What methods are primarily used for staging colorectal cancer, particularly for T and N stages?

The primary methods used for staging colorectal cancer, particularly for assessing T (tumor) and N (node) stages, include total colonoscopy and endoscopic ultrasound (EUS).

Total colonoscopy allows for direct visualization of the entire colon, enabling the identification of tumors and allowing for biopsies to be performed to assess the histological characteristics of the cancer. This method is critical for understanding the extent of the tumor (depth of invasion into the bowel wall) and for evaluating regional lymph nodes for any metastatic disease.

Endoscopic ultrasound is particularly valuable for staging rectal cancers. It provides excellent imagery for evaluating the depth of tumor invasion and the involvement of perirectal lymph nodes, which is essential for determining the staging and treatment approach. EUS has a high sensitivity and specificity for accurately determining the T stage and can help guide surgical planning.

While imaging methods such as CT scans and MRIs can provide useful information about distant metastases and overall disease spread, they are less reliable in assessing the specifics of the T and N staging directly compared to the aforementioned techniques. Therefore, total colonoscopy and endoscopic ultrasound are considered the gold standards for such staging assessments in colorectal cancer.