CA19-9 as the most significant prognostic indicator of metastatic colorectal cancer

Colorectal cancer is the third leading cause of cancer-related mortality in Taiwan. We became interested in searching for the factors predictive of survival. Serum CA19-9 (carbohydrate antigen 19-9) level has been reported as a factor predictive of survival in patients with colorectal cancer. A few articles have reported that patients with metastatic colorectal cancer who have normal (< or = 37 U/mL) serum CA19-9 levels survived significantly longer than those with higher serum CA19-9 levels. However, these reports are contradictory and lack definite conclusions. This study was carried out in an effort to evaluate the prognostic significance of serum CA19-9 levels in patients with metastatic colorectal cancer in Taiwan.

Between 1991 and 1994, a total of 128 patients with histologically confirmed metastatic colorectal cancers were evaluated retrospectively at Veterans General Hospital-Taipei. All patients had measurable metastatic lesions and life expectancies of more than 3 months. 5-Fluorouracil-based chemotherapy, either in a weekly bolus regimen or a monthly 5-day bolus schedule, were administered to all of them. Data on age, sex, performance status, location of primary tumor, extent of metastases, site of metastases, histological differentiation, serum CEA (carcinoembryonic antigen) and CA19-9 levels were analyzed before chemotherapy to determine their association with survival. Blood samples for CEA and CA19-9 measurement were analyzed using the radioimmunoassay method. Multivariate analysis by the Cox's proportional hazards regression model was performed to determine independent prognostic factors among all of the possible variables.

By univariate analysis, serum CA19-9 levels (P < 0.001) and performance status of the patients (P = 0.022) were identified as prognostic factors, while age, sex, location of primary tumor, site of metastasis, histological differentiation, and pre-treatment serum CEA levels were not considered significant. By multivariate analysis, serum CA19-9 levels (P < 0.001) and performance status of the patients (P = 0.014) were still found as independent prognostic factors of these patients.

The data from our study indicate that serum CA19-9 level is the most significant prognostic indicator of patients with metastatic colorectal cancer. It is recommended that stratification for further clinical trials for patients with metastatic colorectal cancer should be carried out according to serum CA19-9 levels.