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

Abstract

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 (ĸ=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 (ĸ=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 (ĸ=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.

Figures

Figure 1 a–c.

Schematic images of T staging (a, b) according to 2010 TNM and evaluation of retroperitoneal surgical margin (RSM) involvement (c). RSM involvement was evaluated as being present if the minimum distance between the tumor or metastatic lymph node and the RSM was less than 1 mm.

Figure 2

Axial CT image of a 69-year-old woman whose cecal tumor was suspicious for invasion of ileum (arrow). Both observers assessed the cecal lesion as T4b, but it was proven to be T3 tumor pathologically (overstaging).

Figure 3 a, b.

Reconstructed coronal (a) and axial (b) MDCT images of a 69-year-old man demonstrating no extramural invasion (arrows). Both observers assessed the ascending colon tumor as T2. It was a pathologically proven T4a tumor (understaging).

Figure 4 a, b.

Coronal multiplanar reconstruction MDCT images (a, b) show cecal tumor and enlarged lymph nodes larger than 5 mm in size suggesting malignancy (arrows). Both observers staged the lymph nodes as N1. However, pathology revealed that the lymph node enlargement was caused by a benign inflammatory reaction (N0).

Figure 5 a, b.

Axial (a) and coronal reformatted (b) MDCT images of a 54-year-old-woman with pathologically proven pT4aN0, RSM-positive sigmoid colon tumor. Both observers assessed RSM as negative. First observer, T4aN0 RSM-; second observer, T4aN1 RSM−.

Figure 6 a–c.

Axial (a) and coronal reformatted (b, c) MDCT images of a 74-year-old man with sigmoid colon cancer. Both observers assessed RSM (arrow) as positive. Pathology, T4aN0 RSM+; first observer, T4aN1 RSM+; second observer, T4bN0 RSM+.

Figure 7 a–c.

Axial CT images (a, b) through the mid-ascending colon show the primary tumor, an enlarged lymph node, and the RSM (arrows). Sagittal multiplanar reconstruction image (c) demonstrates the RSM and an enlarged lymph node (LN) abutting the RSM. Both observers assessed the tumor as RSM-positive. However, the enlarged lymph node that appears malignant on CT was reported as a benign node on histopathology. Pathology reported negative RSM.