Here is the design of a clinical trial:

Official Title: A Double-blind, Randomised Controlled Trial Evaluating the Safety and Efficacy of Antifibrinolytics (Tranexamic Acid) in Patients With Haematological Malignancies With Severe Thrombocytopenia

Included conditions:
- Hematologic Neoplasms
- Hemorrhage
- Hematopoietic Stem Cell Transplantation

Study Armgroups:
- {'label': 'Intervention Arm', 'type': 'EXPERIMENTAL', 'description': 'Tranexamic acid (TXA). Dose schedule TXA 1g every eight hours IV or 1.5g every eight hours PO.', 'interventionNames': ['Drug: Tranexamic acid (TXA).']}
- {'label': 'Control Arm', 'type': 'PLACEBO_COMPARATOR', 'description': 'Placebo (saline) if administration is IV. Placebo tablet matched for appearance to TXA if oral.', 'interventionNames': ['Drug: Placebo']}

Interventions:
- {'type': 'DRUG', 'name': 'Tranexamic acid (TXA).', 'description': 'IV or oral preparation. IV tranexamic acid or Oral tablet of tranexamic acid.', 'armGroupLabels': ['Intervention Arm'], 'otherNames': ['Cyklokapron®', 'trans-4-(aminomethyl)cyclohexanecarboxylic acid', 'Lysteda']}
- {'type': 'DRUG', 'name': 'Placebo', 'description': 'IV (saline) or oral placebo tablets', 'armGroupLabels': ['Control Arm'], 'otherNames': ['Placebo for tranexamic acid']}

Primary Outcomes:
- {'measure': 'The proportion of patients who die or have bleeding of WHO grade 2 or above by WHO criteria during the first 30 days from the first dose of trial treatment, or planned first dose for those participants who do not receive treatment.', 'description': 'The proportion of patients who die or have bleeding of WHO grade 2 or above by WHO criteria during the first 30 days from the first dose of trial treatment, or planned first dose for those participants who do not receive treatment.\n\nA time-to-event analysis will be used to determine this proportion to ensure that all patients are included in the primary outcome analysis, not just those who are followed up for the full 30 days. Any patients lost to follow-up will be included in the analysis and censored at the time that they were lost.', 'timeFrame': 'The first 30 days from first dose of trial treatment'}

Please estimate the sample size based on the assumption: 
The trial is designed with 80% power to detect an 11% absolute decrease in bleeding rates, with a significance level of 0.05. An additional 5% of patients are included to account for those who may not receive the trial treatment. The trial is not powered to definitively establish the safety of the treatment regarding VTE frequency.
Sample size
        Based on the experience of similar patients in the TOPPS trial [9], in the absence of anti-fibrinolytic therapy, it is anticipated that 43% of eligible patients will experience death or WHO grade 2 bleeding or higher within the first 30âdays of the TREATT trial. We judged that a 26% relative reduction in bleeding rates would be sufficient to change clinical practice because it would be necessary to treat only 8.9 patients to have an impact on 1 patient provided that no new safety issues related to anti-fibrinolysis in the thrombocytopenic population are uncovered. We thus evaluated the planned sample size of the trial relative to this hypothesised effect. We plan to recruit 616 participants to the TREATT trial. The primary endpoint will be analysed by using the KaplanâMeier (KM) method to estimate the probability of bleeding or death within 30âdays in the analysis populations. Power and sample size calculations are based on a log-rank test for comparing two survival curves, as described in Collett [28]. Under the assumption that anti-fibrinolysis results in a decrease of death or WHO grade 2 bleeding from 43% to 32%, the 616 patients planned to be recruited will provide 80% power to detect an observed absolute decrease in bleeding rates of 11% (a relative reduction of 26% with a number needed to treat (NNT) of 8.9) and will be judged statistically significant at the two-sided 0.05 level. The planned trial size of 616 subjects includes an additional 5% of patients above the required sample size of 586. This 5% figure is more than the proportion of patients within TOPPS (4%) who dropped their platelet count below 50âÃâ109/L but did not drop their platelet below 30âÃâ109/L. This therefore accounts for the number of patients within the trial who are randomly assigned but never receive the trial treatment.
        We do not expect there to be a problem with the assessment of the primary outcome since, in the recent TOPPS trial conducted by our group and using the same bleeding assessment tool, completeness of bleeding outcome documentation was excellent. A bleeding assessment was completed on 95% (17,138/18,000) of study days. The majority of patients had bleeding information completed on each trial day (median of 30âdays). There were also only 6 deaths (1% of patients) while on the trial.
        This trial is not powered to definitively establish the safety of the treatment with respect to the frequency of venous thromboembolism (VTE). However, with the planned enrolment of 616 patients, observed differences in frequency of VTE of 3.6% in the placebo arm and 5% or less in the TXA arm would result in a 95% confidence interval that excluded a relative risk of 3.5.