Table 6.

Assessment methods of the colorectal primary tumor and multi-organ metastases

Tumor lesion	Assessment methods
Primary tumor	1. Colonoscopy should be conducted to determine the location of the primary tumor, tumor size, the proportion of the intestinal lumen that the tumor occupies, and biopsy should be used to confirm the pathology of the tumor (including molecular biology tests, RAS/BRAF gene status, microsatellite instability status, and HER2 status)
	2. Enhanced CT of the entire abdomen
Lung metastases	1. High-resolution chest CT scan1
	2. Enhanced chest CT scan (when mediastinal lymph node metastases are present)
	3. Evaluation of lung function
Liver metastases	Contrast-enhanced MRI of the liver1
Other metastases	1. Contrast-enhanced MRI of the pelvis (when pelvic implantation metastases are present)
	2. Bone ECT (when symptoms associated with bone metastases are present)
	3. PET-CT2

¹For patients with only liver metastases as extrapulmonary metastases, it is recommended that high-resolution chest CT scan be used for resectability assessment of lung lesions. Additionally, enhanced CT of the entire abdomen and contrast-enhanced MRI of the liver should be used to for resectability assessment of liver metastases [61–63]. In addition to assessment for technical resectability, biological behavior assessment should also be considered. Currently, it is believed that patients with more than five liver metastases, more than three lung metastases, and who exhibit progression after neoadjuvant treatment have poor outcomes after radical resection [64, 65]

²PET-CT is only used when it is impossible to determine the nature of lung lesions and extrapulmonary lesions. Currently, it is believed that PET-CT has greater value for intrapulmonary lesions > 1 cm [66]