Study on Olaparib Plus Abiraterone as First-line Therapy in Men With Metastatic Castration-resistant Prostate Cancer (China Cohort): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study on Olaparib Plus Abiraterone as First-line Therapy in Men With Metastatic Castration-resistant Prostate Cancer (China Cohort) (NCT05171816), a randomized phase 3 study. The primary outcome is Radiological Progression Free Survival (rPFS).

2. Clinical Question

The registry record describes a phase III study in men with metastatic castration-resistant prostate cancer (mCRPC). Its central question is whether adding olaparib to abiraterone changes the time until radiological progression or death, compared with adding placebo to abiraterone. The study is described as a China cohort of the PROpel Study.

The primary endpoint is time-to-event, so the analysis concerns both whether an event occurs and how long participants remain without that event during follow-up. The registry record also lists overall survival, subsequent therapy or death, pain progression, opiate use, skeletal-related events, later progression or death, and patient-reported measures as secondary outcomes. The posted numerical results cover a subset of those outcomes. The record does not report the rationale for selecting the population or the original sample-size justification.

3. Trial Design

This is a randomized, quadruple-masked, parallel-group phase III study sponsored by AstraZeneca. The official title describes it as double-blind and placebo-controlled as well as multicentre. The registry record lists planned enrollment as 110 and status as active, not recruiting. The recorded study start date is 2021-06-24, and the primary completion date is 2024-01-22. The study title identifies the cohort as China.

Participants were assigned to olaparib plus abiraterone or placebo plus abiraterone. The posted arm titles specify olaparib 300 mg twice daily plus abiraterone 1000 mg once daily, or matching placebo twice daily plus abiraterone 1000 mg once daily. The arm descriptions say the olaparib and matching placebo tablets were available as 100 milligrams or 150 milligrams; the descriptions in the registry record are truncated, so further dosing details are not reported in the registry record.

The stated treatment objective is to evaluate efficacy and safety in people with mCRPC who had not received prior cytotoxic chemotherapy or new hormonal agents at the mCRPC stage. Random allocation and a parallel-group comparison support comparison of the assigned treatment strategies, while masking is intended to reduce the influence of treatment knowledge on participant or study-team assessments. The record does not specify which parties are included in its quadruple-masking label.

The primary rPFS outcome was assessed using tumour imaging by CT or MRI and bone scan. Imaging was scheduled every 8 weeks from randomisation to week 24, then every 12 weeks until RECIST progression. Follow-up for this endpoint ranged from 479 days (approx 16 months) at minimum to 913 days (approx 30 months) at maximum. The record identifies the primary analysis population as the FAS. Details of the randomisation procedure, allocation concealment, sites, treatment discontinuation rules, and the original statistical design assumptions 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:

Analysis population for the primary outcome, as defined in the registry: Full Analysis Set (FAS)

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.

Population: Full analysis set

6. Primary Endpoint

The registry lists the primary outcome as Radiological Progression Free Survival (rPFS), measured over Tumour imaging CT/MRI and bone scan were assessed every 8 weeks from randomisation to week 24 and then every 12 weeks until RECIST progression. Patients were followed up for 479 days (approx 16 months) at minimum and 913 days (approx 30 months) at maximum.

Radiological progression-free survival measures the time from randomisation until the earlier of radiological progression or death from any cause in the absence of progression. It is a time-to-event endpoint: participants contribute information about how long they remain free of the defined event, rather than only whether they experienced it by a single fixed date. The definition applies regardless of whether a participant withdraws from randomised therapy or receives another anticancer therapy before progression.

The registry record describes progression using RECIST v1.1 and PCWG3 criteria. Under RECIST v1.1, progression includes the specified increase in the sum of target-lesion diameters, unequivocal progression in non-target lesions, or a new lesion. The record specifies an increase of 20% and an absolute increase of at least 5mm from nadir for the target-lesion criterion. For bone scans, PCWG3 progression requires 2 or more new lesions under the stated comparison rules, with a confirmatory scan required.

As a general statistical concept, rPFS is used because it captures disease progression and death in one endpoint and uses information about event timing. It can therefore describe the course of disease control during follow-up without treating all participants as if they had the same observation duration. Its interpretation depends on consistent outcome assessment and on the rules used to handle participants whose event time is not observed; those analysis details are not reported in the registry record beyond the endpoint definition and assessment schedule.

7. Results Posted in the Registry

• Olaparib 300 mg bd + Abiraterone 1000 mg qd vs Placebo bd + Abiraterone 1000 mg qd: hazard ratio 1.43 (95% CI 0.83–2.48), reported p = 0.259 (as reported in the registry).

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Overall Survival (OS)

• Endpoint type: Time to event: compared as a hazard ratio.
• Test: Hazard ratio as reported by the sponsor (Log Rank); it was not recalculated.
• Result:
  • Olaparib 300 mg bd + Abiraterone 1000 mg qd vs Placebo bd + Abiraterone 1000 mg qd: hazard ratio 1.14 (95% CI 0.57–2.29), reported p = 0.725 (as reported in the registry).
• Interpretation:
  • The 95% confidence interval includes no difference (a ratio of 1), so these data do not show a statistically significant difference between Olaparib 300 mg bd + Abiraterone 1000 mg qd vs Placebo bd + Abiraterone 1000 mg qd and the control. The interval gives the range of effects that remain compatible with the data.

Time to First Subsequent Anticancer Therapy or Death (TFST)

• Endpoint type: Time to event: compared as a hazard ratio.
• Test: Hazard ratio as reported by the sponsor (Log Rank); it was not recalculated.
• Result:
  • Olaparib 300 mg bd + Abiraterone 1000 mg qd vs Placebo bd + Abiraterone 1000 mg qd: hazard ratio 0.99 (95% CI 0.60–1.64), reported p = 0.972 (as reported in the registry).
• Interpretation:
  • The 95% confidence interval includes no difference (a ratio of 1), so these data do not show a statistically significant difference between Olaparib 300 mg bd + Abiraterone 1000 mg qd vs Placebo bd + Abiraterone 1000 mg qd and the control. The interval gives the range of effects that remain compatible with the data.

Time to Pain Progression (TTPP)

• Endpoint type: Time to event: compared as a hazard ratio.
• Test: Hazard ratio as reported by the sponsor (Log Rank); it was not recalculated.
• Result:
  • Olaparib 300 mg bd + Abiraterone 1000 mg qd vs Placebo bd + Abiraterone 1000 mg qd: hazard ratio 0.68 (95% CI 0.20–2.06), reported p = 0.494 (as reported in the registry).
• Interpretation:
  • The 95% confidence interval includes no difference (a ratio of 1), so these data do not show a statistically significant difference between Olaparib 300 mg bd + Abiraterone 1000 mg qd vs Placebo bd + Abiraterone 1000 mg qd and the control. The interval gives the range of effects that remain compatible with the data.

The registry record lists 9 outcome measures, including overall survival, time to first subsequent anticancer therapy or death, pain progression, opiate use, symptomatic skeletal-related events, second progression or death, and changes in pain and prostate cancer quality-of-life measures. Numerical results are posted for a subset of these outcomes. This gives some context about how the study assessed outcomes beyond radiological progression, but it does not constitute a complete account of every listed secondary measure.

Across the posted secondary time-to-event comparisons, the estimates and confidence intervals vary, and the intervals are broad. In general, that pattern means the secondary results do not provide a uniformly precise picture of effects across the different outcomes. The posted primary result remains the main basis for the primary endpoint interpretation; secondary outcomes can add context, but they do not resolve uncertainty in the primary comparison merely by being assessed alongside it.

Secondary endpoints address different aspects of disease course, survival, symptoms, subsequent treatment, and patient-reported experience. They may differ in event frequency, assessment schedule, and follow-up, so their estimates are not interchangeable with rPFS. Nor should a finding for one secondary outcome automatically be taken to establish a corresponding effect on another.

As a general statistical consideration, testing multiple endpoints or conducting multiple analyses creates more opportunities for apparently notable findings to occur by chance. An unadjusted p-value does not account for that broader family of tests. The registry record lists 6 analyses but does not report a multiplicity strategy, hierarchy, or adjustment for secondary outcomes. Consequently, unadjusted secondary results carry less weight than a prespecified primary result and should be treated as exploratory unless the analysis plan establishes otherwise. The record does not report such a plan, so no stronger claim about confirmatory status is warranted.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Overall Survival (OS)
• Time to First Subsequent Anticancer Therapy or Death (TFST)
• Time to Pain Progression (TTPP)
• Time to Opiate Use
• Time to a Symptomatic Skeletal-Related Event (SSRE)
• Time to Second Progression or Death (PFS2)
• Change From Baseline in BPI-SF Pain Severity and Pain Interference
• Change From Baseline in Functional Assessment of Cancer Therapy- Prostate Cancer (FACT-P)

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is a time-to-event measure, and the posted comparison uses a Log Rank method and reports a hazard ratio. These statistics answer related but different questions: the hazard ratio describes a relative event rate under the analysis model, while the Log Rank test assesses evidence of a difference in event-time distributions over follow-up. The registry record identifies the primary population as the Full Analysis Set (FAS), but it does not define the FAS further.

What does a median time-to-event estimate represent?

As a general statistical explanation, the median time-to-event is the time by which half of the population represented by the estimate has experienced the event, under the method used to account for incomplete follow-up. It is not an average, and it does not describe the event time of every participant. The primary arm estimate is 14.75 months. The corresponding comparator median is not reported in the registry record, so the posted medians alone do not support a direct two-arm median contrast.

Time-to-event analyses can include participants whose event has not been observed by the end of their available follow-up. Such observations are commonly treated as censored at the last time they were known to be event-free. This is a general explanation of the method, not a statement that the registry record specifies its censoring rules: the detailed censoring and analysis procedures are not reported in the registry record. Results can be affected by how follow-up ends and by whether assumptions about censoring are reasonable.

What does a hazard ratio describe?

In general, a hazard ratio compares the instantaneous rates of experiencing an event between groups among participants still at risk at a given time. A value of 1 is the reference for equal rates under the model; values on either side indicate a relative difference whose interpretation depends on which group is in the numerator and how the event is coded. The reported primary hazard ratio is 1.43. The registry record does not provide enough detail to add a directional interpretation beyond the comparison label and the estimate itself.

A hazard ratio is not a ratio of medians and does not mean that one group’s median time is a corresponding multiple of the other’s. Its usual single-number interpretation also relies on how the relative event rate behaves over time. The registry record does not report whether proportional-hazards assumptions were assessed or whether time-varying effects were examined. The estimate should be read alongside its confidence interval and the endpoint definition, not on its own.

How should the Log Rank result be read?

The Log Rank test is a general method for comparing time-to-event distributions while using event timing across follow-up. The reported p-value for primary rPFS is 0.259. A p-value measures how unusual the test result would be under a specified null model and the test assumptions; it is not a measure of the probability that treatment groups are the same. It also does not measure effect size, precision, or clinical importance. The p-value and hazard ratio are complementary: one addresses compatibility with a null comparison, while the other gives an estimated relative effect.

The record reports a 95% confidence interval for the hazard ratio, from 0.83 to 2.48. In general, a confidence interval represents uncertainty around an estimate under the method used to construct it. It indicates a range of values reasonably compatible with the data and model, rather than a range in which an individual participant’s outcome will fall. Because the interval includes 1 and spans values on both sides of it, the estimate does not pin down a clear relative effect.

What is and is not documented?

The record reports randomized allocation, quadruple masking, a parallel model, the FAS for the primary endpoint, and the Log Rank result. It does not report the original primary analysis plan, the rationale for the selected analysis method, the handling of missing outcome data, the treatment of protocol deviations, or the details of any sensitivity analyses. Those omissions limit how fully the analysis can be independently reconstructed. They do not by themselves show that a particular analysis choice was inappropriate; they mean that the relevant information is not reported in the registry record.

The record also lists 9 outcome measures and 6 analyses. The multiplicity strategy across endpoints and analyses is not reported in the registry record. As a general point, evaluating many outcomes or analyses without a prespecified approach can increase the chance of highlighting a result that appears notable by chance. This is one reason secondary findings are generally interpreted more cautiously than a prespecified primary result, especially when no multiplicity adjustment is described.

11. Confidence Intervals and Precision

The primary median rPFS estimate is 14.75 months, with a 95% confidence interval from 12.06 to 22.11 months. This interval expresses uncertainty around the estimated median for the olaparib-plus-abiraterone group under the estimation method. It is not a range of individual survival times, and it does not show where every participant’s outcome lies. The comparator-arm median and its interval are not reported in the registry record.

For the primary comparison, the reported hazard ratio is 1.43 and its 95% confidence interval is 0.83 to 2.48. The interval includes 1, the reference value for equal relative event rates, and also extends to values below and above 1. This means the posted estimate is not highly precise about the direction or magnitude of the relative effect. The p-value of 0.259 is consistent with that uncertainty, but it should not be used as a substitute for reading the interval.

As a general statistical concept, a narrower confidence interval indicates greater precision under the model, while a wider interval indicates greater uncertainty. Precision depends on the amount and timing of event information as well as on the analysis method; the number assigned to a group alone does not convey all of that information for a time-to-event outcome. The registry record gives the arm counts for the primary endpoint and the follow-up range, but does not report the number of primary events or all details needed to assess the precision independently.

Confidence intervals are compatible ranges under specified statistical assumptions, not guarantees that the true effect lies inside them. They also do not determine whether an effect is clinically important. The registry record does not provide a threshold for clinical importance, a noninferiority or equivalence margin, or a detailed precision target for the primary estimate. Accordingly, the confidence interval supports describing the result as uncertain rather than as proof of no difference.

12. 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 illustrations are based on the observed effect and are not the original trial design calculation. The registry record does not report the trial’s own sample-size justification or original design assumptions. For these illustrations, the stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is the stated fraction of the observed effect. For time-to-event outcomes, the figures are total events required, not participants per arm. For other outcome types, figures would be participants per arm; the time-to-event planning figures should therefore be read as event targets.

The 80% power column describes the planned event target for a hypothetical study designed to have an 80% chance of detecting the specified effect under the stated assumptions, if that effect and the other assumptions hold. The 90% power column gives the corresponding event target for a higher chance of detection. These are planning quantities, not observed counts and not evidence that the current trial had a particular probability of detecting an effect.

Each planning row uses a different fraction of the observed effect: 100%, 75%, or 50%. Smaller effects are harder to distinguish from random variation and therefore require more event information, which means a larger event target in a time-to-event design. The rows illustrate that relationship rather than forecast the number of events that will occur in this study. The values depend on the observed effect, so they should not be treated as independently established treatment effects.

This is not observed power. Observed power is not a useful substitute for interpreting the estimated effect and its uncertainty after the data have been analyzed. The planning figures instead show how event requirements change under specified hypothetical assumptions. They do not indicate that the trial met those targets; the registry record does not report the total number of primary events in the posted outcome summary.

13. 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

d is the total number of events needed (Schoenfeld's formula) with 1:1 allocation and proportional hazards.

Worked calculation for this trial

1. Hazard ratio HR = 1.430, so ln(HR) = 0.3577.
2. d = 4 × (1.96 + 0.842)² / [ln(1.430)]² = 245.4, rounded up to 246 events in total 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
hr <- 1.43                              # observed hazard ratio
events_needed <- function(power, frac = 1) ceiling(round(4 * (z_a + qnorm(power))^2 / log(hr^frac)^2, 6))   # Schoenfeld, 1:1 allocation
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: events = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(events_needed(0.80, f), big.mark = ","), format(events_needed(0.90, f), big.mark = ",")))

# Simulation: given d total events under proportional hazards, events in the treatment arm are Binomial(d, hr / (1 + hr)).
# The score (log-rank type) statistic is (D1 - d / 2) / sqrt(d / 4).
set.seed(5171816)
d    <- events_needed(0.80)
reps <- 20000
D1 <- rbinom(reps, d, hr / (1 + hr))
z  <- (D1 - d / 2) / sqrt(d / 4)
cat(sprintf("Simulated power with %s events: %.3f (%d replicates)\n", format(d, big.mark = ","), mean(abs(z) > z_a), reps))

Output from running the code

100% of observed effect: events = 246 (80% power), 329 (90% power)
 75% of observed effect: events = 437 (80% power), 585 (90% power)
 50% of observed effect: events = 982 (80% power), 1,315 (90% power)
Simulated power with 246 events: 0.792 (20000 replicates)

The simulation uses the fact that, with d events in total and proportional hazards, the number of events in the treatment arm is binomial. It is an approximation that conditions on the total number of events, and it should land close to the target power.

14. Analyses Reported by the Sponsor

The registry record reports the sponsor’s primary analysis as a Log Rank comparison with a hazard ratio of 1.43, a 95% confidence interval from 0.83 to 2.48, and p = 0.259. The posted primary comparison gives the same figures, and the record does not flag a discrepancy between the sponsor analysis and the posted result. The sponsor analysis is therefore the appropriate reported result to use for the primary comparison.

These are the sponsor-reported inferential statistics, not an independently reconstructed treatment effect. For time-to-event outcomes, the reported hazard ratio is used rather than attempting to derive a new comparison from medians. A median from one arm cannot be used to reconstruct a hazard ratio, and the comparator median is not reported for primary rPFS.

Any planning illustrations based on the observed effect answer a different question from the sponsor’s analysis. They describe hypothetical event requirements under stated assumptions and do not replace the reported estimate, confidence interval, or test. The registry record does not report additional details about the sponsor’s model specification, adjustment variables, or sensitivity analyses. Those details cannot be inferred from the matching estimates.

15. Multiplicity, Missing Data and Analysis Populations

The registry record identifies rPFS as the primary outcome and lists 9 outcome measures, with 6 analyses. It also lists multiple secondary endpoints, including survival, subsequent therapy, symptoms, skeletal events, progression, and patient-reported outcomes. The record does not report how the family of endpoints and analyses was handled statistically. In particular, a prespecified testing hierarchy, multiplicity adjustment, or allocation of the overall type I error is not reported in the registry record.

As a general explanation, when multiple hypotheses are tested, the chance of at least one apparently positive result can increase if each is judged in isolation at the same threshold. A prespecified strategy can address this, for example by controlling error across a family or by setting an order for testing. Without a documented strategy, individual secondary p-values should not be interpreted as if they were the sole confirmatory test. This is a limitation of what the registry record documents; it is not evidence that the full study protocol lacked a strategy.

The primary endpoint population is named as the Full Analysis Set (FAS). The registry record does not report a detailed definition of this population, the handling of participants with protocol deviations, or the analysis population used for each secondary endpoint. It also does not report the extent or reasons for missing outcome data, the missing-data assumptions, or sensitivity analyses for missingness. These details matter because time-to-event results depend on observation and follow-up, while patient-reported outcomes can be affected by missing assessments.

The primary endpoint schedule is described, as is the follow-up range, but the registry record does not provide the number of events or a complete account of censoring and withdrawal handling. It does not report interim analyses or stopping rules. Those details are relevant to understanding the conduct and interpretation of the analysis, but should not be guessed from the study design label or the posted results. The absence of these details in the registry record limits independent assessment of the statistical plan and does not establish that the analyses were improperly conducted.

16. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pneumonia (7.4%), cataract (3.7%), death (3.7%), covid-19 (3.7%), urinary tract infection (3.7%).

The registry record reports serious adverse events in 23 of 54 participants in the olaparib-plus-abiraterone group and 21 of 56 in the placebo-plus-abiraterone group. It reports other adverse events in 53 of 54 and 54 of 56, respectively. Deaths are listed for 18 and 16 participants, respectively. These are counts in the posted safety summary; the record does not provide further detail about event timing, duration, severity grading, relatedness, or reasons for discontinuation.

The listed serious adverse-event terms include pneumonia (7.4%), cataract (3.7%), death (3.7%), Covid-19 (3.7%), urinary tract infection (3.7%), and type 2 diabetes mellitus (3.6%). These are the terms identified among the top serious events in the record, not a complete description of every safety event. A term’s listing does not establish that it was caused by study treatment. The deaths listed in the safety summary should not be treated as treatment-related deaths without information on attribution, which is not reported in the registry record.

Counts should be read alongside the group sizes and the study’s follow-up, and not as proof that the safety profiles are the same or different. The registry record’s safety summary does not report a comparative statistical analysis or uncertainty intervals for these counts. It therefore supports a descriptive account of reported events, not a definitive estimate of comparative safety.

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

The posted primary result describes an estimated median rPFS of 14.75 months in the olaparib-plus-abiraterone group, with a 95% confidence interval from 12.06 to 22.11 months. It also reports a hazard ratio of 1.43, with a 95% confidence interval from 0.83 to 2.48 and p = 0.259. Together, these statistics show substantial uncertainty about the comparative primary endpoint. The comparator median is not reported in the registry record.

The result does not establish that the two treatment strategies are equivalent, nor does it establish a clear difference. A non-significant p-value is not proof of no effect. Equivalence or noninferiority would require an appropriate design and a prespecified margin; neither is reported in the registry record. The confidence interval includes 1 and spans relative estimates on either side of that reference, so the data as posted do not identify a precise relative effect.

The results also do not establish what would happen for an individual participant. A group-level time-to-event estimate is not a personalized prognosis. The record does not support conclusions about people outside the described study population, such as those with different prior treatment histories or disease circumstances. No clinical advice follows from these statistics.

Safety counts provide descriptive information about reported adverse events, but do not by themselves determine causation or comparative risk. The registry record does not provide the detailed event attribution and comparative safety analysis needed to make those judgments. Likewise, secondary outcomes may add context, but their interpretation is limited by the breadth of endpoints and the absence of a reported multiplicity strategy.

The appropriate reading is therefore bounded: the registry record documents a randomized comparison and reports a primary time-to-event estimate with substantial uncertainty, along with selected secondary and safety information. It does not, by itself, settle the magnitude or direction of the primary effect, demonstrate equivalence, or establish a treatment recommendation.

18. Why This Trial Matters Statistically

This trial is statistically informative because it uses randomized, masked, parallel-group allocation to compare two strategies that share abiraterone and differ in whether olaparib or matching placebo is added. Randomization is a design feature intended to support a fair comparison of assigned strategies, while masking can reduce some forms of influence on assessment and reporting. The registry record identifies quadruple masking, although it does not specify which parties that label covers.

The primary endpoint combines radiological progression and death in a time-to-event measure. This makes the timing of outcomes relevant and allows follow-up of differing lengths to contribute information. The record describes repeated imaging assessments and a follow-up range from 479 days (approx 16 months) at minimum to 913 days (approx 30 months) at maximum, offering important context for interpreting the estimate.

The posted result also illustrates why effect estimates, confidence intervals, and p-values should be read together. The hazard ratio is 1.43, but its 95% confidence interval ranges from 0.83 to 2.48 and the p-value is 0.259. A point estimate alone could invite a stronger conclusion than the uncertainty supports. Conversely, a p-value above a conventional threshold does not show that the treatment strategies are equivalent.

Finally, the record includes outcomes beyond rPFS, such as survival, pain, subsequent therapy, and patient-reported measures. This broad outcome set can describe different dimensions of a trial, but it also makes transparent reporting of analysis plans and multiplicity important. The record’s missing analysis details are a reason to interpret secondary findings cautiously, not a basis for assuming that unreported methods were or were not used.

19. 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 result has a broad confidence interval, and the comparator-arm median rPFS is not reported in the registry record. The primary endpoint is therefore best interpreted through the reported hazard ratio and its interval, not through an unavailable comparison of medians. The record also does not report the number of primary events, limiting assessment of the information underlying the time-to-event estimate.

Follow-up varied from 479 days (approx 16 months) at minimum to 913 days (approx 30 months) at maximum. This range means participants were not all observed for the same duration; the detailed censoring rules and the handling of withdrawals or missing assessments are not reported in the registry record. Longer-term results may not be captured by the posted follow-up summary.

The registry record states the primary analysis population is the FAS but does not define it in detail. It does not report the full statistical analysis plan, proportional-hazards assessments, covariate adjustment, sensitivity analyses, interim analyses, stopping rules, or the multiplicity strategy. These omissions limit independent evaluation of how the analysis was specified and how robust the results are to alternative choices.

The safety information is also limited to posted counts and selected serious adverse-event terms. Detailed attribution, grading, timing, exposure duration, and comparative uncertainty are not reported in the registry record. The posted results include numerical information for only a subset of the listed secondary outcomes, so the secondary-outcome pattern cannot be treated as a complete account of every planned measure.

These limitations concern the amount and detail of information reported in the registry record. They do not establish that the study lacked procedures or analyses that are not recorded there. The original sample-size justification and design assumptions are not reported; planning illustrations based on the observed effect should not be mistaken for those original design calculations.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Study on Olaparib Plus Abiraterone as First-line Therapy in Men With Metastatic Castration-resistant Prostate Cancer (China Cohort) — NCT05171816.
• Registry record last updated 2026-08-28; status last verified 2026-08.
• Results first posted 2025-06-29.
• 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.

23. Record Summary

The registry record describes a randomized, quadruple-masked, parallel-group phase III study of olaparib plus abiraterone versus placebo plus abiraterone in men with metastatic castration-resistant prostate cancer. It is identified as the China cohort of the PROpel Study. Planned enrollment is 110, and the status is active, not recruiting.

The primary endpoint is rPFS in the FAS. The posted olaparib-plus-abiraterone median is 14.75 months, with a 95% confidence interval from 12.06 to 22.11 months; a comparator median is not reported. The sponsor-reported hazard ratio is 1.43, with a 95% confidence interval from 0.83 to 2.48 and p = 0.259 by Log Rank. The interval and test result leave uncertainty about the comparative effect.

Selected secondary outcomes and safety counts are reported, but the registry record does not report a multiplicity strategy, detailed missing-data procedures, or the original sample-size justification. The secondary and safety information should therefore be interpreted descriptively and with appropriate caution.