CT Colonography is highly sensitive and cost effective in detection
of colorectal carcinoma. CT has good sensitivity for the detection of colon cancers with
tumors that have spread beyond the bowel wall, however, it remains a
challenge in detecting nodal involvement, which could have considerable
consequences given the increasing interest in neoadjuvant treatment for
This finding was published in the November 2016 issue of the American Journal of Roentgenology
"Diagnostic Accuracy of CT for Local Staging of Colon Cancer: A Systematic Review and Meta-Analysis." The article, which is available on AJR
's website through open access, indicates that thin-slice CT may be an effective tool in identifying nodal involvement.
‘The use of thin slice CT improved the detection of tumor invasion beyond the bowel wall, as well as the detection of malignant lymph nodes.’
"Detecting nodal involvement with CT is unreliable," Elias Nerad,
radiologist at Catharina Hospital Eindhoven and researcher at
Netherlands Cancer Institute in Amsterdam, The Netherlands, said.
use of thin slices improved the detection of tumor invasion beyond the
bowel wall, as well as the detection of malignant lymph nodes, and is
therefore advocated. Also, evidence suggests that CT colonography
improves the accuracy of CT in the local staging of colon tumors, which
could have a major clinical effect if neoadjuvant chemotherapy is
adopted in the treatment of colon cancer."
CT colonography is a technique that uses optimal bowel wall
distention and 3D reconstruction of the colon (creating a virtual
colonoscopy), which distinguishes it from regular CT of the abdomen. The
meta-analysis provided by study coauthor Nerad, et al. was limited to
two CT colonography studies because the majority of them identified in
the literature search included rectal tumors that were inseparable from
the colon tumors and thus were excluded.
Nerad said, "Furthermore, CT colonography can also be used
as a (local) staging tool, making it a very interesting potential
subgroup in our meta-analysis."
Overall, the research was based on the meta-analysis of 13 studies
describing the accuracy of CT in the staging of colon carcinomas. In the
literature, colon and rectal cancers are combined despite the fact that
they differ in terms of anatomy, diagnostic workup, and treatment. This
study does make a clear distinction between the two and aims to
exclusively determine the diagnostic accuracy of CT for staging colon
cancer only and to evaluate whether CT can help in differentiating high-
from low-risk colon cancer tumors.
Therapy for rectal cancer is based on staging with MRI or endorectal
ultrasound, the study said. For the treatment of MRI-staged high-risk
rectal tumors, defined as tumors with involvement of the mesorectal
fascia, guidelines recommend neoadjuvant chemoradiotherapy.
In contrast, colon cancer is mainly staged with CT and there are no
guidelines for the use of neoadjuvant treatment for colon cancer.
However, this will most likely change in the near future, if ongoing
studies confirm earlier reports that patients with aggressive colon
tumors benefit from a neoadjuvant treatment.
The meta-analysis provided by Nerad et al. specifically focuses on
the diagnostic accuracy of CT for staging colon cancer and to evaluate
whether CT can select patients for neoadjuvant treatment (i.e.,
aggressive colon tumors).