Sexual Function and Wellbeing in Males With Rectal Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Sexual Function and Wellbeing in Males With Rectal Cancer (NCT01216202), a registered phase not stated study. The primary outcome is Change in Serum Testosterone Levels Between Baseline and After Preoperative Radiotherapy..

2. Clinical Question

The study was motivated by theoretical concerns that preoperative radiotherapy and pelvic surgery might affect hormone levels, spermatogenesis, sexual function, and wellbeing. Its stated approach was longitudinal: measurements were planned before treatment and during a follow-up period of two years. This clinical question is therefore about measured changes over time, rather than a randomized comparison of assigned treatments.

The endpoint description identifies a within-person sequence of blood sampling for men treated with preoperative radiotherapy. However, the comparator group lacks the corresponding later blood sample. That difference limits the role the comparator can play in evaluating change over time. The registry record does not report whether the measured changes were analyzed alongside sexual function, semen samples, or other outcomes, nor does it report results for those measures.

3. Trial Design

The registry describes a longitudinal observational study of men diagnosed with rectal cancer. It lists the study status as completed, enrollment of 178, a start date of 2010-04, and a primary completion date of 2014-05. Karolinska Institutet is listed as the sponsor. The study summary says measurements of androgen hormone levels, semen samples, and sexual function were assessed before treatment and during a follow-up period of two years.

The treatment groups are described by the care received, not by randomized assignment. One group comprised men with rectal cancer treated with preoperative radiotherapy and surgery. The other comprised men with rectal cancer or prostate cancer treated with surgery alone, without radiotherapy. Allocation is not stated in the registry record, and the record does not report randomization. These groups are not a like-for-like control comparison: they differ in the conditions represented, and the later blood-sampling time point for the primary endpoint is not available in the surgery-alone group.

The primary endpoint is change in serum testosterone from baseline to after radiotherapy and before surgery. Blood samples were fasting morning venous samples, and testosterone was analyzed at the Department of Clinical Chemistry, Karolinska University Hospital, using commercial assays. The registry describes the second sample as collected the week before surgery. It reports a median elapsed time from the start of radiotherapy to that sample of 38 days, ranging from 3 to 195 days, depending on the preoperative treatment regimen.

The registry lists three outcome measures and two analyses. It does not report the protocol’s sample-size justification, the detailed statistical analysis plan, or the number of participants with usable endpoint measurements. The record also does not report whether follow-up measurements were complete for all enrolled participants.

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: 18 months after start of inclusion, less than 10% of the participants were treated with surgery alone. To increase the sample size of the unexposed group (no preoperative radiotherapy), 63 men with prostate cancer I to III scheduled for robot assisted prostatectomy were included. Participants with prostate cancer were enrolled at the Urology department at Karolinska University Hospital between May 2012 and January 2013.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: For participants in "No preoperative RT", no blood samples were collected at the time point "after RT/before surgery".

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 Change in Serum Testosterone Levels Between Baseline and After Preoperative Radiotherapy., measured over Baseline and after RT/before surgery..

The primary endpoint is change in serum testosterone levels between baseline and after preoperative radiotherapy, before surgery. Testosterone is a continuous laboratory measure reported in nmol/L. The registry identifies the summary measure as a mean and the dispersion measure as a standard deviation, but it does not report the observed values or the numerical change.

The endpoint is relevant to the study’s stated rationale: the registry describes theoretical reasons to examine whether treatment may affect hormone levels, alongside spermatogenesis, sexual function, and wellbeing. Repeated measurement can describe how a participant’s level differs between two time points. In general, measuring the same participants at both times can help distinguish within-person change from differences between people. That general interpretation requires knowing who contributed both measurements and how the data were analyzed; those details are not reported in the registry record.

The endpoint’s timing needs particular attention. The second blood sample was collected after radiotherapy and before surgery, with the elapsed time from radiotherapy start varying from 3 to 195 days. The registry also says that men in the no-preoperative-radiotherapy group had no blood sample at this later time point. Consequently, the posted description supports a baseline-to-follow-up question for the radiotherapy group, but does not describe a parallel change measure in the comparison group.

The registry record does not report the mean testosterone at either time point, the mean change, a confidence interval, or a p-value. It therefore does not permit an estimate of the magnitude or precision of the endpoint change.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The endpoint is continuous: testosterone is measured on a numerical scale, with units of nmol/L. The registry specifies a mean as the summary measure and a standard deviation as the measure of dispersion. A mean describes the average level or change in a group. A standard deviation describes how spread out individual measurements are around that mean. Neither statistic is reported for the primary endpoint in the registry record, so the average change and the variability among participants cannot be evaluated.

What does a change score represent?

In general, a change score is the later measurement minus the earlier measurement for the same participant, or a summary of those individual changes. It describes the direction and size of within-person differences over time. This is distinct from comparing the average measurements of two different groups at one time point. For a change estimate to be interpretable, the analysis should make clear which participants had both measurements and how incomplete pairs were handled. The registry record does not report those details or the numerical change.

What does a confidence interval add?

In general, a confidence interval expresses uncertainty around an estimated quantity, such as a mean change. A narrower interval indicates greater statistical precision, while a wider interval indicates less precision. It does not eliminate bias from study design, measurement, or participant selection. The registry record does not report a confidence interval for the primary endpoint, so the precision of the estimated change is not available.

What would a p-value address?

In general, a p-value assesses how compatible data are with a specified statistical model and a null hypothesis. It is not the probability that the null hypothesis is true, nor does it indicate whether an effect is important. Interpreting a p-value requires the test, model, and analysis population to be known. The registry record does not report a primary endpoint p-value or the test used. Statistical significance therefore cannot be assessed from the record.

Why does the design affect the analysis?

The study is described as observational, and allocation is not stated. In general, a treatment comparison in an observational study can reflect differences in the participants or care pathways as well as treatment exposure. Adjustment can sometimes address measured differences, but cannot automatically resolve unmeasured differences. The registry record does not report an adjustment strategy. In addition, the comparison group did not have the later blood sample specified for the primary endpoint. A direct comparison of baseline-to-follow-up change between the described groups is therefore not supported by the endpoint schedule as recorded.

How should planning calculations be read?

General planning calculations can illustrate the number of participants per arm associated with a chosen power under stated assumptions. The stated assumptions for any such illustration are a two-sided significance level of 0.05, equal allocation, a normal approximation, and an effect defined as a stated fraction of the observed effect. These are planning assumptions, not evidence that the completed observational study used that design. Such calculations are not observed power and do not show the probability that a finding is true. The registry record does not report the trial’s own sample-size justification. No planning estimate or observed-effect value is reported in the record details described.

For continuous outcomes, normal-approximation planning calculations generally depend on the effect to be detected and the variability of the measurement. If data are unusually dispersed or the model assumptions do not fit, a simple normal approximation may not describe uncertainty well. This is a general statistical consideration; the registry record does not report diagnostics, distributional assumptions for the observed data, or an analysis model for the primary endpoint.

The record lists three outcome measures and two analyses, but does not report how those outcomes were prioritized in analysis, whether multiple comparisons were planned, or how any multiplicity was handled. It also does not identify an analysis population or state whether estimates were adjusted. These omissions prevent a detailed appraisal of the inferential methods. In particular, the design description alone cannot establish which statistical procedure produced an endpoint estimate.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures and two analyses. It identifies change in serum testosterone as the primary endpoint, but does not report a hierarchy for all outcomes, a prespecified testing sequence, or a multiplicity adjustment. When several outcomes or comparisons are tested, general statistical practice recognizes that the chance of at least one apparently notable result can increase. Whether and how that concern was handled is not reported in the registry record.

The record does not report the number of participants with available baseline and follow-up testosterone measurements, the number excluded from analysis, or reasons for missing measurements. It does not describe imputation, complete-case analysis, or sensitivity analyses for missing data. These details matter because a change endpoint requires usable observations at both time points, and participants with incomplete data may differ from those with complete data. That is a general concern, not evidence that such differences occurred in this study.

The analysis population is not reported in the registry record. The record does not say whether all enrolled participants, only participants who received a particular treatment, or a subset with complete measurements were included in the primary analysis. It also does not report a protocol-defined analysis set.

The comparison group did not have blood samples at the after-radiotherapy, before-surgery time point. This is a feature of the recorded measurement schedule, not simply an unspecified missing-data mechanism. The registry record does not describe a method for estimating a corresponding change in that group. The handling of missing data for the other listed outcome measures is also not reported.

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

The registry record establishes that the study was designed to examine hormone levels and other aspects of wellbeing in men undergoing treatment for rectal cancer, with measurements before treatment and during a two-year follow-up period. For the primary endpoint, it specifies baseline and after-radiotherapy, before-surgery measurements of serum testosterone in the preoperative radiotherapy group. It does not report the numerical results of that comparison.

As a result, the record does not establish whether the average testosterone level rose, fell, or remained similar, nor how variable any individual changes were. It does not provide a confidence interval or a statistical test with which to assess precision or compatibility with a null hypothesis. The absence of a reported result is not evidence that no change occurred; it means the result cannot be evaluated from the registry entries described.

The observational design also limits causal interpretation. The groups were not described as randomized, and allocation is not stated. The surgery-alone group included men with rectal cancer or prostate cancer, while the radiotherapy group is described as men with rectal cancer. Moreover, the comparator group did not have the later blood measurement for the primary endpoint. A before-and-after result in the radiotherapy group, if available, would not by itself show that radiotherapy caused the change.

The registry’s adverse event counts also should not be interpreted as a causal comparison. The record lists 2 deaths in the no-preoperative-RT group and none in the preoperative RT group, but provides no cause, timing, or relationship to treatment. The counts alone do not show whether treatment altered risk.

These limits concern what can be concluded from the registry record, not what the study may have measured or analyzed outside it. The record describes the question and methods of measurement, but the primary numerical result, analysis details, and participant-level completeness are not reported.

12. Why This Trial Matters Statistically

This study illustrates why the distinction between a longitudinal observation and a controlled treatment comparison matters. Repeated measurements can describe how a continuous marker changes within participants. A causal treatment effect, however, requires a design and analysis capable of separating the treatment’s contribution from other influences. The registry describes an observational study and does not state how treatment allocation occurred.

The endpoint schedule is also central to interpretation. The primary question concerns testosterone before and after radiotherapy, but the surgery-alone group had no blood sample at the later time point. This means the comparator does not provide the same pair of measurements for the primary endpoint. Recognizing that distinction prevents a within-group change from being mistaken for a between-group treatment contrast.

Reporting the mean and standard deviation is useful for a continuous outcome, but those summary measures alone would not fully characterize the evidence. A change estimate, its uncertainty, the number of participants analyzed, and the analysis method are also important. Those primary endpoint results and details are not reported in the registry record.

The record also highlights how outcome multiplicity and missing data affect statistical interpretation. It lists three outcome measures and two analyses without describing a testing strategy, analysis population, or missing-data approach. Such omissions make it difficult to assess how robust an inference might be, even when a study’s scientific question is clearly stated.

For clinical researchers and biostatisticians, the lesson is methodological: evaluate measurement timing, comparability of groups, completeness of paired observations, and the precision of estimates before interpreting a treatment-related claim. Here, the record supports a careful account of the intended measurement question, but does not supply the endpoint results needed to quantify the observed change.

13. 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 interpreting the endpoint is that the registry record does not report its results. The mean testosterone values, mean change, standard deviations, confidence interval, and p-value are not reported in the registry record. The number of participants contributing paired measurements is also not reported, so the endpoint’s analysis denominator cannot be assessed.

The comparison groups are not equivalent as described. The preoperative radiotherapy group comprises men with rectal cancer treated with radiotherapy and surgery. The surgery-alone group includes men with rectal cancer or prostate cancer. The record does not report adjustment for differences between these groups, and allocation is not stated. A treatment effect cannot be inferred from the group descriptions alone.

The later blood-sampling time point is specified only for the radiotherapy group. The absence of a corresponding measurement in the no-preoperative-radiotherapy group limits between-group assessment of change. In addition, the elapsed time between radiotherapy start and the second sample ranged from 3 to 195 days. The record does not report whether the analysis accounted for this variation.

The registry does not report assay performance characteristics, a detailed statistical model, participant flow, missing-data handling, or an analysis population for the endpoint. It also does not report the protocol’s sample-size justification or how the three listed outcomes and two analyses were handled for multiplicity. These omissions limit appraisal of precision, bias, and robustness.

Finally, the adverse event summary provides counts without details about causes or timing. It cannot establish whether the recorded deaths were related to treatment. These limitations describe gaps in the registry record and should not be read as proof that the study did not collect or analyze further information.

14. Related Tutorials

15. Related Statistical Calculators

16. Sources

• ClinicalTrials.gov: Sexual Function and Wellbeing in Males With Rectal Cancer — NCT01216202.
• Registry record last updated 2023-10-04; status last verified 2023-10.
• Results first posted 2021-04-02.
• 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.

17. Record Summary

The registry record describes a completed longitudinal observational study sponsored by Karolinska Institutet, with enrollment of 178 and study dates listed as 2010-04 to 2014-05. It examined men with rectal cancer, with a stated interest in androgen hormone levels, semen samples, sexual function, and wellbeing before treatment and during a two-year follow-up period.

The primary endpoint is change in serum testosterone from baseline to after preoperative radiotherapy and before surgery. The radiotherapy group had blood samples at those time points; the surgery-alone comparison group did not have a sample at the later time point. The record lists three outcome measures and two analyses but does not report the primary endpoint result, analysis method, analysis population, or missing-data approach.

The study is observational, and allocation is not stated. The registry’s adverse event counts include 2 deaths in the no-preoperative-RT group; the record does not describe their causes or relationship to treatment. The posted record therefore provides the study question and measurement context, but not enough endpoint results to assess the magnitude or precision of testosterone change.