Assuming a prevalence of metastasised prostate cancer of 20% and a true (unknown) sensitivity of FCH PET/CT of 95%, 205 patients are sufficient to show that the sensitivity of the FCH PET/CT is greater than 80% with a power of 80% at significance level 5%. The size of the confidence interval for specificity of FCH PET/CT is expected to become reasonable small. In opposition to lymphadenectomy, FCH PET/CT results may point to metastases in neighbouring regions which gives an additional benefit to FCH PET/CT justifying a test level for sensitivity of 80%."