The role of multidetector CT in local staging and evaluation of retroperitoneal surgical margin involvement in colon cancer

PURPOSE

We aimed to evaluate preoperative T and N staging and retroperitoneal surgical margin (RSM) involvement in colon cancer using multidetector computed tomography (MDCT).

METHODS

In this retrospective study, preoperative MDCTs of 141 patients with colon adenocarcinoma were evaluated in terms of T and N staging and retroperitoneal surgical margin involvement by two observers. Results were compared with histopathology.

RESULTS

In determining extramural invasion, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of MDCT were 81%, 50%, 95%, 26%, and 81% for observer 1 and 87%, 75%, 97%, 27%, and 84% for observer 2, respectively. Moderate interobserver agreement was observed (κ=0.425). In determining T stage of the tumor, accuracy of MDCT was 55% for observer 1 and 51% for observer 2. In the detection of lymph node metastasis, sensitivity, specificity, PPV, NPV, and accuracy of MDCT were 84%, 46%, 60%, 74% and 64% for observer 1 and 84%, 56%, 65%, 78%, and 70% for observer 2, respectively. Interobserver agreement was substantial (κ=0.650). RSM was involved in six cases (4.7%). When only retroperitoneal colon segments were considered, 1.6% of subjects demonstrated RSM involvement. Four of the six RSM-positive tumors were located on sigmoid colon and one tumor was on transverse colon and caecum. Considering all colon tumors, in the detection of RSM involvement, sensitivity and specificity of MDCT were 33% and 81% for observer 1 and 50% and 80% for observer 2. Interobserver agreement was moderate (κ=0.518).

CONCLUSION

MDCT is a promising technique with moderate interobserver agreement in detection of extramural invasion, lymph node metastases, and RSM involvement in colon carcinomas.With the advent of technological improvements, computed tomography (CT) became one of the important diagnostic tools in the evaluation of local characteristics, preoperative staging, and prognostic factors of colon cancers (1). CT is recommended by EURECCA consensus group for staging of colon cancers (2). Extramural invasion (EMI) is an important factor affecting the prognosis in patients with colon cancer (3). Preoperative CT can detect EMI in colon cancers with high sensitivity (4). In addition, CT-based T staging can be used to stratify patients into good and poor prognosis (4, 5).Correlation between local recurrence and circumferential resection margin involvement in rectal cancer suggests the importance of retroperitoneal surgical margin (RSM) involvement in retroperitoneal ascending and descending colon tumors. RSM involvement is defined as less than 1 mm distance between RSM and primary adenocarcinoma or metastatic retroperitoneal lymph node in descending and ascending colon cancers (6). Studies suggest that RSM positivity may be a predictor and an independent prognostic indicator showing local recurrence in colon cancers (7).Classical colon cancer treatment is based on histopathologic prognostic factors in the resected specimen (1). However, at the present time, with the development of more effective chemotherapeutic agents and higher accuracy in preoperative staging, neoadjuvant treatments are preferred in patients with high-risk colon cancer (2, 8). Preoperative radiologic assessment of EMI and RSM positivity can decrease the local recurrence risk through timely recommendation of neoadjuvant chemotherapy which would lead to regression of metastatic lymph nodes, retroperitoneal extension, and tumor burden (6–8). Since severe adverse effects can be observed, neoadjuvant treatment should be administered to patients who would benefit the most from it. The aim of this study was to evaluate preoperative T and N staging and RSM involvement in colon cancer using multidetector CT (MDCT) and compare them with histopathology results.