Tetracycline as a Prophylaxis for Rash in Patients With NSCLC Receiving Treatment With BIBW2992 (Afatinib): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Tetracycline as a Prophylaxis for Rash in Patients With NSCLC Receiving Treatment With BIBW2992 (Afatinib) (NCT01880515), a randomized phase 2 study. The primary outcome is Frequency of Participants Who Experienced Any Grade of Rash As Characterized By The Common Toxicity Criteria for Adverse Effects (CTCAE) V4.0.

2. Clinical Question

The clinical question is about the frequency of rash, not about tumor response, survival, or the full range of treatment harms. The registry lists quality of life and progression-free survival among secondary outcomes, but the available summary does not provide results for those outcomes. It also does not report the detailed clinical circumstances or participant-level data needed to assess how rash developed over time or how treatment exposure varied across individuals.

3. Trial Design

The registry identifies this as a randomized, parallel-group, open-label phase II trial with single masking. Its stated focus is prevention of rash among patients with NSCLC receiving BIBW2992, or afatinib. The sponsor is Instituto Nacional de Cancerologia de Mexico. The record lists the study as completed, with a start date of 2010-12 and primary completion in 2014-07.

The planned contrast was between pre-emptive tetracycline plus general dermatological recommendations and general dermatological recommendations without pre-emptive tetracycline. In the latter group, tetracycline could be used after week 4 of assessment if grade 3-4 rash occurred. This makes the comparison one between treatment strategies rather than a simple contrast between ever receiving tetracycline and never receiving it: the comparator strategy allowed conditional later use.

The registry records 107 enrolled. The primary-outcome description states that 45 participants were assigned to reactive treatment and 45 to pre-emptive tetracycline; the arm records likewise list 45 for each group. The registry does not explain the relationship between the enrollment figure and those group counts, so the reasons for that difference are not reported in the registry record.

Random assignment supports a between-group comparison by aiming to balance participant characteristics, while the primary-outcome description says the groups did not differ in demographics, disease stage, or dermatological baseline characteristics. The masking label is single, but the record does not identify which participants, clinicians, outcome assessors, or other personnel were masked. The detailed allocation procedure and any concealment procedures are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Forty five patients were assigned to receive reactive treatment; the other 45 received pre-emptive tetracycline.There were no differences among demographics, disease stage and dermatological baseline characteristics between treatment groups.

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: A total of 107 patients were enrolled. Due to progression and lost to follow-up, only 90 patients were evaluated for dermatological toxicities. Forty five patients were assigned to receive reactive treatment; the other 45 received pre-emptive tetracycline.

6. Primary Endpoint

The registry lists the primary outcome as Frequency of Participants Who Experienced Any Grade of Rash As Characterized By The Common Toxicity Criteria for Adverse Effects (CTCAE) V4.0, measured over Percentage of adverse events at week 8.

The primary endpoint is the frequency of participants who experienced any grade of rash, characterized using the Common Toxicity Criteria for Adverse Effects (CTCAE) version 4.0. The stated timeframe is the percentage of adverse events at week 8, and the description compares rash from initiation of BIBW2992 through week 8. The arm values are percentages: 44.5 for tetracycline and 75.5 for no pre-emptive tetracycline.

Using any grade of rash gives a broad measure of how often the event was recorded, rather than restricting the endpoint to severe rash. This can capture events across the CTCAE grading scale, while the grading framework provides a common way to classify severity. The endpoint is relevant to the stated prevention question because it counts participants experiencing rash during a specified period of afatinib treatment.

Frequency alone does not describe the full clinical course. It does not show the severity distribution, duration, timing of onset, recurrence, or impact on treatment interruptions. The registry’s primary result also does not establish whether rash was assessed consistently at every time point or how missing assessments were handled. Those details are not reported in the registry record. The endpoint should therefore be read as a reported week-8 frequency measure, not as a complete account of dermatological burden or treatment tolerability.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a risk ratio express?

A risk ratio compares the frequency of an outcome in one group with the frequency in another. A value of 1 corresponds to equal frequencies on the relative scale; values below or above 1 indicate that the numerator group has a lower or higher frequency than the denominator group. The registry reports a risk ratio of .4, with a 95% confidence interval from 0.17 to 0.99. Because the registry does not specify the analysis ordering in its text, the reported ratio is best read together with the arm percentages: 44.5 for tetracycline and 75.5 for no pre-emptive tetracycline.

How should the confidence interval be read?

A confidence interval describes uncertainty around an estimate using a method that, under its assumptions, would produce intervals containing the underlying value at the stated rate over repeated studies. It is not a range containing a specified proportion of individual participant outcomes, and it does not guarantee that the true value lies inside this particular interval. The 95% interval extends from 0.17 to 0.99. The upper limit is close to 1, so the interval includes values close to no relative difference. A confidence interval conveys both the direction and precision of an estimate, but its interpretation depends on the design, measurement, and analysis being appropriate.

What does the endpoint count?

The primary endpoint counts participants who experienced any grade of rash according to CTCAE version 4.0, with the stated assessment period through week 8 after starting BIBW2992. The registry presents the arm values as percentages and describes the endpoint as the frequency of participants experiencing rash. This is a binary outcome for the stated period: a participant either meets the recorded any-grade-rash criterion or does not. That summary does not retain the full information about severity or timing. The registry does not give a grade-by-grade distribution or a detailed account of assessment schedules.

Why can the treatment strategies matter to interpretation?

The comparator group was not described as permanently prohibited from tetracycline. Its arm description allows tetracycline after week 4 if grade 3-4 rash occurred. Consequently, the comparison is between starting tetracycline pre-emptively and beginning with dermatological recommendations while allowing specified reactive use. In general, such a strategy comparison estimates the contrast associated with the assigned approaches, not the biological effect of receiving versus never receiving a drug. The registry does not report how many comparator participants received later tetracycline, so the extent of that treatment is not reported in the registry record.

What can be inferred from the reported summary?

The reported arm percentages and risk ratio permit a descriptive comparison, with the confidence interval conveying uncertainty around the relative estimate. They do not establish the analysis population, missing-data approach, adjustment strategy, or handling of deviations from assigned treatment. Those details are not reported in the registry record. The record gives no p-value for the primary comparison, and an unreported p-value should not be inferred from the interval. Nor does a confidence interval describe the probability that a treatment strategy is beneficial for an individual.

In general, a count-based endpoint can be affected by how outcomes are assessed and by whether participants with incomplete follow-up are included in the denominator. The registry summary does not explain these details. It also does not state whether the analysis followed an intention-to-treat approach, used a per-protocol population, or applied another analysis population. These are important qualifications when interpreting a randomized comparison, because exclusions or missing observations after assignment can affect the comparability created by randomization.

How should the planning illustrations be understood?

The sample-size assumptions describe planning illustrations based on the observed effect, not the trial’s original design calculations. They use a two-sided significance level of 0.05, equal allocation between the arms, and a normal approximation; the effect to detect is specified as a fraction of the observed effect. For time-to-event outcomes, the stated convention is to give the total number of events; for other outcomes, it is participants per arm. These are prospective planning scenarios, not observed power and not evidence about the probability that the completed trial detected an effect. The registry does not report the original sample-size justification, so it is not possible to establish whether the trial’s enrollment target was based on these assumptions.

10. Analyses Reported by the Sponsor

The registry’s own reported analysis gives a risk ratio of .4 with a 95% confidence interval from 0.17 to 0.99. The posted arm percentages are 44.5 for tetracycline and 75.5 for no pre-emptive tetracycline. These figures are compatible in direction: the group assigned pre-emptive tetracycline has the lower reported rash frequency, and the reported relative estimate is below 1.

The registry does not report a p-value or describe the statistical method used to obtain the risk ratio and confidence interval. It also does not provide an adjusted estimate or enough detail to reproduce the sponsor’s analysis from participant-level records. There is no discrepancy flag for the posted result, so there is no identified conflict requiring a recalculated estimate to take precedence over the registry analysis. Any simple unadjusted recalculation from summary values would not replace the sponsor’s own analysis and could differ because of rounding or analytic choices. The numerical interpretation should therefore remain anchored to the registry’s stated risk ratio, confidence interval, and arm percentages.

The registry record does not describe whether the sponsor’s analysis used all randomized participants, how it handled missing observations, or whether any covariates were included. Those methodological details are not reported in the registry record.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists three secondary outcomes: quality of life, progression-free survival, and progression-free survival. The repeated progression-free-survival label is present in the record; the listed outcomes should not be treated as evidence of three different clinical constructs. The record states that there are four outcome measures and two analyses, but it does not provide a multiplicity strategy explaining how the primary and secondary comparisons were handled together.

Multiplicity arises when several outcomes or analyses are considered, because repeated testing can increase the chance of at least one apparently notable result under a null hypothesis. In general, prespecified testing hierarchies or other adjustments can address that concern. The registry does not report whether any such approach was used. The primary outcome should therefore be interpreted as the reported primary comparison, without assuming that it was protected by a particular multiplicity procedure. Results for the listed secondary outcomes are not reported in the registry record.

The registry does not state how missing rash assessments were handled, whether the endpoint denominator included all assigned participants, or whether any participants were excluded from the primary analysis. It also does not report the analysis population definition, such as an intention-to-treat or per-protocol population. These omissions limit assessment of whether the randomized groups remained comparable in the analysis and whether incomplete follow-up could influence the percentages.

The record’s enrollment figure is 107, while the primary-outcome description reports 45 assigned to reactive treatment and 45 to pre-emptive tetracycline; the arm records list 45 in each group. The relationship between those figures is not reported in the registry record. The available information does not establish whether the difference reflects screening, eligibility, randomization, outcome availability, or another reason, so no explanation should be assumed.

12. 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 0% reporting threshold.

The registry’s adverse-event figures list zero serious adverse events and zero other adverse events in each treatment group, with 45 at risk in each group for both categories. These are the recorded counts in this registry summary. They should not be read as proof that no adverse events occurred in the trial: the record does not provide event narratives, a list of terms, or a description of the completeness of adverse-event reporting. The serious-event terms list is empty, and deaths are not reported in the registry record.

Safety counts also require context about observation time, definitions, collection procedures, and whether events were attributed to treatment. The registry summary does not report those details. The arm descriptions indicate different tetracycline strategies, including conditional later use in the comparator group, but the record does not state how many participants received that later treatment. The zero counts therefore describe the posted adverse-event fields and cannot establish comparative safety or characterize all possible harms.

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

The primary result describes a lower reported percentage of any-grade rash at week 8 in the group assigned pre-emptive tetracycline than in the group assigned dermatological recommendations without pre-emptive tetracycline. The registry reports the arm percentages as 44.5 and 75.5, respectively, and a risk ratio of .4 with a 95% confidence interval from 0.17 to 0.99. Together, these figures describe the direction and uncertainty of the reported comparison.

The result does not establish that the same contrast would occur in other populations or treatment settings. The registry record concerns patients with NSCLC receiving BIBW2992 and describes a specific tetracycline strategy alongside dermatological recommendations. The comparator could receive tetracycline after week 4 for grade 3-4 rash, so the comparison is not simply preventive use versus complete non-use. The record does not report the extent of later use or adherence to the assigned approaches.

The result also does not describe rash severity by grade, duration, time to onset, recurrence, or consequences for dose administration. It does not establish an effect on quality of life, progression-free survival, or any other secondary outcome; those results are not reported in the registry record. Nor do the posted percentages alone resolve questions about missing follow-up, analysis population, or outcome assessment procedures.

The confidence interval indicates that the relative estimate is uncertain, with its upper limit close to 1. The record supplies no p-value for the primary analysis, and no unreported test result should be assumed. The observed comparison is not an individual prediction, and the planning illustrations based on the observed effect are not evidence of observed power. This is a statistical reading of the recorded outcome, not medical advice or a general recommendation about treatment.

14. Why This Trial Matters Statistically

This trial is statistically useful as an example of how a focused prevention question can be expressed through a randomized comparison and a defined event-frequency endpoint. The study compares pre-emptive tetracycline plus dermatological recommendations with recommendations alone at the outset, while allowing conditional tetracycline use in the comparator strategy after week 4. Recognizing that structure is essential: the estimated contrast pertains to the assigned strategies described in the record.

The primary result combines an absolute presentation, the reported percentages in each group, with a relative presentation, the risk ratio and confidence interval. These are complementary summaries. Percentages give the outcome frequency within each arm, while the risk ratio describes the relative comparison. The confidence interval signals that the estimate has uncertainty and that the upper end is close to the relative no-difference value. Reading all these features together is more informative than treating one estimate as definitive.

The record also illustrates why trial interpretation depends on reporting beyond a headline result. The enrollment figure and group counts are not reconciled in the registry, and details about missing data, analysis populations, masking roles, multiplicity, and the analysis method are absent. Secondary outcomes are listed without results. Such gaps do not erase the reported primary comparison, but they constrain how confidently its scope and robustness can be assessed.

Finally, planning calculations based on an observed effect should be distinguished from a trial’s original design and from observed power. They can illustrate future planning under stated assumptions, but they cannot establish what the original investigators planned or explain the completed trial’s precision. This distinction is important for statistical readers using trial results to understand both the estimate and the limits of the record.

15. 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 does not identify who was masked despite labeling the trial single blind. It does not provide the randomization sequence method, allocation concealment procedure, or detailed protocol. The primary-outcome description says the groups did not differ in demographics, disease stage, and dermatological baseline characteristics, but no characteristics table or detailed values are reported in the registry record.

The primary endpoint is described as a percentage of participants with any grade of rash by week 8, but the record does not explain how outcomes were assessed, how often assessment occurred, or how missing observations were handled. There is no grade-specific breakdown, and the summary does not report duration, onset, recurrence, or treatment interruption. The analysis population and handling of adherence or treatment deviations are also not reported.

The reported group counts are 45 per arm, while the registry enrollment is 107; the record does not explain the relationship between these figures. The comparator description permits tetracycline after week 4 in case of grade 3-4 rash, but the number receiving later treatment is not reported. These omissions limit the ability to distinguish the effect of assignment from the effect of treatment actually received.

The analysis method, covariate adjustment, p-value, and multiplicity approach are not reported in the registry record. Secondary outcomes are listed, but results are absent. Safety figures list zero serious and zero other adverse events in each arm, but event collection and observation details are not described, and deaths are not reported. These registry-level limitations constrain interpretation without changing the reported values themselves.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Tetracycline as a Prophylaxis for Rash in Patients With NSCLC Receiving Treatment With BIBW2992 (Afatinib) — NCT01880515.
• Registry record last updated 2025-05-11; status last verified 2025-04.
• Results first posted 2017-04-12.
• 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.

19. Record Summary

The registry record describes a completed randomized, parallel-group, open-label phase II trial with single masking, sponsored by Instituto Nacional de Cancerologia de Mexico. It concerns patients with NSCLC receiving BIBW2992 (afatinib) and compares pre-emptive tetracycline plus dermatological recommendations with recommendations without pre-emptive tetracycline. The latter strategy allowed tetracycline after week 4 for grade 3-4 rash.

The primary endpoint is the percentage experiencing any grade of rash according to CTCAE version 4.0 through week 8. The posted percentages are 44.5 for tetracycline and 75.5 for no pre-emptive tetracycline. The registry reports a risk ratio of .4 and a 95% confidence interval from 0.17 to 0.99. The analysis method, p-value, missing-data handling, and analysis population are not reported in the registry record. Quality of life and progression-free survival are listed as secondary outcomes, but their results are not reported.