completion of 2024-10-14, and status of terminated. It states that primary outcome data were not collected and lists no analyses. The safety summary records 0 serious adverse events and 0 deaths, with 4 affected for other adverse events in the listed group. The reason for termination and detailed analysis methods are not reported in the registry record.