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 CyberKnife Radiosurgery For Low & Intermediate Risk Prostate Cancer: Emulating HDR Brachytherapy Dosimetry (NCT00643617), a na na study. The primary outcome is Risk for Gastrointestinal (GI) and Genitourinary (GU) Toxicity.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00643617 |
| Phase | NA |
| Condition | Prostate Cancer, Prostatic Cancer, Prostatic Neoplasms |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 307 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Accuray Incorporated |
| Results posted | Yes |
2. Clinical Question
Population
People with low-risk or intermediate-risk prostate cancer treated in a prospective evaluation of CyberKnife stereotactic radiosurgery. The registry describes the intended population as people with early-stage, organ-confined prostate cancer. It does not report additional eligibility details in this record.
Intervention
CyberKnife stereotactic radiosurgery, with separate low-risk and intermediate-risk cohorts. The described heterogeneous-dose regimen was 38 Gy delivered in 4 fractions of 9.5 Gy per fraction.
Comparator
There was no randomized comparator. The registry identifies a single-group model and does not specify an allocation method. The low-risk and intermediate-risk cohorts are not a like-for-like control comparison.
Primary question
The primary safety question was to estimate acute and late Grade 3-5 gastrointestinal and genitourinary toxicity rates during the 5 years following treatment. The registry also describes Kaplan-Meier estimates for 5-yr and 10-yr follow-up.
The study also set out to evaluate quality of life over time. Listed secondary outcomes include disease control and survival, the American Urological Association Symptom Index, and urinary, bowel, and sexual domains of the Expanded Prostate Cancer Index Composite. These outcomes address different aspects of follow-up and should not be conflated with the primary safety endpoint.
The endpoint description defines acute adverse events as those occurring within 3 months of treatment and late events as those developing after 3 months. For the toxicity-rate calculation, it specifies the first Grade 3 or higher adverse event per patient when the event was assessed as possibly, probably, or definitely related to CyberKnife treatment. The registry record does not report the resulting estimates in the information available for this analysis.
3. Trial Design
This was a prospective evaluation sponsored by Accuray Incorporated. The registry classifies it as a single-group study, with allocation recorded as NA and masking recorded as none. The study was marked completed. Enrollment was 307. The listed start date is 2007-10-22, and the primary completion date is 2022-04-07.
The evaluation covered low-risk and intermediate-risk prostate cancer cohorts. The registry lists CyberKnife stereotactic radiosurgery interventions for each risk group. Its arm description specifies a heterogeneous dose of 38 Gy delivered in 4 fractions of 9.5 Gy per fraction. The record does not describe a randomized allocation or a concurrent control arm. The two risk cohorts therefore should not be treated as randomized treatment groups or as a direct estimate of treatment differences.
The primary safety endpoint concerned Grade 3-5 gastrointestinal and genitourinary toxicities, with a five-year primary safety measurement timeframe. Sites and patients had the option of continuing follow-up through 10 years. The outcome description says that Kaplan-Meier estimates for 5-yr and 10-yr are reported, but the corresponding estimates are not reported in the registry record.
The record lists eight outcome measures and 0 analysis entries. It identifies disease control and survival outcomes, along with quality-of-life assessments, as secondary outcomes. It does not report a statistical analysis plan, the sample-size justification, or further details of participant follow-up and analysis populations. Phase is recorded as NA. These registry descriptors provide the study’s broad structure, but they are not a substitute for details of the protocol or a full statistical report.
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: Of these 307 subjects, 48 patients did not receive study treatment and were withdrawn from the study. Reasons for withdrawal included meeting exclusion criteria after central pathology review, insurance did not approve participation in a clinical study, or patient decision to withdraw prior to receiving treatment. 259 subjects were assigned to either the "Low Risk" or "Intermediate Risk" groups after central pathology review results.
Overall Study
| Stage | Low Risk | Intermediate Risk |
|---|---|---|
| STARTED | 112 | 147 |
| 10-yr Follow up | 36 | 33 |
| COMPLETED | 64 | 87 |
| NOT COMPLETED | 48 | 60 |
Reasons for not completing this period:
| Reason | Low Risk | Intermediate Risk |
|---|---|---|
| Death | 6 | 9 |
| Lost to Follow-up | 42 | 51 |
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 | CyberKnife Stereotactic Radiosurgery - Low Risk | CyberKnife Stereotactic Radiosurgery - Intermediate Risk | Total |
|---|---|---|---|---|
| Participants analysed | 112 | 147 | 259 | |
| Age, Continuous | years | 67.2 (45.5 to 81.9) | 68.4 (52.6 to 87.6) | 67.8 (45.5 to 87.6) |
| Sex: Female, Male: Female | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Male | Participants | 112 | 147 | 259 |
| Race/Ethnicity, Customized: American Indian or Alaska Native | Participants | 1 | 1 | 2 |
| Race/Ethnicity, Customized: Asian | Participants | 0 | 2 | 2 |
| Race/Ethnicity, Customized: Black/African American | Participants | 5 | 3 | 8 |
| Race/Ethnicity, Customized: Hispanic/Latino | Participants | 1 | 12 | 13 |
| Race/Ethnicity, Customized: Native Hawaiian or Pacific Islander | Participants | 0 | 2 | 2 |
| Race/Ethnicity, Customized: White | Participants | 105 | 127 | 232 |
| Region of Enrollment: United States | Participants | 112 | 147 | 259 |
| Tumor Clinical Stage (CS): T1b = Tumor incidental histological finding in >5% of tissue resected | Participants | 0 | 0 | 0 |
| Tumor Clinical Stage (CS): T1c = Tumor identified by needle biopsy found in one or both sides, but not palpable | Participants | 85 | 98 | 183 |
| Tumor Clinical Stage (CS): T2a = Tumor involves ½ of one side or less | Participants | 27 | 46 | 73 |
| Tumor Clinical Stage (CS): T2b = Tumor involves >½ of one side but not both sides | Participants | 0 | 3 | 3 |
| Total Gleason Score: Gleason 2 - 6 | Participants | 112 | 11 | 123 |
| Total Gleason Score: Gleason 7 | Participants | 0 | 136 | 136 |
| Prostate Specific Antigen (PSA) | ng/mL | 4.72 (0.1 to 9.2) | 6.31 (0.9 to 19.3) | 5.6 (0.1 to 19.3) |
| Eastern Cooperative Oncology Group (ECOG) Performance Status: 0 = Fully active, able to carry on all pre-disease performance without restric | Participants | 109 | 137 | 246 |
| Eastern Cooperative Oncology Group (ECOG) Performance Status: 1 = Restricted in physically strenuous activity | Participants | 2 | 9 | 11 |
| Eastern Cooperative Oncology Group (ECOG) Performance Status: 2 = Capable of all selfcare but unable to carry out any work activities | Participants | 0 | 0 | 0 |
| Eastern Cooperative Oncology Group (ECOG) Performance Status: 3 = Capable of only limited selfcare | Participants | 0 | 0 | 0 |
| Eastern Cooperative Oncology Group (ECOG) Performance Status: Unreported | Participants | 1 | 1 | 2 |
| American Joint Committee on Cancer (AJCC) 6th Edition Risk Group: Low: CS T1b-T2a, Gleason 2-6, PSA ≤ 10 ng/ml | Participants | 112 | 0 | 112 |
| American Joint Committee on Cancer (AJCC) 6th Edition Risk Group: Intermediate: CS T2b, Gleason 2-6, PSA ≤ 10 ng/ml | Participants | 0 | 2 | 2 |
| American Joint Committee on Cancer (AJCC) 6th Edition Risk Group: Intermediate: CS T1b-T2b, and Gleason 2-6, PSA ≤ 20 ng/ml | Participants | 0 | 9 | 9 |
| American Joint Committee on Cancer (AJCC) 6th Edition Risk Group: Intermediate: CS T1b-T2b and Gleason 7, PSA ≤ 10 ng/ml | Participants | 0 | 136 | 136 |
6. Primary Endpoint
The registry lists the primary outcome as Risk for Gastrointestinal (GI) and Genitourinary (GU) Toxicity, measured over Primary Safety Endpoint was measured at 5 years. Sites and patients had the option of continuing follow-up through 10 years..
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | percentage of participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint was the rate of acute and late Grade 3-5 gastrointestinal and genitourinary toxicities observed after CyberKnife treatment in the low-risk and intermediate-risk cohorts. The registry describes the endpoint as a percentage of participants and gives a primary safety measurement timeframe of 5 years. Sites and patients could continue follow-up through 10 years, and the outcome description specifies Kaplan-Meier estimates for 5-yr and 10-yr.
The event definition is based on the first Grade 3 or higher adverse event per patient that was considered possibly, probably, or definitely related to treatment. Acute events were those occurring within 3 months of treatment; events developing after 3 months were considered late. The registry states that CTCAE Version 3.0 was used to determine severity. It describes Grade 3 as severe or medically significant but not immediately life-threatening, Grade 4 as life-threatening, and Grade 5 as death related to the adverse event.
This endpoint is used to describe serious toxicity over follow-up rather than to compare treatment with an untreated or alternative-treatment group. General: time-to-event methods such as Kaplan-Meier estimation can account for different lengths of observed follow-up, provided the required event and censoring information is available. The registry record does not report the endpoint estimates or the underlying follow-up details needed to assess them.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record defines a clinically important safety question: how often severe gastrointestinal or genitourinary toxicities occurred after treatment, with acute and late events distinguished by their timing. It also specifies that the first qualifying Grade 3 or higher event per patient is counted for the treatment-related toxicity-rate endpoint. However, the record does not report the resulting five-year or ten-year Kaplan-Meier estimates. The principal endpoint therefore cannot be quantified from the information.
The adverse-event summaries contain counts for the two risk groups. In the low-risk group, 17 participants were affected among 112 at risk in the serious-event summary, and 103 were affected among 112 at risk in the other-event summary; 9 deaths are listed. In the intermediate-risk group, 25 participants were affected among 147 at risk in the serious-event summary, and 142 were affected among 147 at risk in the other-event summary; 14 deaths are listed. These summaries do not, by themselves, establish which events met the primary endpoint definition, when events occurred, or whether events were considered related to treatment. They should not be substituted for the missing primary endpoint estimates.
The record also lists the most frequent serious-event terms with their reported percentages: Other Malignancy, 5.4%; Infection, 3.6%; Death NOS, 2.7%; CNS Ischemia, 2.0%; Syncope (fainting), 1.8%; and Cardiac Ischemia/Infarction, 1.4%. The terms and percentages are part of the serious-event summary, not the defined primary toxicity-rate result. The record does not provide enough detail in this information to interpret these terms as treatment-related or as Grade 3-5 gastrointestinal or genitourinary toxicity.
There is no randomized comparison. The two risk cohorts differ by risk classification and are not a like-for-like control comparison, so their summaries cannot establish a causal contrast between treatments or risk groups. General: an estimate is more informative when accompanied by its uncertainty, such as a confidence interval, which describes a range of values compatible with the data and model. The primary endpoint’s interval estimates are not reported in the registry record. Without those estimates and their uncertainty, the precision of the primary safety findings cannot be assessed.
The registry lists 307 enrolled participants, but it does not report how many contributed to each primary endpoint estimate, how missing follow-up was handled, or which analysis population was used. Consequently, the adverse-event counts should be read as descriptive registry summaries rather than as a complete account of the primary endpoint analysis. No conclusion about the frequency of the specified primary toxicity endpoint can be drawn from those counts alone.
9. Statistical Methods Explained
The registry describes the primary outcome as an event-rate endpoint expressed as a percentage of participants. Its definition combines a severity threshold, event timing, and an attribution condition: the first Grade 3 or higher gastrointestinal or genitourinary adverse event per patient, occurring acutely or late, and assessed as possibly, probably, or definitely related to CyberKnife treatment. The record identifies CTCAE Version 3.0 as the severity framework.
What does the timing distinction mean?
The endpoint description classifies events occurring within 3 months of treatment as acute and events developing after 3 months as late. This distinction separates events by when they develop; it does not, on its own, demonstrate their cause. The outcome description refers to a primary safety measurement at 5 years and says sites and patients could choose to continue follow-up through 10 years. It also specifies Kaplan-Meier estimates for 5-yr and 10-yr. The corresponding estimates and details of how follow-up ended for individual participants are not reported in the registry record.
General: time-to-event analysis is useful when participants can have different lengths of follow-up and the timing of events matters. Kaplan-Meier estimation uses observed event times and accounts for participants whose event time is not observed before follow-up ends by treating those observations as censored, subject to assumptions about censoring. The resulting estimate is not simply the proportion of all enrolled participants with an event at a fixed point. Interpretation depends on knowing the event definition, follow-up, and censoring approach. The registry record does not report the details needed to assess those assumptions or to reproduce the estimates.
Why does the endpoint use the first qualifying event?
Counting the first Grade 3 or higher qualifying event per patient creates a participant-level endpoint in which repeat events do not count repeatedly toward the same person’s endpoint. This helps define what the reported rate is intended to represent. It does not describe the total burden of recurrent events, their duration, or their severity beyond the stated grade threshold. The registry description does not provide event-level results or additional rules for handling multiple events of different types.
General: event definitions affect estimates. A threshold-based endpoint includes events that meet its stated criteria and excludes those that do not. Here, the description sets the threshold at Grade 3 or higher, specifies gastrointestinal and genitourinary events, and requires a stated level of possible relationship to treatment. The descriptive serious-event summaries have a different scope unless their events are also shown to meet all of those criteria. They cannot be assumed to be equivalent to the primary endpoint.
What can a percentage estimate tell a reader?
A percentage expresses the frequency of participants with a defined event in relation to a stated denominator. For time-to-event estimates, the interpretation also depends on the time point and method used. A point estimate alone does not communicate how uncertain it is. General: a confidence interval conveys statistical uncertainty around an estimate under the analysis assumptions. A narrow interval indicates greater precision than a wide interval, while neither interval nor point estimate alone establishes causality in a nonrandomized study. The registry record does not report the primary endpoint values or their confidence intervals in the information available for this analysis.
The study has no randomized comparator, and its two cohorts are defined by prostate cancer risk group. General: randomization can help balance measured and unmeasured baseline characteristics across comparison groups; without it, differences between groups may reflect their characteristics as well as treatment or follow-up. In this single-group record, the cohort summaries are descriptive, not a randomized contrast. The registry record does not report an adjusted comparison or a statistical model for comparing the risk groups.
The record includes planning assumptions for sample-size illustrations: a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. Such calculations are planning illustrations, not observed power and not evidence that the study was designed around those assumptions. The record does not report the trial’s own sample-size justification. The available information also does not include the numerical illustration results or the observed effect used for them, so no planning sample size can be interpreted from this record alone.
General: over-dispersion occurs when observed variability exceeds what a statistical model assumes. It can make standard errors too small if the model does not account for the extra variability. The registry record does not identify an over-dispersion model or report an analysis where this issue can be assessed. No claim about over-dispersion is warranted for these results.
The registry lists 0 analysis entries. It does not report a statistical analysis plan, endpoint-specific model details, confidence intervals, or analysis-population definitions in this record. Those omissions limit assessment of how the stated outcome was estimated and how precisely it was estimated.
10. Multiplicity, Missing Data and Analysis Populations
The record lists eight outcome measures, including the primary safety outcome and secondary outcomes for disease control and survival and several quality-of-life domains. It does not report a multiplicity adjustment or a strategy for controlling the chance of false-positive findings across multiple outcomes or analyses. It also lists 0 analysis entries, so the registry record does not specify which outcome comparisons or statistical tests were conducted.
The record does not report how missing outcome data were handled, how loss to follow-up was addressed, or whether any imputation method was used. For the primary endpoint, the option of continuing follow-up through 10 years is stated, but the number of participants followed to each time point and the censoring rules are not reported in the registry record. These details matter when interpreting time-to-event estimates because participants may contribute different amounts of observed follow-up.
The analysis population is not reported in the registry record. Although overall enrollment is listed as 307, the available record does not specify how many participants entered each endpoint analysis, whether all enrolled participants were included, or how exclusions were handled. The low-risk and intermediate-risk summaries give their own at-risk counts, but those counts do not establish the analysis population for the primary endpoint.
The registry does not report a prespecified hierarchy for primary and secondary outcomes, interim analyses, stopping rules, or a protocol-based missing-data plan. Their absence from this record should not be interpreted as evidence that such procedures were or were not used; those details are not reported in the registry record. Without this information, it is not possible to assess the handling of multiplicity, missingness, or analysis-population selection in the study’s statistical results.
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 |
|---|---|---|---|
| Low Risk | 17 | 112 | 15.2% |
| Intermediate Risk | 25 | 147 | 17.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Low Risk | 9 of 112 |
| Intermediate Risk | 14 of 147 |
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 |
|---|---|
| Low Risk | 103 of 112 |
| Intermediate Risk | 142 of 147 |
Most frequent serious adverse event terms
| Event term | Organ system | Low Risk | Intermediate Risk |
|---|---|---|---|
| Other Malignancy | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 6 of 112 | 6 of 147 |
| Death NOS | General disorders | 2 of 112 | 4 of 147 |
| Infection | Infections and infestations | 4 of 112 | 2 of 147 |
| CNS Ischemia | Nervous system disorders | 1 of 112 | 3 of 147 |
| Hemorrhage/Bleeding | Gastrointestinal disorders | 1 of 112 | 2 of 147 |
| Cardiac Ischemia/Infarction | Cardiac disorders | 0 of 112 | 2 of 147 |
| Cardiopulmonary Arrest | Cardiac disorders | 1 of 112 | 1 of 147 |
| Coronary Artery Disease | Cardiac disorders | 1 of 112 | 1 of 147 |
| Syncope (fainting) | Nervous system disorders | 2 of 112 | 0 of 147 |
| Cardiac arrhythmia | Cardiac disorders | 1 of 112 | 0 of 147 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Low Risk | Intermediate Risk |
|---|---|---|---|
| Urinary Frequency/Urgency | Renal and urinary disorders | 75 of 112 | 110 of 147 |
| Pain - GU | Renal and urinary disorders | 59 of 112 | 81 of 147 |
| Diarrhea | Gastrointestinal disorders | 39 of 112 | 52 of 147 |
| Urinary Retention | Renal and urinary disorders | 34 of 112 | 54 of 147 |
| Fatigue | General disorders | 36 of 112 | 36 of 147 |
| Erectile Dysfunction | Reproductive system and breast disorders | 26 of 112 | 32 of 147 |
| Hemorrhage/Bleeding - GU | Renal and urinary disorders | 16 of 112 | 36 of 147 |
| Urinary Incontinence | Renal and urinary disorders | 12 of 112 | 23 of 147 |
| Constipation | Gastrointestinal disorders | 15 of 112 | 18 of 147 |
| GI Pain | Gastrointestinal disorders | 10 of 112 | 21 of 147 |
Serious events with the highest arm-level rate: other malignancy (5.4%), infection (3.6%), death nos (2.7%), cns ischemia (2.0%), syncope (fainting) (1.8%).
The adverse-event summary lists 17 affected participants among 112 at risk for the low-risk group’s serious-event summary and 25 among 147 at risk for the intermediate-risk group’s serious-event summary. It separately lists 103 affected among 112 at risk and 142 among 147 at risk in the other-event summaries. Death counts are listed as 9 for the low-risk group and 14 for the intermediate-risk group. These are descriptive counts as recorded; they are not the primary endpoint’s Kaplan-Meier estimates.
The most frequent serious-event terms are reported as Other Malignancy, 5.4%; Infection, 3.6%; Death NOS, 2.7%; CNS Ischemia, 2.0%; Syncope (fainting), 1.8%; and Cardiac Ischemia/Infarction, 1.4%. The registry does not establish in this summary that these terms were caused by CyberKnife treatment, met the primary endpoint’s Grade 3-5 definition, or were gastrointestinal or genitourinary toxicities. The listed death counts likewise should not be treated as treatment-related deaths without that attribution.
General: serious adverse-event summaries and a protocol-defined toxicity endpoint can use different definitions and denominators. A reader should keep the event categories separate and avoid treating these figures as a treatment-versus-control comparison. The registry record does not report additional detail about event timing, severity, or relationship to treatment for the summarized terms.
12. What the Result Does, and Does Not, Mean
The record documents a prospective evaluation of CyberKnife stereotactic radiosurgery in low-risk and intermediate-risk prostate cancer and defines a primary safety outcome focused on Grade 3-5 gastrointestinal and genitourinary toxicities. It specifies how acute and late events are distinguished and which level of treatment relationship qualifies an event. These definitions clarify what the study intended to measure.
The available record does not report the primary endpoint’s five-year or ten-year estimates, their uncertainty, or details needed to evaluate follow-up and censoring. Thus, it cannot establish the observed frequency or precision of the specified toxicities. The serious-event counts and listed event-term percentages provide separate descriptive information, but they cannot fill that gap or be assumed to represent the primary endpoint.
The study is single-group, with no randomized comparator. Its low-risk and intermediate-risk groups are cohorts, not control and treatment arms. Their figures do not provide a randomized estimate of a treatment effect, and differences between their summaries cannot be attributed to risk category or treatment without suitable analysis and supporting information. The record also does not report an adjusted comparative analysis.
The study’s aims included quality-of-life assessment over time, and several quality-of-life outcomes are listed. The information available does not report their numerical results or the statistical analyses used. Listing an outcome indicates that it was part of the registry record, but does not show its observed course or the certainty of an estimate.
These distinctions do not imply that the treatment is effective or ineffective, or that a particular adverse event was caused by treatment. They describe what can and cannot be concluded from the statistical information recorded. The record supports understanding the study’s design, endpoint definitions, and broad adverse-event summaries, but the primary outcome results and analysis details are not reported in the registry record.
13. Why This Trial Matters Statistically
This trial is statistically informative as an example of a prospective, single-group safety evaluation that defines a time-based toxicity endpoint. It distinguishes acute events from late events, specifies a Grade 3 or higher threshold, and limits the endpoint to events considered at least possibly related to treatment. These choices make clear that an endpoint is not merely a general count of adverse events: its event definition determines which observations contribute to the result.
The study also illustrates why a time-to-event estimate is distinct from a simple event count. The primary safety description specifies Kaplan-Meier estimates for 5-yr and 10-yr, while the record separately lists at-risk and affected counts for adverse-event summaries. Without the endpoint estimates, intervals, and follow-up details, those counts cannot be used as substitutes. Clear reporting of time points, censoring, denominators, and uncertainty is important for readers assessing long-term safety.
The design is equally important to interpretation. A single-group study without randomization can describe outcomes in the enrolled cohorts, but it does not provide a randomized control comparison. The low-risk and intermediate-risk cohorts are not interchangeable comparison arms. This limits what statistical contrasts could mean, even if group-specific values are available.
Finally, the record lists secondary disease-control, survival, and quality-of-life outcomes but does not report their analysis details in the available information. The case underscores the value of reporting prespecified analysis methods, missing-data handling, analysis populations, and uncertainty alongside outcome estimates. Without those elements, readers can understand the intended questions and definitions, but have limited ability to evaluate the precision and robustness of findings.
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 important limitation for interpreting the primary safety question is that the registry record does not report its numerical five-year or ten-year estimates. It also does not provide confidence intervals or detailed follow-up and censoring information. As a result, the frequency and precision of the defined Grade 3-5 gastrointestinal and genitourinary toxicity endpoint cannot be evaluated from this record.
The study is identified as single-group, with allocation recorded as NA and no masking. There is no randomized comparator, and the low-risk and intermediate-risk cohorts are not a like-for-like control comparison. Findings from these cohorts cannot establish a causal treatment contrast. The record also does not report an adjusted comparison that might address differences between cohorts.
The adverse-event summaries have limited endpoint-specific detail in the record. They do not establish whether each event met the primary endpoint’s severity, organ-system, timing, and treatment-relatedness criteria. The listed deaths and serious-event terms therefore should not be equated with treatment-related primary endpoint events. The record does not report participant-level analysis details or the denominators used for every outcome.
Other limitations arise from missing statistical reporting: the analysis plan, sample-size justification, analysis population, handling of missing data, and multiplicity strategy are not reported in the registry record. The registry lists 0 analysis entries despite listing eight outcome measures. The status is completed, but the information in this record is insufficient to assess the robustness of outcome analyses or the extent of follow-up for each endpoint.
These limitations concern what can be assessed from the registry record. They do not establish that analyses or procedures were not conducted; those details are not reported in the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: CyberKnife Radiosurgery For Low & Intermediate Risk Prostate Cancer: Emulating HDR Brachytherapy Dosimetry — NCT00643617.
- Registry record last updated 2023-05-09; status last verified 2023-05.
- Results first posted 2023-05-09.
- 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.
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18. Record Summary
NCT00643617 is a completed, prospective, single-group evaluation of CyberKnife stereotactic radiosurgery for low- and intermediate-risk prostate cancer, sponsored by Accuray Incorporated. Enrollment was 307. The listed start date is 2007-10-22, and the primary completion date is 2022-04-07. Allocation is recorded as NA, masking as none, and phase as NA.
The primary safety endpoint concerns acute and late Grade 3-5 gastrointestinal and genitourinary toxicities, with a five-year measurement timeframe and an option for follow-up through 10 years. Its description specifies Kaplan-Meier estimates for 5-yr and 10-yr. The endpoint estimates and their uncertainty are not reported in the registry record.
The record lists eight outcome measures and 0 analysis entries. It includes separate adverse-event summaries for low-risk and intermediate-risk groups, but these are not a randomized comparison and should not be treated as the primary endpoint results. The statistical analysis plan, sample-size justification, missing-data methods, and analysis populations are not reported in the registry record.