Endorectal ultrasound and the preoperative staging of rectal cancer.

Abstract

Over the past century, many staging systems have been proposed for rectal cancer with varying complexity. These staging systems are mainly based on pathology and thus are generally applicable postoperatively. In 1932, Cuthbert Dukes, from St Mark’s Hospital in London, described the original Dukes’ staging system for rectal cancer (5). He described three stages: A, B, and C. Stage A being confined to the bowel wall, B through the bowel wall, and C involving regional lymph nodes. This staging system was later modified by Kirklin in 1949 and by Astler and Coller in 1954 (6, 7). Astler and Coller’s modification subdivide B and C stages based on partial versus full-thickness invasion of the muscularis propria. A fourth category (Dukes’ D), although not originally described, has been used to designate distant metastatic disease. Although more complex, these staging systems have more prognostic significance than the original Dukes criteria. At present, the tumor, regional nodes, metastasis (TNM) classification system, originally proposed by the American Joint Committee on Cancer (AJCC) in 1977, is the most commonly used staging system (8) (Table 1). This system takes into account depth of bowel wall invasion, regional lymph node involvement and distant metastatic disease. Preoperative staging of rectal cancer by ERUS employs a modification of the TNM system, which was first described by Hildebrandt in 1985 (9) (Table 2). The prefix “u” is used to designate the use of ultrasonography, as opposed to the prefix “p” which denotes pathologic stage. Of note, this system does not designate whether metastatic disease is present, since ERUS is not able to define distant disease. Nor does it describe the number of positive lymph nodes present. The specifics of this staging system are described later. Correspondence: W. Douglas Wong, M.D. Division of Colorectal Surgery Memorial Sloan-Kettering Cancer Center 1275 York Avenue New York, NY 10021 Email: wongd@mskcc.org INTRODUCTION