| Abstract: |
This document aims to provide recommendations on the role of imaging in the diagnosis of squamous cell anal cancer, focusing on its use in locoregional and systemic assessment during initial staging, posttreatment evaluation, and surveillance. For initial locoregional staging, MRI of the pelvis and FDG-PET/CT are usually appropriate to complement clinical and digital rectal examinations, because they offer additional information regarding locoregional tumor invasion and nodal metastases. For metastatic disease assessment, which is rare in the initial presentation and commonly associated with recurrence—with lymph nodes, liver, and lungs being the most common sites of disease—CT and FDG-PET/CT are usually appropriate for detecting distant nodal metastases and other sites of metastatic disease. MRI of the abdomen may be appropriate as a problem-solving tool, particularly in assessing small or indeterminate liver lesions. For patients who have completed locoregional treatment, most typically achieve clinical complete response; consequently, few require surgery unless there is persistent disease or recurrence. The role of posttreatment imaging assessment is still debatable; however, in cases in which surgery is indicated, MRI and FDG-PET/CT are usually appropriate for assessing local tumor invasion and nodal metastases. 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 process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation. © 2025 American College of Radiology |
