ESR Essentials: Imaging in colorectal cancer-practice recommendations by ESGAR

Abstract

Colorectal cancer (CRC) is a significant global health concern. Diagnostic imaging, using different modalities, has a pivotal role in CRC, from early detection (i.e., screening) to follow-up. The role of imaging in CRC screening depends on each country's approach: if an organized screening program is in place, the role of CT colonography (CTC) is limited to the study of either individuals with a positive stool test unwilling/unable to undergo colonoscopy (CC) or in patients with incomplete CC. Although CC is the most common modality to diagnose CRC, CRC can be also incidentally detected during a routine abdominal imaging examination or at the emergency room in patients presenting with intestinal occlusion/subocclusion or perforation. Staging is a crucial aspect of CRC management, guiding treatment decisions and providing valuable prognostic information. An accurate local staging is mandatory in both rectal and colon cancer to drive the appropriate therapeutic workflow. Important limitations of US, CT, and MR in N-staging can be partially solved by FDG PET/CT. Distant staging is usually managed by CT, with MR and FDG PET/CT which can be used as problem-solving techniques. Follow-up is performed according to the general recommendations of the oncological societies. CLINICAL RELEVANCE STATEMENT: It is essential to summarize each phase of colorectal cancer workup, differentiating the management for colon and rectal cancer supported by the main international guidelines and literature data, with the aim to inform the community on the best practice imaging in colorectal cancer. KEY POINTS: • Colorectal cancer is a prevalent disease that lends itself to imaging at each stage of detection and management. • Various imaging modalities can be used as adjuncts to, or in place of, direct visualization methods of screening and are necessary for evaluating metastatic disease. • Reevaluation of follow-up strategies should be considered depending on patients' individual risk of recurrence.

Keywords: CT; Colon cancer; Imaging; MR; Rectal cancer.

Fig. 1

The flowchart of colorectal cancer screening. gFOBT, guaiac-based fecal occult blood test; FIT, fecal immunochemical test

Fig. 2

Rectal cancer local staging. T stage is represented in a, from Tis, limited to the mucosa, to T4b, involving other organs. In b are shown the most important high-risk factors, tumor deposit in the mesorectal fat, extramural venous invasion, and mesorectal fascia involvement, that are not influence on TNM staging

Fig. 3

Key points regarding screening of colorectal cancer, the performance of CTC, and the advantages of CT and MRI