COLUMBUS, Ohio--Rectal cancer is treated with a wide variety of operations and adjuvant therapy. This variety makes extensive preoperative evaluation mandatory, said Karamjit Khanduja, MD, chief of the Division of Colon and Rectal Surgery, Mt. Carmel Health, Columbus, Oho.
In a presentation at the Ohio State University-James Cancer Hospital and Research Institute 4th Annual Oncology Update, he said that endorectal ultrasound, a relatively new tool, is rapidly becoming a standard method of assessing tumors, while several standard laboratory tests are proving less crucial than once thought in evaluating rectal cancer.
Recent advances in the treatment of rectal cancer have broadened the number of surgical options available, including total mesorectal excision and transanal endoscopic microsurgery. Chemoradiation therapy, often given after surgery, has also proved beneficial when performed before an operation, Dr. Khanduja said.
To choose among the many treatment options available, the surgeon must carefully evaluate patient factors, tumor characteristics, and the extent of distant metastasis. A thorough, detailed staging of the tumor is essential. To determine whether preoperative chemoradiation is appropriate, for example, the surgeon must carefully determine the extent of local disease.
Colon cancer, by contrast, has fewer treatment options and, thus, requires less preoperative evaluation. Limited staging is adequate to make a decision regarding treatment for colon cancer, he said.
Endorectal Ultrasound
Endorectal ultrasound with rigid sigmoidoscopy should be used to determine which tumors are good candidates for preoperative chemoradiation therapy (Figures 1A, 1B, and 2). "If you want to do preoperative chemoradiation, then you must do ultrasound," Dr. Khanduja said. Ultrasound’s accuracy range for tumor size is 80% to 95%, while its accuracy for lymph node involvement is 60% to 80%. Accuracy improves with experience.
Preoperative chemoradiation is appropriate for UT3 and UT3N1 or N2 rectal cancers (U = by ultrasound staging), Dr. Khanduja said. Studies have shown that preoperative chemoradiation therapy is safe, results in the downstaging of tumors, and increases the surgeon’s ability to perform sphincter-saving operations. In 8% to 25% of patients, it eradicates the tumor completely, he said, citing the progress report of NSABP Protocol R-03 [Dis Colon Rectum 40(2):131-139, 1997].
A CT scan is necessary to determine the presence of metastatic liver disease. The decision of whether to provide preoperative chemoradiation will be guided by the CT scan results. "I find that in staging rectal cancers, especially large tumors, the CT scan complements the ultrasound," Dr. Khanduja said. He noted that preoperative CT is unnecessary in most cases of colon cancer. A CT scan can also provide information regarding renal function status.
By shrinking tumors, preoperative therapy can increase the number of sphincter-saving surgeries performed. Thus, he said, determining the functional status of the anal sphincter, and the feasibility of a sphincter-saving operation, is an essential part of the preoperative evaluation.
If CT is done, than no additional advantage is gained by performing magnetic resonance imaging (MRI), since MRI of rectal cancer has results similar to those of CT scans and is not accurate in determining depth of wall involvement or presence of adenopathy. The routine use of MRI is not recommended, Dr. Khanduja said. He did point out that the addition of an endorectal surface coil has been shown to improve the procedure’s accuracy from 50% to almost 85%.
CEA Levels
Measuring the level of the tumor marker CEA preoperatively is "very essential," Dr. Khanduja said. It usually returns to normal within 1 month of surgery. Persistent elevation implies residual disease, while a fall to normal after surgery followed by a consistent steady rise indicates recurrent cancer in up to 95% of patients.
Preoperative tests that are less important to conduct include liver function studies and routine genitourinary assessment. Liver function studies, whether elevated or not, correlate poorly with actual liver metastasis. CT scans are the best way to measure distant disease, he said.
Excretory urography results are abnormal in 26% to 43% of patients, but are a poor predictor of genitourinary complications. Indeed, regardless of whether the test is normal, abnormal, or not done, the literature shows that the rate of genitourinary complications is the same, Dr. Khanduja said. As a result, routine preoperative genitourinary assessment is not recommended.
