[Importance of FDG-PET/computed tomography in colorectal cancer].

BACKGROUND: Hybrid imaging FDG PET/CT (18F‑fluordeoxyglucose positron emission tomography/computed tomography) has gained increasing importance in oncology in recent years. DIAGNOSIS: A focal increase in FDG uptake in the gastrointestinal tract may be due to colorectal carcinoma. Such a finding requires further clarification. PRIMARY STAGING: Staging of the primary and locoregional lymph nodes remains a domain of established imaging modalities as FDG PET/CT does not provide a clear additional benefit. Liver metastases can be detected with high sensitivity by FDG PET/CT, but MRI is superior in small lesions. RADIATION THERAPY PLANNING: So far FDG PET/CT plays a subordinate role in the radiation therapy planning of rectal cancer. However, it can potentially contribute to the optimization of planning target volumes. THERAPY MONITORING: FDG PET/CT is suitable for monitoring therapy because morphological and metabolic changes of the tumor can be detected in early stages. This enables early detection of nonresponders after beginning neoadjuvant chemoradiation therapy of rectal cancer. FDG PET/CT can also be used for therapy control of liver metastases, especially after local therapeutic procedures. DETECTION OF RECURRENCE: With clinical suspicion of local recurrence and increased tumor markers, FDG PET/CT is a valuable tool as tumor recurrence can be detected with high sensitivity and specificity.