Here is the design of a clinical trial:

Official Title: RecurIndex Guided Avoidance of Regional Nodal Irradiation for Node Positive Breast Cancer

Included conditions:
- Breast Cancer
- Radiation

Study Armgroups:
- {'label': 'Arm I (Clinical low-risk, RecurIndex high-risk)', 'type': 'EXPERIMENTAL', 'description': 'Regional nodal irradiation (RNI) was given along with whole breast irradiation (WBI) or Chest wall irradiation (CWI) for breast-conserving patients and total mastectomy patients, respectively.', 'interventionNames': ['Radiation: regional nodal irradiation', 'Radiation: WBI', 'Radiation: chestwall XRT']}
- {'label': 'Arm II (Clinical low-risk, RecurIndex high-risk)', 'type': 'ACTIVE_COMPARATOR', 'description': 'No Regional nodal irradiation (RNI) , whole breast irradiation (WBI) for breast-conserving patients and No Chest wall irradiation (CWI) for total mastectomy patients.', 'interventionNames': ['Radiation: WBI']}

Interventions:
- {'type': 'RADIATION', 'name': 'regional nodal irradiation', 'description': 'external-beam radiotherapy (XRT)', 'armGroupLabels': ['Arm I (Clinical low-risk, RecurIndex high-risk)']}
- {'type': 'RADIATION', 'name': 'WBI', 'description': 'Whole Breast Irradiation', 'armGroupLabels': ['Arm I (Clinical low-risk, RecurIndex high-risk)', 'Arm II (Clinical low-risk, RecurIndex high-risk)']}
- {'type': 'RADIATION', 'name': 'chestwall XRT', 'description': 'chestwall irradiation', 'armGroupLabels': ['Arm I (Clinical low-risk, RecurIndex high-risk)']}

Primary Outcomes:
- {'measure': 'Invasive disease-free survival (IDFS)', 'description': 'defined as the time between randomization and either local recur, distant metastases or death occurred', 'timeFrame': '5 years'}

Please estimate the sample size based on the assumption: 
One-sided significance level (α) of 0.025, power (1-β) of 0.8, and a potential 20% dropout rate.
Sample size estimation
        This study is designed for superiority, referring to authoritative postoperative radiotherapy studies MA2010 and EORTC 2292211 for N1 patients, in which the 5-year IDFS in the radiotherapy group and the control group was 90.7% vs 81.9% and 87.7% vs 77.1%, respectively. In the domestic RecurIndex external validation retrospective study21 for patients with N1 breast cancer, the 5-year IDFS in the high RecurIndex-LRR risk group was 81.1% vs 69.7% in the postoperative radiotherapy group and the control group, respectively. It is expected that the 5-year IDFS for the clinically low LRR risk and high RecurIndex-LRR risk population in the experimental group and control group in this study will be 89% and 82%, respectively. The superiority margin is set to improve the primary endpoint IDFS by â¥7% (HR=0.587) in the postoperative radiotherapy research group compared with the control group. With a one-sided significance level (Î±) of 0.025 and a power (1âÎ²) of 0.8, assuming the experimental group performs better than the control group, the required sample size for each group was calculated as 216 cases per group using PASS V.15.0 software. The allocation ratio between the experimental and control groups was set at 1:1. Considering a 5-year enrolment period, 5-year follow-up period and potential 20% dropout rate (mainly considering the need for further 10-year and 15-year long-term efficacy follow-up after reaching the 5-year endpoint), each group will need 270 cases, totalling 540 cases.