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 An Observational Study of Radiotherapy After Injection of SpaceOAR Hydrogel (NCT05735652), a registered phase not stated study. The primary outcome is Change of Dose Rectum Volume Receiving Radiation Between Radiotherapy Plannings Pre and Post SpaceOAR Hydrogel Injection..
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05735652 |
| Phase | Phase not stated |
| Condition | Prostate Cancer |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 14 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Boston Scientific Corporation |
| Results posted | Yes |
2. Clinical Question
The study asks whether radiotherapy planning measurements and safety outcomes can be described in patients with localized T1-T2 prostate cancer in China after SpaceOAR Hydrogel injection. Its primary question concerns the change in rectal volume receiving radiation between planning before and after injection. The registry describes the study as observational, so the record does not establish a randomized comparison of hydrogel with no hydrogel or with another treatment.
Population
Patients with localized T1-T2 prostate cancer in China who received SpaceOAR Hydrogel are the population described. The registry reports enrollment of 14. Further detail on the analyzed population, eligibility criteria, or participant characteristics is not reported in the registry record.
Intervention
The intervention listed is SpaceOAR Hydrogel, a device. The study concerns patients who received the hydrogel and received or were expected to receive radiotherapy. Because the design is observational, the registry does not describe randomized assignment to hydrogel.
Comparator
No like-for-like control group is reported. The primary endpoint compares radiotherapy planning measurements made before and after hydrogel injection, rather than outcomes between randomized groups. Allocation is not stated, and the record cautions that the arms are not a control comparison.
Primary question
How does the rectal volume receiving radiation differ between planning before and after SpaceOAR Hydrogel injection? The endpoint is expressed in cc, with the mean and standard deviation specified. A numerical change, uncertainty estimate, or statistical test result is not reported in the registry record.
3. Trial Design
NCT05735652 is an observational study sponsored by Boston Scientific Corporation. Its title concerns radiotherapy after SpaceOAR Hydrogel injection in localized T1-T2 prostate cancer in China. The registry lists the status as completed, enrollment of 14, a start date of 2022-11-03, and primary completion on 2024-04-30.
The listed group consists of subjects with localized T1-T2 prostate cancer in China who were injected with SpaceOAR Hydrogel. The study objective is to evaluate safety and effectiveness by collecting clinical data related to radiotherapy. The intervention is identified as a device; no randomized assignment is described. The registry explicitly notes that allocation is not stated and that the arms are not a like-for-like control comparison. Consequently, the pre- and post-injection planning measurements are the relevant comparison for the primary question, not a randomized between-group contrast.
The primary outcome concerns the change in rectal volume receiving radiation between radiotherapy planning before and after injection. The specified unit is cc, the summary measure is the mean, and the stated dispersion measure is the standard deviation. Its timeframe is post-injection gel surgery 1-10 days. The registry also lists urinary, bowel and sexual function, quality of life measured with EQ-5D-5L, prostate-to-rectum distance, and adverse events related to SpaceOAR Hydrogel among secondary outcome descriptions.
The record identifies six outcome measures but reports zero analyses. Numerical results for the primary endpoint are not reported in the registry record. A protocol, statistical analysis plan, sample-size justification, and explanation of any interim analyses 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
| Stage | Observational Study of 14 Cases, Single Arm |
|---|---|
| STARTED | 14 |
| COMPLETED | 14 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Potential subjects for this study are patients with localized prostate cancer enrolled in the SpaceOAR Hainan Real World Study (U0720) who have been treated with SpaceOAR hydrogel at a hospital in the Boao Licheng Medical Pilot Area in Hainan and have received or will receive radiation therapy at the study center.
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: For subjects who have already completed radiotherapy before study kick-off, clinical data will be collected retrospectively, such as data related to radiotherapy, AE (if any) and MRI (if any), and follow up will be performed, if applicable. For subjects who receive therapy after study kick-off, radiotherapy relevant clinical data will be collected, and follow up visits after radiotherapy will be scheduled to assess urinary, bowel, sexual functions and AE.
| Characteristic | Unit | Single Arm Obsevational Study Total 14 Cases |
|---|---|---|
| Participants analysed | 14 | |
| Age, Continuous | years | 74.1 (SD 7.9) |
| Sex/Gender, Customized: Count of Participants – Male | Participants | 14 |
| Sex/Gender, Customized: Count of Participants – Female | Participants | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 14 |
| 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 | 0 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
6. Primary Endpoint
The registry lists the primary outcome as Change of Dose Rectum Volume Receiving Radiation Between Radiotherapy Plannings Pre and Post SpaceOAR Hydrogel Injection., measured over Post injection gel surgery 1-10 days.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | cc |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the change in the volume of the rectum receiving radiation, comparing radiotherapy planning before and after SpaceOAR Hydrogel injection. The measurement is derived from dose-volume histograms based on CT simulation scans and is expressed in cc. The registry specifies the mean as the summary measure and the standard deviation as the measure of dispersion. The stated timeframe is post-injection gel surgery 1-10 days.
This endpoint is intended to characterize how the planned radiation exposure to rectal volume differs across the two planning time points. A dose-volume histogram relates radiation dose to the volume of an organ receiving that dose; using a volume measure gives a quantitative description of the rectal exposure represented in the plan. That makes the endpoint relevant to assessing the planning changes that the study set out to describe. This explanation is general and does not establish a clinical benefit or a biological effect.
The registry record does not report the mean change, standard deviation, number of participants contributing to the endpoint, confidence interval, or test result. It also does not state the precise dose threshold defining the rectal volume measurement. Without those details, the direction, magnitude, and precision of any change cannot be assessed from the posted results.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record defines a clinically focused planning question, but it does not provide numerical results for the primary endpoint. Although the endpoint is specified as a change in mean rectal volume receiving radiation, there is no posted mean change, standard deviation, confidence interval, or hypothesis-test result. The stated unit, cc, describes how the volume is measured; it does not indicate the magnitude or direction of a result. The record therefore does not permit an assessment of how large or precisely estimated the planning change was.
The observational design is important to interpretation. The study describes patients who received SpaceOAR Hydrogel and radiotherapy, rather than a randomized comparison with a concurrent untreated or alternative-treatment group. The primary contrast is between planning measurements before and after injection. A within-patient pre/post comparison can describe change over time, but by itself it does not isolate the hydrogel as the cause of a difference. Other changes in planning, measurement, or care could also contribute. The registry does not report adjustment methods that might address such factors.
The registry reports enrollment of 14 and lists one group. That enrollment count should not be taken as the number analyzed for the primary outcome: the endpoint-specific analysis population and completeness are not reported. The record lists zero analyses, so it does not provide an analysis result with which to judge statistical uncertainty or consistency. The completed status indicates the registry’s study status, not that a particular endpoint result was posted.
Safety information is available as counts for the listed group: 1 subject affected by a serious adverse event, 4 affected by other adverse events, and 0 deaths. The top serious-event term is compression fracture of the lumbo2 vertebrae, reported as 7.1%. These counts are descriptive. The registry’s summary does not provide event timing, exposure-adjusted rates, a comparison group, or enough detail to establish whether an event was caused by the hydrogel or radiotherapy.
The study objective includes safety and effectiveness, but the posted record supports only a limited statistical interpretation. It identifies outcomes and enrollment and gives selected adverse-event counts. It does not report the primary endpoint estimate or enough analytic detail to determine precision, missing-data effects, or how secondary outcomes were handled. No conclusion about treatment effectiveness or comparative safety can be drawn from the record alone.
9. Statistical Methods Explained
The primary outcome is continuous: rectal volume receiving radiation is measured in cc. For a continuous measure, a mean describes the average value or average change in the analyzed observations. A standard deviation describes how spread out individual values are around that mean. These are distinct quantities: the mean summarizes location, while the standard deviation summarizes variability. The registry specifies both measures but reports neither numerical value for the primary endpoint.
What does a pre/post change represent?
The endpoint compares planning before and after SpaceOAR Hydrogel injection. In a paired analysis, each participant’s measurements at the two time points are linked, and the analysis focuses on within-person differences. This can account for stable differences between participants because each person serves as their own reference. The analysis still depends on having usable measurements at both time points and on an appropriate treatment of those differences. The registry does not report whether the analysis was paired, how incomplete pairs were handled, or what statistical test was used.
As a general statistical principle, the standard deviation of individual measurements is not the same as the standard deviation of within-person changes. The variability of changes depends in part on how closely the pre- and post-injection measurements are related. A report of the mean change and its uncertainty would help readers judge both the estimated direction and its precision. The registry record does not report those results, so no estimate or uncertainty can be interpreted.
How should uncertainty be assessed?
A confidence interval is a range of values compatible with the data and the assumptions of the method. Its width conveys precision: a narrower interval indicates more precision under the method’s assumptions, while a wider interval indicates less. A p-value, when used, measures how unusual the data would be under a specified null hypothesis and statistical model; it is not a measure of clinical importance. Neither a confidence interval nor a p-value for the primary outcome is reported in the registry record. There is therefore no basis for describing the primary result as statistically significant or nonsignificant.
For any analysis of a continuous endpoint, distributional shape and influential observations can matter, especially in a small study. The mean and standard deviation can be sensitive to unusually large or small measurements. A careful report could describe the distribution, the number contributing at each time point, and any sensitivity analyses. Such information is not reported in the registry record. These are general considerations, not claims about the data in this study.
What can the planning assumptions tell readers?
The registry’s sample-size assumptions describe planning illustrations based on the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The assumptions define the effect to detect as a stated fraction of the observed effect. The registry record does not provide the primary effect estimate needed to evaluate those illustrations. More importantly, the assumptions are not a description of this observational study’s actual design: it lists a single group and no randomized two-arm allocation.
Sample-size illustrations are prospective planning calculations under chosen assumptions. They do not establish the probability that this completed study detected an effect, and they are not observed power. Any interpretation must distinguish a hypothetical future design from the data collected in the present study. The record does not report a trial-specific sample-size justification or protocol rationale.
Why does the observational design matter statistically?
Without random allocation or a like-for-like control group, a pre/post difference is descriptive and is not automatically a causal effect of the hydrogel. Changes between planning time points may reflect the intervention, but may also reflect other differences in measurement or planning. Statistical adjustment can sometimes address measured factors, but cannot ensure control of unmeasured differences. The registry does not report an adjusted analysis or the details needed to assess one. This design limitation remains separate from the precision of any estimate: a precise estimate of a pre/post change would not, by itself, prove that the hydrogel caused it.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists six outcome measures, including the primary rectal-volume change and secondary assessments of urinary, bowel and sexual function, quality of life on the EQ-5D-5L scale, prostate-to-rectum distance, and adverse events. It reports zero analyses. No multiplicity strategy, hierarchy among secondary outcomes, or prespecified approach to interpreting multiple tests is reported in the registry record. When many outcomes are examined, the chance of at least one apparently unusual result can increase; statistical plans commonly address this by identifying a primary outcome and specifying how secondary analyses will be interpreted. This is a general concern, not evidence that any particular analysis was conducted.
Missing-data methods are not reported in the registry record. The record does not state how many participants had measurements at each time point, how missing measurements were handled, or whether an analysis required complete pre- and post-injection observations. Those details matter because an endpoint estimate based on a subset may differ from one based on everyone enrolled, and the reason for missingness can affect interpretation.
The analysis populations are also not reported in the registry record. Enrollment is reported as 14, but the number contributing to each outcome cannot be inferred from that figure. There is no description of exclusions, deviations, or a population definition for efficacy or safety analyses. The registry does not report an analysis plan, interim-analysis approach, or sensitivity analyses. These omissions limit assessment of selection, multiplicity, and robustness; they do not establish that any particular procedure was or was not used outside the posted 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 |
|---|---|---|---|
| Subjects With Localized T1-T2 Prostate Cancer in China Who Were Injected With SpaceOAR Hydrogel | 1 | 14 | 7.1% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Subjects With Localized T1-T2 Prostate Cancer in China Who Were Injected With SpaceOAR Hydrogel | 0 of 14 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Subjects With Localized T1-T2 Prostate Cancer in China Who Were Injected With SpaceOAR Hydrogel | 4 of 14 |
Most frequent serious adverse event terms
| Event term | Organ system | Subjects With Localized T1-T2 Prostate Cancer in China Who Were Injected With SpaceOAR Hydrogel |
|---|---|---|
| compression fracture of the lumbo2 vertebrae | Surgical and medical procedures | 1 of 14 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Subjects With Localized T1-T2 Prostate Cancer in China Who Were Injected With SpaceOAR Hydrogel |
|---|---|---|
| Coronavirus 2019 (COVID-19) | Infections and infestations | 4 of 14 |
Serious events with the highest arm-level rate: compression fracture of the lumbo2 vertebrae (7.1%).
For the listed group of subjects with localized T1-T2 prostate cancer in China who received SpaceOAR Hydrogel, the registry reports 14 subjects at risk for serious adverse events and 1 affected by a serious adverse event. For other adverse events, it reports 14 at risk and 4 affected. The reported death count is 0. These are counts for the group, not a comparison between hydrogel and a control group.
The top serious adverse-event term is compression fracture of the lumbo2 vertebrae, with 7.1% reported. The registry summary does not provide the event’s timing, duration, severity details beyond its serious-event classification, or a comparison rate. Although a secondary outcome is described as adverse events related to SpaceOAR Hydrogel, the posted counts do not by themselves establish causation or show which events were judged related.
These figures should be read as descriptive safety information for the study group. They do not establish the frequency of events in a broader population or permit a comparative safety estimate. A fuller assessment would require details on event definitions, follow-up, attribution, and the population included in safety monitoring; those details are not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The record documents an observational study of radiotherapy planning and safety in patients with localized T1-T2 prostate cancer in China after SpaceOAR Hydrogel injection. Its primary endpoint is clearly identified as a change in rectal volume receiving radiation between pre- and post-injection planning. The endpoint is measured in cc, and the registry specifies the mean and standard deviation as its summary statistics. These details establish what the study intended to measure.
They do not establish what the study found. The registry record does not report a numerical primary-endpoint result, its variability, a confidence interval, or a statistical test. Consequently, the direction and size of the change, and the precision of any estimate, cannot be determined from the posted results. The listed completed status and enrollment of 14 do not substitute for those endpoint results.
The design also limits the claims that could be supported even if a pre/post difference were reported. There is no reported randomized control group, and the registry says allocation is not stated and the arms are not a like-for-like comparison. A before-and-after contrast can describe how measurements changed in the observed group, but cannot alone attribute that change to SpaceOAR Hydrogel.
The adverse-event counts provide limited descriptive information: 1 serious-event-affected subject, 4 affected by other adverse events, and 0 deaths are reported. The serious-event term and its percentage are listed, but no comparison, detailed event follow-up, or attribution is given. These data cannot establish comparative safety.
Thus, the registry record identifies a relevant planning endpoint and reports selected safety counts, but does not support a conclusion about the magnitude of the primary change, its statistical precision, treatment effectiveness, or comparative safety. Those interpretations require results and analytic details not reported in the registry record.
13. Why This Trial Matters Statistically
This study raises a practical statistical question: whether rectal radiation-volume measurements differ between planning before and after SpaceOAR Hydrogel injection in an observational clinical setting. The pre/post structure can be informative because it compares measurements within the same participants rather than relying solely on differences between separate groups. Its usefulness depends on clear reporting of the paired measurements, the size and variability of the change, and the participants contributing data.
The registry specifies a mean and standard deviation and identifies the measurement unit, which helps define the intended endpoint. But an endpoint definition is not a result. Without a reported estimate and uncertainty, readers cannot distinguish a potentially meaningful change from a small or imprecisely estimated one. The absence of reported analyses also prevents assessment of how the specified measure was analyzed.
The study is statistically important as a reminder that observational before-and-after evidence has a different interpretation from a randomized comparison. Within-person measurement can address stable participant differences, but it does not control for every factor that may change between measurements. The design therefore calls for cautious language about association and change, rather than causal attribution.
The record also illustrates why safety counts need context. The reported serious and other adverse-event counts are useful descriptive elements, but without a control group, event timing, follow-up detail, and attribution, they cannot provide a comparative risk estimate. Transparent reporting of outcomes, analysis populations, missingness, and methods would make the findings more interpretable for clinicians and researchers.
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 primary limitation for interpretation is that the registry record does not report a numerical result for the primary endpoint. The mean change, standard deviation, confidence interval, and test result are absent, as is the number contributing paired measurements. This prevents evaluation of the endpoint’s magnitude, precision, and completeness.
The study is observational and has no reported like-for-like control group. The registry states that allocation is not stated and that arms are not a control comparison. A pre/post change, if reported, could not by itself establish that SpaceOAR Hydrogel caused the change. The record does not describe adjustment for other factors or provide enough information to assess confounding.
Enrollment is 14, but the registry does not report the outcome-specific analysis populations or missing-data handling. It also does not report a statistical analysis plan, sample-size justification, interim analyses, or methods for addressing multiple outcomes. The listed outcome measures therefore cannot be interpreted alongside a documented analysis strategy.
Safety reporting is limited to group counts and a top serious-event term. Event timing, follow-up, attribution, and comparison data are not reported in the registry record. Finally, details such as the exact radiation-dose threshold for the rectal-volume endpoint and participant characteristics beyond the stated cancer stage and location are not reported. These limitations describe gaps in the posted record, not proof that the study team did not collect additional information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: An Observational Study of Radiotherapy After Injection of SpaceOAR Hydrogel — NCT05735652.
- Registry record last updated 2025-05-30; status last verified 2025-05.
- Results first posted 2025-03-26.
- 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
NCT05735652 is a completed observational study sponsored by Boston Scientific Corporation. It lists enrollment of 14 and concerns patients in China with localized T1-T2 prostate cancer who received SpaceOAR Hydrogel and radiotherapy. The registry reports a start date of 2022-11-03 and primary completion on 2024-04-30.
The primary endpoint is the change in rectal volume receiving radiation between planning before and after hydrogel injection, measured in cc. The mean and standard deviation are specified, but numerical endpoint results and analyses are not reported in the registry record. Safety counts include 1 subject affected by a serious adverse event, 4 affected by other adverse events, and 0 deaths; the top serious-event term is compression fracture of the lumbo2 vertebrae, reported as 7.1%. The observational design and absence of a like-for-like control limit causal and comparative interpretation.