Patterns of neoplastic spread in colorectal cancer: implications for surveillance CT studies.

ABSTRACT

OBJECTIVE: This study was performed to assess patterns of metastatic disease shown on CT in colorectal cancer and to determine the diagnostic yield of routine pelvic CT in follow-up surveillance. MATERIALS AND METHODS: Pathology records and 3073 CT studies of 1119 patients with colorectal cancer were retrospectively reviewed. Primary tumor site, site of abdominal or pelvic metastases (liver, peritoneum, lymph nodes, local recurrence, or other), and incidental nonmetastatic pelvic disease were recorded. The superior iliac crests were considered the border between the abdomen (above) and the pelvis (below). RESULTS: Metastatic disease was present in 34% (1040/3073) of all CT studies 33% (1007/3073) in the abdomen and 7% (227/3073) in the pelvis. Six percent (194/3073) of studies had metastases in both abdomen and pelvis. Forty-one percent (404/991) of studies showing abdominal primary colonic tumors showed metastatic disease 40% (400/991) in the abdomen and 8% (78/991) in the pelvis. Four studies (0.4%; 4/991) in four different patients with abdominal primary colon tumors had isolated pelvic metastases; three of these were primary tumors of the cecum. Thirty-one percent (636/2082) of studies showing pelvic primary colonic tumors showed metastatic disease 29% (607/2082) in the abdomen and 7% (149/2082) in the pelvis. Twenty-nine studies (1%; 29/2082) in 26 patients with pelvic primary colonic tumors revealed isolated pelvic metastases. CONCLUSION: In colorectal tumors arising within the abdomen, pelvic metastases are uncommon and isolated pelvic metastases are rare. Routine pelvic CT performed in the follow-up surveillance of patients with colorectal cancer with primary tumors arising in the abdominal portion of the colon has a low diagnostic yield.