Fulvestrant (Faslodex) + Anastrozole (Arimidex) vs Anastrozole: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Fulvestrant (Faslodex) + Anastrozole (Arimidex) vs Anastrozole (NCT00543127), a randomized phase 3 study. The primary outcome is Disease Free Survival (DFS) Events.

2. Clinical Question

The clinical question is whether the registry’s recorded event counts differ between the two randomized treatment groups. The primary outcome is a count of participants with an event, rather than a time-to-event estimate that accounts for when each event occurred. The registry also lists breast cancer-specific survival events, overall survival events, and time-to-recurrence events as secondary outcomes.

The record describes a Phase III trial and lists an intended enrollment of 870. Its status is terminated. The reason for termination and whether it affected the planned conduct or interpretation are not reported in the registry record. The comparison therefore needs to be read as a report of posted event counts and their statistical uncertainty, not as a complete account of why the trial ended or every analysis that may have been planned.

3. Trial Design

This was a randomized, parallel-group Phase III trial comparing fulvestrant plus anastrozole with anastrozole alone. The record lists no masking, so the trial was not masked according to the registry entry. It lists an intended enrollment of 870 and a terminated status. The reason for termination is not reported in the registry record.

The combination group was assigned fulvestrant and anastrozole. The fulvestrant regimen included a loading dose on day 0, further injections on days 14 and 28, and then injections every 28 days for 3 years. Anastrozole was taken orally once daily for 5 years. The comparison group was assigned anastrozole orally once daily for 5 years. These are the regimens described in the registry; details about adherence or treatment received are not reported in the registry record.

The brief summary describes postmenopausal women with early breast cancer and hormone receptor-positive, HER2-negative tumors. It also says randomization was to be stratified by center, positive-node category, previous chemotherapy, and hormone-receptor status. The record does not report the details of how these strata were implemented or whether the analysis accounted for them.

The primary outcome was disease-free survival events through up to 5 years, recorded as the number of participants with an event. The registry defines an event as local or distant recurrence, a new primary breast tumor, or death from any cause. The primary statistical analysis was described as intent to treat and to include all randomized patients. The posted primary counts are 49 of 433 in the fulvestrant-plus-anastrozole group and 62 of 437 in the anastrozole group. Whether every randomized participant contributed to the posted outcome counts, and how missing outcome information was handled, 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

Analysis population for the primary outcome, as defined in the registry: Primary statistical analyses of the efficacy outcome variables will be based on an intent-to-treat (ITT) method and will include all randomised patients

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Disease Free Survival (DFS) Events, measured over Up to 5 years.

Disease-free survival (DFS) events are the primary outcome. The registry counts a participant as having an event if there is evidence of local or distant recurrence, a new primary breast tumor, or death from any cause. The timeframe is up to 5 years. The posted measure is the number of participants with an event in each group, rather than a duration or a rate of events over person-time.

This composite outcome brings together recurrence, a new primary breast tumor, and death from any cause. In general, combining clinically distinct events can provide a broad measure of disease-free status, but the components may differ in their frequency and meaning. The registry does not report how many of the primary events fell into each component, so the overall count cannot show which event type contributed most to the comparison.

The record states that primary efficacy analyses were to use an intent-to-treat approach, including all randomized patients. That principle keeps participants in their randomized groups for analysis, regardless of treatment actually received. The posted counts are 49 participants among 433 assigned to fulvestrant plus anastrozole and 62 among 437 assigned to anastrozole. The record does not report event timing, censoring details, or an analysis of time to first event for the primary outcome. Consequently, the count comparison describes whether an event was recorded during the stated timeframe, but does not convey when events occurred or how follow-up time was distributed.

7. Results Posted in the Registry

• Anastrozole: 14.2% (62/437) versus 11.3% (49/433) on control; risk difference 2.9 percentage points (95% CI -1.6 to 7.3), risk ratio 1.25 (0.88–1.78); unadjusted two-proportion z-test p = 0.204.

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.

Breast Cancer Specific Survival (BCsS) Events

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Anastrozole: 4.1% (18/437) versus 3.9% (17/433) on control; risk difference 0.2 percentage points (95% CI -2.4 to 2.8), risk ratio 1.05 (0.55–2.01); unadjusted two-proportion z-test p = 0.885.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Anastrozole and the control. The interval gives the range of effects that remain compatible with the data.

Overall Survival (OS) Event

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Anastrozole: 7.8% (34/437) versus 6.5% (28/433) on control; risk difference 1.3 percentage points (95% CI -2.1 to 4.7), risk ratio 1.20 (0.74–1.95); unadjusted two-proportion z-test p = 0.451.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Anastrozole and the control. The interval gives the range of effects that remain compatible with the data.

Time to Recurrence (TR) Event

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Anastrozole: 10.5% (46/437) versus 8.3% (36/433) on control; risk difference 2.2 percentage points (95% CI -1.7 to 6.1), risk ratio 1.27 (0.84–1.92); unadjusted two-proportion z-test p = 0.264.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Anastrozole and the control. The interval gives the range of effects that remain compatible with the data.

The registry posts three secondary event-count outcomes: breast cancer-specific survival, overall survival, and time to recurrence. Across these outcomes, the comparison estimates are uncertain, with confidence intervals that include the no-difference value for the reported measure. This broad pattern does not provide a precise secondary signal that resolves the uncertainty in the primary disease-free survival comparison.

The secondary outcomes are related to the primary endpoint but do not measure the same thing. Disease-free survival combines local or distant recurrence, new primary breast tumor, and death from any cause. The secondary measures separately name breast cancer-specific survival events, overall survival events, and recurrence events. The registry does not report how the components overlap with the primary endpoint or the timing of events, so these outcomes cannot be combined or treated as interchangeable.

Unadjusted secondary results carry less weight when several outcomes are examined, because the chance of at least one apparently noteworthy result can increase as the number of comparisons grows. In general, a prespecified testing hierarchy or multiplicity adjustment can help control that issue. The registry record does not report whether such a strategy was planned or used, and it lists no reported analyses. The secondary comparisons should therefore be considered descriptive rather than definitive evidence of separate effects.

These endpoints can still add context by showing which kinds of outcomes were tracked and the general direction and uncertainty of the comparisons. They do not compensate for the lack of analysis details or establish a consistent effect across outcomes. The primary result remains the central efficacy comparison, while the secondary results should be interpreted cautiously and in light of their unadjusted status.

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

• Breast Cancer Specific Survival (BCsS) Events
• Overall Survival (OS) Event
• Time to Recurrence (TR) Event

9. Statistical Interpretation

10. Statistical Methods Explained

What kind of outcome is being compared?

The primary endpoint is binary at the participant level: each participant is counted as having or not having a disease-free survival event during the stated timeframe. The registry reports event counts and group sizes. In general, a binary outcome can be summarized as a proportion in each group and compared using a difference, ratio, or odds ratio. These measures answer related but distinct questions and use different scales.

The posted comparison gives a risk difference of 0.029 for anastrozole relative to fulvestrant plus anastrozole. A positive difference means the recorded event proportion is higher in the group named first in that comparison, anastrozole, than in the combination group. The point estimate is accompanied by a confidence interval from -0.016 to 0.073. The registry also reports a relative risk of 1.254 and an odds ratio of 1.296, each with its own interval. In general, a risk difference expresses an absolute contrast between proportions, while a relative risk compares those proportions multiplicatively and an odds ratio compares the odds. They are not interchangeable descriptions.

What does a confidence interval convey?

In general, a confidence interval represents statistical uncertainty around an estimate under the assumptions of the method used. A wider interval indicates less precision than a narrower one. An interval that includes the value corresponding to no difference does not provide a clear distinction from no difference under that measure; it also does not prove that the true difference is exactly zero. For the primary risk difference, the interval includes zero. The interval’s lower and upper limits indicate that the data are compatible with effects in either direction.

What does the p-value say?

The unadjusted p-value for the primary comparison is 0.204. In general, a p-value measures how unusual data at least as discrepant as those observed would be under a specified null hypothesis and statistical model. It is not the probability that the null hypothesis is true, nor does it measure clinical importance. The registry calls this value unadjusted; it does not report a multiplicity adjustment or a formal analysis plan for the posted comparisons. The p-value should therefore be read alongside the estimate and confidence interval, not as a standalone verdict.

What does intent to treat mean?

The registry says primary efficacy analyses were to use an intent-to-treat method and include all randomized participants. In general, this means participants are analyzed in their assigned groups, preserving the comparison created by randomization. The posted group counts are 433 and 437, while the stated enrollment target is 870. The record does not explain whether all randomized participants were included in the outcome denominators, how missing observations were addressed, or whether the intended approach was followed in the posted results.

What can be learned from the counts?

The event counts describe how many participants in each group were recorded as experiencing the composite outcome. The primary count is 49 in the combination group and 62 in the anastrozole group. Because the measure is a count over a period of up to 5 years, it does not describe the time to an event or account explicitly for differences in follow-up duration. In general, time-to-event methods can use information about when events occur and about censoring; the registry record does not report such an analysis for the primary endpoint.

There is also no breakdown of the composite endpoint into local recurrence, distant recurrence, new primary breast tumor, and death from any cause. The total count therefore cannot identify which component accounts for the observed pattern. Further details on event adjudication, outcome ascertainment, and follow-up completeness are not reported in the registry record.

What do the secondary comparisons add?

The registry lists three secondary count outcomes: breast cancer-specific survival events, overall survival events, and time-to-recurrence events. It posts estimates and unadjusted p-values for these outcomes, but no reported analyses are listed. In general, secondary endpoints can add context, but interpretation is less secure when many outcomes are examined without a prespecified multiplicity strategy. The record does not state whether these outcomes were confirmatory, how testing was ordered, or whether any adjustment was planned.

What analysis details are unavailable?

The record does not report the statistical model or methods used to produce the posted estimates, the confidence-interval procedure, any covariate adjustment, interim analyses, or the original statistical analysis plan. It does report the trial as randomized, parallel-group, and unmasked, and describes stratification factors in the brief summary. Whether those factors were used in the posted analysis is not reported in the registry record. These gaps limit the ability to assess model choices, prespecification, and the relationship between the planned and posted analyses.

11. Confidence Intervals and Precision

The primary risk-difference estimate is 0.029, with a confidence interval from -0.016 to 0.073. The interval spans zero, so the posted data are compatible with no risk difference and with effects in either direction. The estimate’s positive direction indicates a higher recorded event proportion in the anastrozole group relative to the combination group, but the interval shows that this direction is not resolved with precision.

In general, a confidence interval conveys uncertainty about an estimate under a specified statistical method. Its width reflects both the amount of information in the data and the variability assumed by the method. An interval that includes zero for a risk difference does not prove equivalence or establish that the groups have identical outcomes. It means the posted data do not rule out zero difference at the interval’s stated confidence level. The confidence level and the specific interval procedure are not reported in the registry record.

The relative risk is 1.254, with an interval from 0.883 to 1.78. The odds ratio is 1.296, with an interval from 0.868 to 1.934. Both intervals include 1, the no-association value for those measures. Their ranges are also broad enough to include values on either side of that reference point, reinforcing that the estimates are uncertain rather than precise declarations of a single effect.

The unadjusted p-value is 0.204. It is consistent with the uncertainty reflected in the intervals, but it does not quantify the probability that a treatment difference exists. The termination status and missing details about the analysis plan, missing data, and follow-up further constrain interpretation. The registry does not report enough information to determine how those factors affected precision.

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 figures are illustrations based on the observed effect, not the trial’s original design assumptions. They use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each scenario uses the stated fraction of the observed effect as the effect to detect. The trial’s own original sample-size assumptions and justification are not reported in the registry record.

For the binary outcomes, the planning figures are participants per arm. The 80% power column describes the participant count per arm that would give an 80% chance of detecting the stated effect under the planning assumptions if that effect were true. The 90% power column gives the corresponding per-arm count for a 90% chance. These are prospective planning concepts, not descriptions of what the completed trial achieved.

The scenarios consider planning for 100%, 75%, and 50% of the observed effect. Smaller effects are harder to distinguish from random variation and therefore require more participants under the same assumptions. These figures can help show how demanding a future study might be if it sought to detect effects smaller than the observed estimate. They should not be read as recommendations or as evidence that a particular study size is sufficient for the clinical question.

This is not observed power. Observed power is not a useful substitute for interpreting the estimate and its confidence interval after the data have been collected. The registry record does not state that the trial was designed using these illustrative assumptions; the listed planning method is separate from the trial’s original design.

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

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.113; treatment proportion p₁ = 0.142; average p̄ = 0.128.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.4717 = 0.9245.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.4713 = 0.3966.
4. n = (0.9245 + 0.3966)² / (0.0287)² = 2,117.3, rounded up to 2,118 participants per arm 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
p0 <- 0.113163972286374                          # control proportion
p1 <- 0.14187643020595                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(543127)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 2,118 (80% power), 2,835 (90% power)
 75% of observed effect: n per arm = 3,675 (80% power), 4,919 (90% power)
 50% of observed effect: n per arm = 8,062 (80% power), 10,792 (90% power)
power.prop.test: 2117.3 
Simulated power at n = 2,118 per arm: 0.802 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary endpoint and three secondary endpoints, each with a posted comparison. It does not report a multiplicity-control plan, a hierarchy for testing outcomes, or a statistical analysis plan specifying which comparisons were confirmatory. When several hypotheses are tested, the chance of at least one false-positive finding can rise. In general, prespecification and adjustment methods can address this concern, but the registry record does not say whether either was used. The posted secondary p-values are identified as unadjusted and should not be treated as if they account for all outcomes examined.

The registry describes an intent-to-treat approach for primary efficacy analyses, including all randomized patients. This is an important stated analysis population, but the record does not report the analysis population actually used for each posted endpoint or explain the relationship between randomized participants and outcome denominators. The primary denominators are 433 and 437. How missing outcome information was handled, whether any participants were excluded from an analysis, and whether the posted data fully follow the stated intent-to-treat approach are not reported in the registry record.

Missing data can affect both the estimated event proportions and their uncertainty. In general, interpretation depends on how much information is missing and whether missingness is related to outcomes or treatment assignment. The record does not report missing-data counts, reasons, assumptions, or sensitivity analyses. It also does not report loss to follow-up, outcome ascertainment procedures, or censoring details.

The trial status is terminated, but the reason for termination and any effect on the planned analyses are not reported in the registry record. Interim analyses, stopping rules, data-monitoring decisions, and the statistical analysis plan are also not reported. These omissions do not demonstrate that a particular problem occurred; they limit the reader’s ability to assess prespecification, completeness, and the possible effects of missing information or multiple testing.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

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: fracture (1.1%), cns cerebrovascular ischemia (0.9%), colon cancer (0.7%), infection with normal anc or grade 1 or 2 neutrophils - pulmonary/upper respiratory lung (pneumonia) (0.7%), cholelithiasis (0.7%).

The registry lists serious adverse event information for 415 participants at risk in the fulvestrant-plus-anastrozole group and 437 in the anastrozole group. It records 40 participants with a serious adverse event in the combination group and 61 in the anastrozole group. For other adverse events, the listed at-risk counts are 415 and 437, with 192 and 197 participants affected, respectively.

These are participant counts, and the serious and other adverse-event categories should be kept distinct. The record does not provide a statistical comparison or confidence intervals for these figures. It also does not report the number of deaths in the adverse-event summary. The listed serious adverse-event terms include fracture at 1.1%, CNS cerebrovascular ischemia at 0.9%, colon cancer at 0.7%, pulmonary or upper respiratory infection at 0.7%, cholelithiasis at 0.7%, and vascular access-related thrombosis or embolism at 0.7%.

In general, adverse-event summaries describe reported safety observations and are not, by themselves, proof that an event was caused by a treatment. The registry record does not provide event-level detail, duration, severity beyond the serious classification, or an explanation of how the listed percentages were derived. These figures should be read as posted safety counts and terms, not as a complete causal or comparative safety assessment.

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

The registry records disease-free survival events in both randomized groups and posts a risk-difference estimate favoring neither group with enough precision to establish a clear difference. The estimate is 0.029 for anastrozole relative to fulvestrant plus anastrozole, with a confidence interval from -0.016 to 0.073 and an unadjusted p-value of 0.204. The interval includes zero and allows effects in either direction. The result therefore describes an uncertain comparison, not a definitive finding that the groups are the same or that one regimen is superior.

The primary endpoint combines local or distant recurrence, a new primary breast tumor, and death from any cause. The registry reports the total number of participants with an event, not the separate counts for each component or the time at which events occurred. It is not possible from these counts to determine which component drove the observed comparison, whether events occurred earlier in one group, or how differences in follow-up might matter.

The record identifies the trial as terminated but does not state why. It also does not report the original sample-size justification, interim analyses, missing-data handling, a multiplicity strategy, or the full analysis plan. These gaps mean the posted numbers cannot answer questions about whether the study achieved its planned objectives or whether all analyses were conducted as intended.

The secondary outcomes and adverse-event counts provide additional descriptive information, but their interpretation is limited by the lack of reported analysis details and, for secondary comparisons, their unadjusted status. The results should not be converted into treatment advice or a broader claim about clinical effectiveness. They support a narrower conclusion: the registry’s posted event counts yield an imprecise estimate of the difference in the primary outcome through up to 5 years, with important context about trial conduct and analysis absent from the registry record.

17. Why This Trial Matters Statistically

This trial illustrates why an event-count comparison needs more than the direction of the point estimate. The primary risk difference is positive for the anastrozole comparison, but its confidence interval includes zero and extends in both directions. The estimate alone could suggest a pattern; the interval makes clear that the data are not precise enough to establish that pattern as a reliable difference.

It also illustrates the interpretive trade-offs of a composite endpoint. Disease-free survival combines recurrence, a new primary breast tumor, and death from any cause. That definition gives the outcome a broad scope, but without component counts the overall result does not identify what type of event contributes to it. The count-based endpoint also does not show event timing, an important distinction from a reported time-to-event analysis.

The registry states an intent-to-treat approach, while leaving key details about missing data, outcome denominators, multiplicity, and the statistical analysis plan unreported. Those details matter because they help readers evaluate whether randomization was preserved in analysis, how uncertainty was quantified, and whether secondary findings were prespecified. Their absence is a limitation of the available record, not evidence that a particular analysis choice was made.

Finally, the status is terminated, but the reason is not stated. A status label alone cannot explain the circumstances of the trial’s ending or the implications for the posted results. Statistical interpretation therefore depends on separating the documented estimates from questions the registry record does not answer.

18. 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 registry record leaves several trial-specific uncertainties. The study is listed as terminated, but the reason and timing relative to outcome collection and analysis are not reported. It is therefore not possible to assess from the record whether termination affected follow-up, enrollment, or the planned evaluation.

The primary endpoint is a count of participants with a composite event through up to 5 years. The record does not provide component-specific counts, event timing, follow-up completeness, censoring information, or details of how outcomes were ascertained. These omissions constrain interpretation of what contributed to the composite and whether the count captures the timing of events consistently across groups.

The record describes intent-to-treat analysis but does not report how missing outcomes were handled or whether all randomized participants were included in each posted denominator. It does not provide an account of exclusions, adherence, treatment discontinuation, or protocol deviations. These aspects can affect the meaning of an assigned-group comparison, but no direction or magnitude of their effect can be inferred from the record.

Randomization was stratified according to factors named in the brief summary, but the registry does not state whether these factors were used in the posted analysis. It does not report the original sample-size justification, interim analyses, stopping rules, or the full statistical analysis plan. The secondary outcomes have unadjusted comparisons, and no multiplicity strategy is reported. Finally, the safety summary lacks a reported death count and does not present comparative uncertainty estimates. Together, these record-level omissions limit assessment of the design-to-analysis path and the completeness of the available results.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Fulvestrant (Faslodex) + Anastrozole (Arimidex) vs Anastrozole — NCT00543127.
• Registry record last updated 2023-03-10; status last verified 2023-03.
• Results first posted 2019-04-05.
• 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.

22. Record Summary

The registry record describes a randomized, parallel-group Phase III trial of fulvestrant plus anastrozole versus anastrozole alone in postmenopausal women with early breast cancer and positive hormone receptors. It lists no masking, an intended enrollment of 870, and a terminated status. The reason for termination is not reported in the registry record.

The primary endpoint is disease-free survival events through up to 5 years, defined as local or distant recurrence, a new primary breast tumor, or death from any cause. Posted counts are 49 of 433 participants in the combination group and 62 of 437 in the anastrozole group. The risk-difference estimate is 0.029, with a confidence interval from -0.016 to 0.073 and an unadjusted p-value of 0.204.

The registry also posts three secondary event-count outcomes and adverse-event summaries. No reported analyses are listed. Details on the original statistical plan, missing-data handling, multiplicity, interim analyses, and the reason for termination are not reported in the registry record.