Here is the design of a clinical trial:

Official Title: Lateral Nodal Recurrence in Rectal Cancer

Included conditions:
- Rectal Cancer

Study Armgroups:

Interventions:

Primary Outcomes:
- {'measure': 'Lateral local recurrence', 'description': 'Lateral local recurrence diagnosed during the follow up', 'timeFrame': '3 years'}

Please estimate the sample size based on the assumption: 
A one-group χ2 test with a 5% two-sided significance level and 90% power is used. A drop-out rate of 5% is considered. An interim analysis will be conducted after the inclusion of the first 75 participants to evaluate early indicators of effectiveness and safety.
Sample size
        The sample size is based on a historical control group with an average 3-year LLR rate of 13% (11% Snapshot and 16% Consortium) in low LARC with LLNs â¥7.0âmm after (C)RT+TME (without LLND), which is the current standard treatment in Europe.5 6 14 It is hypothesised that (C)RT+TME+LLND can reduce this rate to 6%, as found by the Consortium study. A one-group Ï2 test with a 5% two-sided significance level will have 90% power to detect the difference between the null hypothesis proportion of 0.13 and the alternative proportion of 0.06 when the sample size is 190. If correcting for a drop-out rate of 5%, 200 patients are needed. Included patients in need of more extensive surgery (ie, pelvic exenteration or presumed inability to spare the hypogastric nerves on MRI) will be registered and analysed as a separate cohort since these more extensive tumours have higher LLR rates and cannot undergo nerve-sparing LLND.
        Annually, approximately 882 patients present with low LARC and are treated with neoadjuvant therapy in the Netherlands.14 Considering 122 (14%) of these patients have LLNs â¥7.0âmm, a minimum 2.5-year inclusion period is needed to achieve the estimated sample size (expecting 60% of eligible patients to be enrolled).14 As some of the eligible patients will undergo open surgery, it is expected that the inclusion period may require an extension. An interim analysis will be carried out after the inclusion of the first 75 participants. The goal of this interim analysis is to evaluate early indicators of effectiveness concerning oncological outcomes, particularly LLR rate, and to evaluate safety by examining short-term surgical complications (within 90 days) and early functional outcomes (urogenital dysfunction within 3 months). The results will help improve the preoperative information provided to patients. If the interim analysis reveals a high LLR rate that suggests that the hypothesis may not be achievable or significant morbidity within 3âmonths of surgery, the study team will consider to prompt the study ahead of time.
        Additionally, patients with rectal cancer and an LLN of 5.0â6.9âmm SA with at least one malignant feature will be investigated. For this analysis, a sample size calculation is impossible due to limited data. Therefore, all eligible patients in this group will be collected during the study period.