Here is the design of a clinical trial:

Official Title: Phase IIb Randomised Clinical Trial Repurposing ATRA as a Stromal Targeting Agent in a Novel Drug Combination for Pancreatic Cancer

Included conditions:
- Pancreatic Cancer

Study Armgroups:
- {'label': 'Gemcitabine + nab-paclitaxel', 'type': 'ACTIVE_COMPARATOR', 'description': 'Patients will receive Gemcitabine and nab-Paclitaxel in 28 day cycles until disease progression.', 'interventionNames': ['Drug: Gemcitabine', 'Drug: nab-paclitaxel']}
- {'label': 'Gemcitabine + nab-paclitaxel + ATRA', 'type': 'EXPERIMENTAL', 'description': 'Patients will receive ATRA, Gemcitabine and nab-Paclitaxel in 28 day cycles. ATRA will be administered for 6 cycles whereas Gemcitabine/nab-Paclitaxel will be administered until disease progression.', 'interventionNames': ['Drug: ATRA', 'Drug: Gemcitabine', 'Drug: nab-paclitaxel']}

Interventions:
- {'type': 'DRUG', 'name': 'ATRA', 'description': '45 mg/m2 orally (in two divided doses) from days 1 to 15 of each cycle', 'armGroupLabels': ['Gemcitabine + nab-paclitaxel + ATRA'], 'otherNames': ['Tretinoin', 'Vesanoid']}
- {'type': 'DRUG', 'name': 'Gemcitabine', 'description': '1000mg/m2 IV on days 1, 8 and 15 of a 28 day cycle', 'armGroupLabels': ['Gemcitabine + nab-paclitaxel', 'Gemcitabine + nab-paclitaxel + ATRA']}
- {'type': 'DRUG', 'name': 'nab-paclitaxel', 'description': '125mg/m2 IV on days 1, 8 and 15 of a 28 day cycle', 'armGroupLabels': ['Gemcitabine + nab-paclitaxel', 'Gemcitabine + nab-paclitaxel + ATRA'], 'otherNames': ['Abraxane']}

Primary Outcomes:
- {'measure': 'To assess the efficacy of ATRA when given in combination with gemcitabine and nab-paclitaxel based on progression free survival (PFS).', 'description': 'PFS defined as the time from the date of randomisation to the date of first documented tumour progression or death from any cause, whichever occurs first.', 'timeFrame': 'Assessed 8 weekly until progression or death or end of trial, whichever comes first'}

Please estimate the sample size based on the assumption: 
The study is designed to have 90% power at the 20% one-sided level of statistical significance (equivalent to 80% power at the 10% one-sided level of statistical significance), with no dropouts expected. An informal assessment for futility may be conducted at 43 PFS events using a Lan-DeMets spending function with a Pocock type boundary.
Sample size
        The sample size is based on the primary outcome measure. The estimated median PFS is 10Â months for the control arm (gemcitabineâ+ânab-paclitaxel). Using a group sequential design, this study is designed to have 90% power at the 20% one-sided level of statistical significance (equivalent to 80% power at the 10% one-sided level of statistical significance) to detect a 50% improvement in median PFS (i.e. an estimated hazard ratio of 0.667) leading to an estimated median PFS of 15Â months. This design requires 170 patients (129 PFS events), randomised 1:1 between the two arms (85 patients in the control arm and 85 patients in the experimental arm), with no dropouts expected. It may be possible to conduct an informal assessment for futility at 43 PFS events (estimated at approximately 20Â months)( using a Lan-DeMets spending function with a Pocock type boundary). If the observed hazard ratio is greater than 1.121 in favour of the control arm, the trial may be stopped for futility, if considered appropriate.