CT and MRI in Preoperative Colon Cancer Staging

Colonic Neoplasms

colon, cancer, computed tomography, magnetic resonance, diffusion, preoperative, staging

The objective of this study is the evaluation of different imaging methods for the optimal preoperative staging of colon cancer patients. Imaging findings will be compared with the histopathologic results of the specimen following surgical resection.

Over the last years a significant improvement in the treatment of patients with colon cancer has been reported. This has been attributed to the improvement of the staging techniques, as well as the optimization of the surgical management. However, the current five-year survival rates of colon cancer patients in European countries ranges from 32% to 64%. This variation could be due to treatment discrepancies and the lack of adherence to the international guidelines. Surgical treatment of colon cancer includes the radical resection of the tumour (colectomy). Following resection, the specimen is histopathologically examined, the disease is staged and further treatment is determined. Neoadjuvant treatment (radiotherapy or/and chemotherapy) for colon cancer has not been yet approved, unlike rectal cancer, where neoadjuvant treatment is recommended for specific disease stages. Preoperative staging of colon cancer aims to identify those patients with remote metastatic disease, who will, more likely, not benefit from upward surgery. Recent developments in colon cancer management, demanding more precise local disease staging, to identify those patients who will likely benefit from neoadjuvant chemotherapy, are still at a clinical trial stage. Preoperative treatment depends on the disease stage, which is defined by the tumour's invasion in the colonic wall, the dissemination in nearby organs or lymph nodes, and the presence of distal metastases. The stage is first evaluated radiologically and then confirmed via histopathological examination of the specimen. Imaging is an already approved tool for the staging of colonic cancer, while in some studies the combination of different imaging methods has been reported to improve the initial evaluation. Over the last years, evaluation of the circumferential resection margin (CRM) is also recommended in the preoperative staging of patients with colon cancer. This assessment is particularly important for tumours located at the cecum, right, or left colon, since these areas lack of mobile mesocolon and therefore it is possible to infiltrate the retroperitoneal resection margin. Nevertheless, the retroperitoneal invasion of these tumours has not been evaluated adequately as a preoperative marker for both local recurrence and for the selection of patients who may benefit from neoadjuvant treatment. In various studies the percentage of retroperitoneal resection margin's infiltration was between 7-10% for cecum and right colon adenocarcinomas, while its presence was identified as a risk factor for local recurrence. The retroperitoneal surface infiltration was preoperatively evaluated with the combination of imaging methods and the findings were postoperatively compared with the histopathological features of the specimen. A more precise, imaging based, preoperative staging, could lead to a more targeted neoadjuvant treatment for patients with advanced disease, with the introduction of chemo- and/or radiotherapy. This approach could result to the downstaging of the tumour, with better short and long term oncological results.

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