*2.7.3 Positron emission tomography PET*

Positron emission tomography PET with computed tomography is an additional method for functional staging by imaging in the following cases: [1] in unconvincing computed tomography and magnetic resonance data for primary tumor or distant visceral metastases with elevated values of tumor markers; [2] for N-staging; 3) for M-staging. Disadvantages are the high cost and low availability of the method. Inaccuracies in the differentiation of changes in the mesorectum and pelvic lymph nodes and inaccuracies in the assessment of mucinous tumors are known. It also cannot stratify patients with complete and incomplete response (**Figure 14**).
