ACR Appropriateness Criteria ® Pretreatment Staging of Colorectal Cancer

Abstract

Colorectal cancers are common tumors in the United States and appropriate imaging is essential to direct appropriate care. Staging and treatment differs between tumors arising in the colon versus the rectum. Local staging for colon cancer is less integral to directing therapy given radical resection is often standard. Surgical options for rectal carcinoma are more varied and rely on accurate assessment of the sphincter, circumferential resection margins, and peritoneal reflection. These important anatomic landmarks are best appreciated on high-resolution imaging with transrectal ultrasound or MRI. When metastatic disease is suspected, imaging modalities that provide a global view of the body, such as CT with contrast or PET/CT may be indicated. Rectal cancer often metastasizes to the liver and so MRI of the liver with and without contrast provides accurate staging for liver metastases. This article focuses on local and distant staging and reviews the appropriateness of different imaging for both variants. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Imaging of Colorectal Liver Metastases: New Developments and Pending Issues

“…Therefore, the authors wonder if something would change even if the guidelines were written by radiologists. Unfortunately, there were no differences in the imaging approach for colorectal metastatic disease evaluation in the Appropriateness Criteria-Pretreatment Staging of Colorectal Cancer drafted by the American College of Radiology (ACR) in 2017 [4]. They stated that, despite differences in locoregional staging between colon and rectal cancer, the evaluation of distant metastases has the same approach; "it is difficult to determine the best imaging modality for patients with CRLM" [29].…”

“…They stated that, despite differences in locoregional staging between colon and rectal cancer, the evaluation of distant metastases has the same approach; "it is difficult to determine the best imaging modality for patients with CRLM" [29]. Moreover, they specified that "the available evidence supports that both MRI and CT detect liver lesions with high accuracy" [4].…”

“…On the one hand, the current paradigm of treatment is to remove all liver metastases if feasible because survival for patients with liver metastases is <1% at five years. Hence, the accurate depiction of the size, distribution, and number of liver metastases is the primary goal of staging [2][3][4]. On the other hand, in a consecutive medicolegal necropsy series, benign hepatic tumors and tumor-like conditions, excluding liver cysts, occurred in 52% of males, having an increasing incidence with age [35,36].…”

“…The complexity of both hepatic vascularization and the microenvironment supports the development of cancer cell invasion, permitting increased trapping of tumor cells in the small sinusoids. In particular, the portal vein represents the primary inflow of tumor cell emboli carried in the blood from tumors located in other organs [2][3][4].…”

Value of MRI morphologic features with pT1‐2 rectal cancer in determining lymph node metastasis

“…3,4 Magnetic resonance imaging (MRI), with its excellent soft-tissue resolution, is believed to be the best noninvasive imaging tool and is recommended to evaluate tumor stage by the NCCN guideline, radiology committee, and consensus. 5,6 Despite many efforts these years, whether there are any metastatic lymph nodes (LNs) remains a challenge. The enlarged LNs can be reactive hyperplasia or inflammatory LNs, while small ones (mainly <5 mm) could contain metastatic cancer cells.…”