Evaluation of a direct radioimmunoassay for carcinoembryonic antigen

Adjuvant chemoimmuno- and immunotherapy in Dukes' stage B2 and C colorectal carcinoma: a 7-year follow-up analysis

A prospectively randomised controlled clinical trial of adjuvant therapy was undertaken, at a single-centre, population-based cancer institute, in patients with Dukes' stages B2 and C colorectal carcinoma after curative surgery. Between 1976 and 1983, 253 patients were randomised to either control (no further therapy after surgery), immunotherapy (oral bacille Calmette-Guérin [BCG] 120 mg once a month) for 5 years or chemoimmunotherapy (oral BCG as above with methyl-cyclohexyl-chloroethyl nitrosourea [meCCNU] 130 mg/m2 on day 1 and 5-fluorouracil [5-FU] 325 mg/m2/day on days 1-5 and 375 mg/m2/day on days 36-40) repeated every 10 weeks for 8 cycles. The median follow-up of patients is now 6.95 years. Of the control, immunotherapy, and chemoimmunotherapy groups 22.35%, 39.28%, and 28.57%, respectively, have relapsed. The log-rank analysis of results shows no disease-free or overall survival advantage for patients receiving adjuvant therapy compared with the control group. Patients receiving adjuvant immunotherapy for stage B2 appear to have a significantly inferior disease-free survival compared with other groups, but their overall survival is similar. There are no significant differences in disease-free or overall survival in the three groups of patients with stage C tumour. Of 82 patients dying, 78.05% died of progressive colorectal carcinoma, 13 patients developed a second malignancy; the remainder died of seemingly unrelated causes.

Carcinoembryonic antigen levels as an indicator of the primary site in metastatic disease of unknown origin

In 542 patients with metastatic disease arising from a known primary site, elevated CEA levels (greater than 10 ng/ml) were most often associated with metastatic disease originating from entodermally derived organs, breast, and mucinous ovarian primaries. This observation held true, in general, in a small series of 32 patients with metastatic disease arising from a primary site that had been unknown, but that was identified. Thus, although a CEA level below 10 ng/ml is of no use in pointing to a particular primary site, a value above 10 ng/ml suggests the site is more likely to be in an entodermally derived organ, breast or ovary containing a mucinous carcinoma. If liver metastases are present, there is an increased probability that the primary site will be found in the large bowel or pancreas.

Evaluation of a commercial enzyme radioimmunoassay kit for serum carcinoembryonic antigen

An enzyme immunoassay kit for carcinoembryonic antigen (CEA) that uses plastic beads coated with guinea-pig anti-CEA as first antibody and goat anti-CEA conjugated with horseradish peroxidase as second antibody has been evaluated. The method does not involve perchloric acid extraction and therefore avoids a dialysis procedure. It is accurate, sensitive, and inexpensive to operate, and provides values comparable to those obtained with the Roche-CEA Z-Gel radioimmunoassay.

A direct competitive binding radioimmunoassay for carcinoembryonic antigen

We have incorporated commercially available CEA standard and antiserum into the triple isotope double antibody radioimmunoassay and we have evaluated this assay for the routine determination of CEA. The competitive protein binding (CPB) assay for CEA can be performed directly on serum or plasma without perchloric acid extraction. The assay sensitivity was 0.98 ng/ml, and the day-to-day precision as defined by the coefficient of variation was 12.5% and 13.3% for mean values of 7.6 and 23.9 ng CEA/ml, respectively. The normal range (X +/- 2 S.D.) for CEA determined with the direct CPB method was 3.2--6.2 ng CEA/ml for non-smokers. The upper limit of normal for smokers was 10.0 ng/ml. A method comparison study (Roche perchloric acid extraction vs. direct CPB) showed excellent agreement between the methods for plasma samples containing less than 20.0 ng CEA/ml. The least square analysis parameters were: N = 116, slope = 1.01, y-intercept = 3.5 ng/ml, Sy/x -2.05 ng/ml, and the correlation coefficient was 0.79. Recovery and dilution studies showed no demonstrable non-specific interference due to serum proteins in the direct CPB assay. The clinical significance of the direct CPB assay for CEA was assessed by correlating serial CEA values with the clinical status of patients with breast and colorectal cancer. Increasing CEA values correlated with progressive or recurrent neoplastic disease, and decreasing CEA values correlated with response of the patient to therapy. No false positive direct CPB values for CEA were observed in the clinical study or in the method comparison study. Our laboratory and clinical evaluation demonstrate that the direct CPB method is an accurate and reliable method for the quantitation of CEA. In addition, the method permits high volume analysis and eliminates the hazards to safety that are associated with perchloric acid.

Value of serial CEA determinations in a surgical adjuvant trial of colorectal and gastric carcinoma

At the Cross Cancer Institute in Edmonton, a concurrently controlled, randomized, prospective surgical adjuvant trial involving Dukes' B2 and C colorectal carcinoma and gastric carcinoma (T1-4, No-2, Mo) has been activated for the last two years. To date, a total of 150 patients have been entered into the three arms of the trial (namely control, immunotherapy, and chemoimmunotherapy). Of these, 127 cases are colorectal carcinoma and 28 are gastric cancer. As part of the protocol, serial CEA determinations are obtained in all patients on a regular three-monthly basis. So far, 28 patients have confirmed recurrence (colorectal 20, gastric 8) demonstrated clinically or radiologically. Out of these 28 patients, 25 (89.2%) had CEA greater than 2.5 ng/ml months before actual demonstration of recurrence. However, if one uses a cutoff of 5.0 ng/ml as significant, that is, one standard deviation from the usual accepted value, then 21 out of 28 (75%) had persistent, elevated CEA's months before the recurrence manifested itself clinically or radiologically. The CEA profiles of three representative cases from each arm of the adjuvant trial are included. It is suggested that serial CEA determinations will be an invaluable adjunctive test in following patients in an adjuvant trial setting.

Predictive value of plasma CEA in patients with colorectal carcinoma

Two years follow-up of 46 patients with colorectal carcinoma resected "for cure" shows that of the nine patients with an elevated (less than 5 ng/ml) CEA plasma titer one to six months after surgery, only one, or 11%, had remained disease free. Of the 38 patients with normal (less than 5 ng/ml) plasma CEA, 27, or 71%, were free of disease two years after surgery. In another 85 patients presenting six months to ten years after resection "for cure" of their colorectal carcinoma, normal CEA levels were found in 73, and only five, or 6.4%, of these presented with disease progression when followed for two years; of the 12 patients that presented with CEA values less than 5 ng/ml, disease progression was evident in eight or 67%; in eight patients with CEA levels of greater than 10 ng/ml, the proportion of patients with disease progression increased to 87.5% (7/8). When a patient with a history of colorectal cancer, but seemingly free of disease, presents with levels not only repeatedly above normal (greater than 5 ng/ml) but above the levels found in some nonmalignant conditions (greater than 10 ng/ml), thorough re-examination of the patient to locate the site of possible disease progression is indicated. In 14 such patients further diagnostic methods showed local recurrences in four, metastasis limited to the liver in six, and other metastasis in four. In conclusion, in patients with colorectal carcinoma postoperative elevated CEA plasma levels are a sign of poor prognosis. Consistently elevated CEA levels (greater than 10 ng/ml) are a strong indication of disease progression.