High-performance CT features supporting accurate pre-operative tumor staging in colon cancer

Jianhua Yuan ¹ Cangzheng Jin ² Jianrong Si ^1* Baobao Liu ³ Xiaohan Si ⁴ Jianzhi Chen ⁵

• ¹ Department of Radiology, Guangdong Provincial Hospital of Integrated Traditional Chinese and Western Medicine, Foshan, China
• ² Department of Radiology, The Sixth Affiliated Hospital, School of Medicine, South China University of Technology, Foshan, China
• ³ Department of Pathology, Guangdong Provincial Hospital of Integrated Traditional Chinese and Western Medicine (affiliated to Guangzhou Kingmed Diagnostics Group Co Ltd), Foshan, China
• ⁴ Ecosystem Change and Population Health Research Group, School of Public Health and Social Work, Queensland University of Technology, Brisbane, Australia
• ⁵ Department of Pathology, The Sixth Affiliated Hospital, School of Medicine, South China University of Technology, Foshan, 528234, China, Foshan, China

Background and aims: Accurate pre-treatment tumor staging is essential for treatment decision-making. Multi-slice spiral computed tomography (CT) is currently the standard method for preoperative clinical tumor staging, but accurately applying the CT findings in tumor staging remains a challenge due to the poor pathological understanding of the CT signs. We aimed to pathologically interpret the key CT findings in order to identify reliable markers for pre-treatment staging of colon cancer.The following CT features from 136 colon adenocarcinomas were analyzed: colon wall pliability, outline contour, pericolic fat attenuations and vascularity, tumor fusion with adjacent organs, ascites, tumor size and relevance between tumor and retroperitoneal fascia. These CT features were corroborated with histopathological findings. The diagnostic performance of these was further analyzed. Results: Based on the postoperative pathological tumor staging (pT), 136 colon adenocarcinomas were classified into four stages: pT1 (n=5), pT2 (n=7), pT3 (n=96) and pT4 (n=28). Key findings include (1) soft colon wall is a characteristic of the pT1 tumors while stiff colon wall is a characteristic of the pT2~4 tumors. Pathologically, stiff colon wall reflects the infiltration of tumor cells with desmoplastic reaction (DR) in muscularis propria; (2) small protuberances may help exclude the pT2 tumors. Histopathologically, small protuberances in pT2 cancer represent the pure DR on the surface of lamina propria, whereas the small protuberances in pT3~4 cancers represent the sub-serosal or extra-serosal cancer cell foci enwrapped by DR; (3) presence of large protuberances, extensive reticulonodular fat stranding, fusion with surrounding organs and ascites are diagnostic of pT4 tumors; (4) presence of extra-fascial nodules/streaks on CT scan could accurately diagnose the ascending/descending colon cancer of pT4 stage. Histologically, presence of the above five CT features (large protuberances, extensive reticulonodular fat stranding, fusion with surrounding organs, ascites and extra-fascial nodules/streaks) reflect the farther and deeper infiltration of tumor cells in serosa or retroperitoneal fascia involvement.Our studies have identified multiple CT features that are practically useful in identifying and differntiating different statges of colon cancer prior to surgical procedures. These high-performance markers will provide valuable insights to the clinicians in making appropriate decisions in the management of colon cancer patients.