Here is the design of a clinical trial:

Official Title: Direct Letters to Relatives at Risk of Hereditary Cancer- a Multi-centre Randomised Controlled Trial of Healthcare-assisted Versus Family-mediated Risk Disclosure at Swedish Cancer Genetics Clinics (DIRECT-study)

Included conditions:
- Familial Breast Cancer
- Familial Colorectal Cancer
- Hereditary Breast and Ovarian Cancer Syndrome
- Hereditary Breast Cancer
- Lynch Syndrome

Study Armgroups:
- {'label': 'Control / Family-mediated disclosure (standard care)', 'type': 'ACTIVE_COMPARATOR', 'description': 'Genetic counseling according to current clinical practice', 'interventionNames': ['Other: Standard care encouraging family-mediated disclosure of hereditary cancer risk']}
- {'label': 'Intervention / Health-care assisted disclosure', 'type': 'EXPERIMENTAL', 'description': 'Genetic counseling according to current clinical practice with the addition of an offer from health care provider to mail letters directly to eligible at-risk relatives.', 'interventionNames': ['Other: Standard care encouraging family-mediated disclosure of hereditary cancer risk', 'Other: Offer of health-care assisted disclosure by sending direct letters to at-risk relatives']}

Interventions:
- {'type': 'OTHER', 'name': 'Standard care encouraging family-mediated disclosure of hereditary cancer risk', 'description': 'At counseling, eligible at-risk relatives (who may benefit from disclosure of risk information) are listed on a specified protocol in collaboration between health care provider and the participant.', 'armGroupLabels': ['Control / Family-mediated disclosure (standard care)', 'Intervention / Health-care assisted disclosure']}
- {'type': 'OTHER', 'name': 'Offer of health-care assisted disclosure by sending direct letters to at-risk relatives', 'description': 'The participant is offered that the health care provider at the cancer genetic unit mail a direct letter with personalized family risk information to all at-risk relatives that participant approve contact with.', 'armGroupLabels': ['Intervention / Health-care assisted disclosure']}

Primary Outcomes:
- {'measure': "Uptake of genetic counselling among the patient's at-risk relatives", 'description': 'Number of potential at-risk relatives who have contacted a Swedish cancer genetic unit out of the total number of potential at-risk relatives for each patient.', 'timeFrame': 'One year (12 months) following the first counselling session when implications of the cancer genetic investigation for the patient´s at-risk relatives is discussed, hence 12 months after t=0.'}

Please estimate the sample size based on the assumption: 
The study aimed for a power of 0.8 and a two-sided 5% significance level. The power analysis was performed using R version 4.2.1 with the pwr package. The effect size was defined using Cohen's h formula.
Sample size {14}
        In 2019, there was no available published data on the uptake of genetic counselling after family-mediated risk disclosure in Sweden. Due to this lack of certainty, we decided to make the sample size calculations based on the assumption that each proband has 4 ARRs in average and the uptake in the control group is 50%. We wanted to be able to detect if at least one more ARR in every second family contacted a cancer genetics clinic in one of the study arms, i.e.., 5 out of 8 ARRs. Based on this, we determined that the study needed the power to detect a difference of 12.5 percentage units (62.5% in intervention, 50% in control group). To detect this difference with a power of 0.8 and a two-sided 5% significance level required 490 listed ARRs (half in each study group). The power analysis was performed in R version 4.2.1 using the pwr package. Effect was defined as Cohens hâ=â2*asin(sqrt(p1))-2*asin(sqrt(p2)) where p1â=â0.625 and p2â=â0.50.
        To allow for subgroup analyses, the recruitment target was set to 600 ARRs. During the study period, clinical guidelines in Sweden changed, putting less focus on familial cancer and more on predictive testing. To adapt to this change, the initial recruitment target of 600 ARRs in total was adopted to 490 ARRs in the most prioritized subgroup, i.e., families with a pathogenic variant identified in a high-risk gene (hereditary breast and ovarian cancer and Lynch syndrome: BRCA1, BRCA2, PALB2, MSH2, MSH6, MLH1, or PMS2).